BadLtBlu99TA

iTrader: (9)

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

DrkPhx

iTrader: (15)

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.

BadLtBlu99TA

iTrader: (9)

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 ?

BadLtBlu99TA

iTrader: (9)

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

DrkPhx

iTrader: (15)

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.

DrkPhx

iTrader: (15)

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.

Doc99SS

iTrader: (2)

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.

405HP_Z06

iTrader: (11)

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?

BadLtBlu99TA

iTrader: (9)

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

BadLtBlu99TA

iTrader: (9)

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

405HP_Z06

iTrader: (11)

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.

Punky K

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.

pdxmotorhead

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