Subaru WRX Forum banner
1 - 8 of 8 Posts

·
Thinking Man's Engine
Joined
·
1,598 Posts
Discussion Starter · #1 ·
Well I believe most of us is already aware of the WRC anti-lag mechanism.

Quick review: When you're off the accelerator, the ECU tells the engine to spray some fuel aft of the exhuast valves, so when it hits the nice and hot catalytic converter, there's some expansion of the fuel vapors, keeping the turbos spooled (with I believe there will always be a minimum of 17 lbs of boost). Not good for the catalytic converter.

To my knowledge I am not aware of any anti-lag mechanisms for the US WRX.

I was browsing through VW's site (http://www.vw.com/engine/index.htm), and they have a clever little bypass valve mechanism. Basically it works by: rerouting some of the air after the compressor back into the turbo air inlet, keeping it spooled.
 

·
Registered
Joined
·
45 Posts
Well first of all you'd have to upgrade to a stand-alone ECU that has anti-lag control built in. I believe most anti-lag systems are pretty much custom built. I can't think of any street-driven cars that would use it. It's very hard on the turbo components since it generates alot of extra heat. I've ridden in an EVO4 with ALS (pro-rally car) and it does sound neat. :)
 

·
Registered
Joined
·
554 Posts
NOS would be fun.
 

·
Thinking Man's Engine
Joined
·
1,598 Posts
Discussion Starter · #5 ·
dw said:
Well first of all you'd have to upgrade to a stand-alone ECU that has anti-lag control built in. I believe most anti-lag systems are pretty much custom built. I can't think of any street-driven cars that would use it. It's very hard on the turbo components since it generates alot of extra heat. I've ridden in an EVO4 with ALS (pro-rally car) and it does sound neat. :)
Well, I pointed out one example, which is the VW 1.8T bypass valve system. That one mass-produced street driven vehicle with an anti-lag system.
 

·
Registered
Joined
·
4 Posts
The bypass valve is used by VW instead of a blow-off to protect the turbo because we use mass-air, the bypass returns air that was already measured by the MAF where it may be subtracted, so that the total flow is recomputed/correct.

Subaru uses a BOV, correct? Do you know if the ECU uses MAF as well, or does it use MAP?

Kinda funny, many of the VW guys want to put in a BOV instead of the bypass valve...for the sound. :rolleyes:

Some have even disconnected the MAF and let the ECU fall-back on MAP just to use the BOV.

I know nothing about the Subaru system, but it might be possible to design-in a bypass sytem, the VW/Audi OEM valves are ~$30-$40, aftermarket is ~$150-200. It's pretty simple, there is an in/out port, and a vacuum control line. Sometimes it is also called a diverter valve, if you want to "google" a bit on the subject.

-Scott
 

·
Registered
Joined
·
45 Posts
The stock WRX BOV actually vents back into the air intake, which goes into the turbo air inlet. That's why you can't really hear it at all unless you modify/remove the resonator or go with a different intake. There are plenty of WRX guys that traded that for atmospheric BOVs so they could hear them, but since it's MAF based that can cause problems. GFB/Forge also make a 50/50 BOV that many people are very happy with. I was more talking about what it would take to put an ALS system into a WRX. The system in the WRX with the BOV does help to keep the turbo spinning when in a no-load situation like shifting, just like that bypass system does. It isn't close to being able to keep the turbo spinning enough to generate 14psi , you need some combustion spinning the turbine. I'm sure the VW uses a smaller turbo so it's not as difficult to keep it spinning. If you watch prorally/WRC and hear what sounds like some backfiring, that's ALS.
 
1 - 8 of 8 Posts
Top