[Diy_efi] : ask the experts #1

[Shannen Durphey]

Pluses and minuses, like everything.

I) Surge tank design

	A.  With return line
		1 simple control of fuel level in tank
		2 removes fuel heated by engine and replaces with cooler fuel from tank
		3 works with pumps that produce very little pressure
		4 purges vapors to main fuel tank
		5 design and mounting of tank must be very considerate of outside forces.
		6 hot soak conditions can fill surge tank and return line with vapor

	B.  Without return line
		1 float controls fuel level
		2 vapors can be trapped with pressure release valve and recovered by vapor
cannister
		3 temperature sensitive: fuel recicrulated by efi system is hot!
		4 can be less sensitive to cornering, acceleration rates.  
			a) only way for fuel to get "out" is through the high pressure pump.
		5 can help prevent vapor formation in LP line and surge tank

I am using a return-less reservoir in one of my retrofits.  It saved considerably on
adding additional fuel lines and modifying the sending unit in tank.  I have not had
trouble with fuel heating to the point of vapor lock in the high pressure side, but
each application will require thought to placement of the reservoir.  Mounting the
reservoir away from the engine and including a small cooler on the return line for
the high pressure side could help tremendously.
	
Shannen

William Shurvinton wrote:
> 
> Hi,
> 
> Was having a discussion on surge pot plumbing in the case where you have a
> LP pump feeding the surge pot. Consenus was that in this case the return
> line to the tank was mainly for removing air that had gotten in and so
> should be fitted with  a restrictor to prevent the LP pump circulating the
> tank contents around every 10 minutes. Wondered if this was generally
> considered a good or bad thing?
> 
> Rgds
> 
> Bill
> 
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