Kinda like the duel tank setup on my work truck? I was thinking of making a fuel cell with a chambered small compartment for race fuel.
I think this would work fine, and function pretty much as a dual tank truck systems does.
I have 2 tanks on my flatbed and it works good, just takes a second or two to switch over.
I've never investigated what is needed to run 2 tanks, but think they both need to have a fuel pump in them as most fuel pumps are mounted inside the tank these days.
I've pondered if this would give me some extra fuel in my 'ol '46, as it seems limited to have one large tank, so it might be possible to add 2 smaller ones. I have been planning to use the original style tank under the seat, and a second in/under the bed. Currently the original tank is there but not being used.
As for separating petrol from high octane fuel, I think it would work well for that.
