i'm curious to find out how to tune with these twin pumps. As I understand it, one pump runs constantly and the other kicks on at a specified time (not sure exactly how, but thats what I recall. Could be wrong). My question is, how do you deal with the "spike" in fuel pressure when the second pump is activated?

For the record, how many on this board are using a twin intank setup?

 

I'm using racetronix twin intank pump and I have a electric fuel pressure gauge in car, haven't noticed spike in pressure.

Don't have any problems with fuel at 490 rwhp and from what I've seen on other cars it's good for 650rwhp.

My second pump is hooked up to a hopps switch that turns pump on at 3psi of boost. Naturally aspirated could use vacumn switch.

 

exactly what I wanted to hear. Thanks for the info. I'll be ordering a hobbs switch as you tell me where . eBay?

 

I would think you need to make sure you have a high capacity FPR in the system, and a decent size return line. I have an outboard Weldon unit and -6AN return, and there is very little pressure change when I switch my second pump on (not Racetronix)... the needle on the pressure gauge twitches perceptably, but not much. I wonder if the stock FPR is large enough to bypass the flow from the dual pump setups. But then if you need dual pumps, you probably already have a well-designed plumbing setup.

 

I actually purchased kit complete from Agustino Racing Engines if you give them a call I'm sure they can hook you up. The reason I went with the twin pumps with hopps switch was so I could use the stock fuel system (aeromotive reg). The second pump only comes on when you actually need the fuel.

 

Fred,
Given that the second pump will only be turning on when the motor sees a certain amount of boost, I would think that when that pump turns on, the motor will actually "need" the fuel and it won't get to the regulator, correct assumption?

 

I turn mine on with the nitrous "arm" switch..... I wouldn't wait until the pressure started to fall off, and then start the second pump with a pressure switch. But then I don't have the option of a "boost" signal to turn the second pump on. The fuel system still has to return 95% of the fuel to the tank at idle.

 

Fred,
Thats very true. I certainly better make sure I don't have fuel pressure falling off before my second pump turns on. I don't think at 2-4 psi of boost that I will have a problem, but then again I'm just guessing. Anyone else have an opinion on whether or not 2-4 psi turn on will be too late?

I'm assuming both pumps are 255 walbros and a single is good for ~500rw, I think I'll be safe. I don't think I can make 500rw on less than 2-4 psi.