What size injectors?

[jdhogg1]

My GN inspired me, so I'm putting a turbo on my 355 LT1 IROC. What size injectors should I run? I'm only going for around 550hp at 5lbs of boost. The turbo is a TO4B and I have DFI.

 

[bison]

42.5 lb injectors are plenty for 550hp on an 8 cylinder. You may want to leave a little more room and go with 50 or 60 lb/hr. Why are you shooting ofr such a conservative hp target? The TO4B is a dinosaur compared to whats available today. Id look for some newer technology and you could get a lot more out of it.

 

[Shaun Tiede]

30Lb will support that HP level.

Only wondering if you'll make that much power with only 5lbs of boost.

 

[FullAuto]

No way a 30lb injector would support that 550hp in the real world. Even with an FMU, you're just asking for a failure. At .55 BSFC, you'd need 100% duty cycle at 70psi to run a 30lb. Those will fail. At .55 BSFC and 85% duty cycle, you'd need to run 48psi to use a 42lb injector to support 550hp.

One thing to realize is most 42lb injectors are rated as Ford injectors at 38.5psi. Aftermarket brand injectors are rated at a higher pressure. So the real difference in a 42lb and 50lb injector is closer than the 8lbs it appears. So if you are wanting to go higher than a 42lb injector, go straight to a 55lb.

If it were me, I'd see the reailty of not sticking to 5psi for long and would go straight to the 55lb injectors. I thought I was buying a little too large when I went with 60lb injectors. The first pull on the dyno untuned they went 92% duty cycle at only 13psi of boost. I should have bought bigger.

 

[Shaun Tiede]

Ok. I stand corrected.
I gotta tell my brain to stop thinking N/A. Ha!

 

[GNsnake]

Get 60's

 

[bison]

Ok. I stand corrected.
I gotta tell my brain to stop thinking N/A. Ha!

NA or not you would still need at least 42 lb/hr on an 8 cylinder with a BSFC of .55. You would be lucky to squeeze 450fwhp out of 30's.

 

[bison]

Get 60's

60's could do 850hp easily and are overkill for his application. I would still use them as long as the cost was the same as smaller injectors.

 

[jdhogg1]

I have Ford 42's on it now, but the engine is a built 355 that's putting out 500hp as it sits. The compression is too high for anything more than 5-6lbs, but the cam is going to bleed some off. I just want to make sure I don't starve it and can change the compression/cam when I go through the engine later.