mechanical pump underdrive

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November 27, 2022, 10:17 AM

wideopen231

mechanical pump underdrive

Wondering if anyone on site has run a mechanical pump with an underdrive. If so results, how much change in flow vs speed and thoughts on it? I guess an overdrive would affect the same but the other side of the coin so to speak so input welcome too.

November 28, 2022, 09:35 PM

Dave Koehler

I will probably regret this but why?

Dave Koehler - Koehler Injection - http://www.koehlerinjection.com
Fuel Injection - Nitrous Charger - Nitrous Master Software - Balancing
99% of fuel injection problems are electric.

November 29, 2022, 05:36 AM

wideopen231

quote:
Originally posted by Dave Koehler:
I will probably regret this but why?

Not sure what to regret? I was just wondering about a pump I have that is little bigger than need and if underdriving it some with drive I have would get it closer on flow instead of bypassing twice as much fuel as going to engine.

I have some old flow numbers from Ralph that show flows on few pumps with straight up drive and then under or over. Only 3 or 4 pumps have comparison numbers. Most seem to linear change. Just researching idea some as to what to expect if I decide to try.

November 29, 2022, 07:12 AM

Dave Koehler

Linear they are, give or take. 10% equals 10%.

Dave Koehler - Koehler Injection - http://www.koehlerinjection.com
Fuel Injection - Nitrous Charger - Nitrous Master Software - Balancing
99% of fuel injection problems are electric.

November 29, 2022, 10:21 AM

wideopen231

Thanks

December 03, 2022, 01:44 AM

Alaskaracer

My Ron's pump is driven at 1/2 engine speed....but it's a different system than what you're running...

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December 03, 2022, 06:01 AM

wideopen231

you mean same speed as cam? Which is normal speed for pump. Asking baout lower than normal spped to reduce pump output.

Have a larger than need pump and figure if get required size at lower rpm has to better for pump life too.

As dave said it runs linear for speed and flow.10% under will give 10% less flow. WHich is what I was thinking and just dbl checking.

December 03, 2022, 10:54 AM

Curly1

Most all pumps for MFI that I know of run half crank speed whether they run off cam (1/2 cranks speed) or pulleys off crank.

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December 03, 2022, 02:18 PM

wideopen231

Best thing about belt drive pump speed simple and cheap if you want to chnnge it.New pulley or pulley and belt.Lot cheaper than the drives from waterman that I am guessing were for fuel guys back in tha day,,Mine cam out of fuel funny parts inventory. Probably what caused me to think about this deal. Hate parts just sitting there wanting to be used.LOL Yea I know whole damn car doing that most of the time.