RomRaider

heres some stuff ive dug up about GPN ECU stuff/antilag and whatnot in general that might help understand this rom better


http://www.specialstage.com/forums/show ... ht=antilag


some quotes i pulled from that thread


since Group N rules prohibit the addition of a switch (despite a lot of US cars that have one)

the car's throttle is cranked open with the idle screw
then you retard the timing in the ECU so it doesn't accelerate (since the throttle is jacked)

so that is why you get the 'rrummpahhh .......rrrumppahhh.......'

and when the rpms go over 4000 rpm, then the retard on the timing is taken away (for 10 seconds, from the last time it was above 4000rpm)

so then, if you take your foot of the gas, you get idle at like 2200 rpm and boost (at no throttle) at around atmosphere

you can make it more aggressive (i.e. more boost) at the expense of higher idle. The things about ice, is you want a low idle.

Finally, this is a typical way to do the antilag on a Group N car where it is illegal to add any switches or throttle control (like some people used to have a solenoid which would crack the throttle a certain amount, depending on the position of the switch, so you had 'aggro' and 'mellow' anti lag setups).

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You're talking mostly about why your car sounds that way at idle WITHOUT the antilag triggered, right? I don't know if the poster understands how antilag works when it is engaged, so it might be confusing that your idle is a consequence of having the throttle cranked for antilag but the timing retarded to a different degree than it is under antilag conditions, in order to stop the engine from revving out without the antilag engaged.

I only know my car, of course, but except for the solenoid+hot switch vs. the idle screw+rpm trigger+timeout I think we're basically the same, right?

So to the original poster: here's how I understand antilag: you want to keep the turbo spinning even when you're not on the gas. In order to do so, you include an alternate map in the ECU that retards the timing about 30 degrees (a huge amount) when you're off the throttle, which means the exhaust valve is already open, and the explosion happens at least partially in the exhaust manifold and blows by the turbo, keeping it spinning (and causing the sx bang backfires).

In order to keep the explosions viable with so much retard (and to keep the exhaust temp relatively cool (and by relative I mean it still gets very hot), you need more fuel in the combustion chambers and manifold than a fully-closed throttle will give you, so you have to artificially open the throttle a little. As Pat notes, add-ons are not legal in GpN, so rules-abiding people use the idle screw or a stock stepper motor to keep the throttle open a little. In an open class car we just add a solenoid plunger that cracks the throttle open a bit by physical means.

The problem with using the idle screw instead of a solenoid or stepper is that you can't switch it off when you're not using the antilag, and we only use the antilag map on the stages. So when you're idling around town you need to keep the idle in check or else the engine will wind out (and now, Pat, I'm beyond my experience with my car but I believe the following is what you're saying) and so you retard the timing a little on the normal (non-antilag) map to keep the idle in place. Hence the wacky cool idle sound on the GpN cars with antilag. You'll notice that open class cars don't do it, because we don't have to compensate for an artificially open throttle when we're not on the stages.

The last piece of the puzzle is the switching from normal to antilag map. Again, for open class cars, we typically just have a switch that swaps to the antilag map, and we flick it just before the stage start (the rise in EGT is alarming if you use it too long - like more than tens of seconds). But again GpN cars aren't allowed to have a switch, so they use a throttle opening pattern to trigger the antilag map. Again I'm beyond my experience but as Pat says, I believe this is ON=a certain amount of time idling above 4000rpm; OFF=a certain amount of time below some RPM, or a hard timout.

Antilag, although one of the coolest things on a turbo rally car, is pretty impractical for the street. It's really hard on the engine and turbo and I think it would destroy a normal catalytic converter in very little time (it's like using the exhaust as a combustion chamber). I doubt anyone but the most devoted street racer has ever fitted it to anything but a competition car.

Still coooooooool, though. I can get 24lbs. of boost on the start line, before dropping the clutch.

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Andrew's post is almost correct, but here is the final part.

Ok, like I originally said,

1) the throttle is jacked open

2) when driving on transits, idling, etc., the timing is retarded so that the jacked throttle doesn't accelerate the engine. Hence the funny idle where it goes and then seems to turn off, but then goes again all of a sudden, etc. kind of like a hot cam.

3) as soon as the rpms go over 4000 rpm, and for the next ten seconds, the retard in #2 is removed. This is called 'in anti-lag mode'

4) when you are off throttle in anti-lag mode, some timing (different than #2 above) is removed only when the throttle is less than a fixed value, say 30%. This gives you the bang bang. This is more basic than what andrew is saying, it is not a different ECU map in this case, it is just a raw value deducted from the actual map.

5) when in anti lag mode, the idle is around 2100 rpm (you can set this to anywhere you want by adjusting the screw) and the boost is at say atmosphere (you can adjust this any way you want by adjusting the off throttle retard). So you can adjust the 'idle boost' to suit conditions (in the snow you want it real real low).

So in a nutshell, it is always on, in my car, and you turn it off by driving below 4000 rpm for more than 10 seconds. You 'arm' it by revving it up.

This is a 'poor mans antilag' setup, to be honest it is far less than ideal because of the potential for overrun. The ECU I am using right now is the Link. A switch is better. Link will sell you a switch but I am not using it. For long transits, I often go under the hood and jack the throttle closed, to save the turbo. Driving around with the bang bang on is a waste of the turbo.

I chose the Link based on cost. Less than a quarter of the price of some of the other Group N units. (Prodrive Pectel, Motec, Autronic, etc.) But the problem is it is not very refined in terms of tuning, the steps are large and it doesn't self-adjust (you constantly have to fiddle the timing/fuel during the day due to temps etc.)

Some of the other units use a 'switch' that is hidden in the wiring loom of the car, i.e. you turn on the rear defroster and all of a sudden the antilag comes on. Some dont bother.

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In order to keep the intake and exhaust full of air, you open the throttle. This can be done manually with the throttle stop screw or by the computer opening the Idle Air Bypass Valve. Naturally, when you do this, you will have no vacuum and the turbo will be spooled up but the engine will be 'idling' at 4000 rpm. So, you retard the spark to sometime way after Top Dead Center to make the engine really inefficient and the idle comes down to 1000 rpm and bangs and pops and is generally pissed off. However, the intake is still full of air and the turbo is still spinning at a good clip due to the burning mixture in the exhaust manifold. When you then stand on the gas, the computer will instantly bring the timing back to normal and you have instant boost.

On stage, if you lift completely off the throttle (below X%) and the engine RPM is above the desired idle speed (which it is because you are still in gear and trying to slow down from warp 6), the computer will again retard the timing so that the engine doesn't try to drive the car (remember it wants to idle at 4000 rpm), but you do have to accomodate the fact that you will get very little engine braking even so. And again, when you jump back on the gas, the timing is instantly advanced back to normal and you have instant power.

On an open class car, you just put a switch on the dash to turn it on or off. If the computer has control of the throttle position, then the car will return to a perfectly normal idle when its off. If the computer doesn't, then you have to play games with the timing even when its off to get the car to idle.

A Group N car cannot have additional switches for such things, so you set up the computer so that it turns on when X happens and turns off when either Y happens or X stops happening. Typically, its set up to turn on when RPMs go above XXXX rpm and turn off if they stay below that RPM for 10-20 seconds.

anything new Andy, your PM was confusing, you didn't release the fixes for the codes yet did you, i've re-read every single post on here and didn't find anything except the old defs with the dwell, idle control, etc.

No, the CEL is not going to get fixed though. At least not anytime soon. It is a CEL with no code behind it and I have no idea what's causing it. Furthermore, I lost my test dummy and I don't want to try things out on just anyone's car because it's very likely that I could brick the ecu doing so. Sorry!

Andy

Hey, I'm still here

HAHA! Care to possibly donate an ecu for testing? Lol! Anything left I can think to try would possibly brick the ecu.

Wish I could, I can do additional testing but am in the middle of a 6spd swap right now too.

I am really sorry to hear that. The MIL is the only thing stopping me from running it 24/7.
Is there anyone that we can ask, possibility in the openecu.org community?
The work you've given the subaru community already is huge, maybe we just need some new eyes on it.
Thanks again for your contributions, lets hope for more this spring.

i got a 03 WRX ECU for sale if your interested. im here in IL


i cant "donate" it since i need the money lol. just did a full 04 STi swap with functional AVCS. i wish i knew bout this rom first and i woulda just went hybrid for antilag lol.

why, what happened to jerod?

head on collision I think, parted out his car on nasioc last I read.

Is the CEL really that big of a deal? What does it disable?

No the 03 ecu wouldn't help me as I have an 04 and there are a few slight changes you need to make to swap the ecu's. I don't want to make those changes.

Jerod did get into an accident and insurance totaled the car. He couldn't buy it back because Illinois law blows. But it wasn't his fault so I guess he's making out pretty good He has a Cadillac CTS-V now.

Yes the CEL is the only issue that I am aware of, and it doesn't disable anything, people just don't like the light.

I had a discussion with a friend of mine yesterday about this, and he said "what if the Group-N cars just always had a light?". It might make sense, if something in the code is overflowing the boundaries it might cause a CEL. This wasn't a commercial ROM so what did they care?

Andy

I think those running the image on a JDM STi ECUs (ckkibue comes to mind) do not get the MIL. ckkibue uses it on a stage rally car, maybe he will chime in to confirm the lack of MIL.

Is he OK?

poor guy, hes the first one that started helping me tune my car. Maybe he has enough money to buy a nice roller supra and start getting crazy

I guess i'll start trying to go through the code, i have lots of exp. with programming from my mechanical engineering classes, i'll give it a shot

Yeah he's fine, was just a bit sore. He was only going about 30mph and some asshat was driving way too fast in the ice. Came up over a curb and turned right into him. Bumper beam/front part of the frame went through the timing belt cover!

Andy