[Diy_efi] Fuel Pump speed controller

[Greg Hermann]

At 11:36 PM 8/3/02, efi_student wrote:
>Maybe not so dumb.  Toyota is using a returnless system on their Group A
>rally car.  From someone very close to the source:

It's NOT a particularly good idea unless they have a means of vapor
control, such as a bypass orifice at the high point of the rail system, and
no "high spots" (vapor traps) in the system between the pump and the
bypass.

The design of fuel system piping needs to be treated just like any other
two phase piping system for best performance.

I agree completely with your comment about stable fuel density--and believe
that a cooler on the return line is a reasonable way to achieve it.

Greg
>
>"The reasoning is, its easer to keep the fuel pressure controlled
>without all the changes in engine temp in the mix. Also the controlled
>fuel evaporative keeps the fuel not only cool but in a controlled
>condition, this also helps with tuning and better mapping across the
>board, as the fuel is not all over the scale in temperature. Another
>benefit is weight, far less plumbing in the car no return line, no
>evaporative lines and fittings, evap tank separator its all gone one
>neat compact unit in the tank looks after all including fuel pressure."
>
>Initially I would have agreed with your analysis, but there is certainly
>something to be said for stable fuel density.  Having come from vacuum
>systems and gas control devices, I have always thought the method of
>controlling fuel pressure pre-regulator a bit at odds with industry best
>practice for gas systems.
>
>Lance
>
>-----Original Message-----
From: diy_efi-admin at diy-efi.org [mailto:diy_efi-admin at diy-efi.org] On
>Behalf Of Greg Hermann
>Sent: Saturday, August 03, 2002 11:14 PM
>To: diy_efi at diy-efi.org
>Subject: RE: [Diy_efi] Fuel Pump speed controller
>
>
>At 12:40 AM 8/4/02, Scott F. Williams wrote:
>>Please educate me as to why you'd want to control the speed/output of
>>the fuel pump. Isn't the fuel pressure regulator the proper way to
>>control the pressure to the fuel rail, etc? I'm obviously missing
>>something here...
>>--
>>Scott F. Williams
>
>If he's talking about a non-return fuel system, would be one reason, but
>that is really a dumb design for performance use.
>
>A better reason is that two controls over a variable will give a MUCH
>tighter, more accurate control over the controlled variable--in this
>case fuel rail pressure.
>
>Kind of like the way heavy trucks use a thermostat AND (sometimes)
>radiator shutters AND (occasionally) a variable pitch cooling fan to
>control coolant temp.
>
>Greg
>
>
>
>
>_______________________________________________
>Diy_efi mailing list
>Diy_efi at diy-efi.org http://www.diy-efi.org/mailman/listinfo/diy_efi
>
>
>_______________________________________________
>Diy_efi mailing list
>Diy_efi at diy-efi.org
>http://www.diy-efi.org/mailman/listinfo/diy_efi



_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://www.diy-efi.org/mailman/listinfo/diy_efi