Troubles with scaled tune for 95# injectors

[mowton]

Not sure if this will help, but here is a worksheet I use to help in the scaling. It isn't perfect as far as user friendliness....but it works. As the file is too big, I renamed it with an .hpt file extension for upload. When you save it rename it with the .xls file extension and open as any excel file.

Ed M

[GNXClone]

Thank you Ed! I will definitely check it out.

[GNXClone]

I found a VERY strange issue this weekend. Apparently it was not my scaled tuning which was the problem.

I could get the car to start and idle. I had to press the accelerator to the floor to start it, but no big deal, I can tune that out later I figure.

The problem was, I would put it in gear and attempt to drive, and it would sputter badly, as if it were on a two-step. The WBO2 would swing wildly super rich to super lean, so I couldn't really tell if it was too much or too little fuel (though it smelled like too much). No matter what I did, I could not keep it from sputtering. Yet it idled smooth.

Finally fed-up, I blamed the FIC injectors, ripped the FICs out and put in some LS3/LS7 42# injectors. (The ZR1 52# injectors have not arrived yet). I then used a known good tune from my 60#'s, changed the injector parms to those from an LS7 tune, copied over the entire T42 transmission section because I just installed a 4L80e and had changed a lot of it. I also re-installed the stock MAF.

The car did the same damn thing, sputtered badly at around 1200 RPM. At this point, I guessed I had a wiring issue. Perhaps the engine would torque and cause an open or a short.

No DTC's were ever set BTW. I did notice that during the sputtering, the status bits indicated open loop and no fuel trim. As soon as the sputtering stopped, and the engine settled back to an idle, closed loop re-enabled.

I did find the crank sensor wire resting on the exhaust manifold and thought for sure I had found the cause. Nope! Fixed that, no change.

Then I thought maybe I had a bad transmission wire since I had to stretch the harness a bit to fit the 4L80e. I couldn't see any bad wires though. On a whim, I pulled the TCM fuse. The car stopped sputtering! Put the fuse back in, it sputtered again. I pulled and re-installed the fuse several times to verify and had the same results each time.

I installed a spare TCM, same results. So the TCM is good. I had built an adapter with two relays and some resistors to convert the 4L60e signals to drive the 4L80e. I removed my adapter, same results, so that was good.

Then I found that if I started the car, but left it in park, I could rev it to the moon without a problem. As soon as I put it in gear, and even if I put it back into park after going into gear, it triggered the sputtering. Definitely TCM related, but what?

As a last resort, I put the stock GTO tune in both the ECM and TCM with a Write Entire, with only the injector parms changed. I had to change my MAP back to a 1-bar since I was running the 2-bar OS previously. This made the problem go away! I could put it in gear and drive and no sputtering at all! It drove pretty well too.

Elated, I put the transmission changes I had made for the 4L80e back in, turned off the rear O2 codes, turned off P1870 diags, disabled catalyst test, etc.

The problem came back!

I was pretty certain by this time it had something to do with the transmission parms, so I put ALL of these back to stock and the problem went away again.

So far I have it narrowed down to either something in the SHIFT PROPERTIES tab, or the TORQUE MGMT tab. I've re-applied all of my other 4L80e settings except for those two tabs and the sputtering is not present. I will narrow it down to the specific item when I get more time.

If anyone would care to look and hypothesize as to what in one of these two tabs would cause the car to sputter at 1200 RPM, please feel free.

It seems to me that for some reason, after going into gear, the TCM sets a fuel cut in the ECM at 1200 RPM. Again, there are no DTC's set whatsoever during the sputtering..at least none that HPT can read.

42#_2 has the bad trans parms in shift props or torque mgmt and causes the engine to fuel cut at 1200 RPM, only after the trans is placed into gear one time, (and even if it is later placed into neutral or park).

42#_4 runs great!

[IDRIVEAG8GT]

What's your stall fuel cutoff rpm set at?

[GNXClone]

What's your stall fuel cutoff rpm set at?

I cannot find "Stall Fuel Cutoff" in my tune. Do you mean "Stall Torque Mgt"? If so, it is 8192 RPM Enable/8190 RPM Disable.

[IDRIVEAG8GT]

Perhaps that's the one. :/ man I'm racking my brains. The BCM is pissed from what I can tell. Need a Tech 2.

[gn2beatu]

For some reason on the one tune the torque reduction is greyed out, as in you cant select it. Wierd, I wonder if something got messed up during the read/write and it is activating torque management and pulling a crap load of timing or adjusting the ETC. Have you tried hand copying from the one tune to the other rather than copy and paste. It might be copying something corrupt. G/L and let us know if that helped.

[GNXClone]

Success!

I put the FIC 95's back in and changed out the transmission tables that I felt were causing the sputtering issue. I'm using my 50% scaled tune, with the MAF enabled to make it easier to start out.

The car is an animal! It'll go sideways from a 50MPH roll. The injector DC never exceeds 41%. So plenty of room for more boost and E85.

My setup is very similar to the ZR1, except I have turbos. I'm using the ZR1 timing tables. I used to have to add methanol to run 14 degrees at peak torque with the 11:1 compression of the stock LS2. This run had 20 degrees advance and zero knock on 93 octane (no meth) with 9.5:1 compression. (LY6 pistons) Glad I made the decision to lower the compression.

Overall I am very happy with the scaled tune now, and I haven't even dialed it in yet.

[mowton]

Sounds good....glad you got it sorted out

[IDRIVEAG8GT]

Success!

I put the FIC 95's back in and changed out the transmission tables that I felt were causing the sputtering issue. I'm using my 50% scaled tune, with the MAF enabled to make it easier to start out.

The car is an animal! It'll go sideways from a 50MPH roll. The injector DC never exceeds 41%. So plenty of room for more boost and E85.

My setup is very similar to the ZR1, except I have turbos. I'm using the ZR1 timing tables. I used to have to add methanol to run 14 degrees at peak torque with the 11:1 compression of the stock LS2. This run had 20 degrees advance and zero knock on 93 octane (no meth) with 9.5:1 compression. (LY6 pistons) Glad I made the decision to lower the compression.

Overall I am very happy with the scaled tune now, and I haven't even dialed it in yet.

Very nice!

[gn2beatu]

Congrats, I sure would like to know what that thing will run in the 1/4 some day when you get it dialed in on the E85. You should shoot me a PM with your tune when its done, as I am going to turbo my LS2 in the spring. Wouldnt mind seeing where you end up on the timing and fueling with the E85, as I was planning on the E85 too. I was thinking of the 103lb injectors, so let me know what boost you end up at and how much injector is left. G/L with the rest of the tuning.