ls1curt

iTrader: (31)

hey, im wiring my second 225 fuel pump in. it goes to a hobbs switch that activates at 1psi. will it be okay if i go to the back of the alternator for the power source to the hobbs?

JaYZeig

iTrader: (11)

im just curious where you got your hobbs? been lookin for one just like that

ls1curt

iTrader: (31)

ebay.

chief455

iTrader: (21)

Answers are here: https://ls1tech.com/forums/fueling-i...ick-cheap.html

I keep seeing my car hit boost from vacuum so quickly I hate to think a pump in the tank will get fuel in the injectors fast enough from a Hobbs signal.

I am going with a toggle switch for my 2nd in tank pump to run if I expect to hit boost.

I've read guys running twin pumps powered full time without issue.
Almost seems like - 'why wait?' - the excess fuel will just run back the return line cooling the pumps until used under boost...

Old Geezer

iTrader: (3)

'I keep seeing my car hit boost from vacuum so quickly I hate to think a pump in the tank will get fuel in the injectors fast enough from a Hobbs signal."`

What level of HP, [boost] will the first pump cover?? UR are assuming that you are out of pump as soon as the boost comes on.... Does it? Data logs showing it go lean at the onset of boost?
If your first pump won't cover at least part of the increased HP, then the pump is suspect....

chief455

iTrader: (21)

Actually my statement is general. I just feel, why wait for fuel demand when the return system cools the pumps with excess and then fuel is there before you need it = no go lean.
It seems the common rational s saving wear on the second pump by using it part time.

Hmmm - by using twins all the time will that equal less demand from what would be the primary pump??

Lonnies Performance

iTrader: (16)

The fact is that the fuel overheats not the pumps.

Every watt of power that a pump draws is turned into heat in the fuel, plus the extra circulation pushes the fuel through the rails & under the hood picking up additional heat. As the fuel gets hot, it then starts to vaporize as it is drawn into the pumps & this is where the pumps cavitate & car vaporlocks. This can either ruin the pump or at minimum strand you on the side of the road until things cool off.

This is also why pump controllers exist for big external pumps as well.

I would not use a hobbs switch in all my dual pumps if I did not feel it was a good thing to do.

Also the pump load is constant at a given pressure. The pump pushes say 255lph, no matter if it is used by the engine or returned to the tank. 2 pumps will do twice the work.

chief455

iTrader: (21)

Lonnie - that makes sense. thanks

chief455

iTrader: (21)

back up - i bought a 2psi Hobbs switch and had already got another Hotwire kit from Racetronics.

Now I see I will have extra plugs to the car utilized by primary pump, not being used by 2nd pump - PCM, pump prime etc.

I feel a relay is needed, how do I go from the alternator / Hobbs / into the relay and out with just the power wire to 2nd fuel pump?
At relay:
Hobbs power into term 86
power to 2nd pump out term 30?

Pocket

iTrader: (22)

30 12v in red
86 12v output to pump gry
85 grd trigger blk
87 12v trigger grn

To use the kit, splice into the ground leg for the hobbs and tee the grn trigger wire to the stock PCM control wire from R9. 30 to the alt output lug and 86 to the pump

98Camarod

iTrader: (43)

For the trigger wire, are you tapping the wire by the pcm? For the 98, it looks like B37. I have my relay for the second pump in the rear along with my battery. Is there not a switch wire back there?