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Electric Water Pump - Pumping Losses

Is Your Water Pump Costing Power?

By Mike Petralia

There are other options as well. One would be to rig up a quick-change system using a bolt-on electric drive, like the kits offered by Moroso, and swap the mechanical belt and fan combo for the electric combo the night before you race. It wouldn't be too much work. After all, you could probably leave the electric motor mounted to the engine and once you remove the fan and belt and bolt on the new drive pulley for the pump, all that's left would be to fabricate some quick clamps for the electric fan and run the wiring with something like Weather-Pak plugs. Another option would be to swap pulleys and belts to an underdrive system for the track only, which is almost as much work as bolting on the electric system and the few extra ponies it brings may not really give you an advantage.

We wanted to see just how much power a belt-driven water pump was robbing. So we bolted a healthy Mouse onto Dyno-Motive's DTS engine dyno and went to work. First testing a Weiand belt driven pump with both under and overdrive pulleys from March Performance, and then we swapped on a Weiand electric pump to regain our pumping losses. The results proved that there is power to be found in pumps and pulleys; you just need to know where to look.

Test Engine Parts List
Short block parts from Powerhouse
Crank #661-861-0125
Pistons #H345NCP .040
Rings Speed Pro E251K
King Bearings, Mains MB 557AM, Rods 807AM
Pioneer Balancer & Flexplate
Federal Mogul gasket set #260-100
Approx price $500

Isky Hyd Roller cam #201265/272
HR lifters #2020
Pushrods #203-96
Timing set #300TS

Edelbrock Equipment
Cylinder Heads-E-Tec 170 #60979
Intake Perf RPM Air Gap #7516
Carb AVS #1806
Valve Covers #4153
Water Pump #8811

Ignition-Performance Distributors HEI w/ Live Wires
Oil system-Moroso

Machine Work & Assembly-Speed-O-Motive

Pumping Losses
We began our testing using a Weiand PN 8240 mechanical water pump, which, although made from aluminum, still runs a stamped-steel impeller, just like the impellers found in stock pumps. We felt this would be most representative of street power. We ran the pump overdriven first, to show the most power-robbing setup. Then we switched pulleys to see how much power could be gained by underdriving it. Lastly, we tossed the belt in favor of an electric pump to find the most power possible. You'll also note that we started all tests at 3,000 rpm. That's because pumping losses below that speed were minimal.

Test 1-Weiand #8240 mechanical pump, March #06061-6152 OVERDRIVE pulleys (5 1/2" water pump, 7" crank) 127-percent overdriven

Test 2-Weiand #8240 mechanical pump, March #06051-6052 UNDERDRIVE pulleys (6 1/4" water pump, 5 1/2" crank) 14-percent underdriven

By Mike Petralia
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