V7 SLR Posted May 12, 2003 Share Posted May 12, 2003 Not sure PC says EWP's in general can't work. I think it's more the fact that the implementation with the variable speed pump controller (which precludes the use of a thermostat) is something that none of us really like. The best implementation, as Miraz said, is to run the EWP flat out all the time and (with a thermostat) bleed coolant from the radiator circuit into the "engine" circuit as required to keep the engine at the desired temperature. This "desired" temperature is dictated solely by the thermostat. In principle, if you do trust your thermostat, the only place you need to measure your coolant temperature is in the radiator. The only reason for measuring temperature there is to feedback to the fan. Without the thermostat you are always pumping relatively cold coolant into the head, which is why PC says you're getting a large gradient across the inlet and outlet. Once all the coolant has got up to temperature the gradient is less but if you have an efficient radiator (like mine) then it will always supply relatively cold coolant. Then again, as Miraz says, with an iron block perhaps this is less of a problem than it would certainly be with a K. Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours Link to comment Share on other sites More sharing options...
Peter Carmichael Posted May 12, 2003 Share Posted May 12, 2003 Once the engine is up to temperature the pumps running full speed, [snip] Surely that's exactly the same as it was with the standard water pump running flat out with the thermostat wide open? Beware of statements beginning with "surely" because they indicators of fundamental misunderstanding. Normal engines do not run consistently with the thermostat wide open. This is your first mistaken assumption. You have also dismissed the value of the bypass circuit. Even with a thermostat wide open, there is still bypass flow and it is this that ensures the temperature gradient across the head is minimised. If you do not have a bypass, the temperature rise across the head equals the temperature drop across the radiator which can be as much as 30 degrees. You are killing your engine. I would not recommend anybody do this to their poor engine. Link to comment Share on other sites More sharing options...
Chelspeed Posted May 12, 2003 Share Posted May 12, 2003 > Beware of statements beginning with "surely" because they indicators of fundamental > misunderstanding. That's a very patronising response, have you been studying at the Arnie Webb school of winding up Blat Chatters? To me "surely" implies this is what I think, but I'd be very grateful if you could please let me know if you think differently. I dismissed the bypass circuit as I was under the impression that it was isolated when the thermostat was open. If that's not the case on the Vauxhall, which sounds to me like it's plumbed totally differently with regard to the thermostat, then I'll need to reconsider. I'll certainly get some form of water temperature measurement in the radiator outlet to see what DT I've got across it. Link to comment Share on other sites More sharing options...
Peter Carmichael Posted May 12, 2003 Share Posted May 12, 2003 I could have written: *NO* and that would have been a terse response. Sorry but I can't win this game. Link to comment Share on other sites More sharing options...
edmandsd Posted May 12, 2003 Share Posted May 12, 2003 Do F1/DTM/Super Tourers use EWP's....if they do, the ones they use are probably ok if installed as they install them. If they don't i'd suggest they don't for very good reasons - other than reg prohibitions of course. Personally i'm happy with what Cosworth designed for my engine back when I was born even if it does cost a small fortune these days ! Has anyone actually measured the power gains, before the gullible ones of us go rushing off to purchase one and at the same time assume their engines are x hp more powerful ? Home of BDR1200 Link to comment Share on other sites More sharing options...
V7 SLR Posted May 13, 2003 Share Posted May 13, 2003 I'm of the opinion that unless the normal mechanical WP is inefficient (might be) then an EWP will consume the same amount of energy which the engine has to deliver. The advantage in my mind is in better control of the cooling, especially when you switch off the engine. Worcs L7 club joint AO.//Membership No. 4379//Azure Blue SLR No. 0077//Se7ens List Tours Link to comment Share on other sites More sharing options...
Miraz Posted May 13, 2003 Share Posted May 13, 2003 My goal was to be able to run the cooling system without running the engine - in order to allow pre-heating and cooling after a hard run. I've not made any attempt to measure power gains (or losses) - an electric pump is likely to be less efficient than a direct mechanical drive, but the standard water pump is designed to become less efficient as the revs rise.... fwiw - I believe that many of the GT cars are running electric cooling systems Edited by - Miraz on 13 May 2003 09:58:24 Link to comment Share on other sites More sharing options...
Chelspeed Posted May 13, 2003 Share Posted May 13, 2003 A centrifugal pump will have a set of performance curves that dictate how it operates, they are HQ curves, head against flowrate. In an engine head is effectively fixed so flow will constant - but only for a constant pump speed. This is where a mechanically driven water pump on an engine must struggle. If it is designed to move enough water at tick over then it must be operating hopelessly away from it's design point at 5000rpm, let alone 9000rpm. Operating away from it's design point will mean it pumps differently to how it should, exactly how this manifests itself will depend on the shape of the pump curves. It could flow more, it could flow less, it could cavitate, it could use loads more power than it should etc etc. If it's designed for 9000rpm then the water wouldn't move at tick over and similar problems. Obviously it does work but a well designed electric pump running at a constant speed must be better. I don't think anyones arguing about this. All we're arguing about is how best to implement the pump into the rest of the system with regard to the pump speed control, the thermostat, bypasses etc etc. Link to comment Share on other sites More sharing options...
Chelspeed Posted May 14, 2003 Share Posted May 14, 2003 Now got a second temp sender on the radiator outlet displaying on the dash and being logged. We'll see what happens on Saturday. I'll take the thermosat with me....... Link to comment Share on other sites More sharing options...
TorAtle Posted July 14, 2003 Share Posted July 14, 2003 Chelspeed, did you measure the temp on each side of the block? One thing I haven't seen mentioned here - with an EWP, is there really a need for a radiator fan? Wouldn't the EWP at full blat be capable of keeping the temp resonably low at engine idle? Link to comment Share on other sites More sharing options...
Graham Perry Posted July 14, 2003 Share Posted July 14, 2003 Not in stationary traffic it won't, or at least it doesn't on mine. Edited by - Graham Perry on 14 Jul 2003 09:12:41 Link to comment Share on other sites More sharing options...
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