Why are aftermarket surge tanks so big?

[MWP]

Not quite 2L/min. Remember that injectors should never be run at 100% duty.
So ~1.7L/min should be your max.

[oldcorollas]

call ti 2L anyway

if you are surging for 2 minutes, then you need to have a roll-over cutoff switch... because your car is on its roof

[wa5]

According to the trip computer in my dead stock VQ (rich bogans VN) Statesman, at Wide Open Throttle my 5litre V8 uses around 85 litres per 100ks...

[thechuckster]

returning fuel to the surge tank means you circulate hot fuel?

am sure there's a discussion about this elsewhere... but i also note that ed's UZA80 has a cooler for the fuel supply

sorry if am a bit cryptic, am onto 4th glass of Merlot.

[Billzilla]

For racing at least, some classes have maximum fuel tank sizes - for example a few years ago in the Malaysian MME endurance race I did.
The rules didn't specifiy anything for the swirl pot, so we ran a huge one (about 5 or 6 litres I think) so we could carry more fuel and reduce the number of pitstops. According to our calculations, if we didn't have that extra bit of fuel up our sleeves it would have meant another pitstop, and so losing a lot of track position.

But for road use, yeah a one litre is heaps.

[YLD-16L]

I ran a 3L surge tank for years but when I relocated all my EFI gear a few years ago I reduced the capacity to around 1.4L and have never had a surge issue.

I return to tank from the rail but touching the steel return line at the tank end after a hard run it's always cool to touch so I'd have no hesitation in plumbing it back into the surge tank in my case.

[SillyCarS]

For racing at least, some classes have maximum fuel tank sizes - for example a few years ago in the Malaysian MME endurance race I did.
The rules didn't specifiy anything for the swirl pot, so we ran a huge one (about 5 or 6 litres I think) so we could carry more fuel and reduce the number of pitstops. According to our calculations, if we didn't have that extra bit of fuel up our sleeves it would have meant another pitstop, and so losing a lot of track position.

But for road use, yeah a one litre is heaps.

i like your style of thinking

my cousin jack did something similar when he used to race a torry of some description, to get around the fuel tank cap they ran 1" fuel lines all around the body of the car and had it all primed up along with the tank

not too bad if its carbied, but fk it would be expensive in EFI hose

[ed]

returning fuel to the surge tank means you circulate hot fuel?ed's UZA80 has a cooler for the fuel supply.

both correct my return runs to the swirl tank, but as my main and return lines get farking hot near the exhaust as the firewall turns under to the floor... i put an inline fuel cooler on the return line before the swirl tank

[LeeRoy]

Why would anyone do that though?
Its obvious that returning to the surge tank means you can get away with a smaller surge tank and possibly smaller low pressure pump.

I wasn't arguing the pro's/con's of this, just getting the figures in there and providing the worst case scenario - which would be a massive fuel pump, return line to main tank, and as small a surge tank as possble. Even still 10 seconds of fuel supply would still occur during a surge of the main tank.

[Smokey228]

Maybe i can ask here and someone can answer then. I have one of Lindens surge tanks, not sure how big, maybe 1L?

I wanna run two 044s from this into 1/2" fuel line, with a 3/8" fuel return. Probably just 1 big lift pump, but would be okay? Will the surge stay full for most driving styles???

Might also be tuned on e85 with 1000cc injectors...???

Cheers,
Jase

[oldcorollas]

044 is what? 300L/h? 2=600L/h = 10L/min =
empty in 6 seconds.

[Hiro]

i like your style of thinking

my cousin jack did something similar when he used to race a torry of some description, to get around the fuel tank cap they ran 1" fuel lines all around the body of the car and had it all primed up along with the tank

Smokey Yunick was doing that 30-40 years ago to get around NASCAR regs....

[benjamin]

One other thing to think about is how often are you going to be running low on fuel in the tank, on the street you might get a little low in the main tank but you won't (or shouldn't) be driving hard enough to be starving the pick up for very long. And in a track situation you should definitely be keeping an eye on your fuel level anyway, probably keep it above half full at the very minimum. Having a massive surge tank would probably only be beneficial in an endurance type race where limited pitstops and getting the highest mileage per tank is of major concern.

And what is the maximum (instantaneous) G forces you can pull in a turn or even acceleration? I honestly don't know what is a respectable effort but even if you make 1 lateral G with half a tank of fuel and the pick up is located at the centre of the tank, the pickup is still going to be submerged.

I really believe that with a street driven car that is occassionally used at track days, a 1L surge tank would be perfectly fine.

[benjamin]

Here's some fully hectic diagrams to show what I mean

the red arrows are showing the G forces (which are all equal in this instance)

[Shakotan_Aaron]

engine isnt under full throttle under braking/cornering so the tank would be more likely to fill upto being full during this time. so by time you open the noise up exiting the corner its full of fuel.

if the tank is completely dry you still have the surge tank full plus the fuel thats in the main/return lines, then as soon as the lift pump comes back into fuel it starts filling the surge tank again. add to that a lot of you guys are talking about EFI tanks which are baffled from factory hence less likely to have fuel surge in the first place.. 1L like the ones i sell should be heaps for most 4cyl appt