Originally Posted by supton
I'm not sure.
Locking the TC will bring down temps, but, if the engine is being wound out, then slippage should be low. Not zero but lower than if closer to stall. And since you're on a hill, with a small engine, it won't be turning low rpm, locked or not. Whatever small drop in rpm won't impact fluid flow through the cooler all that much--locking up would.
Here's the thing: why didn't the engineers do this? might there be some good reason behind not using lockup at moderate to high rpm, when under load? I can't think of a good reason why, but it seems like all the imports I've had seat time in (admitted few) they sure seem to dislike TC lockup. If it's to smooth out the experience, at the cost of longevity--well, outside of glass Honda V6 transmissions it seems imports tend to have robust automatics--thus it might just not be all that much of a hit on longevity.
If you have a temp sensor hooked up now, you can always just try both ways, locked and not, and see what happens. My guess, at 3-4k rpm, it's not going to be a huge difference--just a SWAG.
Good points, thank you. When in D, my trans will normally lock up in 3rd and 4th gear under light to moderate loads. But in D3, it will only lock the torque converter on decel (for more engine braking) or once cruising at around 4K RPMs. When 2nd gear is manually selected lockup is disabled entirely. I can lock it at any time with the switch though.
I have a couple theories on why it doesn't lock up under more load by default. One is driver experience. When the torque converter is locked, the vehicle responds to getting on and off the throttle in a very direct way like a manual transmission, the RPMs are tied to the speed since there is no slip. This is especially noticeable in lower gears. I like that direct feeling, but some may think its unrefined. In lower gears the ECU may leave it unlocked to provide more RPM and torque multiplication also since if it wasn't under load it would be in a higher gear anyways. An unlocked converter makes the engine feel and sound more powerful too since the RPMs will immediately increase when the throttle is pressed since the converter can slip.
The second reason I can think of is possible TCC longevity concerns. They may be concerned that the lockup clutch may not be able to handle maximum torque. I don't know that this is the case though because my TCC seems to handle above stock power and torque just fine. I have put it in 3rd gear, locked it, and mashed it to see if it would slip and it didn't, not that I could feel anyways. I don't know how well the clutch would engage at full throttle under peak torque though, I never tried that because I don't want to fry the clutch. Perhaps the TCC isn't applied under heavy load because it wouldn't be able to engage quickly or completely under so much torque even though it seems to be able to handle it once engaged.
I'm not sure.
Locking the TC will bring down temps, but, if the engine is being wound out, then slippage should be low. Not zero but lower than if closer to stall. And since you're on a hill, with a small engine, it won't be turning low rpm, locked or not. Whatever small drop in rpm won't impact fluid flow through the cooler all that much--locking up would.
Here's the thing: why didn't the engineers do this? might there be some good reason behind not using lockup at moderate to high rpm, when under load? I can't think of a good reason why, but it seems like all the imports I've had seat time in (admitted few) they sure seem to dislike TC lockup. If it's to smooth out the experience, at the cost of longevity--well, outside of glass Honda V6 transmissions it seems imports tend to have robust automatics--thus it might just not be all that much of a hit on longevity.
If you have a temp sensor hooked up now, you can always just try both ways, locked and not, and see what happens. My guess, at 3-4k rpm, it's not going to be a huge difference--just a SWAG.
Good points, thank you. When in D, my trans will normally lock up in 3rd and 4th gear under light to moderate loads. But in D3, it will only lock the torque converter on decel (for more engine braking) or once cruising at around 4K RPMs. When 2nd gear is manually selected lockup is disabled entirely. I can lock it at any time with the switch though.
I have a couple theories on why it doesn't lock up under more load by default. One is driver experience. When the torque converter is locked, the vehicle responds to getting on and off the throttle in a very direct way like a manual transmission, the RPMs are tied to the speed since there is no slip. This is especially noticeable in lower gears. I like that direct feeling, but some may think its unrefined. In lower gears the ECU may leave it unlocked to provide more RPM and torque multiplication also since if it wasn't under load it would be in a higher gear anyways. An unlocked converter makes the engine feel and sound more powerful too since the RPMs will immediately increase when the throttle is pressed since the converter can slip.
The second reason I can think of is possible TCC longevity concerns. They may be concerned that the lockup clutch may not be able to handle maximum torque. I don't know that this is the case though because my TCC seems to handle above stock power and torque just fine. I have put it in 3rd gear, locked it, and mashed it to see if it would slip and it didn't, not that I could feel anyways. I don't know how well the clutch would engage at full throttle under peak torque though, I never tried that because I don't want to fry the clutch. Perhaps the TCC isn't applied under heavy load because it wouldn't be able to engage quickly or completely under so much torque even though it seems to be able to handle it once engaged.
