Surge tank design, does shape matter?

[WhatTurboLag?]

So I was talking to my fabricator about building me a surge tank and based on where I want to put it (passenger side fender well by tail light) he was thinking a square one would be good there, or at least one made to fit that area (not necessarily a square then). So does it matter? I would put in some internal baffling and possibly angle down the bottom into a center feed or something so it has no way of getting starved.


Any input on this? It will be feeding my stock lines, rails, and injectors until I do all that after the motor goes in, then when big power happens it will feed custom fuel lines all the way to the rails.

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[Homemade WRX]

volume and keeping it taller, not shorter, will help. Also keep in mind that fuel sloshes rearward on acceleration, so be sure to keep the pick up rearward as well.

I had been planning to do something similar for my meth injection surge tank.

[berdugo]

I like the Sard surge tank, it makes the setup very compact.

[02WRX2.5]

If setup correctly it should always be 100% full so shape shouldn't matter.

[WhatTurboLag?]

Okay, and on my fuel setup I assume it always will be.


But with that said, does size matter? I wanted a 2 or 3 liter tank but I doubt I need one that big. Is too big bad?

[ckyguy68]

Originally Posted by 02WRX2.5

If setup correctly it should always be 100% full so shape shouldn't matter.

This. You don't have a surge tank to worry about sloshing and baffling. It's supposed to be the solution !

[scby rex]

Size is usually determined by fuel needs. Say a 700 whp e85 system would want atleast a 3ltr tank. A smaller tank would be for pump or race gas on a lower whp. Sard does make a 5ltr though.

[slowgenius]

Originally Posted by ckyguy68

This. You don't have a surge tank to worry about sloshing and baffling. It's supposed to be the solution !

The lift pump is still affected by accelerating, and cornering loads, so the surge tanks volume needs to be sufficient for the extended period of loading to sustain full throttle for track conditions that starve the lift pump. That should determine surge tank size.

If the situation arises that the surge tank starts to empty, the fuel will start to slosh and could suck air also if poorly designed. Baffling or foam, etc may help, but the best design seems to be the cylindrcal tank with the suction on the bottom. The feed and return lines should be oriented to feed the tank along the side, causing the fuel to swirl, helping to keep the fuel against the tank and the feed and suction should be so the swirling fuel enters and exits the same direction as the swirling fuel.