Fuel pumps & tanks

[Wouter de Waal]

>Frederic Breitwieser wrote:
>> 
>> > and the pump would have to pick up fuel an extra 12 inches or so
>> > (which I understand these pumps don't do well).  Maybe these
>> > concerns aren't valid...?
>> 
>> No, they are valid to some extent.  Lifting liquid UP takes more energy
>> than moving it ACROSS.  However, I do have a solution for you, however that
*snip*
>> I'm going to mount the pump inside the tank at the bottom, following the
>> same pump-to-floor height dimensions as before, however the pump will have
>> significantly more fuel on top of it.  Instead of running the lines out the
>> top of the tank, they are going out the front/side panel, once I figure out
>> what kind of wall tubing mounting I can use and keep it liquid-tight.  The
>> idea behind this is the pump doesn't have to pump "up", and the fuel line
>> will go out the front of the tank and not interfere with the fiberglass
>> nose panel, since the front of the vehicle where the tank is is quite low.

Fred, I've been thinking about this... you have to pump the fuel up from the
bottom of the tank to the top of the fuel runners. This is a *constant*
height for the specific car you're looking at. Civil engineers talk about
the 'head', say you're got a 100 feet deep well with a pump at the bottom,
and 101 feet of pipe on the pump, going straight up. The pump only needs a
head of 1 foot to get the water out of the end of the pipe, which is 1 foot
above the water level.

Basically, whether the fuel pipe goes up and across, across and up, or up 10
feet and down 9 to the manifold, once the system is primed the pump is
pumping against a 1 foot head.

And an empty tank requires a bigger pump than a full tank :-)

Wouter