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post #1 of 5 Old 01-24-2008, 04:42 PM Thread Starter
Hot Sauce
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Fuel Injectors

Does anyone know the lbs./hr. rating of stock 2.5L fuel injectors?

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post #2 of 5 Old 01-24-2008, 05:21 PM
Jerry Bransford
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No but if you're thinking of installing higher flow injectors, don't bother. The ECM (engine computer) will cut the FI pulse duration length so the same amount of fuel will get into the combustion chambers no matter how much the injectors are capable of. The ECM wants a specific air-fuel ratio and it'll do whatever it takes to achieve it.

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post #3 of 5 Old 01-24-2008, 08:56 PM Thread Starter
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Quote:
Originally Posted by Jerry Bransford
No but if you're thinking of installing higher flow injectors, don't bother. The ECM (engine computer) will cut the FI pulse duration length so the same amount of fuel will get into the combustion chambers no matter how much the injectors are capable of. The ECM wants a specific air-fuel ratio and it'll do whatever it takes to achieve it.
Actually I wasn't looking to upgrade, just wanted to know. That's good info though. Thanks
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post #4 of 5 Old 08-07-2010, 03:43 PM
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Quote:
Originally Posted by Jerry Bransford View Post
No but if you're thinking of installing higher flow injectors, don't bother. The ECM (engine computer) will cut the FI pulse duration length so the same amount of fuel will get into the combustion chambers no matter how much the injectors are capable of. The ECM wants a specific air-fuel ratio and it'll do whatever it takes to achieve it.
Question Jerry? Why are the guys reporting more power? I have also seen dyno's with 99+ intake and injectors that show more power too? Confused.

'97 Cherokee, 99+ intake, 62mm TB, 703 injectors (new), k&n intake, Hypertech III, 180* stat (1/8" drilled hole), 2.5" manifold 2 tail pipe (Hooker Maxflow & hi flow cat), Perf header, 4.5" zone lift, 32" GY Dura Trac, Rear head rests. Comp cam "231" & Perf head (LS1 BIG valves 2.02/1.62). 3 row alum radiator.
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post #5 of 5 Old 08-07-2010, 04:01 PM
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Quote:
Originally Posted by Jeeper_YJ View Post
Question Jerry? Why are the guys reporting more power? I have also seen dyno's with 99+ intake and injectors that show more power too? Confused.
Test results are mixed on the old vs. new style air intake manifold. And seat-of-the-pants reports on any performance mod are usually highly affected by the placebo effect. Some dyno tests say the different shaped manifold helps, other dynos say it doesn't. I personally don't feel any difference between the power produced by my '04 with the newer rounded manifold vs. my '97 that had the older squared off intake manifold.

And so far as the injectors go, a stock engine isn't going to respond to a different injector with more flow capacity for one reason.... because the computer adjusts the pulse width (spray duration) going to the injector to assure it only sprays exactly only the amount of fuel the computer requires to achieve the required air-fuel ratio. If the injector has more flow capacity, the computer will shorten the pulse width duration so it doesn't spray for as long. That is how the computer is able to keep the air-fuel mixture right where it wants it. The only way to get it to start spraying more fuel is to force more air into the air intake and the only way you'll do that is with something like a supercharger or turbocharger.

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