Dick T. wrote,
>However....most of the last crop of carb cars use what is called a fuel
>recirculation device which is simply a tiny 1/32" hole in a fitting
located
>on the fuel pump "outlet" line. A small hose carefully clamped, runs
this
>tiny amount of continuous fuel flow back into the fuel tank. This
allows
>the pump to have an increased and continuous flow vol. which is more
than
>the engine is actually requiring. The affect is that a larger amount of
>cool fuel is moving through the pump at all times, thereby preventing
the
>dreaded vapor lock.
>Fuel injection cars sometimes have a similar device which has the
affect of
>preventing overheated fuel in pipes atop hot engines.
>I don't think Alpines need to have this return line installed because
there
>is no real history of vapor lock with their present OEM setup.
>However...I am providing this report so that the LIST will have
knowledge
>of the principals and reasons why it is used.
Along the same lines.
All EFI systems employ a pressure return system, that allows
any surplus fuel pressure to bypass the injectors, and return back to
tank, where the huge supply of cool fuel cools the heated
surplus fuel.
The additonal pressure, + the continous fuel flow is a tremendous
preventor of fuel boil.
Ever heard of a EFI engine vapor locking?
Some carburetted cars do similar things, by dumping excess
fuel pressure from the main supply, sometimes through a bowl
cooler, then back to the tank.
The continous flow of gasoline doesnt allow the gasoline to
heat up as much, and along with the cooling effect it provides
on the bowls, vapor lock is generally really tough.
A warning here though.
Systems that have a bleed or shunt regulator, will wear the
eccentric and lever on a mechanical fuel pump at a very high
rate. This since the added continious fuel flow causes the
pump to do more work.
Mechanical pumps employ a return spring to do the pumping,
and the eccentric, only sucks fuel into the pump.
Thus, when fuel is not being consumed, the pump lever
isnt actuated by the eccentric.
Also, the rate of the sprinf is directly porportional to fuel pressure.
Jarrid Gross
This archive was generated by hypermail 2b30 : Tue Sep 05 2000 - 09:57:13 CDT