The red lines are my stock Evo. The blue ones are with the boost restrictor pill removed. HP is solid lines, Torque is dashed, RPM's is dotted. Lemme tell ya, I can certainly feel the difference. The boost increase seems to be most severe around 4500 RPM. You can see the large torque difference there in the graph. So basically you take a car that has a really strong midrange and you give it a stronger midrange. Yeeee-haaaaah!

I wouldn't necessarily recommend this mod due to the high peak boost. Especially if you run ****ty gas (I run 93). I'm sure as hell keeping mine like this though. When stock, my max boost was 1.38 bar (20 PSI). It had only recently been going that high, maybe it's finally getting broken in at 5400 miles It used to peak at 1.31 (19 PSI). Now with the pill removed it hits 1.49 (21.6 PSI). I assume that if I had an aftermarket exhaust, the boost would be dangerously high. Well, even more so.

 

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And you did this with a GTech???

 

Where is the pill at?

 

down below your air box

 

oooops not exactly below it, but near the bottom of it(air box)

 

The data was recorded with a Gtech Pro Competition. I didn't like their analysis software so I wrote my own.

 

Its in the boost solenoid line under the Airbox.. Its the line that runs to the wastegate (looking down at the solenoid its the one to the left) about 2" in, you should either be able to see an indentation where they crimped it to hold it in place, or you can feel it if you squeeze the line between your fingers..

 

and yes.. with an aftermarket exhaust your boost WITH the restrictor will go up to around 20-21psi and 17.5-19.5 (with the solenoid activated) with boost climbing.. What this means is your boost will probably be dangerously high without the pill installed.

 

 

Hey MJ, Evo newbie here...

I'm not sure I understand why boost would increase with an aftermarket exhaust. I can understand how it would improve spool up time which may result in hitting peak boost more quickly, possibly causing a spike before settling down, but why would max boost be much higher unless someone was using some sort of boost controller?

Also, wouldn't removal of the restrictor pill allow for a more aggressive transition of the wastegate state, i.e. the wastegate can open and close more quickly, thus allowing boost to build sooner?

Coming from an Audi S4 I understand the basic theory behind the boost regulation using the BPV and wastegate but I'm not familiar with the nuances of the system in the Evo.

 

I don't think it would be dangerous.. But rather annoying once it starts to get colder, you'll be hitting fuel cut all the time... So boost won't really go to an extremely unsafe level due to the fuel cut..

 

I can tell you that when I had the pill out of my car with my turbo back exhaust (before my XEDE arrived) I had to keep an eye on my boost guage every time I hit the gas. Every time the car started boosting it wanted to go way up.

I floored it once in that configuration (I had been working late and forgot about the pill issue) and hit fuel cut-out at around 3500 RPMS with a full 1.5 bar - pretty scarry.

 

Oh - G-Tech Pro Comp is awsome! I've used mine to baseline and log all my mods!

 

When fuel cut hits, it's like driving into a wall at 35mph... Talk about whiplash...