Electric Water Pumps

[Mike Hart]

Currently in the process of speccing various parts of the cooling system and after doing my research and testing we've landed on an electric water pump to provide a way of ensuring we can balance the whole system. I also found that the largest issues we had with our previous setup (which was on the very limit of overheating) was that the actual water system was causing the biggest issues with poor water flow at low rpms. It seems the standard mechanical pump is incredibly sensitive to being fed water from the rad. It has virtually no ability to pull any water at all and in the case of our dyno with a heat exchanger just below level it couldn't shift anything!

About 5 years ago (when we used to run CBRs) they fitted a Davis Craig pump which ran fine in testing, but then proceeded to go on strike during the endurance. I'm therefore a little worried about reliability and was wondering what everyones experiences were with them? Has anyone successfully used any OEM stuff from road cars such as the Bosch range of production car water pumps. I get the impression these are purely meant as backup systems, so again, reliabilty may be an issue.

Cheers

[Biggy72]

From what I've read you can go one of two routes with the Davies Craig pumps, either two booster pumps in parallel, or a normal small pump that's a little overkill. Other than those two options I've had a hard time finding a small light electric pump that doesn't draw a ton of amps.

But with that said we're going to run a stock pump with a small electric pump to cycle when the car's off for a set period of time or until an engine temp is reached, to keep the engine from heat soaking. The one we got was a Bosch pump off of the climate control unit from a Mercedes. It's tiny and weighs maybe 1/4-1/2 lb. I haven't ran it yet to see what kind of volume of water it puts out, but we shouldn't need much for what it will be used for.

[MalcolmG]

We've had a bit of a mixed bag with the Davies Craig pumps. We've run the EWP85 for the last 3 years. In Germany in 2006 a circlip on the shaft between motor and impeller twisted and jammed, causing the pump to seize and us to miss out on finishing what was a pretty good Autocross run.

Since then we've also had an almost brand new one leak in the seal between the impeller shaft cover and housing (which from memory is an O-ring). Davies Craig do give a nice discount to Formula SAE teams though, and for the most part they are reasonably reliable

[Michael Palaszynski]

Been running a Davies Craig pump for at least three years. The small size is great for packaging. And the small weight of the pump is cool too.

But these pumps are finicky. They do not like to run dry. The rotor will refuse to turn (smoothly that is) without water being pumped through. I believe back in 2005 we also had the same problem with the circlip coming apart due to friction or whatnot.

Basically, always keep the coolant system primed. It's also a good idea to place the pump at the lowest part of the system to ensure the pump has water in it at all times.

[BeaverGuy]

About 2 years ago I was looking into using an electric pump. I compiled flow curves for the entire line of current Bosch pumps as well as the Davies Craig pumps. The Bosch curves were a little difficult to find because I think I had to navigate through one of the European sites to get them. What I found is that very few of the smaller pumps are going to be up to the task without some creative solutions. The reason is they don't flow very much water. In order to get a pump that has comparable flow to the stock pump at high RPMs you will need something that will likely max out your charging system. However, a low volumetric flow rate isn't exactly a bad thing. You just need to account for it in your design.

The problems mentioned of a leaking housing and the jammed motor due to the circlip coming are things I don't believe would happen with the Bosch pumps. The Bosch pumps are all magnetcally coupled meaning no shaft running from the motor into the pump housing. However, they don't list anything with more than about 5gal/min flow, which is about 1/4 of what you could get with a free flowing system at high rpms from the stock pump. The Bosch pumps are fairly nice and readily available for a low price. I purchased two different models. One was an assist pump from a Volkswagen and the second was the intercooler pump from the Ford Lightning. The latter has a decent flow rate and doesn't draw too much current.

[Michael Palaszynski]

The Davies Craig pumps are also manufactured by Bosch. True there is no shaft connecting the impeller but the impeller is retained by a small shaft (approx. 1mm) It's plastic rubbing on metal, with no bushing of any kind.

At least in our case, it wasn't the motor failing, it was the impeller becoming lodged.

Checking out the site, I think this year we're gonna go for a Bosch.

[Chuckster]

I'm not so sure a low flow rate at high RPM is ever good except maybe at light throttle. Nucleate boiling from not maintaining pressure is always a possibility too.

Electric water pumps sort of come and go in road racing. Even a Formula ford needs a lot more battery to run one.

Using an electric one as a scavenge pump with a stock pump to maintain pressure sounds OK.

[Ekasey]

Hey Guys,

I'm unsure if this pump is too big, or if it will work at all, but I have heard a lot of good things about these guys

http://www.stewartcomponents.net/Merchant2/merchant.mvc...egory_Code=ElectPump (http://www.stewartcomponents.net/Merchant2/merchant.mvc?Screen=CTGY&Category_Code=ElectPump)

worth maybe giving them a shout

[Mike Hart]

Thanks for the replies everyone. Now you mention the circlip issue, I seem to remember that it could have been this that caused the failure on our car. It's the kind of thing someone mentions in passing and you forget about!

The two booster pumps in parallel sounds like quite a neat solution that I hadn't thought of. Our chassis design prohibits the use of the standard mechanical pump (it really is truely rubbish anyway!) and with two radiators, it might actually work out better to run a pump per rad. This might also reduce the amount of pipework although I'll have to double check on the water flow diagrams again. Obviously, it also means that if one fails, there is a backup and it might also help with balancing flow through the two rads.

BeaverGuy - The VW one was one of the pumps I'd looked at. I believe they're standard on the 1.8T engines over about 180bhp...so some of the Golfs and most of the TTs. I might pay a visit to a scrappy and see if I can get a couple to test. I'm fairly au fait with the 20VT engines (too much time spent on internet forums!) and I don't recall any issues with water pumps so it would seem that they don't have any issues when in situ. Running them on a bike engine under high stress though is a different ball park all together though of course.....

I'll keep you all updated as to what I find out. Since it's my final year project I'll put any measurements/results I get up here to for future reference http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Pete M]

Originally posted by Mike hart:
The two booster pumps in parallel sounds like quite a neat solution that I hadn't thought of. Our chassis design prohibits the use of the standard mechanical pump (it really is truely rubbish anyway!) and with two radiators, it might actually work out better to run a pump per rad. This might also reduce the amount of pipework although I'll have to double check on the water flow diagrams again. Obviously, it also means that if one fails, there is a backup and it might also help with balancing flow through the two rads.


This is essentially what we do.

[Mike Hart]

The Bosch curves were a little difficult to find because I think I had to navigate through one of the European sites to get them. What I found is that very few of the smaller pumps are going to be up to the task without some creative solutions. The reason is they don't flow very much water.

I don't suppose you happen to have a link do you? I've had a search but can't seem to find them!

[Mike Hart]

Originally posted by Mike hart:
[QUOTE]The Bosch curves were a little difficult to find because I think I had to navigate through one of the European sites to get them. What I found is that very few of the smaller pumps are going to be up to the task without some creative solutions. The reason is they don't flow very much water.

EDIT: Not to worry....found the flow curves now.

Anyone have any idea where to source the pumps from here in the UK? There's a very old post on the forum here: http://fsae.com/eve/forums/a/tpc/f/125607348/m/43810445821
where someone from Bosch replied, but he hasn't been active on here since 2005.

It would seem the most appropriate pump would be Bosch part number 0 392 020 064 which delieves 20l/min and is only .4kg but finding the end supplier part number (ie so I can go down the scappy and find one!) is next to impossible to get hold of. If you searh for it, I just get a load of places in the States.

[Biggy72]

It looks like they came on Ferrari's

http://cgi.ebay.com/ebaymotors/Ferrari-water-recirculat...ash=item140207612225 (http://cgi.ebay.com/ebaymotors/Ferrari-water-recirculation-Pump-355_W0QQitemZ140207612225QQcmdZViewItem?hash=item1 40207612225)