Help - Fuel System Getting Hot

[_5C077Y_]

Hi guys, my fuel system keeps getting hot and I can't figure it out.

Car & Fuel system details:

*Highly modified RB25 with a Wolf 3D V4 ECU

*The fuel system is a Walbro in tank pump with pick up > 10L surge tank > x2 Bosch 044 pumps > twin entry fuel rail > ID 1000cc injectors > return line back to surge tank.

Problems:

*The two Bosh pumps slowly get noisier the further I drive, their not running dry as I keep checking the surge tank and it's always full, after an hour drive you can hear the wine outside the car.

Notes:

*The pumps, surge tank, fuel rail and intake plenum are all hot to touch.

*None of the fuel system is near the exhaust or heat source.

*Pumps are quiet on start up and for the first 20mins of driving before slowly getting louder.

*No blockages in pipes, brand new fuel filters and fuel reg, fuel pressure is stable, constant and accurate.

*I had the car re tuned from avgas to pump fuel (BP Ultimate) 2 months ago in Tas and have since moved to QLD and know that I need to get the tune touched up for the temperatures and humidity levels etc up here.

Any ideas or suggestions for my problem? pumps on their way out, AFR needs adjusting, or it's just in the tune etc?

Thanks for any help and suggestions guys =)

Scott

[scotty nm35]

Its just what happens, the fuel heats up as it goes through the hot engine bay and returns to the small surge tank only to go through the hot engine bay again. Perhaps insulating the fuel rail or adding a fuel cooler to the return line would help?

My Walbro's do the same thing, although it takes a lot longer to heat up all the fuel in my 80L tank. After an hour or more of driving the pumps sound very noisy but they still work fine.

[KiwiRS4T]

^^^as above quite normal. You will find your fuel rail pretty close to a heat source. My Bosch 044 is as noisy as.

Even my work truck will warm up its 300L fuel tank after a while.

You can get fuel coolers (quite expensive) or just put any kind of cooler (trans cooler, oil cooler) in the return line if you want.

[zebra]

As above or a fuel pump controller to turn the pumps down when cruising

[The Dan]

All great suggestions.

Also have you got your boot properly ventilated?

[r31slpr]

Can you use the ecu to have one pump on and switch the other on above a certain duty cycle or load point

[doo doo]

Put the return line back into the tank rather then the surge pot?

[The Dan]

Put the return line back into the tank rather then the surge pot?

The problem with doing that is you then rely solely on the lift pump to keep up with the feed pumps. That equals boom on a 1st-4th straight run

[R31Nismoid]

As above or a fuel pump controller to turn the pumps down when cruising

This.

If just driving around realistically you only need one pump running so have a trigger setup based on speed/throttle/RPM with the Wolf, I'd imagine it would have an input to do something like that.

[kitto]

How have you got your surge tank plumbed?

IE, from top to botton the surge tank is it;

Return to tank > Return from fuel rail > Lift pump in > Main pump feed.

OR

Return from rail > Return to tank > Lift pump in > Main pump feed?

[_5C077Y_]

it's Return from rail > Return to tank > Lift pump in > Main pump feed.

the fuel rail is a custom made 1inch square solid block of aluminium that's been drilled through the same diameter as the hose fittings threads. pic below.

My turbo doesn't kick in till 4,000 RPM so I barely use that around the street.

The cooler sounds like a viable idea.

As for the boot it's standard, only it's been stripped out, surge tank is on the floor on the right side.

[kitto]

it's Return from rail > Return to tank > Lift pump in > Main pump feed..

This correct. Hmm. Fuel cooler may be a good idea.

[_5C077Y_]

[_5C077Y_]

so it sounds like my problem is normal then... but is it normal for the rail and intake to get hot enough to be really uncomfortable to hold your hand on? like a kettle type hot...

[Risking]

I rekon your problem could lie with that giant fuel rail.

If that was a solid billet and youve drilled a 1/2inch hole down the guts of it you have a massive block of alloy to retain heat within.

A thinner extruded rail will dissipate heat alot faster than a solid block of that size.

You may find that the rail is absorbing engine bay heat and dispersing it into the fuel, there is alot of unessisary alloy there to retain temp.

[JonnoHR31]

I had the same problem during summer, bought a small cheap transmission cooler from super shit and put it in the return line near the diff and it's been fine since. Also swapping the return from the rail and the overflow to the main tank around will make it take a little longer to get hot.

[TurboMick]

An old trick is to put a hobbs switch in the cold side piping that's set for -say- 14psi, that switches the earth on the relay for the second pump. Then it's only running when needed.

044's do add a lot of heat, mine are set the same as above and still warm the fuel a bit.

Apparently a single A1000 runs cooler, and much quieter than two 044's, but I haven't personally seen that setup running so can't say for sure.

[discopotato03]

I'd be working out what my maximum fuel requirement was and seeing if you've overkilled your fuel system . Excess fuel going round in circles achieves nothing other than to transfer heat throughout the fuel system . In a lot of ways surge tanks are a PITA and if the original tank could be made to avoid fuel surge you would not need them .

JE found out many years ago that using a roller cell high pressure pump as a lift pump transfered more fuel to the surge tank from you main tank so what was in the surge tank did less circles from tank to rail and back etc etc .

Ideally you want the least material in a metal fuel rail because the less material there is the less heat it can absorb from the engine/bay which means less heat absorbed by the fuel running through it . I'm not sure what injectors you're using but if they are side feeds is the std rail that bad ?

A .

Edited August 26, 2012 by discopotato03

[rob82]

Considering your engine will consume 0.2-0.4l/min to make between 20-40kw (enough for cruising) and your constantly sending minimum 7l/min to the front - what do you think will happen.... Combine that with massive fuel rail block that's close to engine temp of course your going to have issues.

[_5C077Y_]

Alright, cheers for the help guys, appreciate it =) I'll try a few things and see if I can sort out or at least help the problem.

Oh and their full length Injector Dynamics 1000cc Full Length