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Electric Water Pump – 928 4.5 litre

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Old 10-10-2017, 12:01 PM
  #16
dr bob
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Originally Posted by Wisconsin Joe View Post
...


I've been on here for about 4 1/2 years, and while there has been a lot of discussion about water pumps, this is the first time I've heard the idea of an electric one for these cars.

I'd suspect the supplier is not being fully truthful on this.

I'd want to see some proof that their product has been successfully installed in a 928.
I suspect that the supplier chose their words very carefully. They sell pumps to people who own 928's. Likely for their other cars and trucks though.
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Old 10-10-2017, 08:44 PM
  #17
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Hi Guys
Thanks for the other links - I did not find them.

We dream and we dream a little more. Thanks for waking me up

The Australian Bush is far from 928 Friendly....
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Old 10-10-2017, 10:02 PM
  #18
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^^ Even though what they sell is good quality, from my experience, they are in the business of selling electric cooling alternatives to conventional mechanical automotive cooling systems ... so not surprising that they're going to push the 'benefits' of their products without any truly quantitative model specific analysis or data.
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Old 10-11-2017, 04:38 AM
  #19
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Interesting that this is brought up again, I'm thinking about ditching the original water pump in favor of an electric.

Three reasons:
1. Easier to replace an externally mounted pump, in case of failure.

2. Temperature is constantly being monitored and adjusted by a system that is not dependent on engine RPMs.

3. The pump runs after the engine is shut off.

In this forum, I hear concerns raised, regarding engine warm up. Originally, the thermostat redirects water flow during warm up, so it circulates in the engine only. With the Davies Craig system, the thermostat must be removed, and the warm up process works as described on DC website:

"When the ignition is first turned on, the Digital Controller will 'system check' the EWP and it will run the pump for approx 10 seconds. The Digital Controller supplies a six volt PWM- pulse width modulation, (10 seconds on – 30 seconds off) to the Electric Water Pump from a cold start until the engine temperature reaches 20◦C below the target (set) temperature. At this point the Digital Controller then supplies a PWM (10 second on – 10 seconds off) till 5C less, then the Controller will ramp up to full system voltage as and when required searching for and locking onto the target temperature"

This means that water is being pushed(pulsed) around in the whole system, during warm up. I would also prefer that water was circulating in the block only. But I don't think that this DC method of warming up damages anything, as long as the engine is not put under heavy load or high RPMs during warm up (which I certainly don't hope that anybody does anyway........)

Another concern that is raised, is that a huge electric pump is needed, which will put enormous stress on the electrical system. 10 kW was mentioned. Honestly, I don't think we need the capacity of a 10 kW pump to cool the engine. Just for fun and comparison, try and google "10 kw waterpump" and see what monsters shows up......

I think that the recommended pumps from DC will cool the engine fine.

Regarding the issue of rebuilding the engine and engine bay so the original pump is replaced with an idler pulley and the electric pump is placed somewhere else, it's not going to be an issue for me, if I decide to go for the electric pump, since I'm installing the engine in my boat and have ample space to do what I want.

So as I see it, this must be done to convert to electric waterpump(no matter if the engine is in a boat or car):

1. remove thermostat
2. block bypass passage
3. replace waterpump with a blind plate with an idler
4. place the electric waterpump in a good spot
5. connect electrics

Sounds straight forward, but there will probably be some bumps on the road......

Hmmm, I can feel that somebody will say, "go ahead, do it!!!!"
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Old 10-11-2017, 06:47 AM
  #20
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Go ahead- do it!
You are saying exactly what I alluded to in an earlier post in that I suspect the need for initial internal circulation can be circumvented if the control module has sufficient programmable logic capability.
If the system were to be installed in the 928 the radiator could also act as the suction vessel and the pump could be installed inside the wing in the area under the headlight if the bulkhead can be drilled to take a cut for the hose to pass through and then a return line from the pump to the engine.
The 10kW bit I suspect is a red herring in that the pump duty is not going to be anything like that. What I have never seen published is a pump curve for the stock pump- that is what you need to know to ensure that you can replicate the work done by the stock pump.
The pump itself does not generate system pressure, it only serves to circulate the coolant round the system and that probably only needs a differential head of some 12 feet [5 psi], maybe even less, to circulate around the system. Although not specified on their data sheet, this is exactly what their pump generates give or take a little. At the very least I would go with their biggest pump that is rated for 150 litres per minute. How that compares to the stock pump I have no idea at the moment.
Whereas it is an interesting technical challenge I see no way it can ever be an economical proposition for use on the 928.
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Old 10-11-2017, 11:39 AM
  #21
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If you want to introduce another huge headache then go ahead with the conversion.
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Old 10-11-2017, 12:45 PM
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Been there, done that:

https://rennlist.com/forums/928-foru...waterpump.html

Still have that prototype on the shelf. I removed it when I did a timing job in the way back.
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Old 10-11-2017, 05:50 PM
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Originally Posted by hans14914 View Post
Been there, done that:

https://rennlist.com/forums/928-foru...waterpump.html

Still have that prototype on the shelf. I removed it when I did a timing job in the way back.
Seems like it was working ok, why did you remove it?
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Old 10-12-2017, 01:52 PM
  #24
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Flyfish --

The thermostat diverts the coolant flow through the block or radiator based on temperature. This is way different than what's used in "conventional" systems where the thermostat blocks almost all the flow until the coolant reaches normal operating temperature. In those conventional systems, there's a small bypass hose that continuously recirculates warmer water from the heads directly back to the suction side of the pump. Take a careful look at the coolant flow paths in the 928 and way the thermostat functions. There's no good single place to connect an electric pump except where the existing pump lives, since you need to maintain the full thermostat diverter functionality.

In my opinion anyway.
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