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Daox 08-29-2014 06:16 PM

Heating the transmission with engine coolant
I'm just about done with the Civic repairs which means I'll finally get a little time to start on fixing the Tercel. Well, my mind can't stay there, it has to jump ahead. As you may know, I have a pretty short commute of 7 miles. In winter, my cars don't really even get up to full operating temperature for a good portion of the winter (and I don't use much heat either). Also, most of my trips besides work are around 5-10 miles. I don't have you tell you that these short trips are brutal on mpgs. So, I'm constantly thinking of ideas to speed up warm up times.

Well, the Tercel is my blank slate, and my ability to mod is the limit. This car is currently worth its scrap price. However, its my first car and the sentimental attachment is still there. So, I'm not looking to spend huge money, but I'm also wanting to make it what I want, and this means I'm willing to do some things that I wouldn't be with a car that I might sell in the future.

I have a fairly extensive list of ideas that I want to try, but the one I want to talk about in this thread is using engine coolant to help speed up the heating of the transmission (in my case its currently a 4 speed manual with 75W90 oil). Now, if you were listening you heard that my coolant temp sometimes never even gets up to normal operating temperature. Well, lets forget that for now because I plan on solving that issue by insulating the engine block, and I am assuming at this point that warm up times will be drastically improved by that. So, now that I have extra heat again, why not use that to warm up that nice thick transmission fluid?

I did a bunch of googling to see if there was ever testing done to see what kind of gains there were from warming up trans oil. I couldn't find anything. I know BMW did some testing or something with this but I couldn't find it. So, I'm asking the mass of EM knowledge if they have any idea if this would even be worth it?

whatmaycome14 08-29-2014 06:18 PM

Is it auto or manual transmission?

I'm thinking Auto trans would be a lot easier to heat up because the fluid flows in a circuit. You could tap into one of the trans fluid lines and put a small heater and pump that runs off of 110AC in your house.

Manual transmission would have to be modified internally somehow to run a heater. Maybe you could instal a block heater in the transmission housing??

Cobb 08-29-2014 06:30 PM

Im sure you could thread a dip stick heater through a vent and insert it enough so it does not hit any moving parts. Plan B would be use the speed o gear port if it has one.

I believe the military uses heaters on the gear boxes for vehicles used in arctic climates.

Daox 08-29-2014 06:34 PM

1 Attachment(s)
I have a 4 speed manual trans, but this is really applicable to any vehicle. I just shared my specific application I was thinking of.

I'm not talking about using an electric 110V heater. I'm talking about using engine coolant to heat the transmission. Thinner oil, lower viscosity, lower churning losses, especially in winter.

It would be pretty simple to make a heating block out of whatever and bolt it to the trans.

Here is an example:

2000mc 08-29-2014 06:37 PM

I'd hate to move ahead with this before knowing what affect the insulation actually has. On very cold days my car can idle w/o the radiator fan, or blower fan on at 185, with the blower fan on full the heater can pull it down below 150.
Why not just put a block heater on the trans? I'm thinking to do it on my own car

Daox 08-29-2014 06:39 PM

That is a good idea and I may do that too. But, the reason is because more than half of my trips aren't where I can plug in. Also, I could run higher trans temps ALL the time, not just for faster warm up. This would provide benefits even after the car is warmed up.

A passively cooled transmission's temperature is controlled by the ambient temperature. So, anytime its less than say 115F ambient (I don't know what the OEM design criteria is), I'm actually running the trans cooler than is ideal, and thus I have more losses than I could if it was operating at a higher temp.

2000mc 08-29-2014 06:51 PM

This might be a little out there, and not feasible depending on the exhaust design, but might work if the exhaust is on the front of the engine...
Create a HAI, which would help warm up anyway. Do so in such a way that you would box in a fairly long section of the exhaust, which would also draw the prewarmed air over the transmission, on its way to the intake.

pgfpro 08-29-2014 06:59 PM

I'm glad you posted this.

I'm going to now incorporate a turbo coolant transmission heater utilizing the turbo's center cartridge that is already setup for cooling the turbo. This will pull heat away from the turbo and heat the transmission fluid during the cool months.

Thanks :thumbup:

nemo 08-29-2014 07:34 PM

Just Y it off your heater connections. Depending on how your car is set up this will allow the thermostat to stay closed but still circulate through new circuit. I would add a regulator so the flow can be stopped if required. It would be interesting to see if the radiator could be eliminated completly in the winter.

Daox 08-29-2014 08:19 PM

I was thinking something very similar along those lines Nemo. I was thinking I'd tee into the coolant lines going to the throttle body or heater core to get the coolant, pass it through a heating block mounted to trans (something similar to what was shown above) and then tee it back into the system downstream.

To control it, I would ideally like to use a solenoid valve. I would also monitor engine temperature and transmission temperature. Normal operation would be to leave the solenoid closed until the engine is up to 130-140F. This gets it out of its high idle / cold start mode, since the engine is more important to warm up than trans. After the engine hits that temp, the solenoid would open up and the coolant would be used to heat up the transmission. At some set temperature, the solenoid could close if the transmission gets too warm. If not, it would happily run at ~180F just like the engine.

Is this overly complex? Perhaps. But, I will have at least one arduino onboard controlling another modification, so adding a temp sensor and a solenoid valve wouldn't be difficult at all.

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