Solving the fuel starvation under high G loads. Surge tank is needed, but the stuff on the market doesn’t tick every box. I want a swirl-pot style surge tank. The energy of the fuel swirling inside the tank at least partially counteracts the G forces acting on the fuel, so there is much less sloshing, and it ensures every last bit of fuel makes it to the outlet until the tank is dry, unlike a more conventional surge tank that’s just a tall static volume. So as it so often seems, the only way is to make it myself.
I hand cut a bunch of pieces:
The inlets and outlets have a shallow slant cut inside to shroud the in/out flow from the swirl flow in the tank:
Welding it all together:
Went with 1/4″ NPT rather than AN so I have the flexibility to change hose size if desired down the road:
Finished tank:
Installed with AEM 400 in-line pump, Radium in-line filter, AEM high pressure regulator. Bracket against the forward bulkhead supports the tank since it will have a bit of weight to it once full of fuel.
Now with two fuel pumps, the external post-surge tank pump does the heavy lifting and the pump in the main tank is relegated to lift pump duty, so I’ve put a DW300 back in the main tank since that works properly with the pump fixture.
I added a second fuel pump circuit on the wiring side, with a dedicated fuse and relay. Relay is activated by the same fuel pump switch on the dash, so the single switch turns on both pumps, but if I need to troubleshoot one pump or the other I can pull the fuse for the other pump so I’m just activating one.
Dyno Friday to make sure it’s all flowing as expected, then on to track testing.
The only issue is I’d like to anodize the tank both inside and out for longevity. But the inside can’t be anodized if it’s an enclosed tank. I want to make the top of the tank removable with a bolt-on cap, but that requires sealing the cap with an o-ring which means the cap piece needs to be cut either by CNC or waterjet and then have the o-ring groove done in a lathe, neither of which I have the ability to do here right this moment, and I wanted the tank done and start testing immediately. I have drawings off to the waterjet to get those bits made though, once they are done I’ll cut the top off this tank and weld on the new flange that takes the new bolt-on cap, then get both pieces anodized.
Fuel surge/swirl tank report: it works a treat.
Tested at Buttonwillow on Sunday, ran the car round and round till it read completely empty in the main tank, got another half lap out of it and then it started to sputter and came to a stop a few turns later. Towed back to the pits, pulled the top fitting from the surge tank and ran a dipstick down it to see how low we ran it. There was only about 3/4″ of fuel left in the bottom of the surge tank. That’s like, 1/20th of a gallon. Yep, it’s working.