Electric install

[John_S4x4]

Just need some quick help here. I am thinking of installing an electrical item incar, with the following requirements :

Imax = 32.8 Amps
Qmax = 437.2 Watts
Vmax = 26.7 Volts

What's my best best bet for doing it and what whould I need. Would I need to upgrade my alternator ?
Cheers guys

[GreenV8S]

You're quoting the maximum figures, is that what you intend to run it at, or could you use less Voltage/current? If you really need 26V then that will be a bit of a problem since 12v is virtually universal on cars; you'd have to provide a completely new high voltage high current power supply. People do this sort of thing for big sound systems and hydraulic suspension just by putting half a dozen car batteries in the boot. If you're going to sustain that current for any significant time then you'd need to recharge your new supply from the existing 12v supply, which means the current requirements will be extremely high.

What's the electrical supply for - is there any chance of using a mechanical power source instead? You can take a couple of kilowatts off an ancilliary belt no problem.

[John_S4x4]

Hmmmm...If I lose the belt driven water pump (use an eletric pump instead) and put this

http://cgi.ebay.co.uk/MERCEDES-MAN-DA

in it's place, I presume that this could work and I can then do two installs of the device into the car, which would be better. Not so sure about the earthing on this ebay item though.

[GreenV8S]

I strongly advise against replacing the mechanical water pump with an electrical one. Do you actually need 26V? What's it powering?

[John_S4x4]

I actually found out I can run them at 12V, so it looks like it'll be a simplier install. Thanks for the help, GREENV8S

[leorest]

If you intend the power to remain the same then half the volts will require twice the current, so make sure the cables are rated appropriately!

P=I*V

GreenV8S - Out of interest what are the disadvantages on the leccy pump then? Would have though a big plus would be being able to run the cooling system for a few minutes after switch off.

[GreenV8S]

leorest said:

GreenV8S - Out of interest what are the disadvantages on the leccy pump then? Would have though a big plus would be being able to run the cooling system for a few minutes after switch off.

Having pump run-on can be nice to dissipate heat soak. The problem with the leccy pumps is that the common aftermarket ones have pidlingly low flow rates compared to the OEM mechanical pumps. Maybe you can get away with it in engines that are designed from the outset to tolerate low flow rates, but for engines that are designed for a mechanical pump if you fit an EWP you cut the water flow rate by an order of magnitude or more. You can cut the flow rate an awfully long way before the average temperature goes up dramatically, but dropping the flow rate increases temperature variations in the heads which is very bad for durability. Basically if you have a 5kW mechanical pump you need a 5kW electrical pump to replace it; a 200W aftermarket pump doesn't cut the mustard. Even if you put the mechanical and electric pumps in series so you get the 'best of both worlds' the cheap EWPs are so restrictive that they choke the water supply even with the welly of the mechanical pump to keep it going.

[leorest]

Interesting

Thanks

I started to think along the lines that an electric pump would be more efficient but stopped myself when I realised the power is ultimately mechanically derived.

So the problem is cheap, sub-specification pumps rather than the technology.

If you could get/afford an appropriately rated pump then during Wide Open Throttle conditions you could remove the alternator charging load on the engine (electrically or using a clutch). Which should make several kW available for going faster (or pushing that graph higher on the rolling road).
I remember cutting an inch or two off of the fan blades on my 850 mini made it accelerate noticeably faster so the ancillary loads on an engine are quite significant (esp. on little engines). For the relatively short time an engine stays at WOT the ancillaries can be powered from energy stored in the battery.

You're right though there doesn't seem to be enough pros to outweigh the cons.

It's hard to come up with any better ideas for supplying power without understanding the application better… It's a bit like playing 20 questions

Is the power required continuously, intermittently, for 10-minute bursts or for hours at a time?
Is the power required when the engine is on/off?

[GTWayne]

Electric water pumps are still in thier relativly infant stage and development progress is being made swiftly year on year.American firms seem to be pioneering these products with more and more positive results and I for one will be using one on my Ultima project with 650bhp SBC installed.I will let know how it performs.

[Pigeon]

GreenV8S said:

Basically if you have a 5kW mechanical pump you need a 5kW electrical pump to replace it

And a big alternator

[Holst]

John_S4x4 said:

I actually found out I can run them at 12V, so it looks like it'll be a simplier install. Thanks for the help, GREENV8S

I would be intrested to know what your using such a big peltier for?

I have quite a bit of experience using them for computer cooling.

Cant think of why you would want one on a car though. Aircon with a compressor is much more efficent, and a fridge wont need a 437watt Qmax pelt.

[GreenV8S]

Holst said:

I would be intrested to know what your using such a big peltier for?

Is it definitely for a peltier then? Only reason I can think is charge cooling or aircon, and it doesn't seem particularly well suited to either of them. I did read about somebody who had set up a peltier to cool the fuel rail, but I didn't see the sense in it.

[Holst]

The specs he has given are for a commonly avalable TEC.

www.frozencpu.com/exp-04.html

[John_S4x4]

10 out of 10 for Holst Yes, it has crossed my mind to use a Peltier or TEC for charge cooling. I'm thinking about a supercharging project running less than 14psi (only after an extra 80bhp), but no room for an intercooler. I also know about some of the developments in PC cooling and wondered about using the same componants, for cooling the ACT on the intake. Although not as powerfull as an intercooler, the peltier setup is small, lightweight and can get below ambient temps on the peltier.
I was thinking along on the lines of running a pair of fanless heatsinks inside a custom plenum chamber, with the base of the heatsink on the outside plenum wall. Then a pair of 437w peltiers followed by a pair of water blocks fed from the cold side of the car radiator. The pair of peltiers would seem to manage a 60°C temp difference, which is worth having, IMHO.
I can't see it working too well though....as the water would be hot and it would be running at half the voltage and hence less power from the peltier. I suspect if it was that easy, all boosted cars would have them fitted.
I supose that posting on PH is the good way to do things, as there infinetly more people with good advise to give than I have sense
I'll shall have to do some more research and visit here www.kryotherm.ru/soft.html

[Toast King]

Surely the power gains from then engine are ofset by the power drawn by the hoooge altenator and coolers?

Also if heat sinks dont protrude much into the airstream, then there will be little cooling effect as most of the charge will zip striaght by them.

[John_S4x4]

I think that the general rule of thumb is that “You gain approx 0.5 - 1 hp for every 1 °C you can lower the inlet air temperature.” and that was what I was aiming for.
I think I will give up on this idea and go for a chargecooler setup. A much better and proven idea.