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Old 02-01-2012, 01:55 PM   #1
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How to know if over working injectors?

I have an 86 GT stock with a turbo kit. I'm running 42# injectors, 255 fuel pump, 8psi of boost, pro m MAF for 42#, 10 degrease of timing and a burn chip for the A9L. In order to get my A/F right it needs over 60psi of fuel.... Is there something wrong?
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Old 02-01-2012, 03:32 PM   #2
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Re: How to know if over working injectors?

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Originally Posted by Lh3211986 View Post
I have an 86 GT stock with a turbo kit. I'm running 42# injectors, 255 fuel pump, 8psi of boost, pro m MAF for 42#, 10 degrease of timing and a burn chip for the A9L. In order to get my A/F right it needs over 60psi of fuel.... Is there something wrong?
Either your fuel lines or injectors are not moving the "volume" of fuel you need.
To lower the pressure you have to increase the volume to ensure the engine gets enough fuel.


There is a "Fuel Injector Sizing" link in the Useful Mustang Info sticky thread.


If you find that your injectors are sized properly, then you will likely need to upgrade your fuel supply lines and fittings.


I will be using 60 lb injectors, 1/2" ID fuel rails and an AFM 340 LPH fuel pump to feed my SC'd 306. I may still have to upgrade the lines from the engine to the tank to a larger size, depending upon how much power I make and the fuel needed to make it.
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Old 02-01-2012, 03:53 PM   #3
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Thanks for the info and link.

You think is safe for me to race the car like that? When I'm into it the wideband reads 11.7 and driving around its like 15.0 or higher.
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Old 02-01-2012, 04:19 PM   #4
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Re: How to know if over working injectors?

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Thanks for the info and link.

You think is safe for me to race the car like that? When I'm into it the wideband reads 11.7 and driving around its like 15.0 or higher.
The 11.7:1 is a tad on the rich side, but that is more desirable than too lean.
The 15.0:1 is a bit lean, but not way out of line.
Ideally you want a 14.7: ratio at idle and cruising.

Quote:
Originally Posted by AutoSpeed
A well-tuned engine used in normal road conditions has an air/fuel ratio that is constantly varying. At light loads, lean air/fuel ratios are used, while when the engine is required to develop substantial power, richer (ie lower number) air/fuel ratios are used.
Bosch state that most spark ignition engines develop their maximum power at air/fuel ratios of 12.5:1 - 14:1, maximum fuel economy at 16.2:1 - 17.6:1, and good load transitions from about 11:1 - 12.5:1. However, in practical applications, engine air/fuel ratios at maximum power are often richer than the quoted 12.5:1, especially in forced induction engines where the excess fuel is used to cool combustion and so prevent detonation.
There is no one air/fuel ratio where all emissions are minimised. At an air/fuel ratio of 14.7:1 oxides of nitrogen peak, while hydrocarbons and carbon monoxide (CO) increase substantially as the air/fuel ratio richens.
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Old 02-01-2012, 05:12 PM   #5
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Thanks good info, so for now I should be good then. I should be going to the dyno soon.
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