This question was a toss-up between Tuning and Transmission, and this section won.
Basically, I'm finalizing the transmission settings for my '97 2.2, 4-speed Auto Cavy using HPTuners. One of the things I've changed is the settings for the TCC (Torque Converter Clutch, or "lock-up converter"). I noticed that by default, the car is programmed to only to engage the TCC at highway speeds. This makes a certain amount of sense.
About 90% of my driving is at city speed, so I decided to try out a configuration where the TCC comes into play at lower speeds. With some tweaking, I've got it so that the car will lope along at low RPMs through city streets. This seems like it would be more economical, and the car doesn't seem bothered or labored. It only engages at low throttle of course, and disengages quite smoothly when required.
My real question is whether I'm asking for trouble with this. Obviously the TCC will see more use (and possibly abuse) this way, and GM probably kept it disabled at lower speeds on purpose. I don't fancy costly repairs, but I do like how it runs with it engaged. Any opinions?
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For anyone that might wonder, I ended up leaving TCC off during lower speed driving. The engagement was a tad intrusive and harsh at these speeds, and I remained concerned about the wear and tear issues.
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i wish i knew more about auto transmissions and Torque converters.... what does all this mean? what is tcc? is there a way to change this on my DD that will improve gas milage? is there any way what i just said wont make me look like some n00b kid (probobly not)
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Mike wrote:The auto to manual swap is not as involved as you would think.
Get all the parts you need in a pile, and drive the car into it.
They will find their way into the correct places.
Pozr wrote:i wish i knew more about auto transmissions and Torque converters.... what does all this mean? what is tcc? is there a way to change this on my DD that will improve gas milage? is there any way what i just said wont make me look like some n00b kid (probobly not)
In an automatic transmission, the "torque converter" is a device uses a layer of fluid to transmit power from the engine to the gears and driveline. This is a non-direct link, which always allows some amount of slippage. On this upside this results in a smooth transition between gears, and the automatics are less prone to failure through excess power or wear and tear. On the downside, the slippage will lose some small amount of engine power as it is converted to heat.
The answer to this shortfall is the TCC, or torque converter clutch. This is an electric device that will fully engage the engine to the transmission under certain conditions, thus eliminating power loss and slippage, and keeping RPMs a bit lower. On our cars, it is designed to engage at low throttle, at highway speeds in top gear. This is where the most benefit is found, and where it is most likely to stay engaged for long periods.
I found it was possible with HPTuners to have the TCC engage at slower speeds to improve economy during city driving. The problem is that this can result in very low RPMs (900-1200 rpm), which can potentially result in bogging or vibrations. Also, the TCC can be felt slightly as it engages and disengages, and isn't completely instantaneous, so it can be obtrusive in these conditions. I was also concerned about premature failure, as it is not designed to handle such frequent use. City driving is just too irratic. It does work, however, and someone may find it worthwhile to use it in this way.
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Geeky wrote:
In an automatic transmission, the "torque converter" is a device uses a layer of fluid to transmit power from the engine to the gears and driveline. This is a non-direct link, which always allows some amount of slippage. On this upside this results in a smooth transition between gears, and the automatics are less prone to failure through excess power or wear and tear. On the downside, the slippage will lose some small amount of engine power as it is converted to heat.
IT actually is a fluid coupling but it does not use a layer of fluid....the internal turbine and stator create spiral flows that actually drive opposite turbine blades from one end to the other. That is why if you stand on the torque converter (such as when your launching the car) it is possible to "flatten" the blades of the torque converter also of course losing all drive.
One thing most dont know is that the torque converter serves to change the gearing of the transmission...when the impeller is spinning faster then the turbine the stator serves to actually multiply the torque output, so despite slippage still occuring the faster the engine spins the converter the more torque is generated to spin the input shaft of the trans.
As long as your cruising in the city i dont see an issue with the tcc being locked...it is not meant to handle any more then probably 15% load. Above something like 30% TPS reading it unlocks on highway cruise.
Buildin' n' Boostin for 08' - Alex Richards
Alex: Thanks for the revisions. I knew I probably had an over-simplified mental picture of how it worked.
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I drove around with an Autotrans Interceptor for 3 years, with 100% line pressure and minimum TCC lockup delay. It used to engage all the time in the city.... it was great for fuel economy, but it was a harsh ride. I suspect GM makes it that way for comfort reasons, not anything else. If you can stand it... the trans will take it. I also threw nitrous and slicks at that drivetrain, never had a problem in three years.... so.... I'd say, give 'er!
Besides... there's so many of the 4T40E's out there... they're cheap to replace
...j
Geeky wrote:Alex: Thanks for the revisions. I knew I probably had an over-simplified mental picture of how it worked.
no prob...
Fascinating little bitches they is... :-)
Buildin' n' Boostin for 08' - Alex Richards
