Tuesday, May 10, 2016

Water pumps, which one to use and hose routing

We have several water pumps, we need to choose between them and route the lines appropriately.

The motor and motor controller (DMOC) need cooling water, the radiator and heater core are still in the car.   We figure we do not want to connect the motor/DMOC to the heater core as during the winter we will want to heat the cabin and not waste heat in the motor/DMOC.  The plan is to route radiator > pump> DMOC>motor>radiator, any reason to route otherwise?

For the motor/DMOC we suspect we will want a continuous low flow of coolant to prevent hot spots, but should not need the maximum stated 16L/min continuously.   So we have been looking at pump control strategies.  The initial plan was a low flow pump always on, with a high flow pump on a temp controlled relay.  That was until we noted one of the pumps seems to have signal wires.

Size reference, 4" dia.

Looks like it may be able to CAN communicate and maybe spin at different speeds?  But I have not found on the web yet any specifications for it.  Help please.

UPDATE [We have learned that this is a CAN controlled pump.  The Yellow wire is 12v+, the White is GND.
We have been told the red is LIN, and the blue ASD, but that does not jive with CAN.  We have also been told to hold the blue to 12v+ to do a power on test, but that was given by the same informant as the LIN and ASD information which seems incorrect.]

Other choices I have on hand are:

Size reference, 3.5" dia.

Size reference, 4.5" dia.

Size reference, 3" dia.

I figure one of the little ones for the heater core, when the heating element is on, the pump is on+a minute or two shut off delay.


  1. Do you need the whole volume of the radiator or could you bypass the radiator and use the heater core for heat transfer. you'd have to move it, but might save you some pounds, though I'm not sure what volume differences they are in a golf.

  2. Do you also need cooling for the charger or battery? And do you ever plan on heating the interior of the car. I could see keeping the radiator and then having an manual Winter/Summer valve to direct coolant either to the radiator of the heater core.

    The volt has a really complicated system or automatic valves and different cooling heating loops. It is... complicated, but interesting to take a look at.


  3. I do not have a good feel for the amount of heat rejection I will need to dissipate, I highly suspect I will not need the full radiator, and in fact the heater core may be the right size, but I was going to use the heater core to heat the cabin still. I even think that I could get a VW intercooler that would easily fit under a corner of the bumper as designed by VW. If the system is 1/2 as efficient as they say I only need to reject 3500 watts at full power, I suspect I need to reject much more at regen. We have not gone through a weight reduction round yet, just do as little damage to the car as possible to get it operating like a normal Golf from behind the wheel perspective. I suppose I could save weight by filling the radiator only half full. :) I will not be operating near 150F so boil is not a concern, but cavitation still plays in.