higher flow injectors on stock engine

[bass_stalker]

what would happen if i ran injectors with a higher flow rate on a stock engine, stock rate is 22.5 lbs per hour, and the new injectors are 27lbs per hour.

long story short i thought i was getting the same flow as stock but with 4 holes instead of 1 for my 2000 jeep cherokee, what i ended up with was some Bosch ford mustang injectors that have 4 holes and flow at 27 pounds instead of 22.5

[crispy_chick3n]

simply put you will be burning more fuel per cylinder than you were before. i dont think that is quite enough of an increase to run e-85. im not too sure on the math of it, but i think it needs to be right around a 40% increase for e-85. you could take advantage of the larger injectors by somehow increasing the ammount of air getting to the motor, an example would be a ram air intake. if it is running rich, and you are getting shit for fuel milage you could always look into an aftermarket fuel controller. i might be completely wrong. the injectors might be spraying the same ammount of fuel since the computer would be controlling the spray.

[bass_stalker]

well the computer has an adaptive memory, i just dont know what all it changes, this is all i can find on it

This very simple procedure will Erase the “Adaptive Memory” stored inside the PCM and allow a new “Adaptive Memory” to be developed.

After performing this procedure the PCM will re-learn and store into Adaptive Memory your engines performance characteristics.

Please perform these steps exactly as they are written, in the order they are written. This will cause the adaptive memory in the PCM to be erased and cause the PCM to go into Fast Learn Mode adaptive mode.

Disconnect the battery terminals and touch them together for 30 seconds. (This is to discharge the PCM capacitors, which maintain the Adaptive Memory.)
Reconnect the Battery Cables
Turn Ignition Switch to the “On” position but DO NOT start the engine
Turn Headlight “On”
Turn Headlights “Off”
Turn Ignition Key “Off”

The PCM Adaptive memory has now been flashed, or erased from the PCM.

When you start the engine it will be running off a set of pre-programmed tables that come with the PCM from the factory.

When you get the engine up to operating temperature the PCM will start to collect data for the “Adaptive Memory”.

The PCM will collect data for Adaptive Memory for the first 50 Warm-up Cycles.

[crispy_chick3n]

adaptave memory is basically just the computer learning how you drive. adjusting shift points, setting fuel trims and other small tasks that make your car run to "the best of its ability" according to the PCM. as far as i know it doesnt have anything to do with knowing if there is a larger injector in the car. all it sees is that an injector is there and that it is firing when the pcm tells it to. to adjust for larger injectors you would need an aftermarket fuel controller that would be able to adjust the injector pulse width (how long the injector fires for)

[bass_stalker]

alright that makes more sense, i thought thats what it did stock, so i guess i'll have to return these injectors and try to find what i actually nedd

[Dman1320]

tbh, all its going to do is make the engine run rich, and get crappy gas mileage. unless your doing some serious engine mods to increase the amount of fuel needed, and theres nothing wrong with the stock injectors, i wouldnt bother changing them. itll take a bit more power production to make some 22lb injectors tap out and run out of fuel. the reason for that running rich is because in the computer, there is the inector pulse width, which determines how long the injector is held open. but that is based around that stock 22lb injector sizing. you go putting bigger injectors in without any form of tune adjustment, your just dumping in unnessecary fuel, since the bigger injectors are being held open for longer than they need to be to supply the needed fuel.

for the tl;dr section

bad gas mileage, rich running motor unless tuned, no point unless your planning mods to make a decent amount more power than the stock motor

[sully]

I am not sure about Jeep ECM's but I know from my limited tuning experience that your front O2 sensor will adapt fuel trims to maintain a preset air fuel ratio. The larger injector will flow more fuel but the ECM will compensate by reducing the time the injector opens. In stock form the ECM can only do so much but the two injectors are close enough in flow rates that it should be fine. Running rich is bad for fuel mileage and will kill your cats over time but is not harmful to your engine like a lean condition is.

[Rockford96]

the size injector makes little difference its how long the injector remains open for if you put a bigger injector in without a tune the computer will just leave the injector open for a shorter time to keep the fuel trim in the center unless you have supporting mods for bigger injectors like intake exhaust and a tune that will keep them open longer the computer will just shorten the pulse width. without a tune you will see very little difference in anything

[crispy_chick3n]

the size injector makes little difference its how long the injector remains open for if you put a bigger injector in without a tune the computer will just leave the injector open for a shorter time to keep the fuel trim in the center unless you have supporting mods for bigger injectors like intake exhaust and a tune that will keep them open longer the computer will just shorten the pulse width. without a tune you will see very little difference in anything

not entirely true. yes the pcm will adjust for a rich running condition, but it can only adjust so far. thats what long and short term fuel trim do, and they need to be able to move in case anything else causes a rich or a lean condition. with larger injectors the coumputer will see a rich condition and will try to lean it out by giving less fuel, until it hits its pre-determined stop value, then it cant adjust any more, possibly leaving a still rich condition, and possibly throwing a CEL. i have a very in depth knowledge of how the computers on a car work. took a 6 month course just on engine performance.

edit for weird wording

[OrionStang]

Just get the right part.