This is topic HP AND INJECTORS in forum Tech Talk at Northern California Ford Owners  .


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Posted by Silver bullet (Member # 3240) on :
 
Hello everyone,

new to the site and hoping to get educated in are where I don't know JACK, and help people out in area that I do know.

Question: Due to recent mods that I have made I am trying to figure out what size injectors i should be running.

Now basicly i have 24lb injectors and want to know what is the max (plus or minus) HP I can run and still use 24lb injectors?

I am getting my car dyno'd soon. Will a dyno run show if my injectors are holding me back, or if they are not holding me back will a dyno run show me that I am near the end of what my injectors can handle

PLUS does 24lb injector put out more juice with a bigger fuel pump? Or is a stock fuel able to handle anything 24lb injector can toss out.

Finally what size injectors do 2003 cobra have?

Jason
 
Posted by st5150 (Member # 51) on :
 
Hi there. So your motor is an all motor SOHC 4.6L with ported heads? If so, 24 lbs injectors will be fine for you. I believe 2003 Cobras have 42 lbs injectors.
 
Posted by Red97SVT (Member # 2811) on :
 
24s should be plenty for just about any street driven, no power adder, 4.6 GT. I think there good for something like 400 hp unless you're boosted.

Boost increases the amount of air coming in so you need additional fuel to keep the AFR in check. Theoretically with 14 point something pounds of boost (an additional 1 atmosphere) you would need to double the capacity of the injectors to keep up. In reality they would need to be even bigger than 2x.
 
Posted by xchpstang (Member # 1206) on :
 
03 Cobras have 39lb/hr injectors. The formula goes like this: ((injector size*8)/.5)*.8)=max hp

The 8 in the formula figures you have an eight cylinder and the .5 is for the BSFC meaning your engine is tuned to run fairly efficiently. The .8 figures you'll be running at 80% maximum duty cycle so theoretically at 100% duty cycle you could squeeze a little more power out of the injectors although reducing the longevity of the injectors.

Example of maximum hp. of 30 lb injectors:

((30*8)/.5)*.8= 384 hp.
 
Posted by Chosen1 (Member # 1906) on :
 
Here is a good reference site for injector selection....

injector selection page
 




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