2139 replies to this topic

[M111]

why would it be worse

 

 

The mechanical pump is driven directly from the crank via a belt which makes it quite an efficient drive method, now think about where the energy to turn your electric pump comes from & what it has to go through to get there...…..

[The Batman]

so you are saying an already driven alternator (which is way to big for my car) is going to make it worse?

[gaffer1986]

Car manufacturers have started to use electric water pumps because they're slightly more efficient. A mechanical pump is always sapping energy but an electric pump albeit mildly less efficient only runs fast when it needs to and can control the water temp accurately.

My daily has 2 pumps, one that runs off the camshaft from the opposite side of the engine of the cam belt - this happens to be the same pump the veyron uses so my car SEAT is essentially a Bugatti . The other is electric and is used to cool the water cooled intercooler. That way it only needs to cool the intercooler circuit when needed and is therefore more efficient overall.

[BadCop]

They also Do it to keep the Turbos from cooking the oil after engine shutdown.

Alot of warranty Turbos go into mainly rental and leasing cars because the drivers are not aware of the Problem or they dont care...

Ewp keeps the turbo core below 100°C after shutdown.
Without the waterflow it easily reaches 200°C

The third reason is they reach the working temp of the engine faster by barely turning the pump. That helps to meet EU6 Emission Standard.

[rob999]

Good job Josephine isn’t going the turdo route 😄

[M111]

so you are saying an already driven alternator (which is way to big for my car) is going to make it worse?

Have you ever noticed the revs drop when you switch something on with a high current draw such as a heated screen?  If you put more electrical load on the alternator it takes more energy to turn it, its as simple as that.

 

Alternators are only about 60% efficient from what I can find, they waste a lot of energy in the form of heat. Although the actual pump your fitting could be more efficient than O.E pump the electric motor that drives it also gets hot so more wasted energy.

 

I have no figures or tests to back this up, I just cant see how you can gain any power when so much is being wasted to do the same job unless the Honda pump is very poor.

 

I have no idea how much power it takes to drive the O.E pump at high RPM but I have a hard time believing its more than a few HP, especially if you consider how much water a 5HP Honda portable pump can shift (a lot). So at the end of the day lets just guess the OE pump uses up 5HP of the engines power to turn it, the electric one uses more or less the same how can you gain 5-15hp?

 

OE electric pumps are mainly fitted for emissions & packaging reasons.

 

I could be talking complete bollox but this is the way I see it, more than happy to be proven wrong.

Edited by M111, 31 December 2018 - 04:33 PM.

[Nev]

M111 is right, conversion of energy from mechanical to electrical to mechanical is highly likely to be less efficient, particularly if a battery is in the sequence.

Edited by Nev, 31 December 2018 - 04:40 PM.

[gaffer1986]

Whilst this is true Nev you need to remember that a belt driven pump runs more than necessary.

[fiveoclock]

https://auto.howstuf...efit-engine.htm

[The Batman]

Ah yes I see. Can you all provide me with evidence to say a ewp is worse than a mwp than I can review the situation

[JG]

My B9 Audi S4 gets warm in about 2min. I guess due to electric water pump.

It also quite frequently leaves the fans at the end of a journey no matter how it’s been driven.

The Elise by comparison takes forever to get warm.

[gaffer1986]

They're not worse Joe if they run properly, are reliable and the alternator is powerful enough. This is why most manufacturers are starting to use them especially on performance engines.

Your belt driven water pump's rpm is fixed to the engine speed which is not ideal for cold starts and different operating conditions. Your engine's thermal efficiency increases with rpm and load so it doesn't make sense to increase the rpm of your water pump at a fixed rate with the engine as it will be spinning too quickly. I can't see why you would need a thermostat with an electric pump either.

But I'll warn you about Davies Craig pumps as I've heard they're not very reliable. I think Vocky has one but he doesn't track his car where the pump would be under a lot more load in a hot engine bay. This warning I had stopped me fitting one to my car.

[Aerodynamic]

I guess you still want to have a thermostat. And always run the electric pump a little or the water will be very hot locally!?

Id like an electric waterpump to run on full power on the cool down lap.
I recon my engine temp gets higher on the cool down lap because when engine rpm is lower the water pump runs slower.

[vocky]

if you drive a car for a few years, then replace the mechanical pump with an electric pump the benefits can be noted. The engine revs much more easily, it warms up faster and there is zero noticeable difference from the alternator having to power the coolant pump and electronic controller. The Davies Craig system has a 10Amp fuse, so it uses less than 10 Amps.

 

On paper it might say one thing, but in the real world it does another

 

 

[siztenboots]

the other benefit is at high rpm , the pump might cavitate

[fiveoclock]

Ah yes I see. Can you all provide me with evidence to say a ewp is worse than a mwp than I can review the situation

It isnt, carry on with your electric water pump

Edited by fiveoclock, 01 January 2019 - 11:57 AM.

[Arno]

But I'll warn you about Davies Craig pumps as I've heard they're not very reliable. I think Vocky has one but he doesn't track his car where the pump would be under a lot more load in a hot engine bay. This warning I had stopped me fitting one to my car.

 

For their intended purpose (track/racecar use) the Craig Davies pumps are fine. They are simply not expected to get huge runtimes.

 

For a road car I'd look into something like a Pierburg CW400 which is the OEM EWP on BMW's and the like.

 

If you google them you'll see that there's 1 major (external) difference between them.. The electric motor on the Pierburg is massive compared to the Craig Davies.

 

Simply because the former is designed to be run as a single/primray engine waterpump for many, many years/miles and the latter is designed to be used either as a booster-pump (small model, helping keep coolant going at idle or when car is swicthed off) on a road car where failure is not a big issue or a single/main pump, but for fairly limited time use like in competition/track use.

 

Horses-for-courses and designed-for-a-purpose and all that.. 

 

Bye, Arno.

[The Batman]

They're not worse Joe if they run properly, are reliable and the alternator is powerful enough. This is why most manufacturers are starting to use them especially on performance engines.

Your belt driven water pump's rpm is fixed to the engine speed which is not ideal for cold starts and different operating conditions. Your engine's thermal efficiency increases with rpm and load so it doesn't make sense to increase the rpm of your water pump at a fixed rate with the engine as it will be spinning too quickly. I can't see why you would need a thermostat with an electric pump either.

But I'll warn you about Davies Craig pumps as I've heard they're not very reliable. I think Vocky has one but he doesn't track his car where the pump would be under a lot more load in a hot engine bay. This warning I had stopped me fitting one to my car.

I know bud my comment was to shut the haters up

[Nev]

Can you fit an electric pump that changes speed of flow depending on temps? If it just ticks over when at 85 degrees, but pulls loads of current and whirs like a demon at 100+ degrees? That would likely be an overall saving in HP, as it would be demand driven. Ideally the circuitry should be designed as "fail-safe", so it never stops if there is a problem, otherwise you might not notice the temps rapdily build up and melt an engine.

Edited by Nev, 01 January 2019 - 02:34 PM.

[The Batman]

So my ewp has a controller, you set the temperature you want and it will turn on / off keeping it at the desired level, this eliminates the need for a thermostat (less weight )

It also has an external led that can be fitted anywhere and if the pump fails then this will light up.