jspecracer7

For an FC, I've pushed my boost to 14 psi, but I had an FD fuel pump which raised fuel pressure.

helihansen

I currently run 13 on 94 octane. But............. I have pettit unlimited,downpipe,midpipe,catback of course,intake,greddy fmic,supra fuel pump,and non sequential. So..............my conclusion is if you want to run high boost make sure you upgrade your fuel pump. There was a kid on here (kris) who works for toyota in cali. He started a group buy and was selling the supra pumps for like $250 but dont quote me. If you're serious you can call him 1-209-725-9000

or you can find him on aim Suprfast. You are basically limited to whatever your ecu can support and map. Hope that helps

jspecracer7

FOR WHAT CAR?!?!?!?!?! Not all cars have the same fuel setup, so everything is limtied to what comes stock on that particular car. FC, FD, Lancer, WRX, 180sx, S14, GT-R...none of these cars have identical fuel system so the question, "What's the max boost?" can't be answered.

rotarypower101

After a little searchy searchy, I believe he would like to know the limits of the stock FD3S system.



And in his spare time trying to sell this beast and acquire a FD, he is finding out how much boost it will take to put another apex seal through a perfectly good housing. J/K

helihansen

I have an Fd

jspecracer7

stock twins/stock fuel setup can handle quite a bit. I believe Rikki pushed the twins to 19~20 psi on race fuel and 12.5 a/f. However, I'd stick with 15 psi and 93 octane...

ccarlisi

According to Max cooper's fuel calculator the max the stock fuel system can support is 213rwhp. However, I want to note that the calculator also says that the max flywheel horsepower is 251. This seems a little off given the fact that the stock car is supposed to produce 255. So I would assume that the calculator is slightly rich. Your first limitation is the stock ecu's max duty cycle setting of around 63%. An aftermarket ECU will allow you to raise that to the controllable limit of 85-88%.





Someone mentioned that upgrading the fuel pump increases the fuel pressure. This is not entirely accurate. Upgrading the fuel pump increases the fuel flow, allowing the fuel pressure regulator maintain the preset fuel pressure. Therefore, a new pump will prevent the fuel pressure from falling below the preset level of the FPR, but it will not increase the fuel pressure ABOVE the preset amount.

helihansen

I totally agree. You said what I meant. Pump does not have a problem supporting the regulator under higher boost.

jspecracer7

Read what I wrote carefully. When you throw a stock FD fuel pump into an FC, your fuel pressure will increase. It has been PROVEN with aftermarket fuel pressure gauges. I guess it has something to do with the FD pump putting more out at certain voltage levels than the stock FC pump...so much pressure that it raises the fuel pressure up slightly from the stock levels and overriding the stock FPR. No one believed it, not even RETed on the other forums...until someone posted data with 2 different fuel pressure gauges(2 gauges because they thought the first gauge was broke). I had suspected this when I put an FD pump into my FC because of the performance difference below boost, so I took a S-AFC and tuned all the low throttle range into the negative.

j9fd3s

thats not quite right the factory ecu exceeds 85% duty



mike