When tuning to use FAST 33lb Fuel injector , how close to maxed out will they be ???

 

Those are small injectors for a 402 setup. I run the Lucas/Delphi 42lb injectors with the fuel pressure set at 61 psi and I see 77-80% duty cycle at WOT.

 

so there for i will be just about 100% maxed out at WOT ? how do you figure out the mathmatical equation for the right fuel injectors you need ?

 

have you upgraded your fuel lines ? fuel pump ? and regulator ? what should i get here ? IM sure my fuel lines and fuel pump will have to be upgraded too

 

Besides the injectors the only parts of the fuel system I upgraded was a Racetronix fuel pump and Aeromotive fuel pressure regulator. The fuel lines and rails are stock.

 

I don't know about being 100% but I'm sure with those small injectors you will be close. There is a formula that can help calculate fuel system requirements, but I don't have it. Try the fuel section.

 

The equation to calculate the flow rate due to fuel rail pressure change is:

new flow rate = old flow rate * SQRT(new pressure/old pressure)

For example, 33#/hr injectors @ 45psi, will flow what @ 58psi:

new flow rate = 33.0 * SQRT(58/45)
new flow rate = 33.0 * 1.135
new flow rate = 37.5 #/hr

I thought that I was cutting it close with FAST 36#/hr injectors that I purchased. I am only guessing, but I would think that you will be 100% DC at WOT. (36#/hr @ 45psi = 40.8#/hr @ 58psi)

When I'm done with my SD tuning, I will run my engine above 6,000 RPM and be data logging. I can give you a better answer then concerning my DC.

 

Which FAST injectors are you asking about? What is the part number on the injector?

FAST doesn't have a 33lb injector, they go 24,36,42,55,60,65,83,95,160 lb/hr. Are your injector bodies white in color?

Edit: They do have a 33lb/hr injector specifically for the LS2. Is this what you have?

 

Yes i have the specified Fast 33lb fuel injector part # 30332-8 they say they are 33lb/hr , 346.5cc/min

 

people here are confusing me .. alot of people say these fast 33lber will work , but then i got the others that say i will need 36lb or 42lbers

 

Lets look at the problem and do our best to arrive at an accurate answer.

Assumptions:
1. Naturally aspirated 402 ci engine
2. 525 BHP peak
3. 6000 RPM HP peak
4. BSFC of .46
5. Proposed injector size: 33 lb/hr @ 4 Bar

With these assumptions, you will be at around 91% duty cycle using the proposed injectors. You would need a minimum of 38 lb/hr @ 4 Bar injectors to stay under 80% duty cycle.

See the calculation below:


If you disagree with any of the calculation please let me know and I'll correct it.

 

On hp tunner mine maxed out at 100. Which was not enough for me cause my speed was only at 90% and it had plenty more to go but I was maxed out so upgrading to 45pounds on injectors that should give it enough go.

 

I have injectors off a L59 flex fuel they are 39 lb suposedly.. But the supply pressure does make a difference