tgates

i have a 1991 camaro z28 5.7 tpi, with mods. I'v been told to put bigger injectors in my car. I have stock ones in it now.
MODS-
jet stage 2 chip
MSD supercoil kit, cap, rotor, coil, wires and plugs
true ram air intake
air foil
ported plenum
adj fuel pressure regulator
bbk underdrive pullies
high flow cats
cat back exhaust
exhaust cut out

im planning to put more stuff in my car.

How big should the new injectors be? idk how big they are now(stock)

quickchicken

with everything you have the 22's will still do the task. you can run a set of 24's and have some mod room and not have to scale the injectors down to meet your current needs.

tgates

are 30's too big for my car? bc i want to put a cam in my car next summer.

quickchicken

30s are in the range of strong 383 type motors and such. right now 30s would be much for your setup. id go with a set of 24s and get a cam that works well around them or wait till your ready to mod and then detrmine what you need for injectors.

tgates

ok thanks alot man. i'll do the 24's. do you think i'll see a difference in performance?

quickchicken

"maybe" a bit better throttle response but thats about it. i havent seen replacement 22 lb injectors around and some time ago a friend was looking for some 22lb units to replace the stockers in his B4C and upgraded to the
24s with no issues.

Tex95Z

FYI LT1 injectors are 24#, and you can get them used in the classified section here very cheap.

quickchicken

very tru, but i would still have them sent out to be cleaned and flow matched.

palric

i always went the other way with injectors, dropped my 22s down to a 21 and run up pressure thru an AFPR

outstanding throttle response, excellent cold start and hot start characteristics (starts first crank)

Great WOT performance

never seen bigger injectors show up for anything on the dyno. Lots of people do it cause they get convinced going to 24s for 28s will add hp.

Adding fuel for no reason (eg: without bigger heads, cam etc) just makes for poor VE and lost performance... and flood conditions at the O2

quickchicken

iv seen guys go with bigger injectors because of better response and the injector dosent have to work as hard doing the job, these guys also scale them back to the proper rates when going bigger tho.

when you go with a smaller injector and up the FP your putting more work on the injector opening the valve and this leads to premature injector falure.
i learned this long ago from the guys on the mailing list when i first got my formula.

yeah ya get a better atomixzation with higher FP but its a killer on the injectors. you can bump it up more with bigger injectors because they can handle more duty.

Kevin91Z

Putting in bigger injectors, even going from 22lbs to 24lbs REQUIRES using a custom computer chip. Otherwise the car will run rich. The stock computer is already set up rich from the factory. If you add more fuel, the computer cannot compensate.

Its my opinion you dont need bigger injectors unless you change the cam and heads, or you're running a power adder.

Doc87IROCZ

With your mods, you do not need larger injectors. Simply buy a scanner and data log the fuel trim values. If the ECM is adding some fuel as a correction (BLM > 128), then simply increase the fuel pressure. You will then see a drop in the BLM value. The perfectly tuned engine/ECM will be at 128 for the BLM value in all fuel trim cells (FTC). Consider yourself nicely tuned if the BLM values are between 122 and 134. I do not touch the tune in my Eprom if I am between those two values.

tom2

Have similar setup as yours. Went with 23# and the scanner shows normal int and block readings. If your stock injectors are in good condition I'd leave them as is unless the ecm readouts are showing a lean condition.