Fuel Cell question

[NigelC]

Planning on fitting a 38 litre fuel cell in my Group S Alfetta. I assume that there is no need for a return fuel line because we have to continue to use the mechanical fuel pump. Is it fair to say that a fuel return system is only necessary for an electric pump which, I believe, we are not allowed to use.

[Neil Choi]

Nigel,

I think a return fuel line is for fuel injection which doesn't apply to our prehistoric cars.  You can use an electric fuel pump over the mechanical one, we are all using one since the mechanic pump can't deliver enough fuel to our 2000 bhp motor otherwise we will get surges all the time.  Just make sure you have enough flow and pressure to the motor from the pump.  Some of us are using a Carter pump.  Facet is only just ok for a short time.

Also got advised that one should wire in a fuel pump shut off relay to stop pump when ignition stops. One of those gas relay is the go, forgot the brand name, it is pretty common.

And a kill switch which actually kill motor and pump ie not one of those cheapy kill switch which just shuts electricity at the battery but engine still runs due to alternator still feeding ignition.

Hope this helps.

Neil

[NigelC]

Thanks Neil,

will fit a carter pump, correctly wired with the kill switch,

cheers,

Nigel

[Paul Byrne]

G'day Nigel,

I have strayed into group S territory and I may well be wrong re the following, but just in case.....

In Tarmac rally, and I think racing, Cams specifies that  'the pump power supply must 
cut off in a maximum of six seconds after the engine stop'
This means of course that the kill switch is not enough. The usual method of complying in Tarmac rally is to switch off the pump using the signal from the engine oil pressure switch. I use a relay that pulls in when the oil pressure switch closes (no oil pressure) and opens the pump circuit. Otherwise, if the ignition is on, the pump will continue to run. I also have an over ride switch in the panel to prime before first engine start.
No issues or requirement if the mechanical pump is used of course.
Cheers,
Paul

[NigelC]

Thanks Paul,

good advice and I will put a switch inside the car but I must admit  I am a little concerned over the type of relay cutoff I need. There seem to be two options - one linked to the ignition circuit and one linked to oil pressure.  CAMS doesn't seem to be specific.

regards

Nigel

[Paul Byrne]

Hi Nigel,
As long as the fuel pump stops within 6 secs of no engine rotation, with the ignition still on, CAMS don't care how it is achieved.
The oil pressure is one sure way. Another is an ignition circuit triggered device. This is usually a special relay which operates to shut down the fuel pump if the relay sensing circuit is no longer receiving pulses from the ignition system ie no rotation so no distributor 'points' switching.
I have not used the ignition type so can't advise on type/source etc. Oil pressure switch is already there so it made life easy!

Cheers