antilag
 

This directly pertains to Evo's, but also might serve other cars. We all know there are several variations of antilag and I don't want to turn this thread into a debate about it.

On JDM evo's there is a form of antilag stock. All it does is push air into the exhaust manifold when the car is over 4000 RPM's, has been full throttle for 3 seconds and when there is a sudden lift of the throttle. Here is the diagram from the manual:

http://img222.imageshack.us/img222/1271/sasvr5.png

Here is my thought..... Aftermarket manifolds have two ports for the stock antilag setup. If I route the BOV to these ports would it work? I would need a one way valve in there so exhaust gases don't reach the BOV. I would also have to run a speed denity setup so I don't run rich at shifts. So far it seems like the only problem that could come up is if there is too much pressure in the exhaust manifold that the BOV would not let enough gas out of the intake leading to compressor surge. Anyone here have some input?

Am I reading this diagram right, does the standard setup have some sort of funky BPV that vents to the manifold? I don't think you need a speed density system cause that air that bypassing the cylinder head is meeting back up in the manifold. That's gonna make quite the bang when you lift as high revs. :eek:

Search for videos of it, it sounds like a gunshot going off - I'm at work or else I would link you some.

You would need to get tuned for it - good luck, I don't know many US tuners which tune JDM anti-lag setups.

I have been thinking about the speed density thing a lot. You are right as far as the AFR's are concerned inside of the exhaust manifold. Running the stock MAF will make the motor run rich at shifts, but if I did have speed density it would make the gas in the exhaust manifold very lean giving me high EGT's


Sorry, but wrong. This is just adding air, not adding fuel and retarding timing like the antilag you are refering to.

i am pretty sure the air scource comes from the egr system..

You also wouldn't get the bang which is the point of anti-lag.

One item in that diagram is not labeled, so it very could be something within the EGR system. I have heard somewhere on EvoM that it does have something to do with the EGR also. However I really think this way could have potential, might give better results over the stock JDM system, and be much cheaper.

I have been known to be called a ricer in the past, but the bang is not the reason for true antilag. It is just a cool by-product though. If I just wanted the bang I could tune the ecu to retard timing in some cells and call it a day.

I don't think this is anything close to "anti-lag". It may produce some favorable results, but I'd like to try it out myself to verify it because I am not totally convinced on the physics of it. If it was the end-all, be-all, many more people and companies would be doing it because it doesn't look that difficult to implement.

I think it is working on the premise of venting pressurized intake air (like a BOV would) into the exhaust manifold to get a short increase of turbine inlet pressure during shifts. The only problem I see with this is the exhaust manifold pressure could equal or exceed the manifold pressure when this happens. If there is no big pressure differential, then it doesn't work that well (based on the physics). The other problem is that this air isn't very hot either so it might tend to cool the exhaust (once again bad for lag).

It's kind of like a recirculating BOV, but it's vented back into the exhaust manifold. Pretty innovative concept though, as I always wanted to do something with the compressed air, the BOV just wastes into the atmos. It takes work (and therefore fuel) to compress that air. I don't know why they would recirculate it after it goes through the IC though. It makes more sense to do it when there is more pressure and volume.

Sounds like a neat idea. But, wouldn't the exhaust gasses be flowing under much more pressure than the charge air from the BOV?? It's seems like a small blast of air from the BOV would be very insignificant compared to the normal flow of exhaust gasses.

That's why I am skeptical of it, unless I am interpreting it incorrectly???

We don't really know the transient of the exhaust manifold pressure though as you lift throttle. It would go down in theory, but I think it would lag the intake manifold and release of the BOV. This isn't a piece of data that most people are familiar with.

I firmly agree with you guys, but that diagram is right from the UK service manual! For mitsu to have the system on a stock car the intake pressure must be more than the pressure in the exhaust manifold at that time.

No matter what, I am going to try it. I just need to find the appropriate one-way valve. A real big variable that I cannot figure out is how hot the gases hitting the one-way valve will be. I will place the valve as far away from the manifold as possible. Since regular exhaust gases will just be going by the lines and not up it I want to believe the temperature wont be as hot as normal exhaust gases. Also I am worried about using a flapper type valve because I dont want to car to think the faint clanking noise it makes to be knock.

You would have to use another EWG as the valve. That is the only thing you could use within a reasonable budget and that is readily available.

Never thought of that. I would need one with a really light spring though. With a spring as light as I need it, would it even be able to make a seal?

If the front 02 sensor helps control A/F ratio and you throw more air into the manifold, wouldn't that make for a "lean" condition or at least make the sensor look at it that way?

If the USDM ecu isn't calibrated for it, it might throw off the sensor. Then again I don't know where the front 02 sensor on evos are located so if this is wrong entirely ignore me.

I would think that this wouldn't be a problem seeing as the hotside is constantly sucking the exhaust up and when you are boosting the intake manifold is positive pressure. If anything I would think the exhaust manifold would be closer to vacuum than the intake manifold.

You could hook it up just like a BOV. Your ex manifold pressures should not be much more than 2X int manifold pressure with a larger turbo. You would have boost pressure help holding it close on WOT runs, so the spring would not have to hold the entire force of the ex pressure.

Getting the spring right would be the most difficult part, but it is surely something that can be done. You just need to be able to diagnose what is happening with the valve. Is is opening too soon, or not at all, etc?

Spending at least $200 on this is fairly risky. Are you possitive of the effect and have felt the difference first hand?

O2 sensor isn't a problem. I don't want to go too indepth here, but the evo ecu operates in 2 modes. Open loop and closed loop. It uses "closed loop" while idling and cruising. During that time it uses the front O2 sensor to get a 14.7:1 afr. During the time this will be happening I will be in "open loop" which the ecu just uses the air fuel map to put in a certain amount of fuel.

This is why we cant VTA without running rich. With things this way, the ecu will read the afr as if I am recirculating the bov.

The idea of a EWG is great. I am really liking it.

Please don't take this as a dick comment because so far you have been very helpful. I am not possitive of the effect nor have I felt the difference first hand. Have you ever felt the difference with your ITB idea before you did it? The greatest things in life have been figured out by trial and error. No one has thought of anything that could cause serious damage to the motor. At this point the worst thing that could come of this is I get compressor surge and/or feel the normal effects of running VTA with a MAF. My turbo will not take a dump after seeing compressor surge a handful of times.

No offense taken. I was just trying to warn you before you spent a decent amount of money on something that isn't proven. As long as you realize the consequenses, go for it. Don't forget it will be difficult to go back if it doesn't work because you will have to modify your existing manifold.

I would actually rather see you run a BOV-less setup, but use a 2nd throttle body on the turbo inlet. Old F1 teams did this to help reduce lag because the compressor would spin in a vacuum on shifts instead of releasing all of it's energy in compressed air. Just throwing that out there as another "new", rarely used, idea. I think that has a little more merit (in theory) over venting the pressure to the exhaust manifold.

Crap, totally forgot about it running open loop, nvm

Sounds like a cool idea, but then again how will the introduction of cooler air into the exhaust manifold effect air temperature and flow? If the reason people heat wrap/coat their headers is to maintain heat and exhaust velocity, wouldn't this be counter productive? Then again the air might be insignificant in comparison to the heat levels in the manifold... there has to be a reason why mitsu did this on non-US evos.

I'm all for this, would love to see it work. Search google for some videos with this on - there is an evo in a tunnel revving with this and when it backfires it is louder than a shotgun.

I don't have to modify the manifold at all. Aftermarket manifolds (like the one I have) already have the ports. They just have very wide and very short bolts screwed into the holes.

I think I understand what you are trying to say, anything else I could read to fully understand that?