Fuel injectors question
10-28-2009, 06:11 PM
#1
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Fuel injectors question
You ever notice that after you hear something enough part of it makes sense.
Some of the "guys" at local car gatherings know more about Mustangs than anyone on here (I'm being sarcastic!). I hear over and over that I need to replace my stock injectors with larger ones. Their theory is, the more fuel that gets to the engine, the faster it will run. My theory is....it's kinda like filling a bucket with water, when the bucket is full, its full, no matter how large the hose is that the water comes out of!
By the way, I have no major mods, except for the typical JLT CAI, custom tune and gears.
This larger fuel injector thing just doesn't add up to me...
Scott
Some of the "guys" at local car gatherings know more about Mustangs than anyone on here (I'm being sarcastic!). I hear over and over that I need to replace my stock injectors with larger ones. Their theory is, the more fuel that gets to the engine, the faster it will run. My theory is....it's kinda like filling a bucket with water, when the bucket is full, its full, no matter how large the hose is that the water comes out of!
By the way, I have no major mods, except for the typical JLT CAI, custom tune and gears.
This larger fuel injector thing just doesn't add up to me...
Scott
10-28-2009, 06:25 PM
#2
5th Gear Member
Join Date: Jul 2009
Location: Delaware
Posts: 2,215
After market fuel injectors generally add more precision in fuel release (which doesn't matter to a stock or even slightly modified car) and are generally larger, which allows more fuel to be pumped.
Where you really need them is in boosting. If you're not boosting or have seriously changed some internals then you don't need to. Your analogy works both ways though. While you can only fill it till its full, you also need to make sure you're getting enough fuel in there in the allotted amount of time before the spark fires. When you boost and engine, you are increasing the pressure at which combustion takes place. This allows more air in to the cylinder, with that increase you want to make sure that you have an equal increase in fuel to burn with it, otherwise you will get engine lights and it will tell you there isn't enough fuel in the mix.
Every super/turbo kit should come with new injectors and depending on your set up, size, and pressure you will need a certain sized injector to keep up with the needed output of fuel.
In short, I don't think in your current state you will see much of a gain in HP, if anything you will see a drop in mileage and probably carbon build up on your exhaust tips.
Too little and your lean, too much and your rich (or worse, flooded - which on an injected engine your really have to work hard to do)
Where you really need them is in boosting. If you're not boosting or have seriously changed some internals then you don't need to. Your analogy works both ways though. While you can only fill it till its full, you also need to make sure you're getting enough fuel in there in the allotted amount of time before the spark fires. When you boost and engine, you are increasing the pressure at which combustion takes place. This allows more air in to the cylinder, with that increase you want to make sure that you have an equal increase in fuel to burn with it, otherwise you will get engine lights and it will tell you there isn't enough fuel in the mix.
Every super/turbo kit should come with new injectors and depending on your set up, size, and pressure you will need a certain sized injector to keep up with the needed output of fuel.
In short, I don't think in your current state you will see much of a gain in HP, if anything you will see a drop in mileage and probably carbon build up on your exhaust tips.
Too little and your lean, too much and your rich (or worse, flooded - which on an injected engine your really have to work hard to do)
Last edited by JCON; 10-28-2009 at 06:27 PM.
10-28-2009, 07:11 PM
#4
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Location: Hawaii
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stock injectors will take you for a good pit of power
when I supercharged my 5.4 3v, I was able to use my stock injectors for 6 psi. I know many guys running 450 RWHP with those motors and still running stock injectors and 10 psi.
it just depends on the flow capability of the ones you have. bigger doesn't always = better. if the motor can't utilize it, you are just wasting gas
when I supercharged my 5.4 3v, I was able to use my stock injectors for 6 psi. I know many guys running 450 RWHP with those motors and still running stock injectors and 10 psi.
it just depends on the flow capability of the ones you have. bigger doesn't always = better. if the motor can't utilize it, you are just wasting gas
10-28-2009, 08:10 PM
#5
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Location: Oregon
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The above information is great. Something to keep in mind is that engines operate using a certain fuel to air ratio. Unless you're running lean, adding more fuel is going to do nothing for increasing power, and can actually decrease it. As mentioned above, bigger injectors are often needed for forced induction because you start reaching the limit of what an injector can supply. A good way to measure this is based on injector duty cycle. If an injector has to remain open more than 70-80% of the time to supply an engine with the fuel it needs, it's time for bigger injectors.
But let them waste their money. It would probably blow their minds to find out that bigger injectors in an otherwise stock setup do nothing. In many people's minds, money spent automatically equates to power gained.
But let them waste their money. It would probably blow their minds to find out that bigger injectors in an otherwise stock setup do nothing. In many people's minds, money spent automatically equates to power gained.
Last edited by siggyfreud; 10-28-2009 at 09:04 PM.
10-28-2009, 09:23 PM
#7
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Location: Pell City, Alabama
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