fxbdydriver

iTrader: (6)

Hey guys,
Building my first turbo car... My 6.0 lq4 with bw s475 e85 non intercooled. I have a holley dominator fuel pump which is actually two pumps in one, with two separate trigger wires. Pump is louder when both are running so I was considering having the second come on when necessary. Somehow referencing boost? How can this be done safely?

forcd ind

iTrader: (7)

I have the Dom. 1400 pump, and have it set to come on with boost
Since I have the Holley HP, I just picked sec. pump and set it up for
the boost I wanted it to come on-I also wired it thru a 3 way switch,
on/off/on, so if I had a pump failure of the pri pump, I could just flip
the switch and fire up the other pump-also use it testing for leaks
You could use anything to turn on the sec pump, Hobbs sw., etc

oscs

iTrader: (19)

The device your looking for is called a hobbs switch. IMO they are an unnecessary risk. Some guys will swear by them though. I have always had two pumps running all the time on my cars and never once had an issue.

SwampWS6

iTrader: (7)

I was thinking about doing the same thing. Do you see a lot more fuel consumption having them both run all the time? Glad you dont have any issues.

oscs

iTrader: (19)

No, You should never see an increase. The motor will only use what it needs/called for, Thats what the regulator is for. For the guys with return less fuel systems or inadequately sized return lines i could see an issue with fuel overheating or straining the pump. Even when i was N/A i was running dual Walboro 255's and i never had issues. (-10 feed -8 return)

Razor

I run a 12-1800 Holley. I run one pump all the time, the other on a 3 PSI Hobbs.

-12AN feeding pump-->-8AN feeding rails-->-6AN return.

No issues with E85.

MIGHTYMOUSE

iTrader: (59)

i personally don't like the idea of cycling fuel up to the hot engine only to return it to the tank.

i try to use a throttle trigger if possible to stay ahead of the demand... or low low boost like zero.

cavitation is a very real thing and i stay as far from it as possible

fxbdydriver

iTrader: (6)

When you use throttle trigger, you use TPS sensor? I am installing a microsquirt harness, maybe I have spare output to switch second pump?

rkreigh

I believe the MS can trigger the second pump based on the MAP sensor which is the way I'd go

parts left out don't break (hobbs switch) and for sure the Map will be a reliable trigger

hobbs switches are pretty reliable too if installed properly

BUT if that second pump doesn't come on the car could run dangerously lean

I'd think of a simple safeguard in case that happens

the MS stuff is really cool and cost effective with the plug and plan harness

Realcanuk

Pretty sure a hobbs switch is more reliable than the pump itself. Yet to have or hear of a problem with one if wired properly.

I run a Z06 pump with a BAP, which handles all normal daily driving. I then have a Holley 12-1800. One pump comes on at 7 psi, and the second at 15 psi. Having pumps running all the time when not needed just adds heat, and wear on the pump.

If using a hobbs try and use one like the ones racetronix sells that use proper metripak connections. If done properly they wiring on this is as the same as OEM stuff.

oscs

iTrader: (19)

Then you haven't read much. Hobbs switches do fail and I've seen it Happen, it is rare though. I'm my experiences both automotive and industrial speaking the constant starting and stopping of a fluid transfer pump causes far more opportunity for failure and wear.

Realcanuk

I try and go more from personal experience since my reading skills are limited. I have seen many fuel pump, and other parts of the system fail. Yet to see a hobbs fail.

If you want to worry about such things.... feel free...

oscs

iTrader: (19)

Same here and my constant fluid transfer has yielded great results with no failures in any of the vehicles I have ever owned.

Realcanuk

My friend, I never said your system has any issues. I was just saying that hobbs switches are very reliable, as long as wiring is good.

Have a great day. !!!

oscs

iTrader: (19)

I'm not arguing that fact. What I'm saying is, They do and have failed albeit rare. Properly sized feed/return will yield almost no temperatures increases in your fuel and in my opinion both pumps running all the time works well and helps me sleep better at night

Mike454SS

iTrader: (4)

On some vehicles a throttle trigger can help, but I'd put it in parallel with a hobbs switch if using it as you can wind up in boost when you're nowhere near full throttle.

Mike454SS

iTrader: (4)

I agree with you. If you're creative with wiring you can also use LED's to only light up if a pump fails.

On pumps that can take advantage of it, I like to use a speed controller for both pumps.

MIGHTYMOUSE

iTrader: (59)

fuel pumps fail! everybody stop using them.

use what you like. recommend what you have success with.. lots of ways to do it.

i recommend a test button so I know the pump will come on-line when i ask!