Electric water pumps re-visited

[Sam_Q]

CrUZida: courtesy of chris:

http://www.toymods.net//forums/showthread.php?t=26776

I havent had a look at the peak current of the davies craig stuff yet, however I know it will be overkill and I don't know if they will share the data but I will check.

I don't think it's backwards, it should save a lot of power and it unlike the normal aftermarket options allow me to have the normal pump/cooling layout like stock instead of having water that isn't moving untill the thermostat opened. To do things properly with a davies craig pump I would need an external thermostat and a heap of ugly and messy piping.


Tweak: I wouldn't think so, it's my understanding that these run long term constantly and thats what they are made for. I think that motor is steel and I know it isn't that small because I called up VPW and found the dimentions, it has a 110mm diameter and an 80mm body excluding the pulley.

beerhead: 100A at high revs on my engine is about 15 V so thats 2HP assuming a 100% efficient alternator. I still agree with your statement of 1% though. I would of thought that the ignition system needs the 14V though to run properly though?

[Sam_Q]

knightrous: thanks for the tip, they are at the self serve wrecker which is just what I wanted. So I can assume they accept their speed being changed with a pulse width modulator then? I could do a brushless, I could just do a downscaled recipe as what I am getting together for my 3x3 recumbent trike, and that is a 170Kv outrunner motor with a servo tester. Cheap as, I might do a proof of concept first and if I decide to go nuts I will go from there, I seriously doubt it though considering my time limitations.

[_FNQ_rolla_]

Just another thought, maybe this does not have enough flow or you do not want to go this way but maybe the water pump from a water to air intercooler.

like the one in this link http://www.tweakit.net/shop/popup_image.php?pID=6558

[beerhead]

Ah, very true - didnt' think about the voltage issue for the coils - weak spark = fail. I suppose the drop back to 12V will see the injectors not opening as much or as fast either, possibly upsetting the tune.

In the past I designed a system to get rid of the thermostat and digitally regulate the temperature of a motor. The problem being It needs extensive work done making a control module to regulate the system, hopefully I can convince an engineer I know to help me finish the idea at some point. I gave up a while back on the idea, I figured if Davies Craig can't do it, I can't either

[Mr89Cressida]

Couple of reasons Mate.

1) water flow doesn't need to be proportional to engine RPM. ie: an idling motor at standstill should need nearly the same flow as a revving engine at high speed.

2) At high rpm the standard pump takes power to run regardless whether it's needed or not. An electric pump only takes power if it's needed. A bit like Alternators that only charge during deceleration.

3) High RPM could cause cavitation on a standard pump.

edit: I wrote that reply in a hurry. Basically what i'm saying is, the power taken out by the pump is somewhat proportional to impeller RPM. The faster the engine runs, the more power the pump takes from the accessories belt. Often when racing etc, the water pump does not need to spin as fast as the engine is making it, so it can be slowed down with an EWP to save a bit of power. In my opinion though, this power saving would be 2/5's of F-All in the scheme of things, and the other things, like water cavitation and pump durability at high RPM are more important.

Sorry mare but point 2) All Alternators charge all the time unless its a toyota hybrid which is a different system, an alternator chargers all the time reguardless of the engines rpm, what governs the charge rate is the regulator which read the voltage of the battery there for, give more current or less, but always charges... just to clear that up, but all in all you a right the power that the water pump takes is F-all its such a small % that isnt really something to be worried about...

but on point

an elec motor can be used to run a belt to run a water pump but it would have to be big, well what i mean is use heaps of current, best would be a wiper motor or something of the sort, or even better a 240volt and connected to a power inverter...

But easy was is a craig davis elev water pump as mentioned by a few guys...simple compactish and realiable...

[timbosaurus]

^^^ Nope, not true. We turn off the alternator whenever we want.

It increases Fuel Economy significantly to allow the car to run electrical load off the battery, and recharge it hard during decel. Not much use during a long steady highway drive without many decels, but great in the city.

Maybe you're stuck in the 90's.

[Sam_Q]

I mightbe going to plan B here and using this:

http://www.hobbycity.com/hobbycity/s...less_Outrunner

[Shifty]

The early Davies, Craig pumps are crap. The newer design (last 12-18 months onwards) are much much better. The early ones had a lot of problems with leaking etc but the later ones (in my experience) are much better. Taht said, I'm still not overly excited about them because they tend to take up a lot of space and add complexity to your cooling system, but I reckon they're one of the best/easiest options out there.

If you are using an electric motor, it's critical that you use the right one so you need to work out your requirements.

Do you want it to run flat out all the time? Do you want it to be switchable manually, or by a thermo switch, or able to be run at different speeds?

I still think a DC pump is the best way to go.

[Sam_Q]

I think the fact that Davies craig even released such a shit product at the time is pathetic.

So why do you think the DC pump is the way to go?

I was going to do some experiementing and find out how slow I could run it whist still cooling ok and then have that as my low point, this would be anytime when the engine is on. Then have the high setting that comes on when the thermofan comes on. That way it should have the least amount of loss. I have been thinking about making something up where the motor sits on the end of the shaft.

[CrUZida]

I may have missed it, but I'm still not sure why you are going this way?

Is it to save power, or prevent cavitation, something else?

I gather you've already looked at an oversized waterpump pulley?

[Mr89Cressida]

^^^ Nope, not true. We turn off the alternator whenever we want.

It increases Fuel Economy significantly to allow the car to run electrical load off the battery, and recharge it hard during decel. Not much use during a long steady highway drive without many decels, but great in the city.

Maybe you're stuck in the 90's.

and how exactlly do you turn it off? unless you take the belt off or take the main battery cable off, im sorry but there isnt an ON/Off switch on an alternator....

and increase fuel economy by how much exactlly?

[river]

Hi,

Well it could have a clutch, but then you'd have the extra weight of the clutch and associated electromechanical components to engage and disengage it.

You could disengage the charging current, as the more charge the alternator has to put out, the more power it will take from the engine, however, unless the alternator is physically disengaged from being physically driven by the engine, you'll be wasting energy spinning the alternator which is ostensibly doing nothing.

And finally, if the battery is full, then there is no, or insignificant, load from the alternator as it is not required to charge the battery.

I am not commenting on whether the above make any difference to power getting to the back wheels. I'm just throwing up ideas.

seeyuzz
river

[timbosaurus]

First answer... through duty cycle control of the field. If you don't energise the field there is no load on the engine. Yeah, there is still frictional drag through bearings etc. but for all intensive purposes the alternator is not charging and not impacting the engine one little bit... I'd call that 'off'.

To answer your second question, every 10Amps saved gives us ~0.1 point on the windscreen sticker. No, not much, but when it's 10.1L/100k vs 9.9L/100k, it makes a huge difference to sales.

[timbosaurus]

And if I hadn't already mentioned it, the reason we do it is to charge the battery during engine braking as much as possible. ie: Driving downhill, slowing down at lights etc, typically whenever you use the brake the alternator will dump as much charge into battery, loading up the engine, giving you more engine braking.

If you know your battery operates fine at anywhere from 40% to 100% state of charge reliably, without damaging the battery, and you are at 70% state of charge. You can reduce the alternator (or generator to be exact) output and allow the vehicle's electrical load to come from the battery, using less fuel. You'll see the voltage drop to 12ish volts during this time. Potential power output *may* also increase, but not measurably. It might get down to 60% before you first brake, which get's it back up to 65%, then lets it fall to 55% before the next braking event etc. The system will not let it fall dangerously low, and there are unfortunately times when the alternator has to run regardless (high current situations like when the lights and cooling fans are on etc). There are a lot more smarts than I have room to write about here.

All I'm pointing out is that the old way of regulating a cars electrical system to a fixed 14.4 volts is not how it's done anymore. It can be though of as a very crude regenerative braking system without the huge cost of wheel motors etc.

[Mr89Cressida]

Great, lot of info but seems to me your talking about regenative brakeing