Love This

[Chris Conlon]

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 be 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.