Can I do this?

Pistoleye · Mar 29, 2004

24 pound injectors with stock heads and intake? I have a dynomax cat back, Mac cold air kit, and a 100 shot of NOS. and ProM to match the 24s. By the end of the summer i will have a new intake, I already have a adjustable fuel press reg. Can i lean them back till i have more cash or should i wait to put them in?

wytstang · Mar 29, 2004

I would wait and do it all at once instead of taking it apart now then in a few months doing it again. the stock injectors should be fine with your mods that you have. just my .02

urban96 · Mar 29, 2004

i suppose you could but you will need to buy a new MAF calibrated for 24#'s and turn your fuel pressure down a bit

Pistoleye · Mar 29, 2004

I have the MAFfor the #24s...think it is worth putting them in?

baglock1 · Mar 29, 2004

Pistoleye said:
I have the MAFfor the #24s...think it is worth putting them in?

No.

Fast94Cobra · Mar 30, 2004

my numbers are in sig and i have 24lb injectors and it runs great. i would go with something bigger however if i had plans for more power in the future.

Venom351R · Mar 30, 2004

baglock1 said:
No.

ditto. The stock #24's are good for up to 300 HP to the wheels. Once you have done the heads/ cam and Intake then upgrade to #24's. If you put them in now you will need to turn down the fuel PSI. How did you get them? were the given to you or did you get them really cheap?

Rootus · Mar 30, 2004

Striped5.0 said:
If you put them in now you will need to turn down the fuel PSI.

Venom351R · Mar 30, 2004

HairyCanary said:

what do you mean . The stock #19s can handel everything hes got now and will handel alot more mods if you throw in 24's its going to be getting way to much fuel and be running pig rich unless its toned down some. so what are you saying you can run #24's on a pretty much stock Mustang and you wont have to adjust the fuel at all?

Pistoleye · Mar 30, 2004

There is a shop not too far from me that can dyno the car and check A/F ratio, I thought that i could be tuned to run well with the 24s but if they are still gonna be overkill i can wait.

Rootus · Mar 30, 2004

Striped5.0 said:
what do you mean . The stock #19s can handel everything hes got now and will handel alot more mods if you throw in 24's its going to be getting way to much fuel and be running pig rich unless its toned down some. so what are you saying you can run #24's on a pretty much stock Mustang and you wont have to adjust the fuel at all?

Yep, I'm calling BS. Keep the pressure at 39 psi and be done with it.

There is a lot of misunderstanding around here about what exactly fuel pressure does for you. It does NOT cause your injectors to simply flow more or less fuel -- it changes their potential. The EEC is still very much in control of how much fuel is delivered, and it will use feedback from the oxygen sensors to ensure that the mixture is correct. You can get short-term changes in mixture by altering the fuel pressure, but the EEC will correct for those changes given a little time.

Dave

sleeper89 · Mar 30, 2004

HairyCanary said:
Yep, I'm calling BS. Keep the pressure at 39 psi and be done with it.

There is a lot of misunderstanding around here about what exactly fuel pressure does for you. It does NOT cause your injectors to simply flow more or less fuel -- it changes their potential. The EEC is still very much in control of how much fuel is delivered, and it will use feedback from the oxygen sensors to ensure that the mixture is correct. You can get short-term changes in mixture by altering the fuel pressure, but the EEC will correct for those changes given a little time.

Dave

HairyCanary is right. you can swap the inj/maf in at any time without any problems. afpr's are used to dial in a/f ratios at WOT and nothing else. at part throttle the eec controls the amount of fuel induced through pulse width variations based on 02 sensor readings etc. FWIW people usually jack up the fuel pressure to compensate for injectors nearing their maximum duty cycle, or to fix idle issues on BIG injector cars.

to the original poster: you don't *need* to install the injectors now as you still hove some room with the stockers. however, if it were me, and i was running a 100hp+ dry shot on an otherwise stock combo, i'd want the 24's and a 190lph-255lph pump just to be safe.

-steve

VIPERn94Five-0 · Mar 30, 2004

HairyCanary said:
Yep, I'm calling BS. Keep the pressure at 39 psi and be done with it.

There is a lot of misunderstanding around here about what exactly fuel pressure does for you. It does NOT cause your injectors to simply flow more or less fuel -- it changes their potential. The EEC is still very much in control of how much fuel is delivered, and it will use feedback from the oxygen sensors to ensure that the mixture is correct. You can get short-term changes in mixture by altering the fuel pressure, but the EEC will correct for those changes given a little time.

Dave

Bingo....the EEC is still reading the data from the MAF, and the 02's and adjusting for the amount of fuel needed....its not gonna dump more fuel than it needs....i used to think that the bigger injectors would just dump that much more fuel...when in reality they just have the POTENTIAL to dump in more fuel...i wish i had gotten my Pro-M 80mm for 24# injectors instead of the stock 19's....

Anthony

Pistoleye · Mar 30, 2004

Ahhahaha...ok guys so it is ok to run #24s how my car is right now? I do have a 255lph pump and run a 100 shot of NOS.

baglock1 · Mar 30, 2004

Um, why waste your time installing it now?

Zero Signal · Mar 30, 2004

Yeah the computer will change the duty cycle, but it can only change it so much. I'm sure it can easily compensate for 24# injectors. But isn't there an optimum duty cycle given a certain pressure? I remember reading something on that, but can't remember much of it other than that if the duty cycle is too low, it will be counter productive. Do a google search and you'll find the equations for selecting your enjector size based on your max horsepower.

Pistoleye · Mar 30, 2004

cool, thanks fellas!!

Afastgts95 · Mar 30, 2004

injector problems

I just got done replacing my 19 injectors with 24 for the reason of running a gt40 intake bigger throttle body and mass air meter. My car is running like . It feels like its running on 3 cylinders. I have not installed the mass air meter caliberated for 24 injectors is this the problem? All vaccum lines are hooked up right and timing is good.

Rootus · Mar 30, 2004

Afastgts95 said:
I have not installed the mass air meter caliberated for 24 injectors is this the problem?

Yes!

Your computer is trying to figure out why the hell so much fuel is ending up in the cylinders, because it thinks you have 19# injectors installed. The most the computer will adjust fuel delivery is +- 25%.

Dave

Afastgts95 · Mar 30, 2004

the injectors I put in the car have been sitting in my garage for over two years if I drove car home from shop then they should work right? The guy who helped me said my injectors were no good!!!!! Is there any way to test them. My car starts and there is no pinging.

Thanks ,Josh

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