Electric water pump effect on warm up times

[bheadrick]

As for the water pump, an electric water pump for a small block engine is around $175.
$200 for a pwm controller? Your typical water pump is no more than 5A. You can easily have a 12v 10A for $10 to $20.
Granted, that PWM controller is manual control. The ideal system would be temperature controlled. Here is a chip that's specifically designed for temperature regulated fan control. I don't see any reference to how much current it can drive, though.

[serialk11r]

The cooling system has some flexibility built in, I think you could possibly have just 2 speed controller which is VERY easy to DIY.

Just have a PWM circuit that gives you the appropriate amount of pump power for low load driving, and a switch to bypass the PWM circuit (giving the pump full power) when coolant temperature goes up. Perhaps reading exhaust gas temperature would be a better idea though, I dunno.

3 speed pump control wouldn't be that hard either. Say, increase pump speed when EGT goes past a certain level, and then bypass PWM altogether when rpm goes past 4000.

[mja1]

The water pump won't decrease warm up time. This is the purpose of the thermostat, there's no flow through it anyway until operating temp is reached. Why not buy a better quality thermostat around 195-215 deg, and a more efficient/higher quality mech pump (at same gpm as stock)?

Electric pump is still putting out similar or higher gpm (usually at lower pressures, worse for the street), all that's happening is the mechanical stress will be moving from a rugged mech. water pump to the less-rugged alternator. Then the fact that electric pumps have a tendency to fail vs a mechanical that regularly lasts over 100,000 miles. I think there's a misconception that a water pump can be used like a cooling fan, switched on and off as needed. Without any fan you may be able drive forever at highway speeds (not recommended), without a water pump or likewise stuck thermostat you may make it 5 minutes down the road. A stable and relatively cool water temp will allow for the ECU to not jump back and forth from open/closed loop as much, netting better mpg's.

A benefit, for example of electric, would be a drag car where no alternator or thermostat is used (some use restrictor plates instead) and stress on the battery doesn't matter. Where belts flying at high rpm are more of a concern than cooling the motor for 10 seconds at high speeds because the motor's not likely going to overheat enough to crack anything unless its hot-lapped on a broken pump.

Originally Posted by Phantom

What might be better than an electric water pump is a under drive pulley for the water pump. It can be lighter that stock making for less work on the engine and spinning slower it will move a little less coolant say 10%.

underdrive pulley may not make enough difference to gain noticeable mpg, it may net a few hp on high hp applications depending on the efficiency of the water pump. In fact there may be a mpg loss from higher operating temps. Only one way to find out though!

[Tesla]

Newer engines are made of thinner materials and need better coolant circulation to minimise hot spots, unlike old engines which were just big lumps of thick steel. Thermosiphon will not work because by the time you get enough heat differentiation to get a flow, your head will be warped out and all your coolant will just be leaking into the cylinders and sump anyway.
Vote 1 for leaving mechanical water pump, oversize pulley may well be a viable option, but may not provide adequate flow in really hot weather, don't know.

[serialk11r]

mja1, sure on the street, if you're running electrical devices off an alternator, then there's not much of a benefit since the engine only needs to turn say 3000rpm on the street. But once you start using the higher revs say in performance driving, or if you have a set up that gets electrical energy from a more efficient source, then an electric pump makes quite a bit of sense. Since alternators these days attempt to generate more energy under favorable circumstances, the efficiency loss is mitigated somewhat.

I suspect that under low load like on the highway the pump is likely spinning a little too fast already, and since pumping power is approximately the cube of speed, you only need it spinning <30% faster than it needs to before an electric pump spinning at the appropriate speed with 50% efficiency breaks even.

I don't think anyone is talking about turning the pump off, just reducing the speed.

[mja1]

Originally Posted by serialk11r

mja1, sure on the street, if you're running electrical devices off an alternator, then there's not much of a benefit since the engine only needs to turn say 3000rpm on the street. But once you start using the higher revs say in performance driving, or if you have a set up that gets electrical energy from a more efficient source, then an electric pump makes quite a bit of sense. Since alternators these days attempt to generate more energy under favorable circumstances, the efficiency loss is mitigated somewhat.

I suspect that under low load like on the highway the pump is likely spinning a little too fast already, and since pumping power is approximately the cube of speed, you only need it spinning <30% faster than it needs to before an electric pump spinning at the appropriate speed with 50% efficiency breaks even.

I don't think anyone is talking about turning the pump off, just reducing the speed.

The only reason I could see an electric pump being greatly beneficial is on a drag car that has no alternator, or low amp one. Something that spins over 7000-8000rpm where we'd have cavitation of a traditional mech. pump. If we're talking about a circle track or track car, above 3000-4000 rpm the mechanical pump will outflow an electric, at the same gpm the mech pump will have a higher pressure.

Fuel efficiency and freeing up hp/engine efficiency - two different subjects, which the max hp freed by this would be 5-10 hp over an inefficient mech pump, less so vs an efficient one, which isn't going to account for any noticeable acceleration increase. The biggest problem we face with using an electric pump for 'fuel efficiency' on something with an alternator is we're converting mechanical energy to electricity back to mechanical when using an alternator with electric pump. It really doesn't matter how efficient the alt and electric pump are, it will be very close to an efficient mech pump. The only way to make up for this is to turn off the pump or greatly reduce the voltage/speed of pump like you say, but now we're not only flowing less gpm at highway cruise or performance driving we're doing so at much less pressure via the nature of the electric pump does not have nearly the same torque. Meaning the engine will be running at hotter temps. We know that the engine can handle this and we think it will result it better mileage. But everything changes when an ECU is involved, especially with engine temps. But I'm just rambling, if people want to try it out go for it it'd be nice to see results.

[serialk11r]

Um, sorry I don't follow your pressure argument. The cooling loop is what determines the pressure given flow rate. Same flow, same pressure at the pump outlet. Less pressure=less flow.

By the way, 5-10hp is a huge amount of power for people who switch their exhaust system to get maybe 1-2hp. Name another place where you can free up 5hp that easily. The majority of sports cars have 7000rpm on the tach, several have 8000-9000. Even high displacement American V8s that only hit a bit over 6000 see freed up power from an electric water pump.

As was pointed out, electric pumps for even big V8s only draw 6A, which is 72W. Going by 10hp~7000W, you can see that this means the water pump is flowing enough water at below 25% of the power peak revs, aka your water pump never needs to be spinning faster than 1500rpm * whatever the pulley ratio is.

[Frank Lee]

No way that dinky plastic pulley on my Ford is meant to transfer 10 hp! I can't even imagine a 5 hp engine working hard to spin the pump at up to 7k, tops.

[mja1]

Originally Posted by serialk11r

Um, sorry I don't follow your pressure argument. The cooling loop is what determines the pressure given flow rate. Same flow, same pressure at the pump outlet. Less pressure=less flow.

By the way, 5-10hp is a huge amount of power for people who switch their exhaust system to get maybe 1-2hp. Name another place where you can free up 5hp that easily. The majority of sports cars have 7000rpm on the tach, several have 8000-9000. Even high displacement American V8s that only hit a bit over 6000 see freed up power from an electric water pump.

The crank provides more torque than a small electric motor. The electric motor doesn't increase with rpm. I thought we were discussing gas mileage, they are two separate subjects entirely. 10 hp will not drop a 1/4 ET at all by .1, so I don't understand how that's a serious amount of power. Exhaust and CAI will make the same, or a simple tune will make much more than that for much less $, rerouting the belt or removing in the case of v-belts to bypass alt and power steering for a run will net more freed hp, for the price of a 5-20$ belt. Race pumps belong on race cars specified for their purpose. These are not advertised as longevity, reliability, or fuel efficiency pumps for a reason.

[mja1]

Originally Posted by Frank Lee

No way that dinky plastic pulley on my Ford is meant to transfer 10 hp! I can't even imagine a 5 hp engine working hard to spin the pump at up to 7k, tops.

Think of it as 'freeing' 5 hp or more tops, it doesn't 'require' 5-10 hp to run the electric pump. We 'add' a few more driven hp onto the alternator when we make this modification.