foxint

Hi guys….

I know there is a lot of talk about who’s got the best water pump, or whose is the worst….

But has anyone thought about an Electric Water Pump. It increases power and fuel economy and is cheaper than genuine and no more expensive than some OEM pumps….

Here is an Aussie pump. They have sold to owners of 928, but they could not tell me who….

http://daviescraig.com.au/product/ew...combo-12v-8990

Any comments????

jpitman2

I believe latest Mustang and some Audi run EWPs.
FWIW , when DC first released their EWP it was reviewed by a local Aussie web magazine, and DC took out an injunction to prevent them publishing it. It was on autospeed.com, but I cant find it now.
jp 83 Euro S AT 57k

Speedtoys

And..theyre lyin. Unless it was a Chebby drop in a 928...so that must make it a 928 install.

Dave928S

Davies Craig have been around since the 70's and I've used a lot of their equipment. Never had an issue with quality. The fitting principle seems sound, although a bit 'ad hoc' for my liking on a 928. Only flow curve and parasitic HP comparisons of factory vs this system would give you the true picture.

foxint

Hi Guys

Great comments.

Speedtoys said: And..theyre lyin. Unless it was a Chebby drop in a 928...so that must make it a 928 install. - I do not understand. You lost me with the "Chebby". Is this an American term?

I think the concept is sound??

FredR

Well first of all if a mechanically driven pump is going to consume 10kW of power do you really think an electrically driven pump is going to consume significantly less power? The main advantage an electrically driven pump can offer is that it can be controlled on an as-needed basis and it theory ought to be easier to replace.

That being said where would such a pump be fitted on a 928? The stock pump is located within the cooling chamber part of the engine casting and as I can visualise has to be fitted there because depending on the temperature state of the engine the pump has to either circulate coolant internally or, when needed externally around the radiator. Then of course the timing belt has to be supported with a idler that would need a special backing plate to seal off the current pump volute and carry a bearing and idler pinion.

Like most things I dare say it could be done but to me it sounds somewhat pointless given the effort needed to convert. Then of course 10kW at 12 volts is some 830 amps and the stock alternator is challenged at 200 amps or whatever its rated capacity is- I do not believe that figure of 10kW absorbed by the stock pump but you cannot have it both ways!

FredR

Chebby- street speak for Chevrolet or so I understand.

foxint

Sir

Chevrolet - OK. Not many where I come from… As far as I know there is only 1 other 928 in the town…A little like being the only gay in the village (UK TV programme Little Britan)…ha-ha

So are the experts saying it will not fit in the engine bay.

Guys - I am only asking.... not selling the pumps, so I do not have a vested interest either way. But the way the Davies Craig (DC) man said: the pump only works when necessary, whereas the mechanical pump works all the time.

(Plus…I am changing the pump – so thought this would be a good time to consult the experts).

From what I understand – pleas again I am only asking and I purport no expertise in this field – that the old pump impeller is removed and the external pully remains to keep intact the belt drive. I think that is what I understand. I am sure it is far more complex than that.

But it is an interesting value proposition, when considering pumps. If (and I am saying if) it works and is as the DC main said it would manage the cooling better????

Overall great comments and I am looking forward to reading more

FredR

The whole point of floating such concepts is to stimulate discussion as to the possibilities.

This looks to be a nice piece of kit but integrating it at a cost effective price point is the issue. There are plenty of stock pumps with the plastic impeller fallen off so sealing the volute and having something to carry the belt could be solved relatively easily but the seal would still be vulnerable [the stock pump's achilles' heel] .

The main problem I see is the circulation pattern. Water pumps, especially operating at or near boiling point, need to be mounted as low as possible and at the moment I for one cannot see how this can be achieved on a 928 without major surgery as it were to establish the correct flowpath.

The thermostat is a flow diverter- operating without this feature at first glance does not seem to be a very good idea but might just be feasible if the control logic leaves the system dead until the water heats to 80'C or so. Take water out of the bottom of the radiator to feed the pump, close off the re-circulation port [back seal of the thermostat] and energise the pump based upon water temperature as measured at the water bridge and fitment may well be feasible.

Technically interesting but difficult to see how it can be a value proposition unless the pump lasts forever and one does not have to pay for new pumps and just as critical, the labour involved with such. For sure changing out an external electric pump would be little more than a 30 minute job I suspect.

Plenty of scope for discussion

The pump featured on their website [EWP130] is rated for 12 amps which at 12 volts is a power draw of 0.144 kW. So, either their pumps are way undersized or their power saving claims are nonsensical [more likely].

My conclusion- is it doable?- possibly. Could it be cost effective- hmmm?

worf928

Sorry. There is no value proposition here. You can compare the cost of the bare pumps, but for the 'lectric pump the cost of engine/engine-bay modifications alone would likely be a significant fraction - if not above - of the cost of a new Porsche-boxed water pump (which is 2x the cost of other pump options.)

On the other hand, if you want to do this as an engineering challenge over the next few months or years, then you've come to the right place for support.

dr bob

All the stuff that Fred shares on the load for the pump is good.. The idea that you only run the pump when needed is lost in the 928 though; the engine depends on continuous circulation to keep block and head temps even, so that one part of the block doesn't expand a lot more especially during initial warm-up. The thermostat system directs full pump flow through the block during warm-up, then slowly pinches recirculating flow as it moves hotter coolant through the radiator. The load on the 928 pump changes with engine speed but changes little based on temperature.

Your block adapter would add a suction seal in the center of the pump volute, and route that coolant to the inlet of the externally-mounted electric pump. Meanwhile, the timing belt will still need a support roller concentric with the center of that volute, so that suction-side connection will need to come away somewhere away from where the new support bearing and pulley are mounted. Plus you'll want to send the pump-outlet coolant back into the block somewhere, and it can't be through the normal radiator-return port since that nozzle still includes the thermostat. I'm not sure there's enough available real estate on your adapter to get the coolant out and back in with the timing belt and a support bearing and pulley in the way.

Continuing Fred R's reminder: Consider that the alternator might be 80% efficient, pump motor might be 80% efficient. So it would take about 1.5 alternator horsepower to support each 1 electric-pump horsepower. Each Horsepower is around 650 watts or 50 alternator or pump Amps when you have 100% efficiency. So you'll likely want a bigger alternator, more cooling for that too as the inefficiency translates to heat, and you'll need to find room somewhere for the electric pump and it's plumbing and wiring. I think both the electrical math and the space constraints make these pumps a non-option for the 928 as we know it.

Wisconsin Joe

^This.

While the idea of an electric water pump does have a few advantages, fitting it to a 928 would require enough modification and re-engineering to negate any gains.

Dr Bob's post covers some of the technicalities.

An interesting idea, but not really practical.

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.

foxint

Thanks guys.

Great lot of stuff to consider. At the end of the day…I will dream a bit, but take your advice. My wife thinks I dream far too much.

Great comments. Thank you.

FredR

All the great Innovators are dreamers.

Many dreamers do not get the chance to be true Innovators through no fault of their own other than possibly not being forceful enough when projecting their visions!

hacker-pschorr

Previous threads on this idea:

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

https://rennlist.com/forums/928-foru...ater-pump.html

https://rennlist.com/forums/928-foru...ater-pump.html