Hello all. Please can some one explain what I will need to do to convert a 13B from injection to N/A. I\'ve seen some manifolds to fit weber ida\'s for sale in aussie and the states- that would be my prefered carburation but can I get these in the UK ?
And what of the dizzy- what one would I need and will the ones off 12As fit straight into a 13B ?
If your wondering- its to fit into a shoveit and I want N/A due to my liking for clean uncluttered engine bays and enjoying the simple things in life.
And as for 13B over 12A - I had a 12A in my last 7 and when it blew it seemed harder to find good replacement engines but there were more 13Bs around so...
Any help would be really appreciated - Project due to begin as soon as I\'m back in the UK (2 weeks to go..) after a nice little holiday back at home in NZ. My anglegrinder trigger finger is itching..
cheers
alex
im interested in this too. Im considering a webber and manifold for my 12a but dont have a clue where to get one for reasonable money.
Cheers, Ant.
There is usually one guy on e-bay selling a 12a weber manifold. Think he wants about £170 or something for it. You can pick them up from time to time on ausrotary but there are at least 2 different height manifolds. Short one was good for a R100 and i think that the taller one was fine for most other old skoolers.
Maybe a few of the vw websites would be good to look for a weber as alot of them will use 48\'s on their engines.
cheers, michael.
crikey- £190 for the manifold !!! They cost about $195 in aussie. I might price some up here in NZ and if they are cheap I\'ll get one and possibly could bring in another one if someones interested....
So what about the dizzy - i havnt looked hard but presume injected cars dont have dizzys but instead the sparks are ecu controlled ? So I will need a dizzy but which one...
Quote from: yoeddynzcrikey- £190 for the manifold !!! They cost about $195 in aussie. I might price some up here in NZ and if they are cheap I\'ll get one and possibly could bring in another one if someones interested....
So what about the dizzy - i havnt looked hard but presume injected cars dont have dizzys but instead the sparks are ecu controlled ? So I will need a dizzy but which one...
If you want to get me a 12a webber 48 IDA manifold ill certainly buy one from you :)
well I\'m going to find out more about them here in NZ- so far i\'ve seen them for $350 NZD. Next thing I\'d have to work out is how to explain it to customs when they find two manifolds...and do I declare them?
alex
ok- I now have a manifold. A 12 a one because i\'ve ended up with a 12a donor car, but what size weber (40,45,48?) do i use on a standard 4 port 12a and whats the difference between ida\'s and idf\'s?
Now i\'m checking the Vw forums. wow- massive forum!!! scary.
alex
Quote from: yoeddynzok- I now have a manifold. A 12 a one because i\'ve ended up with a 12a donor car, but what size weber (40,45,48?) do i use on a standard 4 port 12a and whats the difference between ida\'s and idf\'s?
Now i\'m checking the Vw forums. wow- massive forum!!! scary.
alex
For what you want to do,stick with the 4 port,if possible get the 48 IDA,stay away from the IDF\'s...the belong on Alfa\'s and Beetle\'s LOLOLOL.:Typing
Ive got a dellorto 48 DHLA carb and manifold for 6 ports.....will also fit the lower 4 port manifold.
looking for £220 or best offer
whats the difference between idf\'s and ida\'s?
and how much do second hand ida 48\'s go for?
and has any one got one for sale?
IDFs are much smaller and worse flowing. IDAs are the daddies for big HP motors. They have a main fuel circuit much better suited to higher RPM and max HP.
second hand IDAs you\'d be lucky to find for less than about £300 each as the beetle guys (me too) love them.
As a beetle owner they are overrated: they are chosen due to their history on the scene. Problem is most of the ones ya get now are spanish carbs and are crap. Italians are the ones to go for (or is it the other way round? lol)
The dellorto 48DHLA flows as well as the IDA and because they are sidedraft are not so saughtafter (read pricey). They have the same power potential and due to the longer manifold on 13bs tend to give better low down torque (required on a 2nd gen, not on my beetle!)
thanks for that info!
well- as i already have the manifold I\'ll have to start looking for a carb. I had a peek in the libary yesterday at a haynes book on webbers and saw the differences- the ida seems to be a lot more simple and claener in design.
So with the 12a being standard as far as ports go will a 48 be to big or can i just choke it down? I think its wise i go for the 48 now so in the future its there for when I want more flow so is choking down a realistic option for now?
And are IDA\'ds still made new?
its an odd situation to be in....The 48 wont be too big i doubt as long as its jetted correctly and the choke sizes arent too big. Just take care not to run it too lean!
Steve
Found this:
http://www.webcon.co.uk/weber/performance_carbs.htm
£438 for a new 48 IDA, and they are in the UK!!!
I\'ve heard repro webers can be dodgy, can anyone shed any light on these? It says these carbs are made using the original tooling in the original European factory!!!
Racing beat are selling 48\'s cheaper at $499. If we can establish whether these carbs are any good i\'d definately be in on a group buy from the US.
I have one of the New IDA carbs on my 13B egi motor and it is excellent, I looked ain to secondhand ones from Australia or the States and the fact that they are probably 30 years old makes them a bit of a gamble, unless you can see one first.Even the specialists said the had bought them with siezed jets and other horrors. I got mine 3 years ago from Eurocarb. I have had no problems getting jets or 40mm venturis, however there are no 43mm ones in the uk suppliers at the moment.
I have no problems with using this on the road and is very dosile, starts and idles well.
Quote from: jon newmanI have one of the New IDA carbs on my 13B egi motor and it is excellent, I looked ain to secondhand ones from Australia or the States and the fact that they are probably 30 years old makes them a bit of a gamble, unless you can see one first.Even the specialists said the had bought them with siezed jets and other horrors. I got mine 3 years ago from Eurocarb. I have had no problems getting jets or 40mm venturis, however there are no 43mm ones in the uk suppliers at the moment.
I have no problems with using this on the road and is very dosile, starts and idles well.
Interesting, thanks...
ask Era what he thinks of \'sideways carbs\'....
\'its gotta be downwards bro...\':guinness
;)
Quote from: dubber91ask Era what he thinks of \'sideways carbs\'....
\'its gotta be downwards bro...\':guinness
;)
In actual fact a carb that does not stand up,is not a carb at all,carbs were meant\\made that way...not lying down !!!!!!!!!!!!!!:yes :guinness
i\'d be up for a group buy from the US too but I wanna wait till i know more about the choke and emulsion tube sizes first so I can order it all in one go and not being mucking about later buying more bits...
who else might be up for a Weber ?
aalex
Side draft carbs are underated! The first car powered by a rotaru to dip into the 9\'s in oz( drag racing that is) was turbocharge, a wee bit of nos but had a side draft weber.!!!I am yet to hear a technical argument for the down draft versus sidedraft carb. That is... one htat say down is better than horizontal. Sure it is a very proven formula, just ask or look at era\'s car. Simple and bloody fast. But why is it that peole shy away from a sidedraft. Or for that matter a dual side draft set up???? There might be not enough room at the side of an engine but you can mount the 2 carbs on top. I have seen this work,
cheers, michael.
Quote from: travellinbobSide draft carbs are underated! The first car powered by a rotaru to dip into the 9\'s in oz( drag racing that is) was turbocharge, a wee bit of nos but had a side draft weber.!!!I am yet to hear a technical argument for the down draft versus sidedraft carb. That is... one htat say down is better than horizontal. Sure it is a very proven formula, just ask or look at era\'s car. Simple and bloody fast. But why is it that peole shy away from a sidedraft. Or for that matter a dual side draft set up???? There might be not enough room at the side of an engine but you can mount the 2 carbs on top. I have seen this work,
cheers, michael.
Sidedrafts are made for FORDS and OPELS...not ROTARIES........:3gears-rh :guinness
how about oddly mounted rotary lumps? cos they would technically be sideys ;)
Theres nowt wrong with em....Ive just yet to convince era :WaveBye
air dont flow easier downwards to sideways or anything, so why should there be a performance difference???
in fact, due to the vaporised nature of fuel, atomisation in the air stream should improve with a sidey ;)
The pictures of Side drafts mounted above the top of a rotary with the manifold doing a full 180 bend to get flow into engine look wrong- i just picture all the fuel getting rammed against the outside of the bend, wetting the walls...
Main thing is I now have this lovely downdraft manifold!!!
One of the things I\'ve always loved about rotarys in NA form is how clean and simple it all looks- and downdraft webbers fit in well with that look.
alex
If my memory serves me correct, a longer inlet manifold gives increased torque at lower revs but less power at high revs. A shorter manifold gives less torque at low revs but more power at high revs.... i think!
I agree though that a straighter run-in to the inlet ports has got to be good, flow is everything.
Racing beat did a side draught Dellorto set-up, think power figures were sub 200bhp.
Checked out Eurocarb as suggested bu Jon. They do new Weber 48s for £325 each so reckon this would be cheaper than importing from the US
http://www.racecar.co.uk/weber/
Quote from: yoeddynzThe pictures of Side drafts mounted above the top of a rotary with the manifold doing a full 180 bend to get flow into engine look wrong- i just picture all the fuel getting rammed against the outside of the bend, wetting the walls...
Main thing is I now have this lovely downdraft manifold!!!
One of the things I\'ve always loved about rotarys in NA form is how clean and simple it all looks- and downdraft webbers fit in well with that look.
alex
:Thumbs-up :Thumbs-up :Thumbs-up :Thumbs-up :Thumbs-up :Thumbsup!
\'If my memory serves me correct, a longer inlet manifold gives increased torque at lower revs but less power at high revs. A shorter manifold gives less torque at low revs but more power at high revs.... i think!\'
read up! tis what i said.....
So is top end power all we care about then? :rollin ;)
if you want the shortest route into the engine, a sidey mounted over the exhaust is the shortest manifold....wouldnt take a lot to do it either :Santa
a sidedraft carb over the rotor is a much neater package, more space efficient...you dont have to hack holes in the bonnet for the velocity stacks and filter either ;)
I found the perfect thing to weld into your bonnet to clearance the carbs era.....whatcha think??? :InLove
(http://www.angiescarr.co.uk/angie/biscuitalu.jpg)
take your pick!:Santa
veeeeery nice. you could store other stuff in them too...
I\'m aware of longer manifolds = more torque but how about the important side of asthetics?
I just love the look of IDA\'s....
(http://i57.photobucket.com/albums/g226/yoeddynz/Niceandclean.jpg)
Quote from: yoeddynz(http://i57.photobucket.com/albums/g226/yoeddynz/Niceandclean.jpg)
That is pure sex for the oldone....:D ....:evillaugh
nah needs new ignition leads, coloured pulleys, and gettin rid of the gay rotor oil filler cap ;)
whats wrong with this?
(http://www.mazdatrix.com/pictures/racing/r-weber.jpg)
(http://www.gruntled.com/Dellorto/MyInstall.jpg)
ok it is messy, but nothing fundamentally wrong with it :Thumbsup!
but that you cant see the pretty polished housings.
****- I just bought a \'gay oil cap\' just before leaving NZ...I thought it looked pretty funky (it was only a tenner!).
I\'ve seen many worse things that can be added to cars/engines. Lexus lights and little leds for starters.
Anyway- how bout this....
(http://i57.photobucket.com/albums/g226/yoeddynz/12Arotary.jpg)
Quote from: dubber91nah needs new ignition leads, coloured pulleys, and gettin rid of the gay rotor oil filler cap ;)
whats wrong with this?
(http://www.mazdatrix.com/pictures/racing/r-weber.jpg)
Yechhhhhhhhhhh !!!!!!!!!!:Nono!
Quote from: dubber91(http://www.gruntled.com/Dellorto/MyInstall.jpg)
ok it is messy, but nothing fundamentally wrong with it :Thumbsup!
yechhhhhhhhhhhhhhhhhh !!!!:Nono!
This is what it should look like,this is the OLD SCHOOL tradition !!!!!!!!!!
Not sure if its IDA but this one\'s a bit tidy! :mmmm
IDA\'s the only WAY
This one\'s from a 14.2 second 12a bridgy, NO NOS, NO TURBO, he he he
Tidy ...but non IDA....:Typing
Quote from: oldoneTidy ...but non IDA....:Typing
What you reckon? Nikki?
The pic is from an Aussie website, they are pretty keen on a carb called a Stuber which I think is a modified Nikki carby.
Quote from: DominicWhat you reckon? Nikki?
The pic is from an Aussie website, they are pretty keen on a carb called a Stuber which I think is a modified Nikki carby.
Modified NIKKI looking at the base setup ...?????/ Howevr could be STUBER,they are using them alot instead of the IDA\'s (cost effective)..:cheers
Quote from: DominicIDA\'s the only WAY
This one\'s from a 14.2 second 12a bridgy, NO NOS, NO TURBO, he he he
why? nowt wrong with a dell!
:p
Quote from: dubber91why? nowt wrong with a dell!
:p
There\'s a lot wrong with mine :Hammer
I have just come off the phone from Eurocarb, they have 6 IDA carbs in stock, I hinted that a few people may be interested in buying carbs so put down how many carbs and contact them for a good group price. The current price is £325 + VAT. The retail price is about £100 more so to start with this is a good price , i paid more 3 years ago.
Quote from: jon newmanI have just come off the phone from Eurocarb, they have 6 IDA carbs in stock, I hinted that a few people may be interested in buying carbs so put down how many carbs and contact them for a good group price. The current price is £325 + VAT. The retail price is about £100 more so to start with this is a good price , i paid more 3 years ago.
Thats good news that they\'ll do a group price, good job!
Well I\'m having one, anyone one else interested? I\'m happy to arrange the purchase (and haggling!) with Eurocarb.
Lol can\'t fit an IDA on the 323 as the bulkhead is in the way :Giggle otherwise I might have been interested.
you do realise that one of the DIY EFI setups and throttle body could well be cheaper, look just as good (just not totally oldschool) and make as much power if not more :) (Devils Advocate)
just built a megasquirt......
just started using a chassis dyno at uni..........
;)
;)
lets take yer IDAs, block up the jets and drill them for injectors.....
best use for em!
:D
I built the mechanical bits for my RX7 (rather poorly I must say) , but chickened out with the ECU etc. Have since built an EFI rally car from a 70\'s shell and I have to say it\'s not that complicated really ... would certainly consider going efi on the 323 once it\'s running. A blow through turbo carb would also be cool though hmmm lots of room for an intercooler or charge cooler in the 323 too !
Have considered EFI and given the money i\'d probably go for it. Carbs are just more appealing at the moment.... simple, cheap, sound great, big flamage :Laugh
I reckon a 48IDA setup would be approx half the price of a good EFI setup. Agree megasquirt could save some coin though. Have done a rough price comparison for the 2 setups:
Weber 48 setup (approx)
Carb £300
Inlet Manifold £100
Fuel pressure regulator £20
Gaskets £20
Air Filter/trumpets £40
Uprated fuel pump £100
Other stuff, jets etc £100
Total £680 approx
EFI Setup (approx)
Throttle body (4 injectors) £400 new
Inlet Manifold £100 new
Fuel Surge Tank £100 new
Microtech LT10S £450 new
Pressure Regulator £30 new
Turbo II Coils £40 second hand
Crank Sensor £50 new
550cc Injectors £40 second hand
Fuel pump £100
Total £1310 approx
Quote from: DominicHave considered EFI and given the money i\'d probably go for it. Carbs are just more appealing at the moment.... simple, cheap, sound great, big flamage :Laugh
I reckon a 48IDA setup would be approx half the price of a good EFI setup. Agree megasquirt could save some coin though. Have done a rough price comparison for the 2 setups:
Weber 48 setup (approx)
Total £680 approx
EFI Setup (approx)
Total £1310 approx
Makes dubber91\'s Dellorto seem cheap, although regulator and pump would still be needed. The Dellorto\'s a nice carb for road use IMHO :Thumbsup!
QuoteIve got a dellorto 48 DHLA carb and manifold for 6 ports.....will also fit the lower 4 port manifold.
looking for £220 or best offer
JON- I would be interested in a good priced carb...I cant find a second hand one yet and even if I did it would probably need new bits plus new emulsion tubes,jets etc?
When one buys a new carb from places such as eurocarb do they fit the tubes,jets etc required for a particular setup in the price?
I\'ve just gone halves with my girlfriend on a mint old triumph 2500S estate for our \'runaround/pick up axles,engines,plants,food\' car and I\'m now very broke for the next month or so!
bugger!
But i\'m very very very inspired by all these pictures!
Quote from: yoeddynzJON- I would be interested in a good priced carb...I cant find a second hand one yet and even if I did it would probably need new bits plus new emulsion tubes,jets etc?
When one buys a new carb from places such as eurocarb do they fit the tubes,jets etc required for a particular setup in the price?
I\'ve just gone halves with my girlfriend on a mint old triumph 2500S estate for our \'runaround/pick up axles,engines,plants,food\' car and I\'m now very broke for the next month or so!
bugger!
But i\'m very very very inspired by all these pictures!
Suggest we kick this thread off again later in the year then to see if anyone else would be interested in the group buy. One question though, when ditching the Nikki carb and emissions stuff to make way for a Weber carb, what is the situation with the oil metering pump? Do you ditch this and run premix or is there a way of injecting oil through the Weber?
Oil metering pump gets binned....and premix.:cool :D
Quote from: oldoneOil metering pump gets binned....and premix.:cool :D
Luuuurve that smell. :yes
Thinking about the IDA thing and reading up on Ausrotary and some other sites I haven\'t yet found any cars running a 48IDA setup on stock ports :Hammer So 48IDA + stock motor = overkill?. Just wondering whether I could have the Weber set-up for stock ports and then re-jetted etc when the engine gets re-built and bridged. Is anybody running a stock motor on IDA\'s or know whether it can be done??? If not i\'ll be sticking to the Nikki until the rebuild. Im guessing a stock engine would run like a pig on a Weber setup as the air velocities through the carb would be slow.
Quote from: DominicLuuuurve that smell. :yes
Thinking about the IDA thing and reading up on Ausrotary and some other sites I haven\'t yet found any cars running a 48IDA setup on stock ports :Hammer So 48IDA + stock motor = overkill?. Just wondering whether I could have the Weber set-up for stock ports and then re-jetted etc when the engine gets re-built and bridged. Is anybody running a stock motor on IDA\'s or know whether it can be done??? If not i\'ll be sticking to the Nikki until the rebuild. Im guessing a stock engine would run like a pig on a Weber setup as the air velocities through the carb would be slow.
All goes about the jetting,smaller air,smaller mains,smaller ram tubes,emulsion tubes etc....stock motors run like a dream with a IDA.....:InLove :guinness
Still got a buzz 10 min later and Ive just been yp to Sainsbury\'s..!!!!!!!!!!!!:3gears-rh :cheers
My motor is stock other than a billet light weight fly wheel and straight through 2.5in exhaust. This lot is in my rx3 so being light it goes rather well.
Flames are a benefit especially at night on country lanes where they reflect off hedges like a mini mobile firework display. My son likes the sound of the flaming but has not experienced the illuminations yet.
any carb will RUN on any car....
I was told i overcarbed a 1600 bug engine with twin weber 44s...
i drove it daily for around a year.... NAH!
anything can be used, but be carefull on choke sizes. Choke down tends to lead to higher driveability.
Steve
Illuminations? I\'ll have what your having please- suggest you son takes more...
I\'ve been looking in the engine bay of my newly aqquired very very rusty 7 donar car and wondering about not only the oil injection but all the other crap that goes with the nikki. I\'ll be running the nikki till i can afford the IDA but the more I look at all the little pipes etc the more I wanna ditch it.
Most of the pollution gear can be scrapped and the tubes coming from the carb blocked off. If i can remember how I will run my nikki carb with mechanical secondaries also.
cheers, michael.
chuck it all and run premix....
Steve
Well- I\'ve started the \'removing engine from car\' thing last night and looking at all the wires heading towards the carb just puts me off keeping the nikki at all! I\'ve never owned a carbed engine with so much wiring!!!
So i\'ll save and by the time engine is all fitted into the chevette (of which i\'m still hunting for) i\'ll buy a webber.
But what about the dizzy? its got two vacuum advance thingees on it!..can i bin one of them or does it need both and why is there two?
What sort of ratio do you need for premix- I was thinking that the little oil pump only injected at high revs/loads.
I\'m waiting on a haynes manual so I can learn more...but till then I will kepp asking questions if thats ok..
cheers all.
alex
the two vacuum advance units are because you have a trailing ignition and a leading ignition, both of which have different advance/retard curves.
a lot of people bin all the electrical junk on the carbs, most of it will be due to the automatic choke system and for emmisiions control. I.e to prevent the petrol vapour from venting out of the carb when the car isn\'t running.
I have not looked yet but do the vacuum pipes feed from the same source and if running a weber does one just run them off the manifold?
I\'m sure I\'ve seen some cars without the pipes visible...surely its not possible to run without the vacuum advance or am I wrong and they are happy on just mechanical advance alone?
Going back to the oil metering pump + 48 IDA question, whilst skimming through a book last night noticed a pic of a race engine running a 48IDA with the oil metering pump still on. The two oil lines were connected up to the carb, will post the picture up at some point. Bit easier than running pre-mix although "I love the smell of Premix in the morning........ smells like.....VICTORY!!! LOL" :D
Quote from: DominicGoing back to the oil metering pump + 48 IDA question, whilst skimming through a book last night noticed a pic of a race engine running a 48IDA with the oil metering pump still on. The two oil lines were connected up to the carb, will post the picture up at some point. Bit easier than running pre-mix although "I love the smell of Premix in the morning........ smells like.....VICTORY!!! LOL" :D
I have seen the damage to motors when the OMP goes on the blink,i.e. setting goes out,pipes get broken etc.The OMP is one component which \'nobody\' bothers to check !! So why run the risk of a motor running \'dry\' ?:Typing
So what the mixture to use then- what sort of ratio?
The weber manifold I have has two blank castings just below top flange- ready to be drilled out for OMP I guess?
Also- the Vacuum pipes to dizzy...can it be run with out vacuum advance ?And if not where do people run the pipes from when running a weber IDA?
Quote from: yoeddynzSo what the mixture to use then- what sort of ratio?
The weber manifold I have has two blank castings just below top flange- ready to be drilled out for OMP I guess?
Also- the Vacuum pipes to dizzy...can it be run with out vacuum advance ?And if not where do people run the pipes from when running a weber IDA?
100ml :10litres of fuel...........the dizzy can be locked on what settings you want,so you dont need the vac advance pipes.:guinness .Personally I keep them on when I run a 12A with a Nikki carb,just to \'help\' the motor a lil.......:driving
Crikey- Thats hardly any oil at all- It does mean one could use that expensive \'royal purple\' oil stuff and not just be burning it away...
How do you lock the dizzy? If locked i presume its still able to advance mechancally- is that right?
I\'ve just had a haynes manual for rx7\'s turn up tonight in the post so its lots of cups of tea and reading on the sofa now...
Quote from: yoeddynzCrikey- Thats hardly any oil at all- It does mean one could use that expensive \'royal purple\' oil stuff and not just be burning it away...
How do you lock the dizzy? If locked i presume its still able to advance mechancally- is that right?
I\'ve just had a haynes manual for rx7\'s turn up tonight in the post so its lots of cups of tea and reading on the sofa now...
Just use bog standard 2 stroke motorbike oil at 100:1 if running premix.....correct???? Good point about the OMP Era, certainly have never checked mine, although this is something they recommend you do in the Haynes manual :Hammer The Haynes book is quite useful but a bit vague in parts, I\'ve been told you\'re better off getting hold of one of the original Rx7 workshop manuals if you can. :cheers
Quote from: DominicJust use bog standard 2 stroke motorbike oil at 100:1 if running premix.....correct???? Good point about the OMP Era, certainly have never checked mine, although this is something they recommend you do in the Haynes manual :Hammer The Haynes book is quite useful but a bit vague in parts, I\'ve been told you\'re better off getting hold of one of the original Rx7 workshop manuals if you can. :cheers
I use Castrol R40 :InLove :InLove and recently (few months ago) been testing and running the Millers 1\\2 synthetic product:InLove .Will only use the Bike products if Im in a pinch !!!!!!!:Hammer
100:1....wow- it seems like such a small amount. So does the OMP only pump in a little at high revs/ load?
OH- by the way...while on the subject of webers etc...there is this selling on the bay right now..
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&ih=017&item=270034332229&rd=1&sspagename=STRK%3AMEWA%3AIT&rd=1
Just dont look right to me.....its an imitation casting of the original and they did not get it right.....bad angles from all sides,wrong porting size,bolts holding carb ???........dunno ..just does not look right ????:3Confused
Quote from: yoeddynz100:1....wow- it seems like such a small amount. So does the OMP only pump in a little at high revs/ load?
The OMP injects oil at all rpms. According to Haynes, output should be 2-2.5cc in 6 minutes at 2000 rpm (engine warmed up). The OMP output increases with rpm. You need to squirt engine oil directly into the carb when doing the test with the oil lines removed to keep the internal engine seals in-tact.
the metering pump is controlled by throttle position not directly linked to rpm. later Rx\'s have it controlled from the ECU. I guess the earlier OMP\'s just inject more than is required to be on the safe side/compensate for the crude method of regulating the flow.
Quote from: MikeLMRthe metering pump is controlled by throttle position not directly linked to rpm. later Rx\'s have it controlled from the ECU. I guess the earlier OMP\'s just inject more than is required to be on the safe side/compensate for the crude method of regulating the flow.
Its all gear driven,so when the rpm goes up so does the injection rate.......:guinness
LoL hadn\'t thought of that :) very clever and simple
Old school bro............yipeeeeeeeeeeeee.....:cheers :InLove
So someone\'s done the maths to work out an equivalent to what the OMP puts out as far as premixing...?
I just wouldnt want to get it wrong.. although I could always just add more to be safe...
I do like the idea of being covered in case the OMP failed- and the idea of not having it and its little lines spoiling the veiw of such a nice lump..
As far as the manifold goes..its a bit different to mine- only having one cast in point for the OMP lines or vacuum. Plus the bolts look wonky but that might just be me?
But its cheap eh..
Quote from: yoeddynzSo someone\'s done the maths to work out an equivalent to what the OMP puts out as far as premixing...?
I just wouldnt want to get it wrong.. although I could always just add more to be safe...
I do like the idea of being covered in case the OMP failed- and the idea of not having it and its little lines spoiling the veiw of such a nice lump..
As far as the manifold goes..its a bit different to mine- only having one cast in point for the OMP lines or vacuum. Plus the bolts look wonky but that might just be me?
But its cheap eh..
If you had the time, some steel/ali tubing and a welder, reckon you could make a much better inlet manifold than any of the cast jobs. Just gotta make sure you get the tube diameters right, and the correct flow proportions into the intake ports (centre plate inlets have smaller cross sectional area). If you fabricated the manifold yourself you could go for much bigger bends to give smoother flow into the block. Wouldn\'t be easy and you\'d ideally need a flow bench to test it but as I said, if you\'ve got the time.... :King
I dont have a workshop dammit- and I\'m a fitter turner by trade so the skills are there (just mouldy) but alas...currently I\'m a cycle mechanic dealing to Oxfords cheap students bikes and no decent facilitys.
But i\'m going to build a workshop soon I hope then......
alex
QuoteSo someone\'s done the maths to work out an equivalent to what the OMP puts out as far as premixing...?
I just wouldnt want to get it wrong.. although I could always just add more to be safe...
I do like the idea of being covered in case the OMP failed- and the idea of not having it and its little lines spoiling the veiw of such a nice lump..
Royal purle have done the maths for you - from their faqs;
QuoteA stock FD twin turbo 13B with the MOP oil injection system can typically use about one quart per 1500 miles under hard street driving. If this vehicle is getting 15 mpg, the gasoline to oil ratio is 400:1. If the oil consumption on this vehicle reduces to 1 quart per 2500 miles and fuel efficiency increases to 20 mpg, the gasoline to oil ratio increases to 600:1. The stock metering oil pump is a great system as it varies with throttle position (load on the engine). Pre-mixing has to be calculated for the ‘worst case’ that will be seen by the engine for that fuel load. Under racing conditions, that’s wide open throttle at racing rpms. This means that at idle, the ratio may be slightly fat (rich).
100:1 is actually a lot of oil, ok for a race car but i would say too much for a street car IMO.
Also as RP say above premix has the downside of forcing you to have a constant amount of oil in the mix, whereas the factory set up varys it.
Quote from: royal purplePre-mixing has to be calculated for the ‘worst case’ that will be seen by the engine for that fuel load. Under racing conditions, that’s wide open throttle at racing rpms. This means that at idle, the ratio may be slightly fat (rich).
In my opinion this statement flys in the face of common sense! With premix if you are drawing in more fuel you will also get more oil. The ratio will remain constant. At idle you will use less fuel and therefore less premix.
Quote from: royal purpleThe stock metering oil pump is a great system as it varies with throttle position (load on the engine).
I think it\'s a crap system. If you use premix you will meet the increased demands of flooring your foot instantly whereas the OMP has to physically catch-up with the sudden extra demand. A case in point if you thrash your car and then stop at the lights you will sometimes see smoke (particualy on the mechanical OMPs) as the OMP lines are still carrying extra oil which is no longer required.
Quote from: mullinsIn my opinion this statement flys in the face of common sense! With premix if you are drawing in more fuel you will also get more oil. The ratio will remain constant. At idle you will use less fuel and therefore less premix.
I think it\'s a crap system. If you use premix you will meet the increased demands of flooring your foot instantly whereas the OMP has to physically catch-up with the sudden extra demand. A case in point if you thrash your car and then stop at the lights you will sometimes see smoke (particualy on the mechanical OMPs) as the OMP lines are still carrying extra oil which is no longer required.
Cant agree more ol chap...:cheers :cool
QuoteIn my opinion this statement flys in the face of common sense! With premix if you are drawing in more fuel you will also get more oil. The ratio will remain constant. At idle you will use less fuel and therefore less premix.
Yeah the ratio will stay the same with premix, whereas the omp will vary it, thats what they are trying to say.
So who of you out there in Rotary world \'premix\' and who uses the OMP? Just to get an idea....
I premixed 100:1 on my last 12A. It seemed to be a good balance.
Premix 100:1....have done so for 12 years:burnout :guinness
With premix do they smell more \'smokey\' ?
And whats the easiest way to premix...oldone- you will have worked this one out after 12 years!!!
alex
If you use a marine 2 stroke oil thats designed to burn clean you shouldn\'t get much smell (rotaries tend to smell of burnt oil anyway). You can then run a good synethic oil in the sump.
Easiest way I found was to get hold of a syringe thingie with a measure on the side. My old man filled up for me one time and got a bit confused with the measure. He ended up putting in 200ml to 20 litres of petrol! I was surprised at how little a difference it made smoke-wise. I don\'t think it has to be an "exact" science. Era might have some better ideas. :chat
Capacity of tank is what 50 litres ish, give or take. Just buy the 1 litre bottles of oil and chuck in half when you fill up. Oil will mix nicely in the tank after a few corners but if you want a really good mix I guess you could half fill tank, add half litre of oil, then top up. Just make sure you\'ve got a few spare bottles of nice oil in the car in case the petrol station has run out...
Mullins - Isn\'t 200ml of oil to 20 litres of petrol the correct mixture, i.e. 100:1?
Yeah sorry I meant 400ml. I used to put the oil in first and then the petrol to help stirr it up.
For the race cars I used to mix my fuel in 20 lit containers ahead of time,for the road car I carry my own premix,as its not for sale at the garages.Bottle is measured in increments of 100ml,pour oil,pour fuel.Easy :cool
cool- easy then. Well I think i\'ll remove the OMP then its even less hanging about looking ugly! I want a nice simple clean looking motor.
Something like this would be nice....
(http://i57.photobucket.com/albums/g226/yoeddynz/Peripheralported12A.jpg)
What does happen to a rotary if it doesnt get its oil supply? I know its going to be bad but is it quick death or just wears out quicker? And how long will they run without the OMP etc before they die?
Lovely Yawpower motor!!:InLove
I must confess that I have blown up a N/A 13B bp engine after Alford sprint race last weekend(8th Oct), front rotor/housing/e shaft and a bearing is Fcuked,
The cause was unknown. as it blocked the e-shaft\'s oil feedholes with build up deposit from brass bearing.
the bearing has stripped its brass and ended up in the sump!.WoW!!
I am going have it rebuilt , ready for Highland speed and Scottish sprint championship next year!.
Its better to blow it up now!! than next year
Funny thing is, the rear one is sooo good as if nothing had happened !
anyway, It\'s nothing to do with pre-mix as I always do it anyway with Mobil Racing 2T fully syntheyic oil.
QuoteWhat does happen to a rotary if it doesnt get its oil supply? I know its going to be bad but is it quick death or just wears out quicker? And how long will they run without the OMP etc before they die?
Just wear out quicker, but i\'ve heard several accounts of people not realising the omp wasnt working for tens of thousands of kilometres to no apparent effect.
So could you get away with mixing in less? How did everyone come to the mixture being 100:1- is that an average of what the OMP puts out or gospel spoken by some mazda god many years back handed down generation to generation....?
Yep- got a link to yawpowers site and cried with joy at the sight of soooooo many shiney parts and sexy machines (yes - I believe that machines can be very sexy -especially when high)
Yoe, How do you able to download the pics? as I am trying to put my blown rotor pics in. its must be a easy way to do it.!
Ian- I joined up to photobucket.com. Its free and I just load photos I want to post from my computer to the site and it then gives me a \'IMG\' link to paste onto any forum page etc.
But dont delete any photos from photobucket site as i\'ve just discovered that no photos on site= no photos on forum!
I\'ve just deleted all the chevette photos from my photobucket account and will have to repost them!!!
I\'d love to see your blown engine (apart..not turboed..)
alex
Yoe,
Thanks, I will try my best as i am quiet a brick about computer!.:confused:.
http://i121.photobucket.com/albums/o229/scot62/DSCF0143.jpg O/D of the rotor bearing,has been spinning along!http://i121.photobucket.com/albums/o229/scot62/DSCF0141.jpg copper from the bearing left its mark at oilways,which has blocked the oil flow.http://i121.photobucket.com/albums/o229/scot62/DSCF0137.jpg copper deris in the sump.http://i121.photobucket.com/albums/o229/scot62/DSCF0135.jpg exhaust port.
Big thank to yoeddynz for the help!:Thumbs-up
I always thought copper slip was a good thing...
Just pack the engine full of banana skins to take up clearances and she\'ll be fine.
Whats the deal with the coin- am I missing something? I couldnt see anything wrong there but maybe I\'m not looking hard enough?
Cheers for pictures.
alex
I premix in 20ltr containers.No probs yet
The deal with coin is to shown how big is the exhaust port.
here is some few pics, old school N/A 13B 4pbp(70\'s)http://i121.photobucket.com/albums/o229/scot62/DSCF0126.jpghttp://i121.photobucket.com/albums/o229/scot62/DSCF0131.jpg http://i121.photobucket.com/albums/o229/scot62/DSCF0144.jpgcopper gone !!
The beauty of photobucket, some more with 48 IDA carb etc..http://i121.photobucket.com/albums/o229/scot62/DSCF0120.jpg http://i121.photobucket.com/albums/o229/scot62/DSCF0099.jpg http://i121.photobucket.com/albums/o229/scot62/DSCF0122.jpg http://i121.photobucket.com/albums/o229/scot62/DSCF0100.jpg two win this year at RAFMA lossiemouth\'s sprintrace.
That cool air box is trick. Shame it covers the engine though. Does it make much difference to hp? Presumably there would be a small ram air effect at higher speeds as well.
Cool- I like the airbox idea too.
All these photos...I cant wait till i\'m able to post some of my chevette with engine installed and running!
If you copy the bottom of the three tags under your photos on your photobucket album and plonk \'em on the forum page then the photos should appear on the page.
Photos of rotarys are so great- such simple clean engine bays.
No cams, no valves, no mess. The simple ideas are always the best. Thats why we love the rotary :god :)
Wish I had some money at the moment. Got so many plans for the rex but cant do any of them.
Quote from: DominicNo cams, no valves, no mess. The simple ideas are always the best. Thats why we love the rotary :god :)
Wish I had some money at the moment. Got so many plans for the rex but cant do any of them.
Amen to that! Want a Cammy sounding rotary, chop some holes in it :D et voila a bridge port.
And easy to clean
Hi Ian, is that a remote filter you use on your car?? Do you mind me asking where you got the bits for it?
Cheers, michael.
Bob,Yes, its remote one and got it from demon Tweek.
A7nty, its a bridge ported motor. lovely one!, got a lovely sound, "Say" from fellow racers and due to the design of the home made exhaust system/Racing Beat down pipe( true duel= two back box only =89db meter)
Yoe/Dom, its working ok, due to turboII bonnet vent and Ram cold air at speed( it\'s cool in North Scotland during the summer)
Hope my english is okay!!
Cheers for that Ian, I am haveing a few bulkhead space issues with my oil filter so might go remote?
cheers, michael.
Bob, you need an oil filter bypass block to replace the stock oil filter holder.
crikey- oil filter and baulkhead clashing! thats something I have not thought about (amongst all the other stuff)...I dont think i\'ll have a problem hopefully.
Back to the naturally aspirated thing.. around june last year I had bought a series 3 for the engine to replace our blown one but unfortuanately after paying all of £150 for the rusted beauty it died thirty miles into my home journey. The engine had twin SU carbs on it...just like Hurleys setup (most likely was perhaps) but the carbs were actually Jappa ones like on a datsun 240 etc.
It ran really well (till it died) and seemed smoother then our nikki carbed car- nice linear acceleration. Never knew back then to look for any sign of OMP..which could have been its cause of death?
Has anyone else experianced this carb setup and if so what you think?
Also- does any one else make this setup other than Hurley?
alex
Quote from: yoeddynzThe engine had twin SU carbs on it...just like Hurleys setup (most likely was perhaps) but the carbs were actually Jappa ones like on a datsun 240 etc.
It ran really well (till it died) and seemed smoother then our nikki carbed car- nice linear acceleration. Never knew back then to look for any sign of OMP..which could have been its cause of death?
Has anyone else experianced this carb setup and if so what you think?
Also- does any one else make this setup other than Hurley?
alex
Haven\'t heard about other SU set-ups for the rotary but it does make sense as they are quite compact units so fit nicely to the side of the engine with no need for big inlet manifolds. Guess you might have problems squeezing in a decent size air filter in though. Hurley claim fuel economy of around 30mpg at motorway speeds and good acceleration. Prefer downdraft myself though on a rotary.
Quote from: DominicHurley claim fuel economy of around 30mpg at motorway speeds and good acceleration.
But does anyone know anyone with a Hurley setup that can prove their claims???
I\'m not saying they\'re lying, but they make a lot of claims on their website and yet no members seem to use them! :confused:
Quote from: mullinsBut does anyone know anyone with a Hurley setup that can prove their claims???
I\'m not saying they\'re lying, but they make a lot of claims on their website and yet no members seem to use them! :confused:
One day is one day,and I am going to pay Hurley a visit,just to see what goes on there and to meet the people,ask some questions...:Typing Clive and those who have been around the island for some time should know all the answers to your questions.......:wiggle
I just can\'t understand where their customer base is? I haven\'t come across anyone with a hurley twin carb setup let alone one of their n/a 3 rotor kits.
I too would be keen to visit them and see their handywork. I\'m surprised they aren\'t in the thick of the scene with a demo car of some sort.
I guess that there must be a few hundred rotory powered cars i nthe uk these days with all the imports etc so a few must make their way to hurleys?
cheers, michael.
Well as for claims about 30mpg this particular rx7 did at least that because it got towed! I\'d love to have been able to run it for a while but alas..
I ended up giving the engine to the bloke who bought our black S3. I wish I\'d kept the manifold etc but at that point I was not expecting to get another rotary.
It was certainly a clean tidy neat setup. And Su\'s are so so easy to understand and strip. Most my Cars in the past have run them.
Quote from: dubber91how about oddly mounted rotary lumps? cos they would technically be sideys ;)
Theres nowt wrong with em....Ive just yet to convince era :WaveBye
air dont flow easier downwards to sideways or anything, so why should there be a performance difference???
in fact, due to the vaporised nature of fuel, atomisation in the air stream should improve with a sidey ;)
http://www.youtube.com/watch?v=rPw1G3pqiwQ
Here is a photos of SU(??) set up
(http://i121.photobucket.com/albums/o229/scot62/dsc00386vl8.jpg)
(http://i121.photobucket.com/albums/o229/scot62/dsc00384qb7.jpg)
Looks lovely. The trouble with SU however is the company went bust years ago, getting overhaul parts for their carbs is very very hard. Believe me I have tried.
Burlen Fuel Supplies have rebuild kits on the shelf.
Able to find it from RoverSDI 2600 (2 SU)
plus i beleive minispares do very good repro rebuild kits...
Steve
just such simple carbs. But no accleration pump always seems to make for less oommph..
yes but you get a surge in fuel when you suddenly open the throttle due to the surge in vacuum before the piston can catch up (I seem to remember being told as much by a mini nut a long while ago) And what about motorbike carbs ? they are a similar constant depression design and are much newer and more commonly available ? (although small)
yeah...I\'ve wondered about bike carbs. clean, simple and cheapish but like you say- possibly too small...?
You can get bike carbs on decent hp pintos and the like so why not a rotor. ??? How hp do you want to make, how drivable do you need it to be and then work out the induction I guess?
just around 500 bhp whilst returning 30mpg at a steady 70mph would be nice.
And no hair dryers in sight please...
Just thought I\'d spark up the ongoing premix/OMP debate with this link to ausrotary.com which discusses the use of an adapted OMP which draws fresh oil from a small separate tank rather than sump oil.
Certainly like the idea of not having to inject sump oil into the chambers (as for normal oil metering pump system) and no need to worry about getting the right fuel/oil ratio each time you fill up (as for the pre-mix option). Just gotta make sure the feeder tank doesn\'t run dry, but it would be easy to fit a low level warning light.
Another advantage of the system is that it enables you to use two different oil types (an advantage of pre-mix over standard OMP) e.g. clean burning 2 stroke oil in the rotor chambers and whatever your preference in the sump, synthetic/mineral....
http://ausrotary.dntinternet.com/forums/viewtopic.php?t=66594&postdays=0&postorder=asc&highlight=omp&start=0
Hi, how you manner getting into Ausrotary as mine not getting access to for 3 weeks
Quote from: ian duncanHi, how you manner getting into Ausrotary as mine not getting access to for 3 weeks
Dunno, didn\'t have any probs getting on the site. Do you have broadband?
Got a broadband but weird!! no access
I haven\'t had any trouble accessing ausrotary.
Omp is in my mind superior to premix, although the setup as in the link above, which adapts the omp to suck fresh 2 stroke instead of sump oil is better again. A couple of things to add to the debate:
When decelerating the omp still injects oil. On the other hand if no fuel is entering the engine, with premix no oil is entering the combustion chamber, and the seals are exposed to wear. Also, premix ratios mean more oil is entering the engine, and oil lowers the octane rating of fuel. This is not a major issue on n/a rotaries, but on cars with forced induction can lead to pinging/detonation.
The omp does need to be checked reasonably regularly to ensure it is working, but I have not had any issue in my cars over several years of having rotary daily drivers, and it saves the hassle of carrying around 2 stroke and trying to explain to anyone who may borrow your car. Also, as I am now running lpg, I can\'t premix ;) but I\'ll still be running the omp on any petrol fueled rotaries I may own in the future.
Guess you\'d save quite a few $$£££££\'s in oil costs over time by running the OMP too cos it is a more efficient way of lubricating the chambers using less oil per engine revolution than pre-mix (most of pre-mix oil is burnt with the fuel)
The problem with an OMP is that it injects the oil pipes which take time to reach the combustion chamber where-as premix is instant. An OMP will never match premix. If you give your car a good fang and then slam on the anchors for a set of lights you car will run rich until the supply via the OMP slows down. If you run premix you run the correct ratio 100% of the time and the OMP just can\'t match that! The other big advantage of premix is you can use an oil which is designed to burn and avoid carbon buildup. Premix wins hands down imo.
Quote from: mullinsThe problem with an OMP is that it injects the oil pipes which take time to reach the combustion chamber where-as premix is instant. An OMP will never match premix. If you give your car a good fang and then slam on the anchors for a set of lights you car will run rich until the supply via the OMP slows down. If you run premix you run the correct ratio 100% of the time and the OMP just can\'t match that! The other big advantage of premix is you can use an oil which is designed to burn and avoid carbon buildup. Premix wins hands down imo.
I can relate to that fact...:cheers That is why we used premix in the race cars and not an omp......... poor response out of low rpm corners and long sweeping on\\off sweeps with the omp etc...:guinness
Quote from: mullinsThe problem with an OMP is that it injects the oil pipes which take time to reach the combustion chamber where-as premix is instant. An OMP will never match premix. If you give your car a good fang and then slam on the anchors for a set of lights you car will run rich until the supply via the OMP slows down. If you run premix you run the correct ratio 100% of the time and the OMP just can\'t match that! The other big advantage of premix is you can use an oil which is designed to burn and avoid carbon buildup. Premix wins hands down imo.
I’ve still got much to learn about the rotary engine so please don’t flame me if my spiel below is a load of codswallop :Hammer . Thought I would add my thoughts to the debate anyhow.
I can understand the OMP lag issue but can’t see this being significant or affecting the longevity of the engine. The OMP lines are constantly full with oil (even at low rpm\'s), and the oil in the lines is incompressible, so the delay in getting oil into the chambers when you hit the go pedal will be very very small. I think it would be fair to assume that there would be enough residual oil in the chambers to cope with this very small period of oil starvation. Appreciate that throttle controlled oil injection (i.e. premix) will be more responsive than rpm controlled oil injection (i.e. OMP) due to the fact that throttle position is the precursor to rpm change but surely we only want oil in the chambers when rpm’s rise, not when the throttle butterflies open up.
Mullins, agreed…. with premix you can run a good oil, but I was referring to the link to ausrotary.com that I posted earlier, this discusses the use of a standalone oil tank which the OMP draws from so you can use one type of oil in the sump and another clean burning oil in the combustion chambers.
Not trying to flame pre-mix, just trying to weigh up the two (well.... now 3 options!) i.e.
1) Pre-mix using nice clean oil in the fuel
2) OMP sucking dirty sump oil
3) Modified OMP fed by standalone header tank filled with nice clean oil
Not sure whether I agree with the statement that pre-mix runs the correct ratio 100% of the time, in fact I think there are cases where this could be the opposite. E.g. for your example.... If you blast the car then drop down off the revs approaching lights, as the car is decelerating, with pre-mix, very little oil will be entering the chambers as the throttle will be almost closed....... combustion in the chambers will still be occurring however, therefore during the slow down/coast period, the engine wont be getting much oil. With OMP, as the car comes down off the throttle, even though the throttle is closed the OMP will still inject oil into the chambers because the OMP pump is governed by rpm not throttle position, therefore the engine’s lubricating demands are still met during this period. Surely it\'s more important to govern oil injection on rpm rather than throttle position. I guess this depends heavily on how the oil is injected….. my comment above may only be correct if oil is injected from the OMP directly into the chambers…… probably wouldn’t be correct though if injected into carb as lack of vacuum would prevent the oil being drawn into the chambers.
As said before, not trying to say which is best... just putting two sides to the argument. TBH though, I think the OMP system has many benefits over pre-mix (although you gotta love the pre-mix smell), such as:
- Less oil used (is this correct???)
- Less complicated operation (fewer idiots like me juggling oil bottles on the gas station forecourt)
- If option 3) of a modified OMP fed by a standalone header tank is used then different oil types can be used in sump and chambers (e.g. synthetic/mineral in sump, nice clean 2 stroke oil in chambers), therefore sharing one of the main benefits of running pre-mix, i.e. not sucking up grim contaminated sump oil for use in the rotor chambers
- RPM controlled oil injection (surely this is preferable to throttle position controlled oil injection?)
- I’m sure there’s another one but I forgot it!
The drawback of the OMP system is the OMP pump can fail, but the units seem very reliable.
Right, off to get my flameproof coat :chat
^ No flame required, good questions/arguements.
Even if the OMP is used the oil is still injected & mixed (with fuel) via the carb so a lot of the "advantages" in your post aren\'t really so (de-acceleration senerio etc).
Although the flow of oil maybe constant if you have a rush of fuel/revs you need the increased oil flow to match the fuel to keep the correct ratio. The increased oil flow has to travel from the bottom of the engine (just above the sump) to the top of the engine almost instantly and physically this isn\'t possible. With premix it\'s already there.
Hope this makes sense. Usual disclaimer applies!:WaveBye
On a N\\A high performance motor in racing conditions or a cheecky road going brapper,you will commit motor suicide if you go with the omp,on a sedate road going motor and driving like a nun,the omp is perfect !!!!:D :cool Remember the omp is gear driven and runs at a given ratio\\ask deliverance,premix is available at any given chosen ratio and imm at that,rather have too much oil on overrun than too little.........:Typing
I would just like to add, that my car did nearly 30MPG on its last scotland trip. unknow engine mileage and turbo charged, I was not hanging around either...that runs an 1.75 SU, also, the car was actually listed when i rebuilt the carb with parts from Burlan Fuel supplies. SU\'s maybe simple, but they work very well when you know how to set them correctly. You have to have the needles set at the correct angle, the float level smack on, correct measured seat depth, correct oil, and level. then you can set the mixture and tickover......
Not sure whether I agree with the statement that pre-mix runs the correct ratio 100% of the time, in fact I think there are cases where this could be the opposite. E.g. for your example.... If you blast the car then drop down off the revs approaching lights, as the car is decelerating, with pre-mix, very little oil will be entering the chambers as the throttle will be almost closed....... combustion in the chambers will still be occurring however, therefore during the slow down/coast period, the engine wont be getting much oil. With OMP, as the car comes down off the throttle, even though the throttle is closed the OMP will still inject oil into the chambers because the OMP pump is governed by rpm not throttle position, therefore the engine’s lubricating demands are still met during this period
if combustion still occurrs...there must be fuel.....if theres fuel theres oil. there is also residual oil from previous induced strokes. The retardation of ignition timing increases unburned fuels, thus, \'unused\' oil. I think in reality there is very little practical difference in this scenario
Steve
Quote from: dubber91Not sure whether I agree with the statement that pre-mix runs the correct ratio 100% of the time, in fact I think there are cases where this could be the opposite. E.g. for your example.... If you blast the car then drop down off the revs approaching lights, as the car is decelerating, with pre-mix, very little oil will be entering the chambers as the throttle will be almost closed....... combustion in the chambers will still be occurring however, therefore during the slow down/coast period, the engine wont be getting much oil. With OMP, as the car comes down off the throttle, even though the throttle is closed the OMP will still inject oil into the chambers because the OMP pump is governed by rpm not throttle position, therefore the engine’s lubricating demands are still met during this period
if combustion still occurrs...there must be fuel.....if theres fuel theres oil. there is also residual oil from previous induced strokes. The retardation of ignition timing increases unburned fuels, thus, \'unused\' oil. I think in reality there is very little practical difference in this scenario
Steve
In a carbed car it is true that a (very) small amount of fuel continues to enter the engine on overrun, however most injection setups cut all fuel until the engine falls below a give rpm (for example 2000rpm) as a means of saving fuel. Blast the engine up to 8 or 9 thousand rpm, get off the gas and no fuel and (if running premix) no oil enters the engine at all until it falls below a set rpm.
Also, I find it interesting someone states above that you can vary the amount of oil using premix, but not using the omp? It was my understanding (though I admit to not having done it myself) that the omp can be adjusted to vary the amount of oil it squirts into the chamber.
Finally, if a car is not used regularly it is not at all unheard of for the fuel and oil to seperate in the tank, in Australia most of the racing cars that run premix drain their tanks after every meeting and mix up a fresh batch of premix at the next meeting.
There is no doubt that premixing has its benefits and that the omp has its downfalls, the main one being complexity. Personally though, I feel that a well maintained omp, ideally using an adaptor such as the rotary aviation one so that it draws fresh 2 stroke rather than sump oil, is the best compromise, for me, for the street.
sorry, i was refering to carbed motors... :)
premix all the way for me.
steve
Someones started another topic on this if anyone is interested in more debate
http://www.mazdarotaryclub.com/forums/showthread.php?t=33006
Quote from: metalheadAlso, I find it interesting someone states above that you can vary the amount of oil using premix, but not using the omp? It was my understanding (though I admit to not having done it myself) that the omp can be adjusted to vary the amount of oil it squirts into the chamber.
It can be adjusted by shifting the split pin up or down the rod but it\'s a fiddly job. Much easier just to throw more oil in the tank.
Quote from: mullinsSomeones started another topic on this if anyone is interested in more debate
http://www.mazdarotaryclub.com/forums/showthread.php?t=33006
He, he, he, LOL
Just put up the link to this thread on that thread :Giggle
Our thread\'s better :D
:Giggle It\'s getting outta control....:rollin :chat
Quote from: dubber91Not sure whether I agree with the statement that pre-mix runs the correct ratio 100% of the time, in fact I think there are cases where this could be the opposite. E.g. for your example.... If you blast the car then drop down off the revs approaching lights, as the car is decelerating, with pre-mix, very little oil will be entering the chambers as the throttle will be almost closed....... combustion in the chambers will still be occurring however, therefore during the slow down/coast period, the engine wont be getting much oil. With OMP, as the car comes down off the throttle, even though the throttle is closed the OMP will still inject oil into the chambers because the OMP pump is governed by rpm not throttle position, therefore the engine’s lubricating demands are still met during this period
if combustion still occurrs...there must be fuel.....if theres fuel theres oil. there is also residual oil from previous induced strokes. The retardation of ignition timing increases unburned fuels, thus, \'unused\' oil. I think in reality there is very little practical difference in this scenario
Steve
Probably should re-word the bit I wrote about combustion occuring on overrun when the throttle is closed as its not really relevent and may not even be the case on injected cars. The point of the fact is the rotors are still spinning on overrun, therefore wear is occurring and as metalhead pointed out, only a very small amount of fuel will be entering the rotor chambers on a carbed car and even less/none on a fuel injected car so surely then an OMP system offers better lubrication in this scenario.
At the end of the day its all gonna boil down to personal preference, experience, and the motor in question. Interseting discussion though and I\'m still unclear as to which oil set-ups are \'best\' for different applications :chat
Here\'s a couple more things to throw in the pot:
Did the 787b run pre-mix or OMP?
Or how about the Daytona/IMSA rotaries in the USA?
I\'ve seen pics of IDA fed race rotaries running the OMP, e.g. TWR rx7\'s.
Have to agree with metalhead at the moment, for street car, OMP seems to offer more advantages.
Here\'s something else to throw in the pot:
Some of the drag cars in Oz run no oil injection at all.
Nice thread guys - shame I didn\'t stumble across it before.
My 2p, (4c - given today exchage rate!) worth is...
Not wanting to repeat any of the above, and agreeing with a lot of what has been said, for me I now feel I have the best setup - on a car that doesn\'t get used everyday and was built for good mid-range power and drivability not getting thrashed round a circuit - I have the omp with remote 2-stroke supply and semi-synth in the sump.
I must admit however to using (very roughly measured) premix during the break in period.
I think its the usual \'horses for courses\' - for a standard car, keep things standard, if its tuned and you have the desire to switch to 2-stroke use the OMP and a 2-stroke supply. If its a fire-breathing race car (or you just abuse it) then run premix. All have their advantages and pitfalls.
Mike.
Quote from: DominicProbably should re-word the bit I wrote about combustion occuring on overrun when the throttle is closed as its not really relevent and may not even be the case on injected cars. The point of the fact is the rotors are still spinning on overrun, therefore wear is occurring and as metalhead pointed out, only a very small amount of fuel will be entering the rotor chambers on a carbed car and even less/none on a fuel injected car so surely then an OMP system offers better lubrication in this scenario.
not strictly correct
On the Apexi ECU when on the overun, it still uses part of map therefore petrol is still being injected in small amounts, Ive seen it on the ghost trace on the datalogit. Also when using synth two stroke premix it leaves a small coating on housings and seals, so if there was no oil in the mix on the overun the seals are still protected for that short peroid of time on decel, as the 2 stroke residue would take time to fully burn up. Mr 88GTR can explain it better then me.
Ive seen certain drag cars use no Premix or OMP on mapping sessions
But I think we are all agreed that 2 stroke oil is better then dirty sump oil to lub up the seals
Quote from: MikeNice thread guys - shame I didn\'t stumble across it before.
My 2p, (4c - given today exchage rate!) worth is...
Not wanting to repeat any of the above, and agreeing with a lot of what has been said, for me I now feel I have the best setup - on a car that doesn\'t get used everyday and was built for good mid-range power and drivability not getting thrashed round a circuit - I have the omp with remote 2-stroke supply and semi-synth in the sump.
I must admit however to using (very roughly measured) premix during the break in period.
I think its the usual \'horses for courses\' - for a standard car, keep things standard, if its tuned and you have the desire to switch to 2-stroke use the OMP and a 2-stroke supply. If its a fire-breathing race car (or you just abuse it) then run premix. All have their advantages and pitfalls.
Mike.
Bog standard motor..I would not bother with premix,....:chat however the minute you build a motor to \'give it death\' then you have to take all precautions to protect it and make it perform properly.
Running a full blown race motor down the strip,....\'it might be beneficial\' to run withut ANY oil in the fuel.You can extrude every ounce of power from the fuel....albeit for a very short time,cos the motor will be rebuilt after a few hours of running anyway.Oil in the fuel may lead to \'detonation\' as it does not burn \'equal\' to the fuel.Cant give you tech specs only experience from running with and without.........:cool ;)
Just a note on the references to drag cars - just remember that for most drag cars engine longevity is not a major issue, oil in the combustion chamber lowers the effective octane rating of the fuel, the cars are only designed to run flat out for a few seconds at a time, rebuilds are expected relatively regularly and power is the ultimate aim above all else. It makes sense not to have oil injection with these things considered. Doesn\'t mean it\'s a good idea not to run it if you want a good life out of your street or circuit engine though.
Quote from: metalheadJust a note on the references to drag cars - just remember that for most drag cars engine longevity is not a major issue, oil in the combustion chamber lowers the effective octane rating of the fuel, the cars are only designed to run flat out for a few seconds at a time, rebuilds are expected relatively regularly and power is the ultimate aim above all else. It makes sense not to have oil injection with these things considered. Doesn\'t mean it\'s a good idea not to run it if you want a good life out of your street or circuit engine though.
Are we twins ?????????...............:evillaugh :cool
Quote from: oldoneRunning a full blown race motor down the strip,....\'it might be beneficial\' to run withut ANY oil in the fuel.You can extrude every ounce of power from the fuel....albeit for a very short time,cos the motor will be rebuilt after a few hours of running anyway.Oil in the fuel may lead to \'detonation\' as it does not burn \'equal\' to the fuel.Cant give you tech specs only experience from running with and without.........:cool ;)
Haha, beat me to it.
some Synth 2 stroke will not lower Octane levels, some actually increase AFRs John 88GTR has found some top notch stuff
Guess the issue now is when does pre-mix become preferable to running the OMP. From the various posts in this thread this would appear not to be a specific rpm/engine type/fuelling type/or bhp but a rather hazy \'area\' which seems to be dependent on a a combination of these factors and others. I will do my best to summarise the info gathered from the folks who have contributed to this discussion and put down a few more things that I\'ve just thought of. Please add, amend, or make comment if I have misinterpreted:
Choice of Pre-mix - OMP - or both, dependent on:
1: The kind of driving/thrashing that the motor is going to have to put up with. A thrash motor/flame throwing race car prob better off on pre-mix whereas a stock or fast road car better off on OMP for reasons such as reduced oil consumption, less smell (not that that\'s a bad thing :Giggle ), less hassle with measuring cans.
2: Not really discussed in depth, but a higher revving motor may also be better suited to pre-mix due to the massive heat being produced in the engine and especially, the rotor tips. Reading on the other pre-mix thread http://www.mazdarotaryclub.com/forums/showthread.php?t=33006 BlitzBoy and Grizzly mentioned that tip warping can take place on high power OMP oiled rotors due to the temp difference between the injected oil and the tips (I assume they are referring to motors where the oil is injected directly through the housings rather than through the carb/injectors with the fuel and air). Presumably this applies to both turbo cars (on high boost) and high power N/A cars (high rpms). Pre-mix provides a more homogenous charge air/fuel/oil mix therefore elimating cool spots in the moving chambers and rotor tips (unless OMP is delivering oil to carb/injectors only).
3. Ultimate performance - Ultra high power cars ditching the oiling system in the quest for BIG hp but forking out to rebuild the block every week.
4. Less importantly but maybe still relevant - Whether the engine is Carb or EFI, and if EFI the specific map for the engine could dictate whether pre-mix or OMP is a better option. With a carb engine, the extent of porting could also be a factor, for example a big bridge port will reduce the vacuum in the carb considerably at low rpms and therefore less oil will be drawn into the engine when compared to a stock port motor at low revs.
5. Amount of usage - If a car is running pre-mix and is used very infrequently, oil separation may occur in the tank. This could cause insufficient lubrication to the engine on start up/first few minutes of driving due to the pre-mix oil sitting at the top of the tank.
6. This space reserved for oilman if he\'s reading this :D I\'m sure he\'d have some comments....
Would be interesting to know how many 2nd and 3rd gen rx7 owners are out there running in excess of 400-500hp with the stock OMP and no pre-mix.
Regardless of the above, if running the OMP, the use of a standalone oil tank holding good clean 2 stroke oil from which the OMP draws from has got to be an improvement over the current system of drawing hot, dirty sump oil.
Quote from: Dominic5. Amount of usage - If a car is running pre-mix and is used very infrequently, oil separation may occur in the tank. This could cause insufficient lubrication to the engine on start up/first few minutes of driving due to the pre-mix oil sitting at the top of the tank.
Synth two stroke mixes quite well with petrol from speaking to various people is does not seperate, so the seperation is bit of a myth.
wow! longest thread I\'ve ever started...
I\'ve read all this now with two pints in me (discovered free broadband at my local pub but only 200m away from my garage) - I\'m going to go with premix for the following reasons....
1. I like the idea that once up and running my chevette can be taken on a long trip and so long as I premix I know i\'ll be covered on that front. I would hate to be driving along in the middle of france etc and wondering if the OMP is still working fine(sods law dictates..). I rather just be worried about how much fuel I\'m using...
2. My car will be NA and with that I\'m going for the clean tidy engine bay look and the OMP with its pipes seems like just extra clutter.
3. I like the idea of using good quality synthetic oil for the sump and burning 2 stroke oil for premix.
4. The Idea of having a seperate bottle of oil which you have to check along with the associated extra gubbins sounds like just as much, if not more hassle then just premixing?
i\'ll just have to put a note on the fuel cap for others....