electric water pump

[bzipitidoo]

I'm still liking the notion of replacing the belt driven water pump with an electric one.

There are at least 2 ways, and a large variation in pricing from what I've found so far. There's the idea of hooking an electric motor to the existing water pump and taking the belt off. The other idea is to insert the electric pump in the lower radiator hose, and entirely disable or remove the belt driven pump.

Prices would seem to range from $65 to $250 and higher. Testing indicates a gain of perhaps 5 HP.

Anyone have any experience with this?

[rgathright]

Another forum is having this same discussion.

First, avoid the belt driven option. Why add more mechanical points of failure?

Here is the premier vendor on the market today. Their pumps alternate speed depending on the water temperature in your engine block. The result is a system that will not operate a constant amperage but rather only pulls as much power as you really need. http://www.daviescraig.com.au/

[GasSavers_bobski]

Originally Posted by bzipitidoo

Testing indicates a gain of perhaps 5 HP.

I can't see putting 5 HP into moving water in a halfway efficient manner without 5-6" diameter coolant passages... You're talking about a small outboard boat motor as a coolant pump. I guess it's still possible to burn off that kind of power with a really big water pump under certain conditions. You can only spin the pump so fast and force so much water flow through the engine before the pump starts to cavitate or otherwise lose efficiency. An electric pump would surely free up some power under those conditions, but those aren't the conditions one sees in a engine operated in a fuel-saving manner. It's possible there is some efficiency gain to be had, but it's also possible that the energy lost during conversion (mechanical to electrical via the alternator, and electrical back to mechanical via the pump motor) would outweigh the regulating capabilities of the electric pump, resulting in a net loss in efficiency.

[Sludgy]

I like the idea of an electricall driven water pump AND fan. This would be particularly effective on short trips. Neither the fan or pump would come on until the cylinder head temp rose to 200 or so......

[i-DSi]

Originally Posted by Sludgy

I like the idea of an electricall driven water pump AND fan. This would be particularly effective on short trips. Neither the fan or pump would come on until the cylinder head temp rose to 200 or so......

Hi Sludgy, the idea of not letting your water pump run while warming up the engine is not so good.
The pump should be driven from start on for two very good reasons:
- divide the heat equaly over the whole (!) engine to avoid stress (number one reason)
- transferring heat to your cab heater when needed in winter

The only acceptable compromise is a waterpump at very low revs while warming up.

[Sludgy]

Originally Posted by i-DSi

Hi Sludgy, the idea of not letting your water pump run while warming up the engine is not so good.
The pump should be driven from start on for two very good reasons:
- divide the heat equaly over the whole (!) engine to avoid stress (number one reason)
- transferring heat to your cab heater when needed in winter

The only acceptable compromise is a waterpump at very low revs while warming up.

HHMMM... There's probalby a flaw in your theory about needing a water pump operating while warming up. Any car with a belt driven water pump has a thermostat that throttles the pump. How does a throttled water pump distribute heat to the engine?

[i-DSi]

Originally Posted by Sludgy

HHMMM... There's probalby a flaw in your theory about needing a water pump operating while warming up. Any car with a belt driven water pump has a thermostat that throttles the pump. How does a throttled water pump distribute heat to the engine?

Sorry Sludgy, but there's no flaw in my theory.
The waterpump always circulates the water in the engine block and to the cab heater, also with a completely closed thermostat. I'm 100% sure.
The thermostat will only change the waterpath: instead of returning immediately to the engine block it first goes to the radiator.
The circulating is necessary for an equally divided heat in the block, as I posted. Imagine the stress around the exhaust valves and exhaust ports if the water doesn't flow. Water will start cooking over there already after a minute if there's no flow and the headgasket will break because of stress.
No waterpump that I know is 'throttled'.

[GasSavers_bobski]

Originally Posted by i-DSi

The waterpump always circulates the water in the engine block and to the cab heater

Right... The water pump is throttled when the thermostat is closed, but only to a degree... Flow is never stopped. The pump circulates water through the engine block via a smaller passage at all times. Water can also circulate through the heater core at any time, though there is often a valve on the line which is controlled by the HVAC panel. The thermostat only throttles water flow through the radiator, though it does reduce flow restriction when open due to the added path water can follow from one side of the pump to the other.

[i-DSi]

Originally Posted by bobski

Right... The water pump is throttled when the thermostat is closed, but only to a degree... Flow is never stopped. The pump circulates water through the engine block via a smaller passage at all times. Water can also circulate through the heater core at any time, though there is often a valve on the line which is controlled by the HVAC panel. The thermostat only throttles water flow through the radiator, though it does reduce flow restriction when open due to the added path water can follow from one side of the pump to the other.

OK Bobski, my English is not that good I guess. I imagined a 'throttled' waterpump was one that works harder when coolant temp gets higher.
I see we have the same understanding though on how engine cooling works.

[GasSavers_bobski]

Originally Posted by i-DSi

I imagined a 'throttled' waterpump was one that works harder when coolant temp gets higher.

A throttle is just a device designed to restrict or otherwise regulate something. I guess the confusion is regarding what exactly is being throttled... That is, electrically controlling the speed of the water pump versus controlling water flow with a valve.