SC3800 - Part throttle KR with TCC locked

[scoob8000]

I've been seeing some KR in 4th with the TCC locked, pulling a grade around 60-70mph engine around 2000 rpm.

It shows up right around 4 pounds of boost. If you give it just a touch more throttle it'll unlock.

http://www.hptuners.com/forum/showth...l=1#post171463

This post sums it up perfectly, but I don't seem to have the modifier table Eddie talks about.

I have to pull just about all timing from the high octane table in those cells to make it happy.

Would it just be easier to change my 4th lock/unlock speeds to combat this?

[jtrosky]

This isn't directly realted to your issue, but on my 2012 Impala (3.6L LFX, 6T70 6-speed transmission), I found that I got a lot of KR when just cruising @ 47-50mph in 6th gear when the TCC was locked (which equals out to crusing at around 1200 RPMs). I did just what you are talking about and adjusted the TCC lock/unlock speeds for 6th gear so that it doesn't lockup until 54 is 6th gear (and unlocks at 51) - this way, I'm not "lugging" the engine during low-throttle cruising in 6th gear when the TCC is locked and keeps me slightly above the 1200rpm range where I was getting KR. So far, it seems to have worked - basically, I'm just avoiding staying at 1200RPM in 6th gear when the TCC is locked. I could also just shift into 6th at a higher speed to avoid the issue as well I guess.

Not sure if this is the right way to handle my situation, but it works for me.... Otherwise, I would have to lower the spark advance significantly at 1200 RPM even though it only causes KR when lugging in 6th gear with the TCC locked...

[scoob8000]

One other thing I really didn't notice either, when the engine is loaded like this my LTFT goes to around negative 18 or so. STFT's look fine.

Sadly I don't have any older logs to show if this has always been this way or not.

Would that mean a possble leaking injector and the PCM is leaning the rest of them out to compensate?

[5FDP]

I used to maybe see a degree or two when trying to go up a hill in 4th gear on the freeway, it's mainly because it's such a high load on the engine/trans. I always just let my foot off the gas to unlock it and get back in it to gain speed instead of trying to build boost while locked in 4th. Maybe because it see boost that it's trying to add fuel even though you arent in a PE situation.

[scoob8000]

I used to maybe see a degree or two when trying to go up a hill in 4th gear on the freeway, it's mainly because it's such a high load on the engine/trans. I always just let my foot off the gas to unlock it and get back in it to gain speed instead of trying to build boost while locked in 4th. Maybe because it see boost that it's trying to add fuel even though you arent in a PE situation.

So for now, I'd like to try to combat this by changing my TCC lock/unlock points. I know when I start seeing KR to react, but to anyone else driving and not paying attention..

So here's my table. It's stock:


These values don't match up to when my converter is locking and unlocking, unless I'm totally misunderstanding how it works.

For example, at or above 25% throttle it should lock at 60mph, correct?

Then for it to unlock it 60mph I need to push the throttle to 37.5%?

[jtrosky]

For what it's worth, on my 2012 Impala, I've found the the "Throttle" value in the transmission shift/TCC tables actually corresponds to the "Pedal Position" instead of the throttle position. Not sure if the same thing applied to your car or not, but maybe try seeing if things make more sense if you use the "Pedal Position" PID instead of the throttle PID for the trans table lookups...

Also, becuase you have the lookup speed set to 140 at 31.25% throttle, if you have the throttle at 28% (halfway betwwen 25% and 31.25%), it wouldn't lockup until 100mph (halfway between 60 and 140 mph). At 31% throttle, it won't lockup until about 140mph.

[scoob8000]

For what it's worth, on my 2012 Impala, I've found the the "Throttle" value in the transmission shift/TCC tables actually corresponds to the "Pedal Position" instead of the throttle position. Not sure if the same thing applied to your car or not, but maybe try seeing if things make more sense if you use the "Pedal Position" PID instead of the throttle PID for the trans table lookups...

Also, becuase you have the lookup speed set to 140 at 31.25% throttle, if you have the throttle at 28% (halfway betwwen 25% and 31.25%), it wouldn't lockup until 100mph (halfway between 60 and 140 mph). At 31% throttle, it won't lockup until about 140mph.

Mine isn't drive by wire, so just one sensor.

That's weird how it works. So the speed is a percentage based on throttle position? LOL I'm even more stumped now on what to adjust to make it unlock earlier in 4th.

[jtrosky]

It's not a percentage of throttle, but because you have the lockup speed set to 60mph @ 25% throttle and 140mph @ 31.25% throttle, the lockup speed between 25% and 31.25% throttle would be "scaled" between 60mph and 140mph. I hope that makes sense - that was a pretty bad description...

Basically, the throttle values "between" the throttle positions in the coumn headers, it will scale the speed appropiately.

Does that make any more sense? I'm struggling to put this description into words! :-)

[scoob8000]

It's not a percentage of throttle, but because you have the lockup speed set to 60mph @ 25% throttle and 140mph @ 31.25% throttle, the lockup speed between 25% and 31.25% throttle would be "scaled" between 60mph and 140mph. I hope that makes sense - that was a pretty bad description...

Basically, the throttle values "between" the throttle positions in the coumn headers, it will scale the speed appropiately.

Does that make any more sense? I'm struggling to put this description into words! :-)

Gotcha. I understand that now.

But I still feel like I'm being dumb on the unlock and how they're all set so low. So I take it, as long as I'm over those set speeds it should unlock at say 25% as long as I'm over 40mph?

[scoob8000]

Gotcha. I understand that now.

But I still feel like I'm being dumb on the unlock and how they're all set so low. So I take it, as long as I'm over those set speeds it should unlock at say 25% as long as I'm over 40mph?

Well believe it or not, I found the issue. I had a small exhaust leak between the head and the rear exhaust manifold. Replaced the gasket and that part throttle KR is gone. I was even able to put the timing in those cells back to stock.

All I can figure is the leak being in front of the o2 caused the fuel trims to get out of whack enough..

[jtrosky]

Hmm, I wonder if the exhaust leak was actually causing "false" knock? Nice find - glad that you resolved the issue!