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Old 07-02-2019, 08:24 AM   #11
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Join Date: Nov 2006
Location: Cucamonga CA
Posts: 3,687
Originally Posted by itsnotanova View Post
I'm looking at going to an electric water pump on my rallycross boxster. Anyone know how many gallons per minute the factory water pump puts out?
This is an interesting question and not as simple as it seems. The stock WP is belt driven continuously variable based on rpm. It flows twice the gpm at 6k rpm as it does at 3k rpm, less head losses. Electric pumps also vary in gpm a lot based on head loss. You need to match the electric pump flow to the OEM pump through the system to get it right.

You could run an experiment. Do some math and figure out the actual pump rpm while the motor is turning at 6k. Then rig a drill to drive the pump, run water from one 5 gal bucket through the pump > through the plumbing and radiators, back to the motor, and into a second 5 gal bucket. Fire up the drill to simulate the engine at 6k and time the process to fill bucket #2. This would reveal the max flow needed from an electric pump.

Hook up your chosen pump and test it to make sure it meets or exceeds your minimum required gpm through the system. Allow your t-stat to regulate engine temp by opening and closing as needed to keep coolant at 180F-220F.

I don't know anyone who has measured this on a Boxster but it would be very useful in a racing application. The drag racing guys have been doing this for years on V8s.
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Last edited by Topless; 07-02-2019 at 08:35 AM.
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