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Anyone upgrade they fuel injectors. Where can I get high performance injectors. I don't want Bosch but that is all I have been seeing. Any input would be awesome thanks. I drive a 2005 tj rubicon.
 

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Try 505performance. They deal with strokers and have lots of parts for performance on the 4.0 including injectors. Try eBay, at one point I found a set of 24#/hr ford motorsports for 125$ rebuilt and flow matched
 

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Changing the fuel injectors on a stock motor will gain you nothing but a lighter wallet.
Not true at all. The stock injector design is crap, they fire much like a squirt gun, chrysler used them because they were cheap. The four hole injectors fire a mist not a stream. Better fuel atomization means more power with less fuel. The more even the burn the less fuel that is wasted.
 

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Stock injectors work fine, installing so-called "performance" injectors that can flow more fuel will do literally nothing to improve performance in a non-heavily modified engine.

How can that be? Thank the computer and its partner the 02 sensor. When the 02 sensor says the air/fuel ratio is correct, the PCM shuts the fuel injector off. It keeps the injector on only long enough to achieve the correct air/fuel ratio.

So what happens with a fuel injector that can flow more fuel? The PCM shuts it off quicker.
 

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Increased flow rate provides no advantge. Improved spray pattern is another story.

I replaced the original injectors with Bosch 4-hole models. Major improvement in idle quality and acceleration.
 

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Jerry Bransford said:
Stock injectors work fine, installing so-called "performance" injectors that can flow more fuel will do literally nothing to improve performance in a non-heavily modified engine.

How can that be? Thank the computer and its partner the 02 sensor. When the 02 sensor says the air/fuel ratio is correct, the PCM shuts the fuel injector off. It keeps the injector on only long enough to achieve the correct air/fuel ratio.

So what happens with a fuel injector that can flow more fuel? The PCM shuts it off quicker.
I was told by 505 performance that the 4.0s a/f ratio is determined by the map sensor. One of the few engines that adjust pulse width based on manifold pressure/vacuum which is why strokers don't need an ecu reflash to achieve the proper air fuel mixture, just larger injectors. This is for the 96-06 engines. They sell adjustable fuel pressure regulators for the 87-95 models and air fuel ratio is adjusted with it. I do agree with the other posts that the 4 hole injectors will atomize the fuel for a more compleat and efficient burn. Not attacking you Jerry, just what I've heard
 

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Stock injectors work fine, installing so-called "performance" injectors that can flow more fuel will do literally nothing to improve performance in a non-heavily modified engine.

How can that be? Thank the computer and its partner the 02 sensor. When the 02 sensor says the air/fuel ratio is correct, the PCM shuts the fuel injector off. It keeps the injector on only long enough to achieve the correct air/fuel ratio.

So what happens with a fuel injector that can flow more fuel? The PCM shuts it off quicker.
We are not talking about more fuel, you are correct more fuel will do nothing. We are talking about spray pattern, we are talking about propagating the flame kernel. What catch's fire easier liquid or vapor or in this application mist. Think of it like this, if you dump gas on the ground and light it you will get fire, if you light fuel vapor you will get an explosion. What we are talking about here is a more complete burn with less wasted fuel. A better more complete burn with less wasted fuel = a greater level of efficiency which translates into more power, it's just that simple.
 

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tangofox007 said:
The map sensor does not determine anything. It is just one of many inputs used by the ECM to calculate and adjust the air/fuel ratio.
My understanding was when most engines base the air fuel ratio off the O2 sensors our 4.0s use mainly the map sensor
 

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My understanding was when most engines base the air fuel ratio off the O2 sensors our 4.0s use mainly the map sensor
The TJ's PCM uses input from multiple sources to determine the correct air fuel ratio including the MAP, 02, and IAT sensors. The MAP sensor has a major say in the fuel injector pulse width since it measures how much atmospheric pressure there is, but the 02 sensors also have a key role in setting the ratio, and even the IAT (temperature) sensor does since it tells the PCM how dense the air is since air density varies by temperature. So all of them have significant input on the air fuel ratio.
 
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