TCC Lockup While Coasting

[RonC]

Is there anyway to make the TCC stay locked when you let all the way off the throttle and resume crusing as in slower driving on hilly or curvy roads. It is annoying to have it unlocking and locking all the time and I want to keep it locked. I have not found anything in the program that will do it and have searched for info on this but found nothing. Anyone know how to do this or is it even possible?

Ron

[joecar]

Increase the MPH difference between these two tables (in each gear separately):
TCC->Apply->TCC Apply Speeds (D1001, D1002, D1003)
TCC->Release->TCC Release Speeds (D1004, D1005, D1006)

Make the release speed say 5 MPH lower than the apply speed for the same gear.

And keep these tables at 100% for each gear:
TCC->Release->TCC Throttle Release (D1007, D1008, D1009)

[RonC]

D1007-8-9 are all 100%. D1003 is 34 mph and D1006 is 22 mph. D1002 is 26 mph and D1005 is 21 mph. Is this what you meant? This works fine to keep the TCC locked as long as I have light throttle applied but if I let off completely it unlocks and when I resume it relocks. I believe this is normal, I just want it to stay locked. Am I missing something else?

[joecar]

Hmmm... my F-body stays locked during coasting until the MPH drops below the curve or the brakes are applied...

It could well be otherwise for different OS's or even for the 4L80E...

What model/year vehicle do you have...?

[RonC]

I'm sorry, it's a 2005 Silverado 1500 HD 6.0L 4L80E, OS 5120003c . My 2000 w/4l60E does the same thing. Do you or anyone else know what makes the F body lockup and why mine don't?

[joecar]

I'm sorry, it's a 2005 Silverado 1500 HD 6.0L 4L80E, OS 5120003c . My 2000 w/4l60E does the same thing. Do you or anyone else know what makes the F body lockup and why mine don't?I suspect there may be another set of parameters/tables, as of yet undiscovered.

[RonC]

Thanks joecar.

Is there any chance they might be discovered Ross?

[ChipsByAl]

While on the TCC subject, can the TCC WOT enable/disable parameters be added. Some vehicles have the converter upgraded and can handle the apply under these conditions. Some need it turned off.
Thanks,
AL

[RonC]

Mine will lockup under WOT when programed to. I discovered it by accident when playing with 2nd gear tcc tables.

[dc_justin]

I suspect there may be another set of parameters/tables, as of yet undiscovered.

I suspect that there are a number of TCC tables/parameters that are floating around in the PCM unbeknownst to us... This one, minimum ECT threshold for lockup, etc...

[RonC]

I suspect that there are a number of TCC tables/parameters that are floating around in the PCM unbeknownst to us... This one, minimum ECT threshold for lockup, etc...


Yes, it looks like it. That is the other one that I would like to be able to change. These are the main two that I want to work with but can't in tuning the trans.

[N0DIH]

On the LT1 (circa 1994-1995) it is simply a switch setting.

TCC RELEASE ON LOW TPS (on/off)
TCC RELEASE WITH RAPID TPS DECREASE (on/off)
DOWNSHIFT TURNS TCC OFF (on/off)

By default the LT1 PCM unlocks TCC on decel. You might be fighting this setting if it exists on the newer VCM/PCM's.

[oztracktuning]

Im interested in a solution for this also. It would help; keep the car in DFCO better when it has a aftermarket converter. Once the TCC unlocks the DFCO turns off as well.

[joecar]

Yes, it would be nice to have those parameters... and the other trans parameters. :)

[N0DIH]

That is interestesting, TCC unlocking turns off DFCO? It should not, TCC ~should~ be unlocked on decel.

The key I found is pushing the rpm down as low as you can, and watch the MAP pressure (again, frame of ref is 94 LT1). I could very closely predict the DFCO turn back on point when looking at the datalogs while driving. I don't know if I ever got it below 44 mph, as at that point I am very close to 700 rpm or so.

But there was a surge there that was a pain that I couldn't get out. My goal is being smooth and seamless despite the gains.

I honestly never saw any significant gains with agressive DFCO vs stock DFCO. So I pretty much went stock GM settings with a shorter timer.


Im interested in a solution for this also. It would help; keep the car in DFCO better when it has a aftermarket converter. Once the TCC unlocks the DFCO turns off as well.

[oztracktuning]

TCC has to be unlocked for DFCO otherwise the MAP will rise quickly to idle map and there would be no engine braking effect at all.

[11sprocket]

Surely it's the other way about. If the TCC stayed engaged, it would pull the revs up and drop the MAP.
What I find is that the TCC disengages on closed throttle and the revs drop lower than the 'synchronised' speed meaning they hit 800rpm at just over 40mph. Also, DFCO seems to deactivate at 800rpm even when B3318 is set much lower. :nixweiss: (One for the DFCO thread...)

[N0DIH]

I can say that when DFCO is active, MAP really pulls low. Now how low is dangerous to the engine? Moisture will boil at a lower temp, oil can much easier get sucked past the rings. IIRC, Jesse mentioned that DFCO has caused engine damage on race engines on the dyno after a WOT blast going fuel and broken piston ring lands. (Jesse can you elaborate the issues?). I think he said when you tear down the engine you will see a lot of piston damage.

So I am trying to figure out what other issues might be present. It seems that if you cut off fuel and still have enough air past IAC (throttle cracker?? Not sure, my LT1 doesn't have) would keep the MAP from going so low. I see on the order 10-15 kPa MAP at full DFCO. It is an awfully low vacuum, how hard is that on intake seals, head gaskets, rings, oil consumption, valve guides, valve seals, etc?

So aggressive DFCO may not be the best thing to push for...

I was able to push my DFCO down to around 600 rpm on the low end, much lower than that and it didn't matter, it still came back on anyway. Jesse said engine stall is a big deal to GM so they try hard to avoid it.

[oztracktuning]

Ive seen it stay locked a million times. DFCO is fine - almost no fuel = no heat. Far better to have DFCO activated as much as possible. Its just a matter of keeping it activated whne the brakes are on better :)

[RonC]

I can say that when DFCO is active, MAP really pulls low. Now how low is dangerous to the engine? Moisture will boil at a lower temp, oil can much easier get sucked past the rings. IIRC, Jesse mentioned that DFCO has caused engine damage on race engines on the dyno after a WOT blast going fuel and broken piston ring lands. (Jesse can you elaborate the issues?). I think he said when you tear down the engine you will see a lot of piston damage.

So I am trying to figure out what other issues might be present. It seems that if you cut off fuel and still have enough air past IAC (throttle cracker?? Not sure, my LT1 doesn't have) would keep the MAP from going so low. I see on the order 10-15 kPa MAP at full DFCO. It is an awfully low vacuum, how hard is that on intake seals, head gaskets, rings, oil consumption, valve guides, valve seals, etc?



I don't see any engine problems with extending the DFCO operating range. With DFCO enabled, there is no practical difference in coasting with the converter locked and coasting in gear with a manual trans which we've all been doing for years.

I would just like to have the option to keep the converter locked. My problem is that it is annoying to have it unlocking and locking all the time as I drive a lot of roads with many hills and curves.

[N0DIH]

I'll mess with it and see what my LT1 does on it. I can set mine easily to stay locked on decel.

I'll let you know what issues I see.

[N0DIH]

It is not cool to do... Drove it for 60 miles today (100 or so KM). It is ok on initial decel, but under a light resume to cruise or accelerate it has a rough bump and the dampers in the TC are taking a lot of loading. A heavier throttle apply unlocks the TCC quickly and this is ok.

And if you have DFCO setup, it can interfere in say 40-55 mph (65-90 km/h) at light throttle cruise where DFCO is kicking in and the car starts to decel and then throttle is applied when power is needed and the engage/decel gets rough. Not cool at least on my 5000lb/2200+ kg land yacht. I have 3.42's and 28in tall tires.

I don't recommend at all. I would bet TCC life would be greatly shortened.

IF you do not use DFCO, this is quite possibly tolerable, but I still think TCC life would suffer, I don't think the loads on it shifting from negative to positive are good at all.

[oztracktuning]

You need to tweak it and your DFCO timing tables to get it smoother .....it can be done.

[N0DIH]

I don't have much in the DFCO settings like the LS1. Mine are often simpler, but less options to choose from. So I can't vary much more than I already posted the screenshot (again, this is from the Corvette, but very very similar to my current settings)

I have set mine to 750 rpm disable, 950 rpm enable, and a 1.2 sec delay. Enable MAP at 26 kPa, disable MAP at 34 kPA. The only timing setting I have is ignition timing. I can set exit blending too, that is about it.

[Cablebandit]

i think its set to not stay locked on decel to let the revs fall down and save on gas.