Just got done with an 04 STI:

Mods: 3" Turbo back exhaust w/ hi flow cat, Perrin inlet hose, Injen CAI, Stock VF39 turbo / ported wastegate (deadbolt), TopSpeed EcuTek tune

Run #3 was just 3" turbo back exhaust & BOV
Run #9 was after the inlet pipe, intake, and EcuTek reflash.

Both runs are on pump gas 93

 

nice numbers!

 

Why does the power taper so severely? Is it the cat or just the small turbo...or maybe running out of fuel?

 

STI's are harder to tune for especially top end. They have an all aluminum engine so it's tolerance for Knock is pretty low. You have to run them pretty rich in the upper RPM range to prvent this. Their knock sensor isn't so accurate in upper RPM's, all aluminum so there is a LOT of noise. ANd yes a smaller turbo, which basically flows like a 14B which falls off on a 2.0 let alone a 2.5 and then the TMIC.


You have to be extra careful when tuning these cars. If he got like a FP Green and a FMIC, who boy it is much easier.

 

That's a bummer...I've wanted to try an STI for a while but I'm nervous about the motor being fragile. The Evo's I've had could take 23lbs all day long redlining in the south florida sun and just take it...

 

The are not fragile, but certainly not as strong as the 4G63, but nothing really is except for the Sr20DET, maybe. IMHO there was nothing stronger then a 1990 6-bolt 4G63, the stock rods were better then some aftermarket rods.


It's just a harder platform to work on, way longer Exhaust manifold, smaller turbo that can't flow the CFM's needed to fill a 2.5 at high RPM's unless you want hot air, TMIC and heat soak, smaller injectors.


Generally when tuning an EJ20 or STi you need to reduce timing and add fuel, like alot of fuel, 10.8-1 ratio to be safe.

 

It's really not harder to tune, per se, it's just more tedious. Just like tuning a higher compression boosted car vs. a lower compression on.

The main reason why the power drops off so much in the top end is because the 2.5L is way big for that tiny VF-series turbo.

 

I Vote all STi's come with FP Greens and must run 20PSI.

 

Here's an STI dyno worth looking at -- AVO 450 turbo, 93 octane, 19 psi



This bad boy will run up top, big time...

 

That looks a little bit stronger up top

 

oh, they have an "OTHER CARS" section.

 

Why did the car come with such a small turbo??

 

BadzzCR....how much boost was the sti tuned for?

 

spiked about 18-19psi in midrange, then fell to around 14psi by redline.