When are you guys making safley with 32lb injectors

I'm going to be doing a new h/c setup and shooting for around 420rwhp on motor and I was wondering if my 32lb injectors would be enough.

Injector size has to be based on flywheel HP, not on rwHP. Assuming your M6 has about 13% drivetrain losses, you will be shooting for 483 flywheel. Assuming a decent tune (0.465 BSFC), and limiting the injector duty cycle to 85%, you need an injector that can provide 32.7 #/HR at the pressure your fuel system operates at. A 32# SVO, rated at 39.15psi would provide what you need.... marginal, but they will work.

Injector size has to be based on flywheel HP, not on rwHP. Assuming your M6 has about 13% drivetrain losses, you will be shooting for 483 flywheel. Assuming a decent tune (0.465 BSFC), and limiting the injector duty cycle to 85%, you need an injector that can provide 32.7 #/HR at the pressure your fuel system operates at. A 32# SVO, rated at 39.15psi would provide what you need.... marginal, but they will work.

Last time I checked my fuel pressure it was ~50 with the vacume line connected and ~55 with it disconnected. I guess I'll keep my 32's in and see how it does, worst case I'll buy a set of 36's.

I've got 32lb injectors at stock fuel pressure in my mild 383. My injector duty cycle peaks at about 74% with the current setup. I don't know how your setup compares, and I don't have any dyno time on mine yet, so I don't know how useful that info is to you.:)

I've got 32lb injectors at stock fuel pressure in my mild 383. My injector duty cycle peaks at about 74% with the current setup. I don't know how your setup compares, and I don't have any dyno time on mine yet, so I don't know how useful that info is to you.:)

Thats some promising info, I was going to go with the AI 200 CC h/c package, now I'm leaning towards the TEA TFS heads, 317 cfm is :bow:

Well I did some calculations with my scanmaster and injector pulse width and I'm not even at 50% with my 32lb injectors making 375rwhp, so I should be fine with 420+rwhp, atleast I think I should be. I'm getting ~340 grams/sec on my MAF at the the shift point too, so I don't know how that calculates out.

Well I did some calculations with my scanmaster and injector pulse width and I'm not even at 50% with my 32lb injectors making 375rwhp, so I should be fine with 420+rwhp, atleast I think I should be. I'm getting ~340 grams/sec on my MAF at the the shift point too, so I don't know how that calculates out.

Are you sure you used the formula I gave you for duty cycle correctly? There is no way a 32# injector, even running at 55psi (=38#/HR) can produce a DC of less than 50% at 375rwHP. Pick a ridiculously low BSFC like 0.400 #/HR/HP (NASCAR level), and you get:

375rwHP / 0.83 = 431 flywheelHP

431 HP X 0.400 BSFC = 172.4 #/HR

172.4 #/HR / 8 injectors = 21.55 #/HR

21.55 #/HR / 0.50 DC = 43.1 #/HR

A 50% DC would require a 43.10#/HR injector. With a "good" tune you'll be running 0.44 BSFC, and that means you would need a 47.4 #/HR injector to stay under 50% DC.

Or, to put it another way, at 6000rpm, you would have to be seeing an injector pulse width of 10 mSec or less.

Are you sure you used the formula I gave you for duty cycle correctly? There is no way a 32# injector, even running at 55psi (=38#/HR) can produce a DC of less than 50% at 375rwHP. Pick a ridiculously low BSFC like 0.400 #/HR/HP (NASCAR level), and you get:

375rwHP / 0.83 = 431 flywheelHP

431 HP X 0.400 BSFC = 172.4 #/HR

172.4 #/HR / 8 injectors = 21.55 #/HR

21.55 #/HR / 0.50 DC = 43.1 #/HR

A 50% DC would require a 43.10#/HR injector. With a "good" tune you'll be running 0.44 BSFC, and that means you would need a 47.4 #/HR injector to stay under 50% DC.

Or, to put it another way, at 6000rpm, you would have to be seeing an injector pulse width of 10 mSec or less.


I ran it up to 6500 RPM's and the right and left bank never got above 9mSec :confused: I did it a few times too just to be sure.

Defies all logic.

Defies all logic.

Do the scanmasters read injector pulse accuratly? I'm 100% sure it never went above 9mSec.