hotstix

iTrader: (3)

Regarding actual pressure of the surge tank:

We want the surge tank to constantly be "overflowing"? by Overflow I mean returning to the main tank. correct?

Unless it is doing so, than we have no venturi effect via the return in the OEM housing. Correct?

So ideally we would want the surge tank to be constantly overflowing fuel into the return to keep the venturi? If this is the case then we can assume that a slight positive pressure on the surge tank is ideal?

Maybe <5 psi on the surge tank itself?

Thoughts?

Naco

The surge tank itself should not see hardly any positive pressure at all (depends on the combination of pumps being used/amount of fuel needed at any given point). So the venturi effect will still be flow dependent on the FPR return line.

Hiboost

iTrader: (9)

My old setup with dual walbros seemed to overflow the return from the surge tank to the main fuel tank a little bit. I knew this because my lowest fuel pressure at idle was 48 psi, not horrible but indeed it was likely that my surge tank had around 5 psi of extra pressure in it and was constantly overflowing into the main tank unless under boost.

KevinD

iTrader: (56)

you will see pressure in the surge tank with the stock venturi in place anytime the surge tank is completely full (which is almost always). at idle and very light loads that means the rail pressure will be slightly higher, but cruising there is enough fuel consumption to bring the pressure back down to what its regulated at.

you don't necessarily always need to be flowing from the surge tank to the primary tank, but for the venturi to work, that must be the case. any time you pull Gees and the sending unit starves, you wont be returning fuel to the main tank, and any time your engine consumes more fuel then the sending unit can provide, you'll also stop flow to the main tank.

hotstix

iTrader: (3)

Did you port the return?

What about porting the return? This should drop psi all around, yes?

hotstix

iTrader: (3)

bump?

Naco

Sorry to bring this back from the dead, but there is another thing to consider when assembling a surge tank setup.

Not only is the fuel rail return line adding fuel/pressure to the surge tank, but also the in sump fuel pump. As the surge tank fills to capacity, the sump-surge tank circle of flow becomes pressurized (amount depending on sump pump size) and returns fuel back to the sump.

I am currently, in my head, trying to resolve this issue of overflowing the regulator due to the primary surge tank being at a positive pressure. I believe it would require a second surge tank and POSSIBLY a third very, very small pump. But let me work on that part a bit.

Cheers

Hiboost

iTrader: (9)

Oops, never saw this question...

No I never ported the return but I did make sure it wasn't blocked by any debris.

On my new builds I'm going to try an electronic fuel pressure regulator from fuel labs that controls the larger fuel lab pumps at low flow load, that way it won't over-run the regulator when at idle or light cruise and will ramp up to full flow when you need it. I'll post details of how it works once everything is tuned on the dyno in a few weeks.

hotstix

iTrader: (3)

This is basically what Im doing now for my surge tank. Except I used a weldon and fuel pump controller to regulate pump speed at an idle and WOT conditions.

Got my surge tank setup pretty dialed in.