One of the features of the RX8 engine is the no return EFI system.
The pressure regulator is built into the pump with only one hose
going to the fuel injectors. This would greatly simplify our fuel 
systems as right now we have to worry about which tank the fuel is 
returned to. This usually means an expensive dual (one for supply & 
one for return) three way valve (right, left & off) to avoid 
sending returned fuel back to a un selected tank.

If returned fuel IS sent back to an un selected tank one can run out of fuel
rather rapidly. Several crashes have occurred by failure to follow these 
EFI fuel plumbing dictates.

The down side is two RX8 type pumps with built in pressure
regulators would be required. One located in each fuel tank. This limits 
the flexibility of the system as one pump could fail leaving you with only 
the fuel in the tank with the good pump. This can be got around by using 
two low pressure transfer pumps or a fuel sump tank containing both high 
pressure pumps. One main and one backup.

BTW there was mention in the RX8 shop manual about what happens
when the fuel in the tank gets low and heated fuel is returned
to the tank. In a closed system as required by EPA rules this builds
a pressure in the tank due to evaporating hot fuel. In our system we vent
the tanks to the atmosphere so any hot fuel lost to evaporation
reduces our MPG and range slightly.

Paul Lamar
 
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