it wasnt too long ago when a posted a topic of my kit not feeling much faster than stock, but after running with a evo/135i/AMG i can clearly say it made a huge difference.

anyhow. currently my car's running 7PSI, ESM, FPR, no tune, FMIC and im looking for more power. Before ppl starts flaming, i know ill have to change the setup w/ tune, injectors, etc... but would it be possible to run a smaller pulley and just never get passed the rpm that hits 7psi?

 

I would say no, and the reason is because yes, you are right in that you would not be exceeding the 7psi threshold, but the only problem is that your still gonna be boosting MORE than what the ESM thinks you will be boosting. Basically lets say right now at 9k rpms you are seeing 7psi, therefore at 6k rpms youre seeing 5psi. Well if you put a smaller pulley on, you will be seeing 5psi at 4krpm and 7psi at 6krpm (Totally made up numbers by the way, but the point still applies)

Anyways the ESM will be fueling for 5psi at 6k rpms when youre actually making 7psi at 6krpms, so you will still wont be getting enough fuel, I hope that makes sense.

Now if you were able to make the exact same amount of PSI at all the rpms, and then magically make an extra 2-4psi at 8-9krpms then your theory would work, but fortunately that isn't the case (it would suck to not make more midrange power with a smaller pulley)

 

^^^ That's partially right, in that you wont be delivering enough fuel throughout the entire rpm range, since your not just effecting the peak, your effecting the whole powerband, so you must deliver more fuel through the entire rpm range now. The part that is inaccurate is the ESM's duty isn't to supply the fuel, so it could care less what pressure your seeing, its the rising rate fuel pressure regulators job to deliver the right amount of fuel. So as long as you have not exceeded the effective fuel pressure limit, you can just add the fuel you need with the smaller pulley buy cranking down the adjustment some more until your afr levels back out to nominal levels again. I will tell you from experience though that if you are actually seeing 7psi at the manifold/boost gauge, you are right at the max capacity of the rrfpr. In that case you would be assed out with your current set up. Unless of course you cheat and run a water/meth injection set up to deliver the added fuel you need, wile suppressing the added detonation tendency from the extra boost (since you have no way to reduce timing) hit two birds with one stone. But even though Ive played with that set up a lot, its risky and I wouldn't recommend it unless you understand what the potential risk are.

 

if you're goin from 7 to 9. i've seen it done before... car didnt run that great. he put 450cc injectors made it run better but it still had its moments.. it would run perfect under full throttle but regular driving it would struggle every now and then.

you could do it with the right size injectors (if you're running the timing box) but i wouldn't recommend it. if you have an aftermarket ECU... you 100% need a re-tune.

a tuned aftermarket ecu (AEM ,Kpro, Flashpro) will always run better.

 

Running any injector larger then the 360cc the car ecu comes with will not run properly since the calibration of the injector is now off with no way for the stock computer to shorten the injector pulse width. You will inject too much fuel at idle and partial throttle surely and the short/long term effects of this will be fuel washing your cylinders/killing your motor and in the interim generally running poorly. The only way to increase fuel supply safely and effectively with the stock ecu and injectors is to increase fuel pressure and that is up to a point, beyond that your injectors will begin to lock up and bad things can happen.

A larger aftermarket fuel pump and adjustable fpr is how you increase fuel with stock injectors/ecu.

 

How is your car even running well on 7 lbs in the first place without a tune?

 

? What do u mean?

 

Cool thanks guys!!

 

Nm i think maybe i read your post wrong. I saw it say that you had no tune so i was thinking you had nothing controling your fuel.

 

What if you are running a vafc. Would that give a little room to work with. My setup is the same 6lb boost with the 8 or 9 lb pulley on a fmic. I was thinking of taking it to 9lb and just tweak the fuel in the vafc. Thoughts??