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ChazInMT · 06-10-2016, 11:43 AM

You need only one input to a controller to vary the speed, coolant temperature. You can't run too cool or you loose efficiency, you can't run hot because...duh.

So a constant speed electric motor would not be efficient because you would be wasting energy if you were throttling the flow with a thermostat, it would be less efficient than a regular belt drive pump. If you ran it slow enough to be efficient at low speeds, than it would cook your engine on a hot, high heat load, day.

Trust me on this, it takes POWER to circulate the coolant, the power must come from somewhere and just because it is an electric motor driving it now does not by any stretch mean you are using less power. For a given flow rate of coolant, the power required to drive the electric pump will be more than the belt drive pump, by a lot, ~30% shooting from the hip.

Don't get caught up into thinking that just because the engine isn't turning it with the belt, the load goes away.

As I said, there "May" be room for an efficiency gain if you vary the speed based on coolant temperature, and the current set up is really wasting a lot of energy due to spinning the pump too fast for nominal coolant system load and the thermostat is throttling a lot.

But the efficiency gain I think will be small enough that you would have a hard time seeing it on your MPG logs, and the payback time for even a $100 outlay would be very long. If you figure a 5% efficiency gain (Really a pipe dream that) and $3 gallon gas, and a 30 mpg base, it would be 20,000 miles before you break even on the $100 cost. You will not have saved a dime for the first 20,000 miles, after that, you'd be "Saving" $100 every 20,000. If the efficiency gain is smaller 1-2% it will be 60k-80K miles before you see your first penny of benefit.

Don't let facts stand in the way of a good dream I suppose. I post this here only to give others who may be contemplating this more food for thought.

If you think I'm wrong here, by all means let me know where the facts are not correct, it is entirely possible I am not taking something into consideration here. But please, do not let me know how I may be wrong without facts.

06-10-2016, 11:43 AM	#29 (permalink)
ChazInMT Aero Deshi Join Date: Jan 2010 Location: Vero Beach, FL Posts: 1,065 MagMetalCivic - '04 Honda Civic Sedan EX Last 3: 34.25 mpg (US) Thanks: 430 Thanked 669 Times in 358 Posts	You need only one input to a controller to vary the speed, coolant temperature. You can't run too cool or you loose efficiency, you can't run hot because...duh. So a constant speed electric motor would not be efficient because you would be wasting energy if you were throttling the flow with a thermostat, it would be less efficient than a regular belt drive pump. If you ran it slow enough to be efficient at low speeds, than it would cook your engine on a hot, high heat load, day. Trust me on this, it takes POWER to circulate the coolant, the power must come from somewhere and just because it is an electric motor driving it now does not by any stretch mean you are using less power. For a given flow rate of coolant, the power required to drive the electric pump will be more than the belt drive pump, by a lot, ~30% shooting from the hip. Don't get caught up into thinking that just because the engine isn't turning it with the belt, the load goes away. As I said, there "May" be room for an efficiency gain if you vary the speed based on coolant temperature, and the current set up is really wasting a lot of energy due to spinning the pump too fast for nominal coolant system load and the thermostat is throttling a lot. But the efficiency gain I think will be small enough that you would have a hard time seeing it on your MPG logs, and the payback time for even a $100 outlay would be very long. If you figure a 5% efficiency gain (Really a pipe dream that) and $3 gallon gas, and a 30 mpg base, it would be 20,000 miles before you break even on the $100 cost. You will not have saved a dime for the first 20,000 miles, after that, you'd be "Saving" $100 every 20,000. If the efficiency gain is smaller 1-2% it will be 60k-80K miles before you see your first penny of benefit. Don't let facts stand in the way of a good dream I suppose. I post this here only to give others who may be contemplating this more food for thought. If you think I'm wrong here, by all means let me know where the facts are not correct, it is entirely possible I am not taking something into consideration here. But please, do not let me know how I may be wrong without facts.