Locost_Johnh wrote:
Keep in mind also that energy is energy and the more times you convert it the less you get at the end. I don't know what the losses are from a belt, but the water pump driven directly from the crank is pretty efficient. Electric or mechanical you have to move a certain amount of water to cool the engine and that means expending a certain amount of energy to do it. An alternator spins freely (some bearing loss) when there is no load. When you drive an electric water pump with it, the load increases to whatever the mechanical requirement is for that much water, plus the loss in conversion (mech to elec) in the alternator and the loss (elec to mech) at the pump.
So after all that money and fussing around, don't expect a world of difference in your net power at the wheels.
John
I know what you mean, the main problem with the water pump though is that works well enough at 750rpm (engine idle) to effectively cool the engine in rush hour traffic with the air conditioning running etc. So surely when the engine is spinning at over 8,000 rpm there is a lot of wasted energy. Surely it would only take 2 at most 3 times the energy to cool a quickly revving, fast moving engine. Yet it is spinning about 11-12 times as fast at redline.
The pump I looked at had an intelligent controller that keeps the coolant at a chosen temperature range by controlling the speed the coolant goes through the radiator it also keeps the coolant flowing after the engine is turned off to prevent heat soaking.
John Hennessy, you lost me a little with the parts you mentioned but I do really like the ideal of driving the alternator off the drive shaft. I bet I have room directly below which will mean I can remove everything from the front of the engine and drop a lot of rotating mass. I really want to keep a functional battery so I can do track days etc and I just don't like the idea of another thing I could forget at a big event.
As far as gains I think 10 WHP would be nice from both upgrades but less would be fine. It is effectively free HP as you are reducing load on the engine which extends engine life rather then other power upgrades such as boosting which increases pressure on the engine reducing engine life. With the alternator I can drop about 10lbs of mass and lower that mass by about 12" also some rotational engine mass. Not sure about weight from the difference from the pump but it will also be about 12" lower and I can move it around a little like ballast.
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2015 & 2016 EMod Florida State Autocross Champion
2013 & 2014 DSP Florida State Autocross Champion
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