Injector Scaling on a 2002 LM7

I have a 2002 Chevy LM7 using the factory P01 PCM in a 1994 Chevy truck using HPTuners for tuning. I replaced my stock 25lb injectors with a set of 36lb Flex Fuel Injectors.

The 2002 file had 25.2 in the Flow Rate vs. KPA and the 2005 file for the Flex Fuel Injectors starts at 35.4 at 0 KPA and goes up to 38.4 at 80 KPA.

I took the injector data from the stock 2005 Chevy Avalanche Flex Fuel file which varies the injectors vs the KPA. I read somewhere that with a vacuum referenced fuel pressure regulator, which I am running the 2002 factory FPR with the vacuum reference that I should be looking at the 0 KPA column of the 2005 file to fill my injector data for my 2002 file which I did not do. I made it just like the 2005 Flex Fuel file. Should I have used what I described above with the 0 KPA column?

I notice when you get injector data from Injector companies they always mention the LS1, LS2, etc and it varies the injectors for the Flow Rate but they don’t seem to mention LM7 trucks engines.

Thanks

Scott,

Copying known good data from an OE cal with the injectors you'll be using is a smart move.

Can you post pics of what you're seeing? I think that would help clarify your question so we can best answer.

Attached are two pics of the Injector Flow Rate vs. KPA.

I currently have a return style fuel rail with the factory FPR with a vacuum reference. I don't know if the 2005 Chevy Avalanche, which I'm pulling my data from has the same. This is for a gen 3 P01 PCM.

Thanks

Thanks Scott.

Generally if the system is return style with vacuum reference, it will be a 1:1 reference of fuel pressure to intake manifold pressure. That will result in no change in injector flow, as intake manifold pressure changes, because as one goes up so does the other, as one goes down so does the other, so the differential pressure across the outlet of the injector remains constant, and the flow remains constant. In that scenario you get data like the table you posted where all values are the same, labelled 25 lb injectors.

The other table labelled flex fuel injectors shows an increase in flow with an increase in intake manifold vacuum, or put another way, an increase in flow as the pressure in the intake manifold decreases, causing an increase in differential pressure as the injector flows fuel outward. This is indicative of a system without a 1:1 manifold referenced fuel pressure regulator.

If you're putting the flex fuel injectors into the manifold referenced vehicle, you use only the value shown at 0 manifold vacuum, and apply it to all cells.

There is a caveat though. Base fuel pressure may be different between the two vehicles, and that impacts injector flow as well. If that ECU doesn't have another table which accounts for fuel pressure changes, and a sensor to monitor it, which I don't believe yours has, then you'd have to alter the flow rate data in the vacuum reference table IF and only IF the base fuel pressure differs between the vehicles. If they both use base fuel pressure of 58 psi for example, then you can transfer the value unaltered, and apply the 35.4 value as is.

Thank you Mike for the information and the explanation. This helps a lot.

You're very welcome.