Auxiliary water pump? pros + cons - PeachParts Mercedes-Benz Forum

noah brinkman · #1 04-20-2010, 05:36 PM

I have a 1986 300 SDL and was wondering if I were to need or when I need

a new water pump what are the pros+cons of an auxiliary water pump?

I would like to pick-up some horse power in the future

not much but I know the engine can handle it I'm not greedy just maybe

25-50 HP and some torque as well I have 50K on a rebuilt long block

405-410psi for compression all 6 cylinders so I'm pretty healthy there

does anybody have any experiance with these pumps weather positive or neg.

t walgamuth · #2 04-20-2010, 07:07 PM

How's that supposed to work?

rscurtis · #3 04-20-2010, 07:31 PM

I think he's referring to the practice of using an electric motor to drive the engine's water pump. This is a common practice in certain drag racing classes to cut parasitic losses. Personally, I don't see it as a option on a daily driver.

Sev · #4 04-20-2010, 08:50 PM

pretty sure the aux water pump was stock on most w126, could be wrong though. if it was, there's an inlet tube to the heater core which is fed by the aux water pump, so if you're adding this pump to a car that didn't have it, you'd need to modify the heater core to accept the hose coming from the pump

aaa · #5 04-20-2010, 08:53 PM

So how does this increase horsepower? The electricity has to come from somewhere, ie from your HP. I can see how it'd work in a drag race, toss in a fresh battery with no alternator to take hp away...

JHZR2 · #6 04-20-2010, 09:28 PM

+1, power has to come from somewhere.

25-50hp and not greedy? lol, hope that was a joke.

noah brinkman · #7 04-21-2010, 06:48 AM

I meant 25HP
and or 50LBS.

no these did not come with aux. pumps

HP comes from ditching the fan and and that rotational force

in the water pump.

yes! HP comes from somewhere

But I think an electric aux. pump isn't going to drag down
My new optima+
new alternator

Just look up water pump for your cars
I'd bet aux. pump will come up as well
I was just asking

I think benz left some HP on the table

LUVMBDiesels · #8 04-21-2010, 07:32 AM

I would go for an electric fan, but not an electric water pump.
I am assuming you will be removing the mechanical one?
If you look at sites like Summit Racing their electric pumps are for race duty only I think they would overheat if run constantly.

You would also need to alter the thermostat housing and the serpentine belt drive.

Again, not something I would do...

JB3 · #9 04-21-2010, 07:46 AM

Quote:

Originally Posted by noah brinkman

no these did not come with aux. pumps

The 86 version does not have a small electric supplemental water pump for hot air at idle? Its not a full one replacement pump, just an extra one installed for passenger comfort in cold weather during idle conditions.

There might be some confusion replying to your question, as many of the models have one of these little aux pumps, at least almost all the 300Ds do.

My feeling is that removing the stock mechanical water pump may not really produce anything in appreciable power, but it would certainly be a major job altering the engine to use an electric pump. Probably not worth your time.
You would probably do way less work removing A/C for weight (its supposed to freewheel anyway when not in use, so no more parasitic load than an idler pully), or even removing power steering.

If I were you though, I would leave the stock water pump alone, as its reliable and requires little to no maintenance, and work on increasing horsepower through fuel and air delivery. Upgrade the turbo, or modify the pump or injectors if possible.

JHZR2 · #10 04-21-2010, 08:44 AM

Quote:

Originally Posted by noah brinkman

I meant 25HP
and or 50LBS.

no these did not come with aux. pumps

HP comes from ditching the fan and and that rotational force

in the water pump.

yes! HP comes from somewhere

But I think an electric aux. pump isn't going to drag down
My new optima+
new alternator

Just look up water pump for your cars
I'd bet aux. pump will come up as well
I was just asking

I think benz left some HP on the table

You REALLY need to do the calculations. generation efficiency, battery roundtrip storage efficiency and efficiency of the electric pump, versus shaft power from the mechanical device.

IMO the main benefit of the electric fan is that you can control it and not have the wasted power at higher RPMs, when motion through the air provides cooling vice when sitting and a mechanical means can be had.

MB doesw leave power on the table. Turbo boost could be quite a bit higher... however they do this in the name of longevity.

Still, I think even with an electric fan and electric water pump, youre talking a few hp and a few lb-ft... Not 25/50.

LUVMBDiesels · #11 04-21-2010, 09:23 AM

My 1986 300SDL does have the aux water pump for cabin heat.

It has the same climate controls as the 300 SD or other W126 cars.

babymog · #12 04-21-2010, 10:59 AM

Pros: Will work with a broken belt.

Cons: Will only work as long as the battery holds out
Cost of pump, hoses, fan, mounting, new belt routing and associated hardware, larger alternator to handle the loads, electric fan and pump will consume as much HP as the mechanical ones, only through the alternator generating the electricity to run them, heat losses of charging etc. will reduce efficiency, more.

vstech · #13 04-21-2010, 11:30 AM

on race cars, the battery or batteries are in the trunk, and are charged between runs. no alternator. soooo an electric pump gives cooling for the run, and does not sap HP. on the road, the pump would be charged by the alternator, and the resultant HP loss would be more because of efficiencies of the alternator. unless the water pump pumped less water... which could cause an overheat condition in an aluminum headed motor... not wise.

mercmad6.3 · #14 08-05-2010, 11:01 PM

I run a davies Craig EWP as found on all F1 and lemans cars. It uses a panasonic motor just like a computer fan and uses so little power that you would never see any power drain on the engine. I no longer run the stock pump although some folks run the EWP as an auxiliary pump to run in hot weather.
On my 6.3 it's vital to keep heat soak out of the engine to prevent vapor lock. With this in mind ,I use a standard merc aux fan for cooling in traffic and it's wired to a Davies Craig timer along with the pump. When I shut down the car,the pump and fan will keep going on for as long as I set the timer. I like about 3-4 minutes and if the temp drops before that it shuts off.
It doesn't need much time to drop the engine temp and saves battery voltage . Easier starting is just one advantage but extended life of underhood components is another because nothing including the paint is getting cooked because of heat soak.
I find the biggest problem is under cooling because I haven't wired in a thermo switch with cut in temp. If I had this,the pump would only cut in once the engine reached,say 70*C. This would give quicker warm ups and extended engine life.
I can run at 140mph for as long as I can (get away with it...) and the temp stays at 80*C.
In traffic it's exactly the same .
Next project is to wire in a aux pump from a w126 or W124 heater system to provide water flow to the engines cold start so it goes into warm run mode quicker and saves fuel.

Forget those ancient electric pumps driven by wiper motors you see on drag cars,this is the best you can get.

mercmad6.3 · #15 08-06-2010, 03:37 AM

http://www.daviescraig.com.au/

This is my 6.3 with the EWP fitted,it's the black plastic thing connected to the water pipe near the center of the picture