Fuel surge

[bretauto]

This only happens on the track, mainly EC GP circuit with its big sweeping LH corners, I have installed a surge tank in the boot of approximately 1 1/2 ltrs, this is feed by the std intank mx5 pump, from the surge tank to the engine I have a bosch motorsport pump ( more then big enough). the surge tank is vented into the filler neck and also has a return line back to the main tank, the engine return runs back into the main tank. I have bench tested both of the pumps and they seem fine, but still once the fuel level drops below 1/2 a tank the surge begins.
I know that the intank EFI pump is not the best for as a supply pump, but I would have consider it good enough to do the job with out any problems, I have tried a number of different return hose configurations and venting for the tank, thinking it may have been a vapour lock, but nothing seems to work. Next step is to install a different supply pump, and larger surge tank, I don't what to waste any money here, so I would like to hear what setups the track guys are using ? and if anyone else has experienced the same problems ?
Car is a NBA using the se turbo and manifold, 9psi boost
Brett.
I

[NitroDann]

Put an OEM intank filter sock back on.

Dann

[Hellmun]

I've got a 1.5 litre surge tank, stock NB8B pump/pickup feeding it and a 044 feeding an NB8A rail/return line so basically the same setup. The return line goes into the stock fuel tank on mine and I've had no issues at all with surge.

It's hopefully just a badly installed pick-up but it's alarming that you get surge with a 1.5 litre surge tank. I wouldn't have thought the bosche could evacuate 1.5 litres in 3-4 seconds through T1. Whats your base fuel pressure set at? I've got a Sard FPR at the stock 43psi.

On a related note how hot is your fuel getting? I've noticed that the 044 seems to cycle the whole tank really quickly and put heat into it. My surge tank is uncomfortable to touch after about 10 laps and it's making the bosche get louder and louder as the fuel thins with the temperature.

[bretauto]

OEM filter in the tank, and I will recheck it's placement, I will install a new intank pump, it's the original. Surge tank gets hot and every thing in the boot gets hot after a run, but I through this had more to do with the muffler transferring heat, then from the fuel circulation. The car will make it through turn 1 with no surge , the surge happens on the exit of turn 3, it can also some times occur on to the main straight, so it has to be a long corner or several close LH. And yes the 044 pump does get nosier as the fuel heats up. Anyway thanks for the replies, good to know that there are others cars running with similar setups and no problems. Will double check the whole system.

[greenMachine]

OEM filter in the tank, and I will recheck it's placement

Replace it, to be sure to be sure ... and to be even surer, make sure it is oriented the right way, it can go on in two positions, and of course one of them is wrong, leaves it sticking up rather than down (or is that flat?) - you will see as you place in the tank it where it should sit.

If that filter (or the pump) is not flowing properly, your surge tank is not getting enough fuel. Alternatively, if the filter is improperly fitted, it will suck air sooner than it should.

The other thing is, with all that plumbing, is it sealing as the stock system does, and if not might that be part of the problem. But I am guessing that a new pump/filter will fix it - fingers crossed

[speed]

Can you not measure the fuel after the surge tank to confirm the pump is really pumping the amount you are expecting?


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[Boyracer]

If everything is ok they will run down to almost empty with no surge, one of my cars used to surge, I changed the tank and pump and it fixed the problem.

[Dan]

Out of interest why do you route the return back into the main tank and not run it into the surge tank and then run a return back from the surge tank to the main tank?

Seems like the 044 is just draining your surge tank in these corners and it's running back into your main tank faster than your feeder pump can supply it.

[Hellmun]

The problem with that is cycling hot fuel straight back into the engine. It gets pretty warm once it goes through the fuel rail and 044....Hotter the surge tank, thinner the petrol and the 044 struggles to move it. So you lose pressure and fuel density.... This is why I understand it's normal to return the fuel back to the main tank instead. Also appreciate that the 044 is pushing fuel into pressure, the stock pump is running at practically no pressure to feed the surge tank so can flow an incredible amount.

[Dan]

^ Yeh you can do it either way and since you run the same setup it’s obviously possible to work with the return going back to the tank, I was thinking because of the massive difference in sizes of pumps running the return into the surge tank might be a good idea to ensure it stays full.

Not sure if you have seen this before but speaking of temperature and return lines I think this is a cool idea to control temps. It's a surge tank that integrates an FPR onto it to eliminate the return line and create a dead-end system while also submerging the pump into the surge tank. You can’t buy one with a Wally 044 in it but you can get one with a Walbro 255/400 in it.

http://www.radiumauto.com/FST-R-Fuel-Su ... -P348.aspx

[fletchb]

Put an OEM intank filter sock back on.

Dann

Thanks Dann for the heads up, na8 was misbehaving on hillclimbs, changed sock and fuel filter
found my long left, and presto, cured, e85 must clean the system