Love This

[David Cooley]

Chrysler uses a returnless system on the Neon and others...  There system
isn't anything special, it just has a standard FP regulator mounted to the
pump assembly in the tank and the "return" is just open to the inside of the
tank.  Basically they relocated the FP reg from the rail to the pump.
Later,
Dave

-----Original Message-----
From: Chris Conlon <synchris at ricochet.net>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Friday, January 29, 1999 12:52 PM
Subject: RE: Love This


>
>First let me say I'm really glad to hear about this. My possibly-vapor
>lock problem came back yesterday (twas a bit warm), and since it mostly
>seems to happen when the gas is real low (thus hotter), I had sometimes
>wondered about a no-return fuel system. So I am definitely loving this.
>
>I know Toyota uses the system in the 1ZZ-FE and claims lower evap
>emissions as the reason, FWIW. Less vapor lock? I think it could go either
>way depending, but a smallish amount of fuel being recirculated thru
>a hot rail has got to get pretty warm.
>
>I would think the pulsation damper would bee even more critical, maybe
>even something like a small pressurized resevoir would be needed? Does
>anyone know if the actual no-return systems have some such thing?
>
>I didn't see any actual part numbers or prices though. Do I have to
>order these in GM-size lots? Eek.
>
>
>At 08:47 AM 1/29/99 -0600, Roger Heflin wrote:
>
>>Besides the physical conversion, you would need to add a input to the
>>computer that mesaures the pressure from the transducer, and use that
>>pressure to adjust the injector pulsewidths based on pressure.  So
>>beyond physcially converting your would need significant computer
>>adjustements (probably even computer hardware adjustments to get the
>> ...
>
>You could also manage this one with simple analog stuff. Get an
>appropriate switching power supply or chip, and use it to drive the
>fuel pump. Use the pressure transducer output to feed the power
>supply reference input, such that it runs the pump more or less to
>maintain the fuel pressure you want. Soooper easy.
>
>You could even get Bruce's variable fuel pressure scheme with a tiny
>bit more work. Add a reference voltage (from somewhere) representing
>the desired fuel pressure. Put thru a comparator with the transducer
>output. When the FP is too high, charge an integrator; when the FP
>is too low, discharge it. Use the integrator output as reference
>input to the power supply. (A bit of RC filtering may be needed too,
>depending.)
>
>
>Which reminds me, I have a simple circuit that I think will work ok
>for the whole 555 EFI idea. (No 555's though, sorry.) But I have no
>good way to get it to the world. Is there some freeware that'll let
>me enter a simple schematic and end up with a .gif or something? I
>suppose I could dig up a paint program if there's nothing else going.
>
>   Chris C.
>
>