Tuning '94 chev Suburban Big Block

[rsicard]

Really enjoy reading the post by 95GMC_sierra. It is very interesting. Have put my 454 suburban TBI to PFI Edelbrock conversion on the back burner. Right now concentrating on the 1995 Chevrolet C1500 pickup with 350 V8 to be swapped out for 350 Vortec with 454 throttle body. May just end up putting higher pressure capable in-tank fuel pump and use 94-95 TBI two original refurbished injectors. Then tune 16197427 ECU for this combination. Just need the appropriate TBI fuel regulator spring for the higher pressure.

[rsicard]

Gentlemen:

Would like to resolve the TBI to MPFI (batch) injection situation wherein jumpering from 2nd DRP to 4th DRP. Going back to March of 2013 the following was posted:

"Mod'd the 16197427 ECU. Put jumps across the two current sense resistors. Also put a jumper on the Memcal per the photo from HP tuners. Installed the ECU in the Suburban and started it up. Wow does it run shitty. Shut down the truck, removed the ECU, opened it up and removed the Memcal jumper, re-installed it in the Suburban. Ah, back to running smooth. Don't know the pin layout of the Memcal so I will stay away from jumpering it for now. Set up TunerPro RT to record BLM values at idle and off idle. Open loop at idle, it fills the BLM cells with 128. Set up TP to record off idle BLMs. Ran the Suburban for several miles to warm it up, varied the speed, RPMs, gears to fill in as much of the off idle BLM cells as possible. Then came back and parked at the house. Went back to idle BLM map, varied throttle to fill in as much BLM cells as possible. Captured all with MS Excel spreadsheet."

Getting better at tuning GM TBI 7427 ECMs. Trying to reason what happened when going from 2nd DRP to 4th DRP. Wow dId it run shitty. Must have been too lean? Still trying to figure out why it would run lean.

Any ideas you fellows? Please advise. Thanks.

Rolly

[dave w]

I've done a couple MPFI conversions, admittedly with SBC's, using the Memcal jumper. I also removed the sense resistors inside the PCM and installed solid wire were there resistors used to be installed.

Maybe the attached .pdf files will help you set up the .bin file for MPFI? I converted the excel spreadsheet I used to modify the .bin files into .pdf files.

dave w

[rsicard]

Dave:

When you converted to MPFI (batch fire) from TBI and installed the jumper of the MEMCAL, how much change, in engine running quality and, did you have to make to the off idle fuel map? The way it happened for me is that the engine ran rough. Did not have an AFR setup so don't know what happened. Will repeat with AFR setup to get clue as to what is happening. Any experience that can be shared would be greatly appreciated. Thanks for your response.

Rolly

[dave w]

I use an Excel spreadsheet to "Crunch" the data log to correct the AFR's, see attached.

I went "All In"; I modified the memcal, .bin file, and PCM resistors before I started the engine for the first time. I then went to work on the tune immediately after the initial start up.

dave w

[1BadAction]

I went "All In"; I modified the memcal, .bin file, and PCM resistors before I started the engine for the first time. I then went to work on the tune immediately after the initial start up.

dave w

I agree brother, not like you can easily (mechanically) go back to TBI anyways, I don't see why anyone would want to play "just the tip" with this particular conversion. I was going to get a second computer and memcal to do this myself, but then after a few minutes of thinking about it, it hit me... WHY? If I have the kinda time it takes to go back to the TBI intake, then I'll have the truck parked and enough time to convert the ECM back also. Hell the ECM changes are the fastest out of the whole ordeal.

Watching this thread myself, I have about 90% of what it takes to do the conversion on my Suburban. Just need to find the proper RP/Mercruiser injectors and a few other chicken shit items so I can get this thing back together in a timely manner. I hate letting a vehicle sit an extended period of time.

[rsicard]

Dave:

1) Trying to understand the MPFI Definitions v4_0x and how to interpret or make sense of them.
2) When going from 2nd DRP to 4th DRP with the same VE fuel map, that should yield half the fuel to the engine thus a lean mixture. Or, is there a compensating factor hidden somewhere, wherein VE map fueling remains the same?
3) Is the MEMCAL almost totally for limp home mode?
4) When you went from 2nd DRP to 4th DRP on 350 engines, was there something else significant to VE map that changed?

Please advise. Thanks.

Rolly

[rsicard]

Dave:

When going from 2nd DRP to 4th DRP on the SBC engines, was it necessary to adjust fuel pressure or change injectors to a different size? Still seems like it would try to run very lean if the jumpers to MEMCAL and resistors WERE the only change. VE fuel map change? Any other changes?

Please advise. Thanks.

Rolly

[dave w]

Dave:

When going from 2nd DRP to 4th DRP on the SBC engines, was it necessary to adjust fuel pressure or change injectors to a different size? Still seems like it would try to run very lean if the jumpers to MEMCAL and resistors WERE the only change. VE fuel map change? Any other changes?

Please advise. Thanks.

Rolly

I modified the .bin file (CHIP) for MPFI, installed the Memcal Jumper, removed the sense resistors and installed wire were the resistors were.

Maybe you can post the .bin file you modified for MPFI? I'm wondering if maybe there is something missing / not modified in your .bin file?

dave w

[rsicard]

Dave:

The most important question is, WHAT in the .bin file was changed for MPFI?
Attached is my binary file for 1995 C1500 350 TBI 7427 0D BJYM. Found the constants for MPFI and TBI lb/hr fueling.
How is the appropriate on (MPFI) selected? Is this done with the FLAGS section, see attached?

[dave w]

It appears to me the posted .bin file has not been set up for MPFI. Maybe this is not the .bin file you modified for MPFI?

My previous post, with the .pdf files, outlines which Flags, Constants, and Tables in the .bin file must be modified for MPFI.

I think you need to do some homework modifying your .bin file.

dave w