Electric PAS Pump swap

[Ozzy_UK]

Anyone done this?

allegedly worth up to 8.5hp on something like a honda Integra, so must be not dissimilar ammount on the excel...
seems like a good mod to gain some HP and economy... (plus mine squeeks and whines at the best of times...)

I believe you can just rip something like a Toyota MR2 unit off one and wire that in...

Any ideas/advise? Also thinking of binning the water pump and converting to an electric water pump too...

i recon the pair are worth at least 12-15hp total at high rpm...

Oz.

[Lotus-e-Clan]

OZ ...don't get me started.... there are others on this forum who are sick of hearing about it!

I did the EWP conversion years ago.

full details in this very old link.

Lotus-e-Clans EWP conversion

I also removed the PAS pump and fitted a manual rack which is not for everyone I know and there are downsides but as far as increased performance is concerned ..it is true.

How much of this is torque or power release I don't know but it hits the rev limiter quicker ..it's more tractable at low revs (pulls better in 4th (or 5th) from 30 mph)...and it is faster than standard and probably explains why I don't have as much problem against moderns like TVRs Scoobies Boxters etc.


Also saves head gaskets if you do the purge pump circuit link-up trick like I did to prevent heat soak on close down.

[AndyC]

PAS pump may release power, as it's pumping fluid simply to maintain pressure which isn't used much, but water pump will probably make no difference, or make it worse.
The water pump is doing what we need it to do, moving water, and it's that act (overcoming resistance in pipes etc) that uses the energy. If you swap to electric, it has to do the same work, but you will have it powered by electricity which means you'll be pulling more power via the alternator. As the transformation of mechanical to electrical energy and back again is going to be less than 100% efficient (pump gets warm even if the water is cool is the easiest way to prove that), you'll end up loosing out overall. This assumes the turning resistance of the two pumps are approx equal.

That said, if the water pump you replace it with is more effective at cooling the engine and keeping it at its optimum working temperature you may get a gain in power that way.

[Lotus-e-Clan]

PAS pump may release power, as it's pumping fluid simply to maintain pressure which isn't used much, but water pump will probably make no difference, or make it worse.
The water pump is doing what we need it to do, moving water, and it's that act (overcoming resistance in pipes etc) that uses the energy. If you swap to electric, it has to do the same work, but you will have it powered by electricity which means you'll be pulling more power via the alternator. As the transformation of mechanical to electrical energy and back again is going to be less than 100% efficient (pump gets warm even if the water is cool is the easiest way to prove that), you'll end up loosing out overall. This assumes the turning resistance of the two pumps are approx equal.

That said, if the water pump you replace it with is more effective at cooling the engine and keeping it at its optimum working temperature you may get a gain in power that way.

Not quite right as the electronic controller has the pump working at low speed most of the time and you can't decouple the mech water pump from high revs so you notice the difference straight away.

I have done the conversion on two cars (one of which revs to 10k rpm) and the benefits are noticeable.

To get over the work done by the alternator you convert to a large diameter pulley..the only down side is that the charging threshold goes up a few revs to about 1500 rpm (depending on alternator). The max current consumption is 7A (80 l/min EWP) ..in fact you notice the power sap more by the twin fans than the EWP..thats another thing you can chuck away too..only one rad fan needed (more weight savings).

[Danny]

Funny you should mention larger alternator pully Peter, that is on my list of things to do to the race car. It was a tip given to me by a friend who worked on wrc cars.

Dan

[Lotus-e-Clan]

Dan it's down to experience working with Imp engines and 10k rpm! The 1960-70s Imp racers worked that one out and also made them deeper so the belt wouldn't fly off on the overrun!

[Danny]

I'll have to turn my laithe on and experiment!

[Ozzy_UK]

Also saves head gaskets if you do the purge pump circuit link-up trick like I did to prevent heat soak on close down.

its actually the exact opposite reason im doing this, the car is running far far too cold!

cruising down motorway on a hot sunny day im seeing 80C, this week im seeing 75-78C during trips on motorways at 65/70mph...

even on track im not seeing more than 80C!!!

want the car to run at 90-95 all the time rather than going hot cold hot cold, as the new electric thermostat fan controller doesnt turn the 1st fan on untill 92 and the 2nd on at 100C, only on hot days on idle/stationary does the 2nd fan ever come on, and then just for very breif periods...

im just really worried im killing the engine running too cold!

also when i do the engine swap i want all the systems to be as modular as possible, so if the water cooling is stand-alone, and ideally if i can make the PAS the same, will simplify things when i come to put in an S2000 engine, as these systems will just need a 12V feed

Oz.

[Lotus-e-Clan]

Oz you won't be aware of heat soak ( which has nothing to do with running temperatures ) unless you have a purge pump fitted.

With the ignition off the temperature gauge isn't working nor are the fans but the heat from the cylinders and pistons can boil the water in the cylinder head. You'd know when it's heat soaking cos the purge pump (if working) comes on after you walk away from the car giving it away. I use a capillary temp gauge on the Clan so it shows the cylinder head temp even with the ignition off...thats when I realised it was worth doing something about heat soak.

BTW you'll lose power if you run a 912 engine with DHLAs @ 90C compared to 82C. With an EWP and temperature controller you can set the engine running temperature to what you want so it makes no difference if your rad is super efficient ...it would just mean the EWP would run at a lower rating to maintain the temp you set.

And this would happen dynamically ie the EWP runs less (and consumes less amps) when:
1. you fit a high efficiency rad (like you have)
2. airflow through the rad is high (ie at speed)
3. air temperatures are low
4. water temps are low (during warm-up)
5. the heater blower is used.

[AndyC]

PAS pump may release power, as it's pumping fluid simply to maintain pressure which isn't used much, but water pump will probably make no difference, or make it worse.
The water pump is doing what we need it to do, moving water, and it's that act (overcoming resistance in pipes etc) that uses the energy. If you swap to electric, it has to do the same work, but you will have it powered by electricity which means you'll be pulling more power via the alternator. As the transformation of mechanical to electrical energy and back again is going to be less than 100% efficient (pump gets warm even if the water is cool is the easiest way to prove that), you'll end up loosing out overall. This assumes the turning resistance of the two pumps are approx equal.

That said, if the water pump you replace it with is more effective at cooling the engine and keeping it at its optimum working temperature you may get a gain in power that way.

Not quite right as the electronic controller has the pump working at low speed most of the time and you can't decouple the mech water pump from high revs so you notice the difference straight away.

I have done the conversion on two cars (one of which revs to 10k rpm) and the benefits are noticeable.

To get over the work done by the alternator you convert to a large diameter pulley..the only down side is that the charging threshold goes up a few revs to about 1500 rpm (depending on alternator). The max current consumption is 7A (80 l/min EWP) ..in fact you notice the power sap more by the twin fans than the EWP..thats another thing you can chuck away too..only one rad fan needed (more weight savings).

I'll agree that at lower engine temps (near idle speed with air flow etc) you will need a lower water flow than the pump gives, so yes EWP will save wasting power, but do you mean our cars need a lot less water flow even what warmed through on a summer's day than the mechanical pump delivers ? If so, then I can see the advantage and may consider it myself.

Re the larger pulley, it's not going to reduce the work done by the alternator, just make it take a longer period of time to re-charge after a start-up drain, after all the alternator doesn't cause much resistance to rotation unless it's having to create electrical energy. I suppose there would be advantages with having it take more time to re-charge the battery in that it's sapping less power but for a longer period, as long as you don't do short journeys & use lots of electrical equipment all the time you can probably get away with a longer re-charge.

[Lotus-e-Clan]

Andy it just doesn't work like that!

An 80 l/min EWP at full chat pulls 7A max which is less current consumption than your head lightst!

At low road speeds in traffic on a hot day the EWP works at full chat until the rad fan cuts in.. then it backs off until the temp rises again. It does a better job than the mech pump which runs MUCH slower in traffic and needs both rad fans to cope. In fact for some installations the superior EWP control and efficiency means you could REDUCE the size of the radiator and save the weight of metal work and extra water!

And the faster you go the more air flow there is through the rad so the EWP backs off ....it only needs enough flow to keep the target temperature steady. The more efficient your rad, the less the need for EWP flow.

It's almost opposite to the way you are thinking.

Bear in mind that for a typical mech water pump 30 -40 l/min is about all it can muster and its flow is linked to revs not temperature. So a 80/l/min EWP is more than adequate for our 912 SE road engines and flow is linked to temperature.

Compare that to the needs of Imp race engines which typically use tiny 2 AMP 25 l/min bilge pump type EWPs that keeps things cool at a constant 9 Krpm...they get away with the smaller pump because they have high air flow nearly all of the time.

Oil cooling @ 9 -10 krpm is another issue mind you!

I've been monitoring the cooling systems of two cars with EWPs for the last 6 years or so including high temperature summer track days and they work in all conditions. The key to success is intelligent electronic temperature control, radiator air flow and rad thermal efficiency.

The larger alternator pulley reduces the engine torque needed to turn the alternator against high current loads so it saps less power per rev from the engine than a smaller pulley ...nothing to do with getting more power out of the alternator or reducing its work....the work to turn it is done by the engine. This tweak is on old one used by racers and is well proven.

[pompey ice]

Oz ,You say the car is running to cold , just a thought, have you a thermostat fitted in the engine block or if you have is it
stuck in the open position , is it the correct one fitted set to open at 90 deg.

cheers Ian

[Lotus-e-Clan]

The thermostat is 82C IIRC.

Doesn't take much extra cooling to make it settle just below 80C unless ragging it. Mine has done that since a rad recore. Same for OZ.

Anyway, most engine wear happens during long warm-ups. 78C isn't a big issue if you get there quickly.

[Danny]

Oz, Do you know how accurate your temp gauge is? I'm assuming that this is an original gauge on the car which is now over 20 years old.
Dan

[fitz]

Presumably with something like the MK2 mr2 PAS pump it would be running permanently? unlike some of the more recent setups where the PAS kicks in when required and is dormant for example when cruising on the motorway