Wiring a dual pump setup in a single pump car

[FredK]

I wish to add a surge tank and Bosch 044 pump to my single fuel pump car, using this:

http://www.intengineering.com/Integrated-Engineering-p8917399-1-2.html

The surge tank will be fed by the stock 318is fuel pump, which is traditionally under the control of the fuel pump relay.

Now, with the addition of a high current 044, I will use best practices in terms of the wiring with regards to electrical safety and weatherproofing. However, I am at a loss as to the control wiring. Do I just have the DME control the 044, and run the in-tank pump 100% of the time? Or should I splice the ON signal from the fuel pump relay between both pumps? Or is there some other scheme that I'm missing?

[purebmw]

have to use a double 87 relay, to activate both pumps... its easy..., leave the same signal to de 85 from the ECM, leave it, anyway, you want to better your flow and volume, not pressure...

(when i say double 87 relay, is a 87-87a relay BOSCH)

[Mr Deagle]

Splice on signal to a separate relay to the 044.

That tank thing is way too much money also.

[FredK]

It's a pricey solution to a problem. I haven't really seen any other off-the-shelf surge tanks, but maybe I'm just not looking hard enough?

[Massive Lee]

Hi Fred. It is indeed pricey. What I used to do is pretty simple.

The pump in the tank can be a pre-pump or a standard high pressure pump. This pump feeds a surge tank thant can be located under the car, most likely where the filter used to be, or in the trunk. This surge tank can be made from a 3" or 4" aluminum tube, capped, and with four 3/8" NPT fittings. Volume can be from 0.5l to 1l - 0.5l means you can run the engine with the feed dry for 45 secondes.

Here's the sequence for the inlets outlets.

- Feed from the intank pump
- Return to the tank (located as high as possible)
- Feed to the main pump (located as low as possible)
- Return from the fuel rail in the engine bay (location doesn't matter)

I used to produce them for the e30 crowd, as well as for our e46 racecar. You can literally feed the engine while the tank is under a couple of liters of fuel. Drifters and racers love it.

Lee

[FredK]

That type of tank is pretty much what I was looking for, but could not find as an off-the-shelf item.

In terms of safety, I'm assuming the best place to put a surge tank would be away from the crumple zones of the car, and outside of the car?

[Massive Lee]

Away from a crumpling zone. That's for sure.
But it could be in or under the car. When using NPT-to-AN fittings, the fuel system becomes bulletproof.

The easy way is to make a surge tank the size of the fuel filter, and swap it. Then perhaps relocate the fuel filter in the same area, or near the firewall.

Lee

[McGyver]

What Blunt and good n tight did was use the early model pump as a lifter or pre-pump for the 044. the 044 was wired in parallel to the original pump and located where the fuel filter is. then the fuel filter is placed in the engine bay along the inner fender. they both used the regular rubber fuel lines (high pressure from the 044 to the engine, and the stock 13mm line from the oem pump to the 044).

[Massive Lee]

^^^^^

Only ftting a second pressure pump will not solve the problem of fuel starving that occures when the pick-up of the pre-pump is not submerged such as in long sweepers when fuel level is under half tank. A surge tank is the safest and most efficient way to solve fuel starvation as the main pump has a fuel reserve at all time.

[BimmerTim]

Blunt and GoodnTight were just looking to feed more fuel to the motor for turboz, but the fuel pump wiring Fred was asking about is is the same concept.

[FredK]

Yep, the wiring is the same concept, the surge tank is another can of worms.

I think I might pull a r3v and just buy some pipe, make two end caps, and have someone weld it for me.

EDIT: Actually, true r3vstyle would be to use aluminized muffler pipe, two caps, and some weld-on steel fittings.

[Massive Lee]

EDIT: Actually, true r3vstyle would be to use aluminized muffler pipe, two caps, and some weld-on steel fittings.

The true r3vstyle engineering would be getting a short section of ABS tubing scrap/leftover from the local harware store's garbage bins, then epoxy two caps. This would be the learing step, before attempting an r3vstyle ABS tubing rollcage. :giggle:

BTW Fred, you will be very happy with your external surge tank. Say farewell to fuel starvation. Our own e46 racecar can race on fuel fume. A motor burns between 0.5l (regular engine) and 1.0l (high po motor) of fuel per minute. So, as long as the pre-pump can feed that much fuel, you are golden. The benefit of the system is that the catch tank is fed by the pre-pump and the fuel return.

I made two dozen units last summer. I can make a batch if there's a demand.

[BimmerTim]

If you did make a batch, I would likely buy one.

[BigD]

How much do the pre-pumps flow? What you did, Lee, is pretty much exactly what I plan to do. I'm not sure what to put into the sides of the tank though. It would be nice if I could just drop in two early pre-pumps. Otherwise, I was thinking of getting a pair of high volume, low pressure aftermarket pumps and installing them on the tank floor, as close to the outside as I can.

The engine will be using 65lb injectors with the A1000 pump for primary feed from the surge.

[Massive Lee]

If you did make a batch, I would likely buy one.

"likely" is not enough to motivate me to produce them ;-)

I don't stock parts anymore. Or just very few. So, the way it would work is that if I have 10 commitments, then I will produce them. Price will be better. A few extras will be made, and available at 50% extra for those not in the list. I am doing the exact same thing with some special projects and it pleases most everyone. People who commit will save.

@ BigD
One single pre-pump is enough. Those will flow a lot of fuel. But it also works fine with the riginal late-model pressure pump. Just plumb a second one after the surge tank toward the fuel rail.