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Al Kittleson
New member
Username: Al38kit

Post Number: 11
Registered: 07-2007
Posted on Tuesday, September 25, 2007 - 06:01 pm:   

I have an IO-520 that was not configured with the two speed electric boost pump. I have bought a new Dukes pump and want to configure it with a two position switch for the high and low setting.

Anyone know what value and rating of resistor or use?

I've heard that the low positions should be one that is roughly half the voltage, but I don't know for sure...

Anyone?
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Roger Spencer
New member
Username: Roger

Post Number: 32
Registered: 05-2001
Posted on Tuesday, September 25, 2007 - 06:39 pm:   

Al
I have an IO-520D as well and have been meditating over which boost pump to purchase. What's the part number on your Dukes pump. Likewise, I would like info on the dropping resistor
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Sven-Ake Eriksson
New member
Username: Sven

Post Number: 27
Registered: 11-1999
Posted on Wednesday, September 26, 2007 - 07:06 am:   

Hi
To get the right value you need to supply power to the pump when it is working with real fluid and approximately the correct flow also. Measure the voltage on the pump connections and the amperage flow into it at the same time. The resistor value is then found by using the following formula. Resistor value=(supply voltage-pump voltage)/(pump amps). Then you choose to set the power rating of the resistor which MUST be higher than (supply voltage-pump voltage)*(pump amps). How much safety factor you need depends on how good you can cool it. Choose a standard high wattage type and mount it where it can get rid of the heat. There are formulas from suppliers that reads out how much you have to derate power rating due to resistor temp. Supply voltage is a nominal 14 volts when using a normal 12 v system with running alternator. The unknown point in this is how much pressure and fuel flow you will need from the pump.
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Al Kittleson
New member
Username: Al38kit

Post Number: 12
Registered: 07-2007
Posted on Wednesday, September 26, 2007 - 02:23 pm:   

I bought PN 4140-00-39NV.

23PSI Max NF
42GPH Min at 16PSI H.B.
14VDC
6.0 AMPS

I think I crossed this to a pump used on an IO-520 on a Bonanza.

I am considering buying an adjustable OHMITE resistor...2 Ohms at 25 watts.

Mouser PN 588-D25K-2.
This one is 2"long, the 50 watt is 4".

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