As title (not with a broken engine, lol), is this ever done, and if not, why not?
You rarely see rotaries running more than about 1bar without either race gas or water injection and lots or prayers, as obviously det is the big killer.
Standard RX7 turbo comp is 9:1? For a hot running turbo engine susceptable to det thats fairly high, but is there a proper reason why people dont go a little lower?
Should massively reduce the chance of det without needing higher octane fuel (ie non pump gas), meaning more boost can be safely run.
In my experiences of owning and driving countless cars which have had the compression lowered, its of little concequence, the low down tradeoff you barely notice as it doesnt affect how soon a car reaches boost (its only a small % you lose, lose a lot less than lairy overlap loses low down, and nothing is that powerful down low anyhow), and once one boost its a huge advantage, as you run a lot more boost.
I mean, even using an RX example, the EGI FCs dont feel mentally more powerful low down do they, despite being .7 of a point higher compression.
One things for sure, an engine thats got 500bhp from higher boost smaller turbo sure as hell is a crapload torquier and nicer to drive than a 500bhp car running 1bar.
Any particular reason? (ie not enough meat on the rotors etc)
Have a read of this on differences between the FC and FD engines, it has info when 13BT run with a 8.5:1 compression rotors
http://se3p.com/index.php?title=RE:FC3S_13BT_vs_FD3S_13B-REW
Main reason is cost, as Mazda dont offer lower compression rotors then stock it would take another 3rd party manufacture. Given stock Rotors are £400 each a pop, a cost to a third party company in R&D would be even more.
You can run up to 1.2 BAR safely on pump gas if you have good tuning and a decent size turbo with a big enough hotside not to cause a build up of heat and restriction.
IMO just run a decent WI system to go past 1.2 BAR and they dont cost the earth, good bang for buck
Interesting link, thanks :)
I have aquamist to go on my car, its a safe bet regardless, but from owning cars running 2bar on pump fuel, even running 1.2bar feels a bit odd, lol.
I presume stock rotors cannot be machined to have a larger dish for slightly lower comp then? SOME pistons have enough meat on them to be modified enough to drop the comp at least half a point and still safe at 2bar+ and 150bhp a piston, but then again most arent. Ive no idea how much meat is on a rotary to know whats safe there.
The thing is on the Rotary engine you don\'t need to push high boost to get good power
Quote from: StavFC;632353Interesting link, thanks :)
I have aquamist to go on my car, its a safe bet regardless, but from owning cars running 2bar on pump fuel, even running 1.2bar feels a bit odd, lol.
.
yes but the amount of power produced by a rotary at low boost it would take a piston engine a lot more boost to produce the same power.
Look at my power 555bhp thats produced only using 18 psi on a T51, it would take more boost say on a Supra to produce the same power.
I assume you can machine the bowl of a rotor to lower the CR but then you run into balancing issues and of course you have to make sure the bowl is done correctly shaped for the combustion and how the flame front is developed etc etc (beyond me and my knowledge to explain lol) therefore it comes down to cost and R&D.
A piston to do is easy you just machine a certain thou off the top and just have to make sure its flat lol
and rotaries with big ports such as a bridge dont really suffer from as much lag as piston engines.
Quote from: Kash_;632354The thing is on the Rotary engine you don\'t need to push high boost to get good power
No they dont but its not about peak power as such.
Quote from: BlitzBoy;632358Look at my power 555bhp thats produced only using 18 psi on a T51, it would take more boost say on a Supra to produce the same power.
Maybe so, but thats down to head/cams as much as anything, ie they could get it at 18psi, but they not stupid, theyd rather run less cam/head and more boost to get far more torque and drivability.
Also they have the oppertunity to push the whole 750odd out of it without too much worries rather than stuck at 555! I mean, the spoolup you have now, plus an extra 200 hose and at least that much extra in torque too, it wont happen, but it would be nice! :mmmm
Quote from: rx jamie;632359and rotaries with big ports such as a bridge dont really suffer from as much lag as piston engines.
They dont for their size, but regardless of when things spool up or what power they are, low boost means low torque.
Mine at mo for example, although its on boost from very low down, and has great power at high rpm, it drives like a powerful but small n/a engine, not much in the way of low/mid torque due to lack of boost.
But an engine running 200bhp per litre almost always has the same torque as power if running 2bar boost.
Regardless of all that, it certainly doesnt sound like something thats easily done on a rotary, and thats all I was interested in, cheers :Thumbsup!
the only people who seem to be lowering compression ratio\'s are the big drag boys in p.r, the u.s and aus
most of them have their own machine shops, quite a few threads about it on rx7club
getting tips from said dragracers on how to do it etc dont bother, you wont even see their motors on show in the pits (covered with blankets and towells)
rotor motors are strange in regards to power figures, take blitzboy for example, 555fwhp and running low 10sec qtrs and terminal speeds that 800+hp supras struggle to do (even with his granny shifting :P)
was having this convo with kevin webb from aus, he was saying the physical limit of pump fuel in a rotary (largeport large turbo)he has found without water is 1.3bar
nose around on rx7 club.com in the racing section, it passes the time for me at work
colum
For torque you just need to port big - boost is the other way to get there - so a combination of both means running much less boost for large torque figures. I think you\'ll find Blitzboys engine also makes a lot of torque due to the porting he\'s had done :driving
So if you\'ve got mild street ports and stock induction then you will not be getting the torque you could get. Induction mods - removing the inlet restrictions, throttle body porting, inlet manifold, and then engine porting.
Same goes for the exhaust
Im getting just under 400 lbs of torque by the way
still dont help the way you change gear :D
col
Mines got modified inlet and exhaust manifolds, not like I think they have much of an effect on torque. Power yes..
But regardless, nothing, barring nitrous (or increasing compression hugely), you do to an engine comes remotely close to boost pressure for giving torque, its not how engines work. Prof, have you got any info on other high hp RXs barring Blitzboy thats not running 1.5bar+ thats got anywhere near as much torque as power?
Most I see seem to have torque in the low 300s even when power is 500+?
His at just under 400 with 550bhp isnt bad. But when 2litre turbos running more boost and pump fuel can have the same power but still 100lbft more, you see where im coming from.
But you cant have it all, just wondered if you can, not the end of the world!
Quote from: mx1311;632390still dont help the way you change gear :D
col
lol at least I dont go through gearboxs like they were packs of clunge protectors
Quote from: BlitzBoy;632393lol at least I dont go through gearboxs like they were packs of clunge protectors
And it begins :D
Quote from: StavFC;632392Mines got modified inlet and exhaust manifolds, not like I think they have much of an effect on torque. Power yes..
But regardless, nothing, barring nitrous (or increasing compression hugely), you do to an engine comes remotely close to boost pressure for giving torque, its not how engines work. Prof, have you got any info on other high hp RXs barring Blitzboy thats not running 1.5bar+ thats got anywhere near as much torque as power?
Most I see seem to have torque in the low 300s even when power is 500+?
His at just under 400 with 550bhp isnt bad. But when 2litre turbos running more boost and pump fuel can have the same power but still 100lbft more, you see where im coming from.
But you cant have it all, just wondered if you can, not the end of the world!
All this and the rotary will still be faster!
100lbfts still won\'t help the piston beat the rotor!
Quote from: Rzla;632410And it begins :D
Private joke between me,"Special Needs" and the "Smiler" lol :rollin
Col just remind Smiler who does the better launches and 60fts lol
My mate Phil who has a semi pro drift FC3S has got a bridgeported engine with a fairly large turbo but its running wastegate spring pressure, so about 0.5bar or so, due to the porting and free flowing air there is oooodles of torque for drifting :)
Quote from: StavFC;632392Mines got modified inlet and exhaust manifolds, not like I think they have much of an effect on torque. Power yes..
But regardless, nothing, barring nitrous (or increasing compression hugely), you do to an engine comes remotely close to boost pressure for giving torque, its not how engines work. Prof, have you got any info on other high hp RXs barring Blitzboy thats not running 1.5bar+ thats got anywhere near as much torque as power?
Most I see seem to have torque in the low 300s even when power is 500+?
His at just under 400 with 550bhp isnt bad. But when 2litre turbos running more boost and pump fuel can have the same power but still 100lbft more, you see where im coming from.
But you cant have it all, just wondered if you can, not the end of the world!
I think the only useful info I can give you are these 2 facts:
1) The design of the combustion chamber (long chamber) means that the engine has less torque than an equivalent piston displacement - but can make much higher horsepower for the displacement. Much like the sports bike engines - higher revving engine will make more top end power. It\'s hard to get large amounts of torque from a rotary unless you are prepared to port the engine. Engines are effectively an air pump - the more air you can push through it the more torque it will make - you can either do that by pushing the air in (supercharger or turbocharger), or you can port the engine and allow it to suck much more air in on it\'s own. The highest torque engines are invariably those that are both ported and running boost. In ascending order of torque and power the porting:
Stock < Street < Bridge < J port < Peripheral Port
(there are degrees of street porting and also bridge porting (like half / full))
Another way to make a load more torque is to add another rotor - triples make sack loads of torque.
2) The relationship between power and torque:
torque * RPM * constant = hp
This means that with higher RPM engines, they can make more power - but not necessarily have high torque.
Why does torque drop after a certain RPM? Torque starts to decrease because the engine cannot breathe as well. Due to the speed, the chamber does not fill with air as well. A designer can get around this problem with "tuned intake" which sets up a resonance to pack the chamber with air, but it only happens at a certain RPM. The next evolution of design is to make a variable system which packs the chambers with air at all RPM; this is usually called "variable tuned intake runners" or something like that and involves valves which open and close to create a different size for the airbox and manifold. Take a look at the 4 rotor LeMans engines that made use of this idea.
Why does power continue to increase after torque decreases? Remember that the
power is essentially the product of the RPM and the
torque. At first, decrease in
torque is small and is not enough to offset the increasing RPM, so the overall product still increases. Eventually the decrease in
torque becomes large enough that it outweighs the increase in RPM and we see the
power start to drop. Because of this, the
power peak will always be after the
torque peak.
So to come back to the porting - which you so readily dismissed in favour of the turbo - it\'s the way on a rotary to make big torque and power - it always has been, turbo\'s can help but work way better on a rotary that\'s ported properly.
^^^^^^^^^^^^
Lovely write up there Prof, just learnt a lot there :)
Matt
All correct info Prof, but simple fact is more boost gives far more torque than any other single thing you can do.
A stock port engine pushing 2bar and 400bhp has massively more torque than a big port engine running 1bar and 400bhp.
But if big boost just isnt happening on pump fuelled rotaries, so be it, knew the situation from the start, not a big deal, was simply a question why.
Quote from: m1tch;632415My mate Phil who has a semi pro drift FC3S has got a bridgeported engine with a fairly large turbo but its running wastegate spring pressure, so about 0.5bar or so, due to the porting and free flowing air there is oooodles of torque for drifting :)
But thats not what we are talking about.
The car still has next no torque for the power level compared to if it was running proper boost.
Even im only running 0.8bar on a ported engine and happily wrecks the tyres in the dry in 3rd if provoked, but they still drive like a fairly powerful high revving small capacity n/a car rather than the usual big boost turbo car, thats why they rarely look like smoke machines.
Quote from: StavFC;632454A stock port engine pushing 2bar and 400bhp has massively more torque than a big port engine running 1bar and 400bhp.
Mathematically improbable... :confused:
The more air you get into the engine the more torque you will have, are you saying that 1bar flowing in this size pipe:
(http://www.aaroncake.net/misc/rebuild/405%20-%20Drivers%20Intercooler%20Pipe%20Painted%20with%20Nipples%20and%20BOV%20Installed.jpg)
Has the same amount of air going into the engine as this pipe:
(http://www.sd-performance.com/UploadFiles/P_245_Straight%20Aluminium%20Pipe%20Hose_1_6435681.JPG)
Im pretty sure that a larger pipe with a lower boost is going to flow as much as the smaller pipe at stupidly high boost - bit like porting in a rotary really, my engine is on stock ports and so needs to be streetported to let more AIR in and therefore increase POWER and TORQUE. I can bolt on a huge turbo and run big big boost, but as the air can\'t get into the engine, the engine will be restricted still as the airflow into the engine isn\'t good enough else everyone wouldn\'t bother with porting at all
This Rotor in the Curtiss-Wright engine - used for industrial purposes and low RPM has buckets of torque due to the large amount of air getting into the engine:
(http://cp_www.tripod.com/rotary/images/pg08_01b.jpg)
I dont know how many big boost turbo engines you have actually played with themselves over the years, but you two have some odd ideas of what does what :confused:
Quote from: Prof;632456Mathematically improbable... :confused:
Why?
Boost makes torque like nothing else even close, ANY engine. Drive any forced induction car with huge torque for its capacity, its running big boost regardless of anything else done, end of story.
Easiest example for people to think of is a restricted engine for class rules, WRC a fine example.
300bhp from a 2litre turbo as the restrictor totally ruins top end airflow, but it has nigh on double that in torque because it runs about 3.5bar peak boost.
300bhp from a 2litre turbo could be done at less than half a bar with "good airflow" and "big ports" and no restrictions at all. But you think it will have over 550lbft?
No.
And exactly same case with a rotary or any type of combustion engine.
I can only presume the Curtis Wright thing was a joke, as its pretty obvious why that makes torque... :confused:
Why do you keep going on about lbft of torque like it is the most important thing in a car?
Rotaries make less torque than a piston, now get over it.
At the same power bands rotaries are still quicker!
Look at Blitzboys for an example.
Is that why when Rotary powered cars that are running 400bhp race scoobys and evos (why do all the AWD owners quote their torque figures?) that have 400bhp and 400lbft torque (the rotary has a lot less torque) still beat the higher torqued piston powered car?
And the rotary was running 0.8bar of boost and the piston 1.2bar+
Yes I was there because it was my brothers rx7 that raced my mates cars and it was not just once it was a number of times and a number of AWD cars.
Im not talking about racing or what can beat what, and regardless, a race is a crapload more variables in a race than power or torque, esp transmission losses a 4wd has a big power disadvantage if all else is equal anyhow.
All of the above has nothing to do with what im saying, so lets not go off topic :)
Rotaries make ....ing good for their "size". Nothing to "get over" so stop being so defensive.
But torque, and more to the point boost matters, simple as. Another, even simpler analogy if it helps...
You drive your rotary, blitzboys rotary, any car, just imagine it was running perfectly, no det, all lovely...
You drive it at 1bar. THEN you drive it again so it ran 1.5bar then drops back to 1bar at peak power, making exactly the same peak power figure. You think it will drive the same all the way thru the revs just because its got the same peak power?
Anyhow, I had my answer about low compression rotors ages ago, believe what you like about the rest, lol
Maybe the point we were trying to make was that without the porting the high boost just won\'t do anything much other than really heat up the intake air pushing your potential for knock right up there.
But if you want to ignore all the advice people give and keep quoting high boost = major torque increase then fine - it\'s not my engine :rolleyes:
Ever wonder why when you look at what a load of people are doing and think - why are they doing it that way - that maybe - just maybe - these people have arrived at this formula because it works - that\'s not to say that other things shouldn\'t be tried - but perhaps it\'s better to ask why is that not done ?
It seems that most of the high power rotaries overseas that run turbo boosted engines only seem to go over 18/19 psi when they use c16 - pump gas on a rotary with boost just seems to have a limit around that point.
No matter what you do - upping the boost beyond that point will just bring trouble - very careful attention to combustion, timing, affects of premix on effective octane of your fuel will all have to be considered.
No matter what - for bigger torque figures with a turbo - you need to port - simple inescapable fact. Perhaps you should up your boost and see how far you get, as an empirical test - at least then you can get your lump ported out nice after you\'ve blown it ;)
Just thought this might help:
Torque is proportional to the air passing through the engine (it\'s an air pump after all)
More air = More Torque.
A Turbo allows more air to be pushed into the engine
Higher boost = more air = more torque.
Porting allows more air to enter the engine
So these two things go hand in hand - which is what we\'ve been trying to say.
Can you post up the photos of the blown water seals when the engine gives up at high boost? Are you going to port it when the engine is apart?
So just to clarify, does porting move peak torque up the rev range, or, because more air is able to enter the engine full stop, does it increase torque at all revs?
I\'m going to forget about things like resonance/pulse tuning, overlap etc for a sec, but I\'ve always thought that large ports = crap low end drivability, but if it\'s letting in more air then it should produce more torque?
Your answers are on Rx7club.com mate have a search.
Also regarding high boost I think heat is the major problem. Thermal inefficiency has always been the rotary\'s weak point, unequal distribution/build up of heat plus running hotter than a piston engine = an unfair sensitivity to intake temps :)
WI + Ice to Air IC/Chargecoolers + Methanol + Big oil coolers.. FT(Big boost)W
The reason we don\'t run high boost is for reliablilty.
Yes 2 bar standard ports with 400bhp will produce more torque than a larger turbo producing 400bhp, look on rx7 club i believe someone ran 10\'s on a gt35r with standard ports this way.
But if you want any kind of reliability you will have to run alot lower boost and than you will have nowhere near the torque or bhp that you would have had if you went for a bigger turbo with some good porting.
Quote from: Andy_k;632535Your answers are on Rx7club.com mate have a search.
Cheers bud I appreciate that, but was hoping to get Prof\'s/people who\'ve already been talking about it\'s ideas
Biggest problem with big ports is the overlap - so if you have boost coming on early, it can leak out your exhaust and cost you power at low rpm\'s.
That\'s why the Renesis has side exhaust ports - because it virtually eliminates the overlap and allows the NA engine to make very good power - but the design also relies on the induction system with multiple intake ports and a kind of tuned intake plenum which acts a little like a supercharger helping to suck more air in.
So to answer Ben\'s question - it does move the torque and power curves up the rev range, but you will also get a wider power band.
This has gone ridiculously off topic, from me simply asking something I now know isnt viable, and I appreciate that, to people doing the equivalent of telling me the world if flat after I walked right round it and didnt fall off, lol.
I dont want to carry on, but as Prof is so determined...
Quote from: Prof;632529Maybe the point we were trying to make was that without the porting the high boost just won\'t do anything much other than really heat up the intake air pushing your potential for knock right up there.
High boost will do nothing without porting? Seriously? Did you not see my two completely obvious and simple examples?
If the turbo is off the map its mostly heat, if it dets for whatever reason its dead, but saying turning up the boost does nothing without porting is either ignoring the obvious examples staring you in the face, or your just trying to be argumentative.
Quote from: Prof;632529Ever wonder why when you look at what a load of people are doing and think - why are they doing it that way - that maybe - just maybe - these people have arrived at this formula because it works - that\'s not to say that other things shouldn\'t be tried - but perhaps it\'s better to ask why is that not done ?
We\'ve already clarified and ive accepted, that you cant run big boost on stock compression on pump fuel.
Its also simple fact that drag rotaries DO run big boost, often well over 2bar, so im not sure what the relevance of the above is.
Quote from: Prof;632529It seems that most of the high power rotaries overseas that run turbo boosted engines only seem to go over 18/19 psi when they use c16 - pump gas on a rotary with boost just seems to have a limit around that point.
18/19 psi on C16? Funny that, as even ive driven the original Dragon drag car with it at 2.3bar (33psi) boost.
Quote from: Prof;632529No matter what - for bigger torque figures with a turbo - you need to port - simple inescapable fact. Perhaps you should up your boost and see how far you get, as an empirical test - at least then you can get your lump ported out nice after you\'ve blown it ;)
Aside from the fact ive mention my engines ported countless times, and if you want big power of course you want to port your engine, im not talking about MY engine or any other in particular, I can only guess this is another attempt to be arsey with me.
Simple fact, you do all the maths you like, but real world fact speaks for itself. Boost = Torque.
Im not talking torque at peak power as you seem to, im talking area under the curve, drivable, midrange, nice to drive, torque.
If you think having huge inlet/exhaust flow and overlap is the best way of getting torque, well, im speechless and wonder if you have any experience of tuning at all. That will create big peak power numbers yes, and at a set boost level it will create high peak torque too, but it will drive like ....e in comparison to the same power created through boost.
Of course you CANT do this on a rotary on pump fuel due to the det issue, but not once did I say you could!
Just incase you are missing the obvious once again, and I could give millions of examples as its not hard...
Restricted small port WRC 2litre turbo engine. 300bhp at 3bar boost. But 550lbft, and that from 3000rpm, absolute weapon to drive.
2litre engine with huge ports, 300degree cams, tubular manifolds, and a GT40 turbo. 300bhp at 0.3bar boost. But how much torque? Id wager barely over 200lbft and absolutely nothing till well over 5000rpm, would be to the extent of dropping out of the powerband on every gearchange.
Fairly common ones lately are stock Nissan SR20 engines pushing 450bhp.
Big HX35s running 1.5bar - Under 350lbft and all above 5000rpm, fast but a bit of a pig to drive.
Far smaller 3071s running nearly 2.5bar- over 400lbft and from far lower, giving a bigger curve and a car far better to drive.
Our TT.
Map1- 1bar held boost all the way through the revs 275bhp and about 250lbft. Feels a bit slow to be fair.
Map2- Peaks at 1.5bar then slowly drops down to 1bar at leak. Still 275bhp but 330lbft and would leave itself, but on map1, for dead.
I really dont know what else to say to you if you cant see whats staring you in the face and dont listen to someone who has real world experience of it.
Oh, forgot...
STREET PORTED (just for prof ;) ) 13B, running a diddy little GT35R at a fairly big 21psi (shame they cant handle on stock compression on pump gas, but thats life), 505rwhp, but lo and behold, thanks to boost pressure, and despite (well, more like thanks to ;) ) not having big ports, 446rwtq.
(http://img.photobucket.com/albums/1003/monkeymagic/20psiGT35R.jpg)
If you cant see whats staring you in the face now Prof (as if my examples above this wasnt enough, as you clearly dont take any notice of my actual personal experiences, lol), well, I darent tell you Santa isnt real either.
Shame this went so ridiculously off topic, as NONE of this is related to my original question, lol
Oooh - you just love an argument - I don\'t - I really was just trying to be helpful - but hey ho.
I do just have to say:
1) The examples you keep giving are all piston engines - not rotary platform - so is it fair to make that comparison - I\'m not so sure.
2) You mention the dragon car in response to my post about 18/19 psi on pump gas - I mentioned overseas - dragon\'s car was a uk car if I remember correctly - please read my post before quoting me. I also said \'most\' - which last time I looked up the definition for that word meant \'not all\' (I am merely pointing out the text here - not trying to out you or provoke argument)
3) Other people have posted on here - people with tuning experience of rotaries - and even a respected engine builder - but never mind their experience - you go with your piston examples :Thumbs-up
I\'m not out to give you a hard time Stav - I\'m not sure I\'ve ever met you - and I\'d have given the same answers to anyone else that asked - this is a forum after all - and a place where people share knowledge.
If you ask a question but don\'t want people to respond - then why post it on a forum. :cool
very interesting thread and some great comments, i think if you want bigger torque your gonna have to drop a triple rotor in there, enough torque for you then?
Quote from: chrisrx7;632556very interesting thread and some great comments, i think if you want bigger torque your gonna have to drop a triple rotor in there, enough torque for you then?
Or wait for Mazda to make the 16C\'s :Thumbs-up
This thread makes me want to find a way of running lots of boost for manly torque.. If I build the most reliable WI system ever I reckon I\'m in with a chance :Thumbsup!
Anyway back on topic, my old street ported 13BT was built by Powergains using low compression Series 4 rotors...
...Which now ironically resides in Prof\'s car!
lol
Quote from: BenLewisMav;632582This thread makes me want to find a way of running lots of boost for manly torque.. If I build the most reliable WI system ever I reckon I\'m in with a chance :Thumbsup!
Anyway back on topic, my old street ported 13BT was built by Powergains using low compression Series 4 rotors...
...Which now ironically resides in Prof\'s car!
lol
:driving Christmas just came early :driving
Apologies for the thread hijack - Ben, you going to be tuning for WI (cutting fuel) or just using it as a safety net ?
lol.... erm you did know that right Prof??
[Merry Xmas if not :Santa... you\'ve only had the engine for a year ha :Hammer]
Anyway, in a way there\'s your answer Stav -Series 4 rotors.
(And tuning for Water injection, doubt I\'ll reach silly psi for any length of time without it)
Quote from: StavFC;632552Oh, forgot...
STREET PORTED (just for prof ;) ) 13B, running a diddy little GT35R at a fairly big 21psi (shame they cant handle on stock compression on pump gas, but thats life), 505rwhp, but lo and behold, thanks to boost pressure, and despite (well, more like thanks to ;) ) not having big ports, 446rwtq.
(http://img.photobucket.com/albums/1003/monkeymagic/20psiGT35R.jpg)
If you cant see whats staring you in the face now Prof (as if my examples above this wasnt enough, as you clearly dont take any notice of my actual personal experiences, lol), well, I darent tell you Santa isnt real either.
Shame this went so ridiculously off topic, as NONE of this is related to my original question, lol
US Dynojet=FAIL :WaveBye
StavFC you have just posted a US dynojet chart they always are show more power and torque by more then 15% to 20% then UK or Aussie dynos, if you stuck my car on a US dynojet I be showing 650hp and touching 500 lbs of torque
bleedy americans always have to big bigger and better :spank
Quote from: BenLewisMav;632590lol.... erm you did know that right Prof??
[Merry Xmas if not :Santa... you\'ve only had the engine for a year ha :Hammer]
Anyway, in a way there\'s your answer Stav -Series 4 rotors.
(And tuning for Water injection, doubt I\'ll reach silly psi for any length of time without it)
I\'d forgotten about the rotors - :Giggle I knew the engine was street ported - and by all accounts - with the same hardware and ancillaries on the block the dyno results were almost exactly the same - so the lower compression rotors haven\'t resulted in any loss of power at the top end.
It needs a dyno run again before I tune for water, as It\'s running just under 1 bar boost now regularly on the street with no issues or overheating, and it would be good to see if I\'ve rescued some of the lost torque from the leaking actuator.
One thing I did notice in the graph that Stav put up - that his AFR\'s were going higher than 12 near the peak power (after peak torque) which doesn\'t give much safety margin - that\'s a good candidate for pulling some timing and WI if ever there was.
Quote from: Prof;632599One thing I did notice in the graph that Stav put up - that his AFR\'s were going higher than 12 near the peak power (after peak torque) which doesn\'t give much safety margin - that\'s a good candidate for pulling some timing and WI if ever there was.
That Dyno chart is not his car Prof, its from a car in the US
jeez, this got out of hand
i am on mrc not driftworks?
Im waiting till I see pictures of ex girlfriends next hahahahaha
Not wet Not wet hahahahahahhahahaha
Quote from: BlitzBoy;632660Im waiting till I see pictures of ex girlfriends next hahahahaha
:rollin I wondered how long it\'d take.
I aint getting my \'old boy\' out !:D :rollin
Good thread, its healthy to have different opinions.
Reminds me of when MRC used to be an interesting forum.
So whats your thoughts on it Ross?
Will be could to get a tuners opinion to :)
Hi Stav,
Back to your original question about compression ratio I will try to help.
If you run more boost then you effectively getting a higher compression ratio anyway, in fact you are getting a variable compression ratio using a turbo due to alot more than 9 to 1 ratio and volumetric efficiency max being acheived,so really it makes little difference to det except that to acheive and equivalent ratio with lower compression rotors you need to run more boost.
Hope this helps.
Regards
Carl
Very interesting and reading it I don\'t think you guys have a vastly differing opinion, essentially approaching the same problem from different angles as I see it.
The original question from stav on lowering compression is a fair one and was answered early on. Seems to me prof is describing how in the rotary world torque is achieved and has always said that combining these changes with high boost will of course give better results.
The statement that higher boost gives better torque returns than anything else is probably true but only over a specific boost range that is very much dependant on the design of the engine in question. Where the upper limit of that band is on a rotary without porting etc etc may be considerably lower than for the average (or not so average) piston engine.
We had a stock mazda engined FD, ran 1.6 bar 357lbs 432.6hp on pump fuel, lasted for a year and half, then boost spiked and died.
Dont agree that lowering compression ratio is pointless, as boost will make up for it.
I agree that lowering compresion ratio is good for more boost, thats why we did it in the drag car.
what was the porting/turbo intercooler setup on that motor ross?
Quote from: DRAGON;632749We had a stock mazda engined FD, ran 1.6 bar 357lbs 432.6hp on pump fuel, lasted for a year and half, then boost spiked and died.
Dont agree that lowering compression ratio is pointless, as boost will make up for it.
I agree that lowering compresion ratio is good for more boost, thats why we did it in the drag car.
Did you use the S4 rotors 8.5 CR or did you manage to machine them yourself Ross?
lower CR and more boost is the way to go, this will give lower PCP\'s (peak cilinder pressure in pistonlanuage) this pcp\'s going over xxxbar will lift you head, bent rods and induce detonation
I\'ll give an example, as I\'m a dieselman, I run lets say 17:1 CR and 2.4 bar of boost, this will give a pressure before combution of approx 180 bar, now lets say I run stock CR of 19.5:1 and run 1.8 bar of boost I get also a pressure before combustion of 180bar the difference whne going from 19.5 to 17:1 CR is relative small, but the amount of more toque I can make running .6 bar more boost (assuming rest of engine etc is all capable) is huge
in rotarylanguage this pressure means risk on detonation and risk to blow a waterseal
also the arguments being made that bigger ports : more torque are vague, especially for NA engines, as huge port NA engine will have less troque down low, and probaly only at high revs a little more, but this little more at higer rpm give the typical plenty of increase in HP, this is because bigger ports: lower gas speed, less %VE at low rpm\'s and worse scanvenging, same with a piston engine, big cams and ports : less torque at lowe rpm\'s
just my 2c
Nice to see a couple of people on here understand the point of lowering compression, and amusing but totally unsurprising that most dont but argue and mock people who dissagree with them. Good old internet heros eh! ;)
As a side note, my boost controller failed the other day and the car ended up running 1.7bar boost, and though thankfully it didnt pop (maybe the water inj saved me), the midrange torque was now HUGE, felt a totally different car, like all cars do when running big boost, something that no porting or bigger turbos can EVER do to the same extent.
If the comp was lower thatd have been safe to do on pump gas.
You "experts" can discuss that all you like.
But as lowering comp isnt an easy thing to do, its a moot point it seems.
Sorry - couldn\'t resist...
(http://www.qweas.com/download/antivirus/anti_spam_tools/screen/geek_superhero.gif)
my bad... :spank
yawninell
this thread still going