20155 SS Sedan Flex Fuel Issue - Negative Torque Reported (-640)

[J'S01SILVY]

I tuned a 15 SS Sedan about one year ago and the customer decided to go with a flex fuel kit. Prior to the flex fuel, the engine and trans drove fine with no issues.

I turned on the flex fuel and flashed in the new tune. No change in fuel composition. Flex fuel sensor was working and read 9.8% alcohol content and the stochiometric ratio changed. The engine ran perfectly fine. However, the transmission was not shifting properly (flaring). I attributed that to the negative 640 foot pounds of torque reading which was causing the transmission not to apply enough pressure during the shift.

I have attached two tunes and two logs:

Original Tune and Original Log
Modified E85 tune and Modified E85 log

Only changes were flex fuel changes and LTFT speeds.

Points in the log where reported torque was -640:

00:11:203 (drop from positive 207 ft lbs)
03:33:343 (drops from positive 207 ft lbs)


Has anyone experienced this issue before?

[07GTS]

both those tunes are identical with all flex disabled

[J'S01SILVY]

Thank you for taking a look.

When I renamed them I accidentally made a duplicate. See attached.

[07GTS]

still need to put some values in the sensor settings for the comp change put 2%, max ethanol % to 85, fuel system diag set to flex enable then set the flex sensor dtc's to mil on first error, maby a 0.05 in the delay and transition volume, also blend factor for the transient fueling ethanol need setting same as the spark blending, not sure about the torque value as the VTT tables dont even have those values in them, log engine torque as well see what thats doing, trans is showing as a manual in the tune but just the tab is set to auto and there are no auto tune with it so TCM was not read or its a manual with a old mechanical trans on it ?

[J'S01SILVY]

still need to put some values in the sensor settings for the comp change put 2%, max ethanol % to 85, fuel system diag set to flex enable then set the flex sensor dtc's to mil on first error, maby a 0.05 in the delay and transition volume, also blend factor for the transient fueling ethanol need setting same as the spark blending, not sure about the torque value as the VTT tables dont even have those values in them, log engine torque as well see what thats doing, trans is showing as a manual in the tune but just the tab is set to auto and there are no auto tune with it so TCM was not read or its a manual with a old mechanical trans on it ?

I will update the tables for the transient blend factor and flex fuel sensor. I'll do a log with those updates.

I read just the engine tune, so that is why there was not trans cal. It has a T43/6L80 in a factory application (SS Sedan).

Do you see anything that would cause the torque reading to read so negative?

[07GTS]

just read both as it dosnt cost any more then u can see what all the trans is doing might show something in there, there are no torque values i can see anywhere that goes that low, log all the engine torque and trans torque pids u see and then go for drive and when it plays up hopefully something will stand out, do read that trans tho as it could be something over there that its doing during a shift or something maby

[4wheelinls1]

just read both as it dosnt cost any more then u can see what all the trans is doing might show something in there, there are no torque values i can see anywhere that goes that low, log all the engine torque and trans torque pids u see and then go for drive and when it plays up hopefully something will stand out, do read that trans tho as it could be something over there that its doing during a shift or something maby

This is good advice. Never seen this before but set up the flex correctly first as the fuel content may not have altered but now the ecu can see it, the stock tune is not built for E10.std.hpt

Attached is a stock Australian Built Flex car you can get the Flex settings from.

[Denver]

Did you get it to work?

[Denver]

I am having the same issue, did anyone get it to work?

[hjtrbo]

Post up your tune. I'll take a look.