Bilge pump mod

[lovemysan]

I read about this guy swapping a 500 gph boat bilge pump on to his sentra in place of using his water pump. Of course he did it for horse power. He daily drove the car for 2 weeks after and reported that it did not overheat. I never went back and looked at the thread for more info.

Someone should try this a cheap electric water pump on there car and no acc belts.

[markweatherill]

Don't forget that the power to run an electric pump comes from the alternator. It isn't free! There are potential mpg gains but they must outweigh the inefficiency of having to drive the alternator to provide juice to run a pump, over the engine driving the pump in the first place.

[MetroMPG]

Perfect for someone who runs without an alternator though. I didn't know there were inline bilge pumps - the one in my boat has to be submerged before it will pump - there's only one hose fitting on it: "out".

[Bill in Houston]

Originally Posted by markweatherill

Don't forget that the power to run an electric pump comes from the alternator. It isn't free! There are potential mpg gains but they must outweigh the inefficiency of having to drive the alternator to provide juice to run a pump, over the engine driving the pump in the first place.

Mark, I think that the idea is that while you are cruising along a flat freeway at 55mph, there's really no need for your water pump to be turning 2000 rpm. The pump is sized so that it pumps enough water for you to pull a trailer up a mountain on a 120 degree day, and it pumps that amount of water all the time. A thermostatically controlled electric pump could be sized more appropriately for a driver's particular use, and would only run when it needed to. It's the same idea as the electric fans on car radiators.

[lovemysan]

I'm not going to try this but someone else might. I wouldn't recommend it on a daily driver either but it would be an interesting experiment. I'm sure there is a cheap marine pump available somewhere that would work. Sadly I don't remember the particulars anymore. It seemed to have been some type of marine pump purchased at walmart for around $25.

[JanGeo]

The motor is a brushed motor in those pumps and will wear out eventually. The one advantage is that you can maintain a constant water flow and that can be helpful if you are running hot and are operating the engine at low rpm because the pump can be running at a higher volume than the belt driven water pump would be running plus at higher RPM you don't overspeed the water pump and cavitate it thus saving power etc.