This thread is mostly about the WRX, but may apply to other cars too.

I recently upgraded my turbo to a VF34 with the goal of running it with the factory ECU while my tuner of choise waits for their Ecutek software. I learned a few things that might be useful to others...

1. The stock ECU and factory boost solenoid basically SUCK with this setup. Boost spikes wildly and puts the engine at risk. Not really driveable at all.

2. MBC's (I used a bleed valve) work as a band aid to get this setup under control. Not very well though... If boost is set to around 15psi, the car is at risk for PTFB lean conditions. If boost is set to a safer level, around 12~13psi, the car is not much fun to drive. Add to this some pretty bad inconsistencies in the powerband, and the car just feels wierd.

3. An EBC could be used, but why pay the $$ when it's almost as much as a reflash?

4. Reflash or other engine management is the best solution, but as I stated above, I'm waiting on that...

So, here's what I figured out in a quick flash of intelligence. Boost under ECU control is good, no PTFB issues, if there's a problem the ECU goes into limp mode, etc... As I learned the hard way, the ECU CANNOT control boost in this setup, so I had to figure something out. Since I had an MBC lying around, and based on some experience with the 3/16" mod, I decided to put the boost control back to stock but with the MBC installed inline between the "T" and the solenoid but after the restrictor. This is a pretty finicky setup to tune, but well worth it when I found the "sweet spot". Too much flow and the boost was out of control again. Too little flow and boost built very slowly, but peaked at 15psi, tapering to about 11psi toward redline. This was encouraging. Once I nailed the setup, my car felt like a BEAST. No holes in the powerband, very good boost response, VERY steady boost peaking at 15psi and tapering to 11psi at redline. If my theory is correct, I should have to worry about PTFB either since boost is ultimately under ECU control.

Any thoughts on this? Am I way out in left field? p.s. sti injectors, bigger fuel pump, and reflash ARE planned for the future, this is just a reliable fix.

 

If the car feels REALLY strong, I'll bet you a Family Guy DVD that your A/Fs are dangerously lean, using stock injectors with the VF30.

 

damn, if I HAD a family guy dvd to put up, i'd go for it. actually, I'm gonna bug Scott about making a few runs with their scan tool to check everything out.

also, i feel that this way is actually safer than simply running an mbc set to 13 or so psi.

 

Anything is safer than an MBC. I would just be concerned that you are making more than the 270ish horsepower that the stock injectors are limited to, which is real easy on the VF30. I would ask Mike Egan at a meet sometime if you can examine the boost line setup on his car. I think by mimicking that, but not adding a bleeder, you shouldl enable your ECU to control boost properly.

 

ok. i'm farily sure i'm NOT to 270 yet, it definitely feels better than stock, but not that much better. I would like to scope out that setup you're telling me about though.

 

Run bigger injectors, an electronic boost controller, and maybe a reflash. If money isn't the issue, get an aftermarket EMS.