Trans temp when dyno tuning

[Milktasd]

So I have recently started playing with sport and sport+ noticed my trans isnt happy until it gets some heat in it. I will drive in normal mode and then switch over. This got me thinking of when you dyno the car.

Are you making pulls with a cold trans? Are you making pulls in drive?

these 10r80s can be a wee bit expensive if buying a built one, so trying to hold that off for as long as possible.

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[DougS550]

So I have recently started playing with sport and sport+ noticed my trans isnt happy until it gets some heat in it. I will drive in normal mode and then switch over. This got me thinking of when you dyno the car.

Are you making pulls with a cold trans? Are you making pulls in drive?

these 10r80s can be a wee bit expensive if buying a built one, so trying to hold that off for as long as possible.

NO, Engine and transmission at operating tempuature. Just like on the first start of the day, you dont WOT until both are warmed up.

 

[HKusp]

An automatic transmission is a fancy hydraulic pump. Generally speaking, hydraulic fluid flows best at or above 170*f.

 

[EFI]

noticed my trans isnt happy until it gets some heat in it.

Of course, it doesn't operate as intended until it's close to being fully warmed up. Just like any other piece of machinery, but especially one as finnicky and complex as the 10R80.

I would not be beating on anything (including the diff) until they are all fully up to temperature. The manual considers normal operating temp for the 10R to be between 204* and 215*, but you don't need to take it that high. Anything in the 170*+ range should be fine.

 

[Angrey]

This is an interesting phenomenon that shifted in the automotive world with the advent of fuel injection. In the old days, cars didn't perform optimally until warm, because of transmission converters. So the generally accepted notion was that in order for a car to run it's best, it needed to be warm.

Now, with fuel injection and variable timing and all the wonderful things we have to eke out every ounce of motor production, we want them to be as cool as possible prior to dyno/drag pass, etc.

But it brings up an interesting aspect as to whether it's still an issue, given that dyno sessions call for dyno'ing on a locked converter and most tunes call for locking the converter upon WOT conditions.

I would agree with the above that if you're not locking the converter, you want the trans to be optimal temp, but if you're locking it up for the pulls, I don't see how room temperature trans fluid is any better or worse than fully warm. The converter isn't working how it normally would when you forced it locked.

I guess if the dyno operator is abusing it through the lower gears to get up to dyno gear, maybe. I've seen some dynos that you can actually test and tune full rips (from stop to max speed in 1:1) and it always looks strange seeing the car rip through the gears on the rollers. But someone correct me if I'm wrong, most dyno sessions on an auto car are locked converter in 1:1 (or a lower gear if that's going to exceed the speed limit on the dyno or in some cases hurt the trans.....i.e. the 7th gear).

 

[EFI]

I don't see how room temperature trans fluid is any better or worse than fully warm.

It's about viscosity and clearances. Fluids are generally spec'd for piece of equipment based on clearances and viscosity at operating temperature. When you operate them at other temps, they are not as efficient. Clutchpacks are very sensitive to viscosity, and as things get more complex then that logic applies even more.

Sure with modern technology things like engines and transmissions can operate smoothly right after starting them, but that doesn't mean they are at their optimal point. Fluids are thicker when cold, but generally clearances remain the same throughout.

 

[Paddles]

It's about viscosity and clearances. Fluids are generally spec'd for piece of equipment based on clearances and viscosity at operating temperature. When you operate them at other temps, they are not as efficient. Clutchpacks are very sensitive to viscosity, and as things get more complex then that logic applies even more.

Sure with modern technology things like engines and transmissions can operate smoothly right after starting them, but that doesn't mean they are at their optimal point. Fluids are thicker when cold, but generally clearances remain the same throughout.

Agreed, plus the fluid expands with heat potentially creating a lower than optimal fluid level when cold.

 

[Angrey]

I don't disagree with any of that, but does it apply when the converter is locked?

 

[EFI]

but does it apply when the converter is locked?

Yes, because engine power still travels through the internal clutchpacks of the transmission, and those are all operated and lubricated by transmission fluid. When going through the gears on a dyno, or applying full power, the fluid that operates the clutches will act differently when cold vs. hot.

It might not have a huge effect on actual power, but the way the transmission shifts and behaves will certainly differ. And the OP's initial issue was not power, but how it behaved.

 

[SnowFox]

Of course, it doesn't operate as intended until it's close to being fully warmed up. Just like any other piece of machinery, but especially one as finnicky and complex as the 10R80.

I would not be beating on anything (including the diff) until they are all fully up to temperature. The manual considers normal operating temp for the 10R to be between 204* and 215*, but you don't need to take it that high. Anything in the 170*+ range should be fine.

Right!

I don't think I've seen my transmission push past 195* yet. Even then it takes forever to get it there.

Sorta makes checking transmission fluid level according to manual a bit of hassle *you need to check it now! Now!...fk to late .."

 

[Angrey]

Yes, because engine power still travels through the internal clutchpacks of the transmission, and those are all operated and lubricated by transmission fluid. When going through the gears on a dyno, or applying full power, the fluid that operates the clutches will act differently when cold vs. hot.

It might not have a huge effect on actual power, but the way the transmission shifts and behaves will certainly differ. And the OP's initial issue was not power, but how it behaved.

You're being resistant to my point. The fluid lubricates the clutches, but you're talking about a single lockup. The point being, that when you FORCE the transmission to lockup, from that point on, the temp of the fluid is irrelevant. And someone correct me if I'm wrong, but no one dyno's an automatic transmission without the converter locked (at least not if they have the option to control it).

With the fluid cold, the converter will either lockup or it won't. From that point, it doesn't matter.

 

[EFI]

With the fluid cold, the converter will either lockup or it won't. From that point, it doesn't matter.

I'm talking about the transmission itself (and the clutches within), not the converter.

But you're welcome to believe what you want to believe, I'm not here to change your opinion on the matter...just state the facts. And you can do with that what you will.

 

[Angrey]

I'm talking about the transmission itself (and the clutches within), not the converter.

But you're welcome to believe what you want to believe, I'm not here to change your opinion on the matter...just state the facts. And you can do with that what you will.

As are you. When MOST people dyno the car, they force the coverter to lock. Which means the fluid temps have nothing to do with it anymore. Running the car hard otherwise on a cold trans, I agree, but once you lock it, it's a non issue. And virtually no one dynos the car without the converter locked. Changing into 1:1 gear at room temp isn't going to hurt the transmission one bit.

 

[Paddles]

As are you. When MOST people dyno the car, they force the coverter to lock. Which means the fluid temps have nothing to do with it anymore. Running the car hard otherwise on a cold trans, I agree, but once you lock it, it's a non issue. And virtually no one dynos the car without the converter locked. Changing into 1:1 gear at room temp isn't going to hurt the transmission one bit.

I see your point, once you're in 1:1 gear going WOT with the converter locked you're basically getting the same power regardless of the fluid. And you no longer have to keep changing gears. Maybe you could have less parasitic draw if warmer fluid means better lubrication but I'm not really sure if that's the case with the A10. I'm also not sure to what degree a WOT pull on cold fluid might affect durability of the transmission but I suspect it isn't as good for it vs doing it warm.

 

[Angrey]

I see your point, once you're in 1:1 gear going WOT with the converter locked you're basically getting the same power regardless of the fluid. And you no longer have to keep changing gears. Maybe you could have less parasitic draw if warmer fluid means better lubrication but I'm not really sure if that's the case with the A10. I'm also not sure to what degree a WOT pull on cold fluid might affect durability of the transmission but I suspect it isn't as good for it vs doing it warm.

Again, I would agree with you if you're doing a WOT pull THROUGH THE GEARS. But if you're just on the dyno and run it at low rpm from 1 up to 7 and lock the converter for the WOT rip, at that point, fluid temp has very little to do with anything.

I'd honestly be MUCH more worried about doing a WOT rip on a cold engine where the pistons and rings aren't fully expanded and the oil is thick and not flowing as well and the pressure is high enough to worry about bypass condition.

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