Heating the transmission with engine coolant

[NHB]

Originally Posted by Daox

I will be using a modified transmission in the car. I'm not willing to test out lower viscosity fluids due to the risk of damaging or reducing the life of the modified transmission. Therefore, I see heating the oil as the only reliable method.

What is the viscosity are you want to get with external heating? What is the reliability difference of the gearbox between heated high viscosity oil and lower temperature low viscosity oil? Heated higher viscosity oil will have the same lubrication qualities as low viscosity oil at lower temperature.

[Daox]

I have no idea what viscosity target I should aim for. I would imagine that the safest route would be to emulate some maximum conditions, and then target that. So, testing will need to be done to find out what the max temperature under high load applications would be without the heater. Then, heat the transmission up to that temperature and hold it there.

[NHB]

Originally Posted by Daox

I have no idea what viscosity target I should aim for. I would imagine that the safest route would be to emulate some maximum conditions, and then target that. So, testing will need to be done to find out what the max temperature under high load applications would be without the heater. Then, heat the transmission up to that temperature and hold it there.

I don't quote understand your logic. You are ready and willing to lower the viscosity by heating the oil but you don't want to use a lower viscosity oil at lower temperature.

[2000mc]

Originally Posted by NHB

I don't quote understand your logic. You are ready and willing to lower the viscosity by heating the oil but you don't want to use a lower viscosity oil at lower temperature.

How would you keep the fluid from ever warming up?

[renault_megane_dci]

Originally Posted by NHB

I don't quote understand your logic. You are ready and willing to lower the viscosity by heating the oil but you don't want to use a lower viscosity oil at lower temperature.

Simple actually :
He wants to reach normal operating temperature faster.
He shain't damage the gearbox with this approach if temperature don't go too high.

If changing oil to a different viscosity, he would give up on Toyota's engineering expertise in designing his gearbox.


I am working in automotive and had this discussion over and over with my father : there is a fair amount of knowledge put in automotive engineering and care should be taken when trying to improve on design, especially high stress parts.

[blownoiler]

Has anyone done the math to see how much fuel saving there would be with gearbox oil that is prewarmed somewhere along a 10 minute journey? Does the average joe actually even get his gearbox oil changed at the required service intervals?...I don't...Does gearbox oil actually "wear out" or does it just get contaminated with slivers of metal from missed shifts! Maybe "reconditioning" the gearbox oil and using it for another 2 years would save more money than what would be saved in fuel costs plus the expense of setting up a pre-warm system.

[nemo]

Daox, Too bad you can't put the heat exchanger inside the transmission right in the oil.

[Daox]

Thanks for explaining things renault_megane_dci.

Originally Posted by blownoiler

Has anyone done the math to see how much fuel saving there would be with gearbox oil that is prewarmed somewhere along a 10 minute journey?

All of the research I could find is in this thread. Sadly, there is nothing saying 'heated oil shows a X% increase vs cold oil'. All I know is it will help. To what degree will need to be tested. Only after can we say it is or isn't worth it.

Its a fun experiment. Some of us are here to save money, some are here to save the environment, some of us are here to have fun and tinker. I'm a fan of all of those.

Originally Posted by nemo

Daox, Too bad you can't put the heat exchanger inside the transmission right in the oil.

Yeah, that would really be ideal. I kind of doubt there is room inside. We'll see when I start taking things apart though. Any ideas on what I could put in there if there is room?

My current thought is to glue (yes glue) a fabricated pan to the transmission housing. The pan will be formed to the outer shape of the housing thus conforming to all its irregularities and maximizing the usable surface area (vs a flat block as previously suggested). This should allow quite a bit of heating surface area. Inside the fabricated pan will be a serpentine path for the coolant to flow. There will be an inlet and outlet on each end of the path for coolant connections. Locktite makes some epoxy for bonding metals that will easily hold up to the temperatures seen. JBweld might also work just fine too.

[blownoiler]

I understand your need to experiment, I do much the same!
Have you thought about using exhaust heat to help the engines coolant get to operating temp faster? A solenoid and some copper pipe tapped into the exhaust could give you a source of heat, which could be used to help the engine warm up quickly, and could also help the gearbox get up to temp faster. It seems a waste to dump it out the exhaust when it could be utilized.

[Daox]

Yep, I have. From earlier in the thread:

Originally Posted by Daox

Also, the engine block is going to be insulated to decrease warm up times and provide heat to the new coolant circuit faster. If that isn't enough, I will also be looking into using exhaust heat to further speed up the warm up process.