Was thinking I could use a 6v mower battery wired in series to my fuel pump on a set of NO/NC relays with a switch. Basically removing the 12v ground/power wires with a set of relays and switching over to 18v before a run. The 6v battery would now be wired into the charging system and would require separate charging. I'm assuming a 275CCA 6v battery would easily last a track visit if only used 20 seconds at a time.

The other option would be to use 2 12v batteries with a battery isolator. (little PC680's would work great) Then you could wire both batteries to the cars charging system and run 24v to the pump for short bursts.

Any foreseeable problems in something like this I'm overlooking? I'm by no means any kind of electrician.

 

2 batteries and an isolator is going to be a heck of a lot more expensive, heavy, and space consuming than just buying the boost a pump...

 

I would probably buy a pump too but you could try this route also:
http://www.amazon.com/gp/aw/d/B00E8D7XYG/

Its a DC to DC voltage amplifier with adjustable output. Ive used them for motor speed control on a few projects and they work great.

 

That's not quite enough current for a fuel pump at elevated voltage.

 

Youre right, I saw the 600w and figured at 16v it would be around 35 amps. I dint see the constant current of 12 amps part. Just get a boost pump haha