External Fuel Pump wiring

[dok33]

Bout to wire up my Bosch 044 external pump and was wondering if anyone had suggestions on how to kick it on. I'm running the stock in-tank pump to a 2L surge tank and then pulling from it using the 044.

I was originally thinking of just using a switched 12v signal but realized that the stock pump may not constantly run when the ignition is on (I think I remember it kicking on for a few seconds until the ignition is cranked) and I don't want the 044 pulling air out of the surge tank. Thoughts?

 

[figgie]

dok

not for anything but doing it that way.. You will run the "sump" dry in no time flat as the OEM flow volume is alot LESS than the 044. Of course you won't see the issue during normal driving but at WOT. By the time you do see the issue. Damage is done.

How it is usually done is that from the fuel tank to the surge tank. You get a high flow low pressure fuel pump (usually used in carb setup). Then the 044 from surge to fuel rail. Done.

 

[dok33]

I did some rough calculations and it looked ok. The 044 flows ~4lpm at 40psi (~3bar), so even without a pump filling the surge tank I'd have about 30secs of fuel available which seems like a long ass WOT run. Am I missing something?

 

[figgie]

I did some rough calculations and it looked ok. The 044 flows ~4lpm at 40psi (~3bar), so even without a pump filling the surge tank I'd have about 30secs of fuel available which seems like a long ass WOT run. Am I missing something?

Bosch rates thier 044 fuel pump at 200lph @ 5 bar. which is 3.3Lpm @ 5 bar.

The issue is that the pumps (both of them) are always running. So the fuel get circulated to the surgepump lots of time if it is not being consumed (ie injected really). So if the fuel supplied is more than being injected than it should be fine. Once that is not the case, then you will quickly start to swallow fuel from the surge tank faster than it can be supplied by the OEM fuel pump.

Keep in mind, on the dyno. You mioght not be at WOT but during the ramp up phase, you are consuming a considerable amount of fuel

 

[gaboonviper85]

this whole idea seems like a tank full of fail!!! Why can't you just use a 255 and be happy like everyone else...going against the grain is usually not the best move...

I have a friend with a supercharged 5.0 and he has a similar setup and he can't go wot for long at all cause his stock pump can't keep up with his t-Rex inline pump...

Good luck but I see the fail train comeing.

 

[dok33]

Pretty much every rally car runs a surge tank setup to prevent fuel starvation so it's not really going against the grain, although I do try to every chance I get . Scott is running the same setup (with the addition of a walbro in-tank) on his almost 700rwhp 2j and it has worked great for him. Plus a 255 won't support 500hp on E85. And before anyone asks, I know my 680cc injectors may be cutting it close as well, but I got 'em cheap so I figured I'd give it a shot...

Not trying to be an ass, but I don't need any advice on the setup itself, I've done the research and have a M.S. in Mechanical Engineering so I can handle the calculations. I just wanted some opinions on how to wire the external pump.

 

[figgie]

this whole idea seems like a tank full of fail!!! Why can't you just use a 255 and be happy like everyone else...going against the grain is usually not the best move...

I have a friend with a supercharged 5.0 and he has a similar setup and he can't go wot for long at all cause his stock pump can't keep up with his t-Rex inline pump...

Good luck but I see the fail train comeing.

because walbro are crap. With any considearable pressure they fall flat on thier face. Sorry. Walbro is not the grain. Never was. It was the grain for the stingy folks that saw price above the flow numbers.

Plus a 255 won't support 500hp on E85. And before anyone asks, I know my 680cc injectors may be cutting it close as well, but I got 'em cheap so I figured I'd give it a shot...



Not trying to be an ass, but I don't need any advice on the setup itself, I've done the research and have a M.S. in Mechanical Engineering so I can handle the calculations. I just wanted some opinions on how to wire the external pump.

Just to be perfectly clear. Those 680 might get you to 500hp but they will be at static open at that point (ie 100% DC) on E85.

Mechanical engineer. How did you do in your fluid mechanic classes?

FYI

The rally cars (specifically the Opel and renault team) use two 044 pumps. The one supplying the surge tank see minimal pressure so it outflows the other 044 that is feeding the rail at pressure. Also in case you are going to drag race. Make sure NOT to head over into an NHRA track as they do not allow surge tanks!

 

[dok33]

Wasn't a big fan of fluids, although my prof was german so all of our test problems were about beer and wine :biglaugh:. My research was in structural adhesive testing so obviously I'm an expert in fuel systems .

My comment was more directed at the "fail train comeing" guy who can't spell. I read your E85 thread and was very impressed, that sumped tank was badass. For the Walbro lover:

HP pump is a little better but still falls on its face:

Good to know about the drag racing, I'm planning to do some test'ntune sessions but no competition. I think I'll be ok at the track here, tech inspection takes all of 10 seconds- they make a lap around the car (not really sure what they're looking for) and you're done.

Any thoughts on the wiring? Do I need to tap into the stock fuel circuit to get the signal for my external pump relay?

Sidenote, found a slick relay setup from Summit, going to run the pump, elec fan, and some other goodies off of it:

 

[figgie]

Wasn't a big fan of fluids, although my prof was german so all of our test problems were about beer and wine :biglaugh:. My research was in structural adhesive testing so obviously I'm an expert in fuel systems .

My comment was more directed at the "fail train comeing" guy who can't spell. I read your E85 thread and was very impressed, that sumped tank was badass. For the Walbro lover:

HP pump is a little better but still falls on its face:

Good to know about the drag racing, I'm planning to do some test'ntune sessions but no competition. I think I'll be ok at the track here, tech inspection takes all of 10 seconds- they make a lap around the car (not really sure what they're looking for) and you're done.

Any thoughts on the wiring? Do I need to tap into the stock fuel circuit to get the signal for my external pump relay?

Sidenote, found a slick relay setup from Summit, going to run the pump, elec fan, and some other goodies off of it:

On the 044. I would only use the stock wiring to kick off a relay that feeds from the battery. 12 gauge minimum as the max amp draw of the 044 is 15.5 Amps.