Wednesday, 22 October 2014

Fuel overflow management

I have been hauled up on several occasions in my Westfield about fuel discharge during track days and sprint/hill climb events. This fuel overflow issues are exactly the same on the Sylva despite my previous efforts. This only happens when the tank is above half full. I fitted a Mocal valve which I thought would cure the problem as it has a dual function a) When the vacuum in the tank exceeds 0.5bar it will ingest air from outside. b) If however the tank pressure increases due to temperature effects (or sloshing) then the valve release in the other direction if that pressure exceeds 0.75bar. By this method the valve can act as a roll over valve and hopefully keep the fuel in the tank.

The problem occurs on track days when the fuel is warming up (so positive pressure) and the corners pull some g, if now the pressure release happens on a right hander then fuel is emitted momentarily till threshold of the valve closing is reached.

I have tried fitting a catch tank (fuel filter bowel) but this only delays the problem till the catch tank is overflowed. This results in dumping fuel from the catch tank onto the ground between sessions.

The answer may be quite simple, let the main tank overflow when positive pressure exists, collect the fuel and suck it back in when the fuel is used up and the pressure becomes negative.


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