L67 Injector IFR help

[bilemke]

Regarding the sloped vs flat IFR table conversation, it is really quite pointless.. (well, at least we could say we are running in circles)

97-03 GTPs.. Same fuel setup. 97s (all I have seen) have stock flat IFR tables from GM. 98-03, all have the same stock sloped table.

So, same fueling parts, different style of stock table data. There has to be another factor in the tuning that accounts for it.

[krunchss]

I think they did it for overall better performance and, similar to what you said, to take better advantage of other multipliers in the PCM. Some we can see, some we can not. Maybe it's similar to what was posted earlier, IFR adjustment is a "coarse" adjustment while adjusting MAF / VE tables is a "finer" adjustment. Fewer MAF / VE table adjustments should result in smoother looking VE / MAF tables.

Oh well, if this topic generated this much talk with no definate answers I am thinking it's not THAT important to my boosted L36. I may tinker with a GTP bin someday, and if I do, I'll probably switch to the sloped IFR then as the sloped IFR likley has better results with the bins they are designed to be in.

Krunch

[5_Liter_Eater]

You got your answer back on page 1. http://www.hptuners.com/forum/showpo...5&postcount=14

Why there are two different cars with the same type of fuel system and one has a flat IFR and the other a sloped IFR I don't know but now you know the reason for a sloped VS: flat IFR and knowing is half the battle.


I'm out.

[99ssei]

Returnless fuel system=sloped IFR
Return fuel system (with a vacuum line attached to the regulator)=flat IFR

So if you know what type of fuel system your car has and what size the injectors are (as well as what pressure they were rated at) then you can determine whether to use flat or sloped and what numbers to use.

I have a 99 SSEi (L67) with a return fuel system and a FPR that has a vacuum line referencing MAP. My IFR table is sloped as is the 00, 01, 02 and 03 models....after reading this thread I'm so confused.

[passingpower]

Me too.
http://www.hptuners.com/forum/showthread.php?t=23979

[99ssei]

I was jut thinking....my vehicle's fuel system utilizes PWM (pulse width modulation). The PCM tells the fuel pump whether to pump low (ex. 20%) or high (ex 100%) depending on the needs of the engine. Whereas in non-PWM systems, the fuel pump is always operating at 100%.

I know that with the GTPs, there is an aftermarket fuel pump "hot wire" kit available to increase voltage to the fuel pump (Casper's). I tried this option, however, it did not work because of the fact I have PWM (pump would not work). Casper's tried developing a solution for me but could not. I wonder if this has anything to do with the sloping?

[passingpower]

I believe that to be the case.

In 2001 they stopped doing that – high speed all the time. But, they never updated the IFR table.
Assumed; the low vacuum slope of the IFR was to compensate for the “high” speed FP mode. The general slope of the IFR was to compensate for the 18 ga. Wiring.
I drive a 2001 with a pump rewire. Therefore I’ll use a flat IFR table.

Additionally, the more I think about this, I think GMPT scaled the whole table down to compensate for future clogging of the injectors as they age and get dirty. They just let the fuel trims make up the difference until the dirty injectors "catch up" with the table.

[krunchss]

Whoa, old thread bump. I never went back to read the whole thread again, but I now believe the ramped IFR may not be related to the type of fuel pressure system that's in the car. I tried ramping the flat IFR in my car once and basically found out that the PCM seems to only look at one cell in the IFR table. I can't remember which cell, likely the first or last cell. Basically I could not "rough" tune my trims using the IFR. Since then, I have been lucky enough for someone to make me a "Hybrid" bin by importing pieces of the L67 file into the L36 file using a hex editor. I can now run the ramped IFR, as well see boost on the 2-bar map I installed, as well as a few other things that should be benneficial to me that I can't recal right now :P

Krunch