A thought...

[Mike Fahrion]

> > 
> > I'm thinking of putting fuel injection on my pontiac 455 in a '78 trans am.
snip
> > I'm thinking, instead of going the 68hc11 route, using a pc.  Instead of
> > building a a/d and d/a board, use two parallel ports.  That would give me
> > 8 ins and 8 outs.  Timing would be resolved by the computer, hell, 386/486
> > motherboards are cheap.
> 
> Yes, but how will you mount it in your car? How much power can you afford 
> to use to run this PC? The benefits might be swallowed by the additional
> Horsepower lost in the new alternator required to run the thing.

I don't think that power consumption or power supply problems will be 
a serious issue.  Maybe as much as 0.1 hp difference.  It is very 
common to run a laptop from cigarette lighters.  A laptop would be 
really nice in some ways, but you may have an interface I/O problem - 
you'd need to take advantage of the PCMCIA slots.  A desktop 
machine/motherboard doesn't sound nearly as convenient - especially 
the display. 

> How will you isloate this computer system and it's connectors from vibration
> inherent in automobiles?

Good point - you'll need to put some thought into this - doesn't 
sound too bad though.  I'd consider a non-mechanical data storage 
format.  Hard drives don't like lots of motion (although that's 
hardly even true anymore) - but my experience is they definately 
don't like to spin at cold temps.

> How do you get timing control tighter than 55 ms? (the timer tick
> on PC boards are 1/18th of a second). 

With programming techniques you can get resolution in the
microseconds (ballpark numbers).

> > Question 1: Am I crazy? Anyone see an inherent flaw in all of this?

crazy? probably :)  

snip
 
> > Question 3: Any suggestions, ideas, or people interested?

I'm interested.....

-mike
mfahrion at bb-elec.com