[Diy_efi] Intro, and q's about fuel economy

[William Shurvinton]

Eep the atomisation spectre again. Having epoxied mounts in for the 2nd set
of injectors on my manifold I keep wondering if I should have fixed on an
upper set as well for experimentation. Nope, its a rotary, it'll never get
good gas mileage :-) Mind you with a tad of H20 I'm interested in finding
where the lean limit is.

Back to the original questions though. Swing over to www.diy-wb.org and
there you can find out how to build a wide-band 02. In a stationary app I
would hazard that EGT +NB + plug cuts might be close, but toy value is
excellent.

As for the actual EFI. If you are not after meeting any emissions regs you
can build very simple EFI. Have a search on how some of the old Bosch stuff
worked. K-jet was all analogue. You can implement a workable EFI system with
a 555 and a few op-amps if you approach it correctly. Especially if you only
have a limited number of operational states.

For reading on economy it is also worth having a read of anything you can
find on aviation engine control. As planes in level flight are effectively
at a single load point and there is very little qualified in terms of EFi
the pilots manually lean the mixtures to get best BSFC, which is not
something you can easily do with a car. If I understand it correctly you
want to open the throttle whilst leaning the mixture until you reach the
lean limit or WOT.  I would be willing to wager that some of the fly by wire
throttles do open up on cruise to reduce pumping losses? Love to know how
they recover from that when you mash the throttle.

Bill
----- Original Message -----
From: "Greg Hermann" <bearbvd at mindspring.com>

> If this engine has an updraft carby, STAY WITH THAT CONFIGURATION !! Aim
> the injector right AT the area where the edge of the throttle butterfly is
> as it begins to open--there is sonic flow there, which will help greatly
in
> atomizing the fuel. An exhaust hot spot in the intake manifold above the
> butterfly is another VERY helpful thing. One could also aim the injector
> directly AT such a hot spot.
>
> Pre heating the fuel (like to 200 or 250 F) before it goes to the injecor
> can be a great help. Takes some clever pipe routing to avoid getting vapor
> to the injector, though.
>
> Using an AIR SHROUDED injector--either from a BMW OR from a  Bosch CIS
> system would also help GREATLY. Quite plausible to control the fuel
> pressure to a CIS (consant flow) injector electronically, and thus keep
> things REAL simple !!
> Last of all--water injection CAN be used to improve efficiency !!
(Shhhh!!!)
>



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