When are you guys making safley with 32lb injectors

[speed_demon24]

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.

[Injuneer]

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.

[speed_demon24]

Originally Posted by Injuneer

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.

[Dave '97 Z28 M6]

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.

[speed_demon24]

Originally Posted by Dave '97 Z28 M6

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

[speed_demon24]

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.

[Injuneer]

Originally Posted by speed_demon24

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.

[speed_demon24]

Originally Posted by Injuneer

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 I did it a few times too just to be sure.

[Injuneer]

Defies all logic.

[speed_demon24]

Originally Posted by Injuneer

Defies all logic.

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