[Diy_efi] Re: Diy_efi digest, Vol 1 #352 - 7 msgs

[Bill Washington]

Gents,
    Here's a simple idea to try to avoid the pump:
Inside the tank put two pickups, one each side of the saddle with a 'Y' 
hose linking them to the single outlet, or in tank fuel pump inlet.
Pressure of overlying fuel on each side will tend to equalise the flow 
from the two sides of the saddle.
    This would not be as good as a low level hose linking the two 
sidesbut should be better and much less complicated than than a transfer 
pump.

Regards
Bill



>--__--__--
>
>Message: 2
From: "Bevan Weiss" <kaizen__ at hotmail.com>
>To: <diy_efi at diy-efi.org>
>Subject: Re: [Diy_efi] Re: Looking for circuit to turn transfer pump off at certain voltages
>Date: Mon, 11 Nov 2002 18:32:13 +1300
>Reply-To: diy_efi at diy-efi.org
>
>
>----- Original Message -----
From: "Toyota Supra" <turbosupramk3 at hotmail.com>
>To: <diy_efi at diy-efi.org>
>Sent: Sunday, November 10, 2002 4:02 PM
>Subject: Re: [Diy_efi] Re: Looking for circuit to turn transfer pump off at
>certain voltages
>
>
>  
>
>>hey bevan, thanks for the reply, maybe this will help clarify ...
>>
>>
>>here are the specifics, my gas tank is a saddle tank, meaning that it has
>>two sides to it like saddle bags on a horse. now the pumps are on the left
>>side, and the mechanical venturi valve that used to transfer the fuel from
>>the right side, had to be removed.
>>
>>so my dilema is, how do i get fuel from the right side of the tank, to the
>>left side where the fuel pumps sit, so that i am not driving around on
>>    
>>
>only
>  
>
>>a 1/2 tank of usable gas, even though the entire tank is full?
>>
>>well, my design thought was to have a transfer pump intank, that drew from
>>the right side, to the left side, at all times that the car was on, except
>>for when the right side of the tank got low on fuel. this is because the
>>fuel acts as a lubricant to the transfer pump, and if it ran dry for any
>>period, it would probably burn up.
>>
>>so the way i decided to control the transfer pump was to use the existing
>>sending unit that is in the right side of the tank (which reads 0 to 3.5v,
>>full being 0v - bone dry being 3.5V) and use that sending units output as
>>    
>>
>a
>  
>
>>reference signal for the circuit, and having that circuit turn a relay off
>>(or on) to control the power to the transfer pump.
>>
>>i appologize if this reads confusing and that it is so long, but i wanted
>>    
>>
>to
>  
>
>>be as detailed as possible. if you think your circuit design would work,
>>    
>>
>i'd
>  
>
>>be very grateful if i could have a copy of it. thank you for the reply
>>    
>>
>
>Hmm, so you can't just have a tube connecting the two saddle-tanks together
>at their lowest point (to distribute the fuel evenly over both tanks), this
>would certainly be the easiest way to let the pump see two tanks.  I realise
>that having the tanks connected in a more vertical manner would be a better
>solution but it may not be worth the trouble.
>
>I can't think of an optimum way of doing this (easily), as even a comparator
>type circuit isn't what you really want, it would mean that the pump is on
>when the tank is near full and off when the tank is getting empty, which
>isn't an optimum idea, you wouldn't be able to use all the fuel this way....
>
>I think perhaps that looking outside the usage of a pump is required... (or
>perhaps a non standard type of usage).
>
>I have no real ideas about this kind of stuff, only the electronics and
>that's not the ideal solution to this one.
>
>FWIW, the comparator circuit that I was refering to was a simple opamp (ie
>741), with a VREF on the non-inverting input that is the switching point of
>your fuel tank, and have the inverting input connected to the actual fuel
>sensor itself (after sufficient low pass filtering).  Then you can add in
>some hysteresis if required/desired simply by applying some feedback to the
>circuit ( a resistor/voltage divider from the output back to the
>non-inverting input).
>
>
>  
>



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