Injector constant

[TheApocalyptican]

I'm using a 7427 in my 454 suburban. Has a cam now and I am running the earlier big block injectors. My calculated flow rate in lbs/hr is 126.3 (off of memory, it's somewhere right around this though). With this set here which is almost double to stock setting, what effect will this have on the ve table before any tuning? Will this make it run richer or leaner than if I left it at the stock 62ish setting? Trying to get a good idea on how the injector constant actually effects the fueling in order to begin setting up the tune before data logging.

[dave w]

The thought that comes to my mind is Base Pulse Width (BPW). If an engine is running 6000 RPM's the EFI system will "Turn On" the injectors for a very LONG time or a very LONG BPW. If an engine is running 600 RPM's the EFI system will "Turn On" the injectors for a very SHORT time or a very SHORT BPW.

The confusing things about injector flow rates"
What an injector is rated to flow?
What an injector is ACTUALLING flowing?
Injector Flow Rate programmed into the CHIP?

The answers to the questions above is often . . . all three are different.

In a perfect world, the injectors will actually flow 126.3 lbs/hr with the chip programming of 126.3 lbs/hr will be perfect so the VE table would be perfect. It's not a perfect world, so we tune.

If for example the injector flow rate was changed to 136.3 lbs/hr the computer will REDUCE the BPW which will LEAN the entire VE Table.

If for example the injector flow rate was changed to 116.3 lbs/hr the computer will INCREASE the BPW which will RICHEN the entire VE Table.

dave w

[Kilroy]

I ran across this site for calculating flow rate https://www.witchhunter.com/injectorcalc1.php

[Dieselsj]

Early big block injectors are 91lb/hr at 13psi. You are maybe 30% higher, not double.

Note the factory BPW setting (at least on my 7747 factory tune) works out to actually 83lb at 13psi when I plug the values into the BPW calculation formula.

[dave w]

Link to gearhead-efi TBI injector flow rates: http://www.gearhead-efi.com/Fuel-Injection/showthread.php?81-GM-Injector-size-color-and-part-numbers

Injector part #17104288 - Pink / Purple - 46pph @13psi - 7.4L / 454 - 94-95 *NOTE: Came with 30 PSI regulator used @ 26-32psi for 67-72pph

dave w

[Dieselsj]

Link to gearhead-efi TBI injector flow rates: http://www.gearhead-efi.com/Fuel-Injection/showthread.php?81-GM-Injector-size-color-and-part-numbers

Injector part #17104288 - Pink / Purple - 46pph @13psi - 7.4L / 454 - 94-95 *NOTE: Came with 30 PSI regulator used @ 26-32psi for 67-72pph

dave w

He said he was running the earlier injectors so I based my post on that.

[dave w]

He said he was running the earlier injectors so I based my post on that.

The gearhead-efi link was for TBI injector flow information only, not intended for any other purpose.

dave w