Bigger Fuel Injectors

[highoctane]

Thinkin of putting in bigger fuel injectors in my 91 grand prix 3.1,
maybe out of a 97-03 GP with a 3.8, any suggestions.

[6SPEED84Z28]

you will need the chip recalibrated with bigger injectors. i used 19#ford 5.0l mustang injectors. ideally you should find out if you need bigger injectors with a scanner and see if they are being overworked at full throttle.

[SappySE107]

I also use the 19 pound mustnag injectors, which are 20.9# on a GM fuel system. If you don't need them, its pointless to go larger. Plus as 6speed said, you have to reprogram the computer to accept the injectors and to keep the engine running properly. In most cases you wont need larger injectors. Stock spec are 16.6#.

[highoctane]

i see, it just seems that sometimes i am starved for gas, but im also gonna check my egr valve and o2 sensors, i think they are both bad...

[SappySE107]

You would have a code if the EGR was bad, its very picky about it. The O2 very well could be a problem without ever throwing a code. If you are talking about not having much power past 5000, thats normal for a 3.1 because the intake manifolds suck.

[z284pwr]

I know this is somewhat different, but I have a datalog showing 87% Duty cycle at 5200 RPM running a little rich, I see 96% Duty Cycle at 5600 RPM...I let off very quickly after that, realizing the motor is out-doing the stock injectors....Only problem I have is the fact that the "bigger" injectors run to rich at idle *Soot on the exhaust* with the lowest possible settings before it dies......
Oh, and yes I have a reason to take a 3.1 to 5600.....with the big injectors so it won't touch 80% Duty Cycle it'll pull well past 6000. Extude Honed Intake and Ported Heads help it breathe quite a bit Thats with a baby cam too....its waiting for the turbo in spring though....

[SappySE107]

you are using 42# injectors with boost, so its very different.

[highoctane]

well about that engine code, my light does come on at idle sometimes, i gotta check the code, i am plannin on takin my egr valve off and cleanin it, maybe that would help, and the 02 sensor is kinda old, 55000 miles that i know of since ive had the car, so it wouldnt hurt to change it, its pretty cheap.

[z284pwr]

Out of curiosity, I've been tryin to find what other motors have for injectors, just for reference, what does the 3800 SC motor have in it? While were at it, what are the Multec-II injectors rated at? Maybe a FAQ or something could be made up of some of the different sizing for people doing research, I'm sure some of the turbo swap guys could use a reference chart to see what different motors have, just and idea....

[6SPEED84Z28]

3800's are 36# or 38# depending on what pressure they are at