Heating the transmission with engine coolant

[Daox]

Originally Posted by pjbgravely

That is strange. In the old days automatics had a lower ration so using an automatic gearing resulted in higher engine speeds.

Yeah, that is the case. However, the gearing is much higher, but the differential gearing is much lower.

Transmission Information

[paulgato]

Oh wait, ...

You want to only feed coolant to the gearbox when the engine is already warmed up, but limit the temperature of the gearbox to about 80 degrees C....?

So you need TWO thermostats.

And as normal wax thermostats OPEN on temperature rise, then this gets quite complicated I think, because really you want one of them to close on temperature rise. You could rig one to open a wide 'bypass' on temperature rise I guess, but that's complicated.

Alternatively, you could use a single 2-port motorised zone valve from a central heating system, which gets its OPEN signal and its CLOSE signal from two thermostat switches, so it is only open between your two desired temperatures. You could use adjustable thermostats so you can tweak the switching points.

(You'd have to find 12v motor/auto versions of these controls, or else use a small inverter, ...but we're only talking an amp or less here.)

[Wonderjava]

all this stuff you wanna do to this car will destroy it. The block you want install on the tranny will not make it warm up faster. The insulated block will cause internal damage from the heat not dissipating.

[Daox]

Originally Posted by paulgato

Oh wait, ...

You want to only feed coolant to the gearbox when the engine is already warmed up, but limit the temperature of the gearbox to about 80 degrees C....?

So you need TWO thermostats.

And as normal wax thermostats OPEN on temperature rise, then this gets quite complicated I think, because really you want one of them to close on temperature rise. You could rig one to open a wide 'bypass' on temperature rise I guess, but that's complicated.

Alternatively, you could use a single 2-port motorised zone valve from a central heating system, which gets its OPEN signal and its CLOSE signal from two thermostat switches, so it is only open between your two desired temperatures. You could use adjustable thermostats so you can tweak the switching points.

(You'd have to find 12v motor/auto versions of these controls, or else use a small inverter, ...but we're only talking an amp or less here.)

I don't have anything designed yet. Its all just discussion at this point.

all this stuff you wanna do to this car will destroy it. The block you want install on the tranny will not make it warm up faster. The insulated block will cause internal damage from the heat not dissipating.

Thats quite a dramatic statement. Care to explain a bit further?

[renault_megane_dci]

Originally Posted by Wonderjava

all this stuff you wanna do to this car will destroy it. The block you want install on the tranny will not make it warm up faster. The insulated block will cause internal damage from the heat not dissipating.

Skin dissipation is at best anecdotal on a water cooled engine ...
Gearbox is another story but advice on monitoring temp as already been given a lot.

[CH1cruisin]

The short commute probably won't make a coolant heater very effective. Having lived in and taken several vehicles to Alaska where I had the same problem, I simply changed all gear boxes to synthetic gear oils.

[NHB]

Originally Posted by maxfnz

- Manual transmissions probably won't benefit from a heater siimply because of the oil viscosities ... most manuals specify a monoweight oil (80, 90) and if multiweight (80-90 or say 75-140) then it's going to get **thicker** as it heats, not thinner. Surely in that case you need cooling, not heating?

That is not going to happen. All gear oils have lower viscosity at higher temperature. Multi-grade oils just have an improved viscosity index which means that their viscosity will change less than the viscosity of a single-grade oil.

[NHB]

Originally Posted by Daox

Seeing as how I am keeping this car for the foreseeable future, I'd rather not experiment with questionable oils. The transmission in the car is going to be modified and I'd like to not jeopardize the longevity of the transmission. Id rather take a couple percent hit on FE than shorten the life of the transmission.

The whole point of this mod is to improve short trip mileage. Putting excess engine heat to use is the method. I should have plenty of extra heat once the engine block is insulated. Super fast warm up is what I'm after for the engine and drivetrain to eliminate the cold start losses. The engine is going to be insulated either way just to have super fast warm up times. So, why not put the extra heat to use for the transmission?

Basically a high viscosity oil at higher temperature is the same oil as a low viscosity oil in lower temperature. Critical viscosity is determined at the highest possible temperature. So the chosen oil grade has to be so thick, that it will survive driving up a mountain in a hot weather with full engine power. This may happen at low speed when air flow is low. Original oil grade is chosen like that. Most likely that means, that usually the oil is too cold to reach the optimal viscosity and an ecomodder will go anywhere near to the critical temperature.

I like the idea. It would be great if the temperature of a gearbox could be regulated. Heat regulation is just not an easy task to do. One of the main problems is that there is no excess heat in engine coolant when it is needed the most and the last thing we wan't is to slow down engine heating process. When the engine is hot, the gearbox is already quite warm and the possible benefits of gear oil heating are mostly lost.

If I would build an oil heating system, I would give a serious thought to an exhaust heat recovery system. Exhaust gasses are hot from the start. Toyota Prius uses this system with great results. The cabin heating system in a Prius performs extremely well in cold temperatures. Also preheating with an electric heater is a nice idea in cold temperatures.

If I was you, I would choose a low viscosity oil with a good viscosity index rating. A low viscosity synthetic oil would give you a lot of those benefits you are looking for. Everything is possible, but everything should be just fine. I googled a bit and found some promising oil grades. A 70W/75 or 75W/85 if your car experiences high load situations. With high load I don't mean highway cruising.
http://www.penriteoil.com.au/POS/GO_POS.pdf

How about reversing everything? A low viscosity oil and an additional cooling system to avoid the viscosity to drop too low? Or a temperature sensor and an extra coffee break when using a high power level a long time.

[American Viking]

Originally Posted by Old Mechanic

Lots of car companies use fluids other than gear lube in trannies. Chrysler used atf in it's manuals in the 1960s. BMW used mineral oil in the 70s, learned that one the hard way. A simple fluid change may give you the most benefit for the least cost.

Try some other fluid like atf, your driving conditions are most extreeme but not on tranny fluid. Is there any risk? Of course, but given your imposed limitations I would try that first.

regards
Mech

That's a good way to destroy the transmission syncros.
Some transmissions are designed to run ATF, but if the trans is supposed to use 75/90 gear oil going with ATF will destroy the Blocker rings.
I'd go with a good synthetic gear oil and a contact
electrical heater a 12V one that you can just wire into the car's system.

Honestly though I think the transmission's temp is the least of your worries.
getting the motor oil and the engine block up to their operating temps is critical for best efficiency.
I'd fit an oil to coolant heat exchanger (one of those oil filter housing sandwich ones), wind some soft copper tubing around the exhaust manifold (or just a small spiral of stainless brake line inside the collector), an expansion tank (say one of those generic coolant overflow tanks) and an auxiliary coolant pump.
Sure, the pump adds electrical load, but that would build heat in the heads faster for better combustion. Everything would warm up faster thanks to the block heating up more evenly.

If you get one of the magnetic drive pumps they can run continuously with very low load on the electrical system.
The side benefit is the car cabin will warmup faster as well.

[Daox]

Guys, please read the thread. I feel like I'm repeating myself quite a bit here.

The transmission coolant loop will be thermostatically controlled. It won't open until the engine coolant is at some set point to avoid prolonged fast idle / fuel enrichment mode. Therefore, it will have zero effect on warm up times. 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.

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.