Re: [Amc-list] EFI install on [anything modest]

[adh@xxxxxxxxxxxxxxxxx (Sandwich Maker)]

" From: Tom Jennings <tomj@xxxxxxx>
" 
" On Mon, 2 Apr 2007, Sandwich Maker wrote:
" 
" > " From: Tom Jennings <tomj@xxxxxxx>
" > "
" > " The only thing I've read "bad" about Howell and others is from
" > " people who tried to set them up without enough sensor feedback,
" > " "open loop", and feedback is the whole POINT of FI. Except for
" > " those few, I've not heard a bad thing about Howell.
" >
" > i disagree about feedback.  it's the only practical way to zero in on
" > perfect mixture under widely and wildly changing conditions, but i've
" > always thought that to a degree it was a crutch for systems that
" > didn't have the proper sensors to read the environment going in.
" 
" I was specifically referring to non-OEMs adding EFI to an
" engine that's either older, modified, rebuilt, customized,
" or otherwise not-factory-unit-to-unit consistent.
" 
" Saab designed a limited feedback FI system for some particular
" engine coming off an assembly line with probably good consistency
" unit to unit. That's not what hobbyists are doing.

agreed, though saab didn't design this system - it was the original
bosch jetronic first seen on the '66 vw squareback.  afaik it had -no-
feedback.

" Isn't it funny though, that a carb basically has one "sensor",
" an air-velocity/partially-mass measuring device aka venturi, and
" with that one crappy old thing meters gas pretty damn well over
" a surprising range of variables. (OK power valves etc count.)

don't forget 'booster' venturii!

" Carbs are lousy at: engine (coolant) temperature compensation,
" economy/partial throttle cruise vs. power "modes", and
" altitude. Chokes and vacuum or progressive-mechanical secondaries
" pick the low-hanging-fruit of the first two, and there's some
" 80's carbs that attempt altitude but we don't hear about those
" any more!

this is all why a simple open-loop system like the jetronic worked so
well.  the only thing it couldn't measure was humidity.

" > this was btw an
" > analog system, based afaik on bendix patents that may have been on the
" > '57 rebel system.
" 
" It would be very interesting to re-visit those older analog
" systems with the electronic gunk we have now! Too bad the
" hardware is all museum quality and availability now. Analog
" servo stuff is something I'm good at (useless skill).

analog stuff can take real math skills which i think is why it's
gotten passed over, but i think it's a shame.  the elegant simplicity
of it all...
________________________________________________________________________
Andrew Hay                                  the genius nature
internet rambler                            is to see what all have seen
adh@xxxxxxxxxxxxxxxxx                       and think what none thought
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