Bendeco

When a fuel injector says 24# per hour does that mean what it does on average or is that the max it will do? If I bought larger injectors would I burn more fuel or the same in average driving? And is there a gain in performance to go to a larger injector? Or will the computer correct the larger injector to just pump what the stock injectors pump out?

John A. Marker

If your engine is still stock, no gain. Your forgetting that there are multiple sensors that measure air going in and burned/unburned fuel going out. This information is fed to the computer and it will compensate for too much fuel by reducing fuel injected. If the injectors are too large, the computer can't compensate enough and you will run pig rich and foul the plugs and eventually destroy your cat.

PatternDayTrader

Don't buy larger injectors thinking your going to gain anything. In all likelihood you will make your car slower. The stoichiometric air-fuel ratio must be maintained for proper performance. More fuel means you must have more oxygen for the proper air/fuel ratio to be maintained. Long story short; you need a bigger engine (or nitrous oxide) before you need bigger injectors.

antfarmer2

Unless you have other mods I would stick with stock. The computer will try to fix it and can be reprogrammed. They put a lot of work in this swapping parts you will most likely just mess it up.

John A. Marker

You need to do two (2) things to help us help you:

1) Fill out your profile with the year of the car.
2) Always include the year of the car in your post. It makes a BIG difference in our replies to you.

I went back to search some of your prior threads. I am under the impression that you have a 84 which has TBI injection....two injectors feeding what looks like a carb body. This form of injection has a low fuel pressure that maxes out about 14 PSI. Completely different injector than what is used for years 85 and newer.

Cliff Harris

Generally there will be no gain since the computer will compensate for the larger injectors. That said, the computer won't know you have larger injectors and will run rich while in open loop mode.

odxr

If the engine cant flow enough air to burn all of the fuel you will get nowhere.And it probably cant.With the prehistoric computor system in an old c4 It probaly cant correct for an injector change.Example-if the 12v on pulse to your stock injectors at idle is 8 milliseconds with a 22lb injector and you replace it with a 42lb injector from your friends wrecked mustang a 42 lb injector at 8ms will deliver almost double the fuel.The answer here is that usually the ecm is retuned to make the larger injectors work.Usually an injector is not worked past an %80 max duty cycle.Does the car have enough mods(built engine with lots of perf parts) to need a larger injector?It all gets back to engineering;There are websites on the net where you plug in the engine size/ # of injestors used and you will get a close caluculation of the. injector size you need.

John A. Marker

If the OP has a 84....all that has been said won't make much difference.

MrWillys

You only need larger injectors if you're going over 80% duty cycle. I get guys that run 36 lb injectors and their logs never hit 60% duty cycle at WOT and it makes it hard to get it to idle because the ECM can't shut off enough fuel. A 24 lb injector at 48 psi is good to 400 hp.
I think he has an 85 which is a 23.8 lb injector installed at 39 psi but rated at 43.5.