I\'ve been looking at DIY ECUs specifically Megasquirt which supports seperate leading and trailing sparks, but would prefer to use VEMs. VEMs doesn\'t support seperate leading and trailing plugs and I wondered if firing both at the same time is an option as I could do this ok? any help appreciated :):Ladys-man
On the subject, also if anyone has ever used these ECUs?
After looking at the ignition timing on the datalogs from the Emanage, I\'ve even seen Trailing fire before Leading !
This so called \'Negative Split\' was in the \'cruise\' part of the map - never under boost, and was only 1 or 2 degrees difference.
That\'s on a chipped ECU - but apparently Mazda do it on the stock maps for the RX8.
I read about trailing before leading whilst in vacuum on rx7club, odd stuff! still wondering if firing both at the same time throughout the map is a viable option?
Surely at high rpms they\'re firing to all intents and purposes simultaneously anyway, aren\'t they, given how quickly each cycle will take? Must be talking about tiny fractions of a second difference? So by extrapolation, it can\'t be too bad a thing... I think :3Confused
Quote from: royal;551040I read about trailing before leading whilst in vacuum on rx7club, odd stuff! still wondering if firing both at the same time throughout the map is a viable option?
I think you really want some split at the top end to resist detonation - the whole point of the 2 plugs was to clean up emissions and also create 2 flame fronts so you didn\'t end up with a load of unburnt charge detting when the flame front (with increasing pressure behind it) caught up with it. The combustion chamber shape is less than ideal - which is why the scallops are there in the rotors to try and \'fatten\' the otherwise long and thin chamber that results.
From what I\'ve read (again mostly on RX7club, but also on teamfc3s.org and more recently on Rx8club as well), you get some gains by eliminating split in the vacuum part of the map, but then need to bring it back in again as you reach peak torque. You can reduce the split slightly again after that.
Mazda seem to have done a lot of research into the timing on the RX8 - some of the new tricks there seem to be adapatable to the older 7\'s.
No split under boost is a big no no for a rotary as it will lead to det.
Infact a wider split is better.
Regards
Carl
Thanks Prof and Carl, VEMs isn\'t looking viable at the moment!
also a lot of rotary race cars, track and drag do not ran a trailing spark at all and just ran on the leading (economy not being a concern)
here is a link with some info on it
http://www.rx7club.com/showthread.php?t=325400
just out interest, would these non rotary ecu\'s be able to run primary and secondary injectors?
Can run up to 8 seperate injectors but I\'m not sure how it would work with secondary injectors that were only coming on in higher revs, still doing my homework!
I stick with the Apexi to be honest matey instead of trying out something different not much to be gained
Its not so much that I\'m bothered about gains, I\'m purposefully dropping 100bhp on the new setup to stop killing other areas like the gearbox. I just like the idea of these things for the DIY aspect and learning about it all. If I\'ve got to spend money on the datalogit and wideband for the Apexi I\'m tempted to spend it on something a bit more flexible.
Hows spending your money on a cheaper EMS more flexiable then the Apexi PFC, the Apexi has lots of good features that some EMS dont have?
You are going to have buy a wideband regardless on what EMS you go for.
Decent EMS that offer more flexiability then the Apexi tend to start off from £600 upwards and soon add up when you add custom loom sensors etc etc
just buy the pro chip ed is selling on fduk then apexi will more than suit your needs and you can still tinker with dataloggit as there are lots of forums on rx7club to give you pointers
oh and mark i wouldnt be suprised if your car just runs on just leading with your new spanky coils, willdays is
haha if thats the case they will be flamage out the back
Quote from: mx1311;551083just buy the pro chip ed is selling on fduk then apexi will more than suit your needs and you can still tinker with dataloggit as there are lots of forums on rx7club to give you pointers
The Apexi pro ecu is no use to me. Granted having spark cut for the limiter would be safer but the chances of it making any difference are very slim. 0 mph limiter is for drag. I\'m on the rx7club forum already, trying to learn a thing or two about whats out there.
Quote from: antnicuk;551070just out interest, would these non rotary ecu\'s be able to run primary and secondary injectors?
On this subject. I\'ve been trying to read a million books over the last week or two to understand how this all works. When I\'ve read about secondary injectors (in a boinger context) it talks about having the secondaries further away from the cylinder in order to break down the fuel but also to cool the intake air. They run the primaries at lower rpm and then swap to the secondaries at high rpm. I assumed this is the same system as in a rotary? could someone confirm this ? :bandit
KevYorks is very keyed up on the haltech, a very flexable piece of kit imo and probably the direction i will eventually go a little further down the line, the map resolution is better for a start and depending on the model you get they have masses of inputs and can run 8 injectors that you can stage at whatever time you like, so you can run alkey and water though some of the injectors.
Quote from: royal;551138. They run the primaries at lower rpm and then swap to the secondaries at high rpm. I assumed this is the same system as in a rotary? could someone confirm this ? :bandit
Correct :cheers
Quote from: steve garbutt;551143KevYorks is very keyed up on the haltech, a very flexable piece of kit imo and probably the direction i will eventually go a little further down the line, the map resolution is better for a start and depending on the model you get they have masses of inputs and can run 8 injectors that you can stage at whatever time you like, so you can run alkey and water though some of the injectors.
Thats interesting, I\'ve noticed lots of people on Rx7club are using that. I\'ll take a look at it a bit more. One of my main things is I want to be able to do everything myself and not be locked into relying on a tuner that isn\'t nearby or able to fix it without notice. Even if later I strike up a relationship with a tuner, at least then I know what I\'m doing and not blind following.
The resolution thing seems like a bit of a red-herring to me? the magic boxes just plot a nice curve through them anyhow don\'t they? I could see how it would make a difference with an engine that was really low reving so you would need to really drill down but the rotary is very high reving so I wouldn\'t have thought you\'d need all that extra resolution as it would just make it more work? all my random guesses though so probably missing a point somewhere??? :King Haltech looks like its got plenty of bells and whistles though and having lots of users already should be less hassle.
There you go Haltech E6X, works out to be £850 landed in the UK includes the Loom for you to wire up into the existing sensors but you will need to get rid of your current ECU loom.
Has lots of features to play with.
http://www.tweakit.net/shop/product_info.php?cPath=57_24_86&products_id=90
woops almost forgot you will need the connector kit as well
http://www.tweakit.net/shop/product_info.php?products_id=84
I run my leading and trailing together from vacuum to about 4-5 psi
that\'s on an apexi pfc.
rgds
Brian
I\'m going to look into the Haltech further but I can\'t really see thats its going to achieve anything for me over the PFC? All in after shipping / VAT thats well over a grand which is nudging Motec territory. The DIY things I\'ve been looking at are around £400 quid and include a built in wideband. They\'ll be a lot more trouble to set up but understanding it all is part of the reason for me looking at it in the first place.
I\'ve just had confirmation that VEMs does handle secondary injectors by the way :) the trailing/leading spark thing is still a worry though. I\'m concerned that the guys who have just run leading plug are all short duration drag cars so completely different to my needs. Do you know anyone that is running just leading plug in any circuit cars? drift cars get very heavy abuse with little air flow so I need to get it right.
Quote from: bnaellis;551166I run my leading and trailing together from vacuum to about 4-5 psi
that\'s on an apexi pfc.
rgds
Brian
Hi mate,
Thanks for posting. Is your car primarily drag or circuit as well?
Does anyone know what the usual split is? I\'ve got primary at 5 degrees and secondary at 15 degrees in my head but can\'t remember where I got that from so may be completely wrong! does this stay the same throughout the boost range or is there anything to benefit from changing it as boost grows?
Quote from: royal;551172Hi mate,
Thanks for posting. Is your car primarily drag or circuit as well?
Does anyone know what the usual split is? I\'ve got primary at 5 degrees and secondary at 15 degrees in my head but can\'t remember where I got that from so may be completely wrong! does this stay the same throughout the boost range or is there anything to benefit from changing it as boost grows?
Primarily a road car, although have not driven it in nearly two years but that\'s another story. It\'s not primary and secondary. it\'s leading and trailing.
It\'s best to experiment on the dyno and see what the benefits are. On some cars I have seen considerable gains in playing with the split, on other\'s it\'s been next to nothing.
Typically the more boost you put through the motor the more yopu increase the split timing.
The splt you mention is typically whats seen at idle.
rgds
Brian
Quote from: royal;551172Does anyone know what the usual split is? I\'ve got primary at 5 degrees and secondary at 15 degrees in my head but can\'t remember where I got that from so may be completely wrong! ?
err I think you are getting confused with injectors now lol
12 degrees split between the Leading and trailing is quite normal on boost
Not much is gained with running less split on boost anyway.
As Bri has said and few other posts before it, running 0 split in some vacuum cells will yield better fuel economy.
Sorry , trying to learn about a thousand things in one go! meant leading and trailing. Thanks for all the answers ;). I\'ll no doubt be back with more questions in about 30 seconds!
Quote from: royal;551170. I\'m concerned that the guys who have just run leading plug are all short duration drag cars so completely different to my needs. Do you know anyone that is running just leading plug in any circuit cars?
James Willaday has been running leading only on the road for the last year, so I think your assumption they are only in short duration drag cars is incorrect.
Trailing spark is for economy to be more efficent and make full use of the charge. for example the Lemans 24 hour car run three sparks per rotor I believe correct me if im wrong though
Road still isn\'t anything like circuit though, regardless of how much of a hooligan James is :D
Wouldn\'t the Lemans car be running 3 sparks more for ignition control or something rather than economy? this is an area where my noviceness comes to the fore lol!
well in a Lemans car you need to be fuel effcient less stops for fuel = better pace for the race
Quoted from an article about the Lemans car
"The R26B Wankel engine benefited from a variable intake system, optimizing air intake for certain vehicle speeds. Two periscope-shaped air intakes were mounted ahead of the rear wing. Each intake assembly was mated to a telescoping-pulley system which was able to vary the height of the protruding periscopes through a stroke of approximately six inches. The extension and retraction of the intakes was governed by the car’s ECU computer depending on vehicle speed. At high speed, the intakes were retracted to decrease drag and smooth airflow over the rear wing, and to reduce the restrictions on the air flow into the engine. At lower speeds, the intakes were extended in order to provide maximum positive pressure to the charge entering the rotors. Also, it benefited from an extra spark plug on each rotor from the 767’s two, making the car more economical and improving combustion. An oil cooler was mounted at the front and the car’s aerodynamics was improved at the sides and top of the bodywork. Like all previous engine, it featured Peripheral Porting in order to achieve the high levels of power from a naturally aspirated motor."
The \'improving combustion\' bit stands out to me! surely having the trailing plug missing would lead to only part of the mixture being ignited and the rest being kicked out the back? loss of power,etc?
This is where you need a dyno to experiment, in terms of pure power you shouldnt see any loss of power if your spark is powerfull enough, reread Profs post its quite good as to why there is two spark plugs per rotor.
I think the reason why some people run without trailing as not to risk the trailing firing before the leading on boost
I think thats a Haltech timing myth that was going around Rx7club. The Haltech timing isn\'t very accurate so people were worried about it. Someone checked with Haltech and they said the trailing firing time is based on the primary so impossible for it to fire before the leading plug. There maybe other issues as I\'ve only been looking at this stuff for a few days.
Repeat question from earlier but want to make sure of some detail, do the primaries deffo swap to the secondary injectors or do the secondary injectors come on AS WELL AS the primaries?
They come online as well as the primaries all four injectors are working past 3800rpm normally, you can tweek transition to smooth it when they come online
Ah right nice one , thanks.
Quote from: BlitzBoy;551203This is where you need a dyno to experiment, in terms of pure power you shouldnt see any loss of power if your spark is powerfull enough, reread Profs post its quite good as to why there is two spark plugs per rotor.
I think the reason why some people run without trailing as not to risk the trailing firing before the leading on boost
If you think about the shape of the housing and the rotor - there is a \'pinch off\' of the combusiton chamber as the rotor face sweeps past the \'inny\' bit of th figure of 8 trochoid. If you look at a model fo the rotary engine - you will see that this is pretty much in the combustion phase - all the charge on the top side of that pinch off would suddenly be reintroduced to all it\'s happily burning friends on the other side :)
Probably very oversimplistic - but I tend to think from their upwards. :D
James car may be running leading only as a safety precaution, if you run trailing and the leading spark/coil fails you will not know and as the engine will still run but it is likely to kill the engine, if you only run leading and it fails, the engine cuts and causes no damage. I was chatting to a tuner who said he was looking to map cars with no trailing after full boost.
Royal, surely you had an ecu in the yellow car?
Yes mate, I have an Apexi PFC and commander. I want to really learn how it all works and really like the idea of a DIY system like the VEMS or Megasquirt rather than a solution in a box so to speak. Just me in tinker mode I suppose. If I\'m going to map the PFC myself I need to buy a wideband and datalogit and for a similar price I can buy the full VEMs system which includes a wideband anyway. The only problem is there doesn\'t seem to be many people who\'ve done it with the VEMS. There\'s a guy with a 3 rotor turbo called bcool on rx7club who I\'m trying to get in touch with. I\'m pretty sure he\'s just using leading plug, but don\'t know how far he\'s got to getting it running.
If I could just confirm if doing leading only is ok then alls well but until then I can\'t make a decision and will have to use what I have. The VEMs guys were talking about adding in a split spark feature but I don\'t know how long that would take.
Isn\'t there a piggyback unit you could use to duplicate/modify the ign. signal for the trailing plugs?
I know with the Apexi AFC(Air flow convertor) you can take the fuelling signals and increase/decrease them (then potentially pass them on to additional injectors, scaled up or down).
Theoretically you could do the same but with an ignition controlling unit, adding a couple of degrees low down, and 10-15deg up top/under boost?
Personally I\'d prefer a compatible ecu, but it could be an option, if such a thing does exist?!
Cleaned as requested
Thanks :)...
Quote from: royal;551372Yes mate, I have an Apexi PFC and commander. I want to really learn how it all works and really like the idea of a DIY system like the VEMS or Megasquirt rather than a solution in a box so to speak. Just me in tinker mode I suppose. If I\'m going to map the PFC myself I need to buy a wideband and datalogit and for a similar price I can buy the full VEMs system which includes a wideband anyway. The only problem is there doesn\'t seem to be many people who\'ve done it with the VEMS. There\'s a guy with a 3 rotor turbo called bcool on rx7club who I\'m trying to get in touch with. I\'m pretty sure he\'s just using leading plug, but don\'t know how far he\'s got to getting it running.
If I could just confirm if doing leading only is ok then alls well but until then I can\'t make a decision and will have to use what I have. The VEMs guys were talking about adding in a split spark feature but I don\'t know how long that would take.
Does the VEMS allow you to add ignition channels, or have more than 1 map and select the channels in that map ?
I was just thinking that maybe you could set up 1 channel for leading, and 2 for trailing. That way you could set the split up by putting the timing you need in one map, then some offset values to get the split in the other map. Since you don\'t have the switch over circuit that the stock ECU has to toggle the trailing ignition firing, you will need 3 channels at a guess. (The trailing plugs are fired by a timing signal, and also a select signal which alternately fires one rotor or the other). That\'s not needed on the leading ignition, as you can use wasted spark.
I\'m not sure prof. I don\'t think you can do it as you say, as someone over there would have suggested that I\'d have thought? From what I can see there\'s only one channel and you can\'t offset it. I\'ll bring it up as I\'m sure it\'ll help me to understand the software better. They are talking of adding a proper trailing spark feature though, just depends how quick that could happen for me.