Originally Posted by ajm8127
That's an ambitious upgrade.
I do not think putting the two pumps inline is a good idea. In the M3 DCT, the air to oil cooler pump is not inline with the main pump. I think some very strange things could happen if the pumps were put inline.
To figure out if pressure drop through the cooler is a big deal or not, we really need to know what the flow rate through the cooling circuit is. Earl's has documentation
comparing the pressure drop in three different types of coolers, but it does not tell you which of their coolers they used for the test, although they do say it is of comparable size to the other units tests. Interesting to note is that SAE 10 weight oil was used for the pressure drop test, which is close to if not slightly higher than the viscosity of LG6 ATF at 100°C.
The only way in my mind to add another pump is to not use the stock cooling ports in the transmission because they are in line with the stock pump. You would need to make new holes somewhere in the transmission to accommodate the new pump and air to oil cooler circuit.
If placing the air to oil cooler between the stock exchanger and the transmission (i.e. inline with the stock cooling circuit and stock pump), the inlets to the thermostat would go between the stock heat exchanger and the transmission, with the two other lines in the thermostat going to the oil cooler. In the PDF you posted, imagine the "engine" represents your transmission, and the "oil filter" represents the stock water to oil heat exchanger.
If you used the pump and had a completely different cooling circuit for the air to oil cooler, the temperature switch should go in the transmission oil pan, and this would activate the pump. You would not need the thermostat in this case because no oil wold flow through the cooler unless the temperature switch told the pump to turn on. You would need to put two additional holes somewhere in the transmission, probably in the pan. I would put the supply to the cooler by the temperature switch and the return from the cooler on the other side of the pan. Some sort of metal part (a bulkhead) would have to be fabricated to attach to the transmission pan and allow you to thread the extra lines in. I would not recommend drilling and tapping the plastic pan. As you can see, this solution would be difficult to implement.
I do not plan on making it that difficult as you describe. My INITIAL plan was to plumb a T-stat in the outlet from the heat exchanger with it opening at 180 F and then have a temp switch to turn on the pump at 190 F. This way only when the aux cooler line was open would the pump be working assuming temp were >190 F. The outlet from the cooler would return to the return line to the transmission. However I do not think a pump is needed anymore.
I just got off the phone with the Tech/sales rep from B&M and asked them about this. He said to me that the stock pump would see NO higher pressure with the cooler plumbed in series and this is usually how the people plumb it. He said that he has not heard of anyone running a second pump for the cooler unless it was the only system and you were bypassing the stock system altogether,...as you mentioned above. So I guess that phone call just saved me a few hundered bucks in pump, lines, fittings, and switches.
In fact, I have the ER Dual Oil coolers which are plumbed in series with the stock pump. This works just fine and I have noticeable oil temp drops. So I am thinking why reinvent the wheel,...right? The same concept seems to work on many cars with more HP than mine. So I will K.I.S.S.
The most recent plan will be for a T-stat to open at ~180 F and allow flow to the aux cooler which will be plumbed in series with the heat exchanger. This makes the most sense to me and I do not think I need to worry about pressure differences with a high quality cooler made for this very purpose. None of the aftermarket coolers show a pump anywhere in the diagram, not even as an optional thing. This setup seems to mimic the M3 the most except it is plumbed in series rather than parallel.
What do you think about this plan guys? I want to pull the trigger on this and put in Temp sensors and get some good info about before and after the cooler to see the benefits. I do not think we can overcool this system so I will put in the largest cooler that will fit.