ecu voltage problem

[Thor Johnson]

On Wed, 30 Apr 1997, Kurt Bilinski wrote:

> At 08:32 AM 4/30/97 -0700, you wrote:
> >I am an FSAE student and we built an EFI computer for the competition.
> >There seems to be a problem running it off the car's power supply, ie the
> >battery.  When it is hooked up to the battery the computer holds pulse
> >widths at around 1 ms per revoltution regardless of throttle position.
> >When we hook it up to the standard voltage regulator used for testing in
> >the lab the car works perfectly with full rpm and throttle range, but
> >can't move because it is attached to an extension cord.  We're using a
> >68hc11 processor.  If anyone has had any weird voltage problems like this
> >any help would be appreciated.  Thank you,
> >
> Get the EE guys over for some serious shielding.  Use a scope to check the
> Vcc lines.  You're getting noise feeding in from somewhere.  They need to
> do bypassing on all the supply lines.
> 
> It's kind of a big deal, maybe get one of the EE prof's over who's good at
> EMI, the students probably won't know.

Been too busy trying to tune ours to read this quickly.  I got around 
that on our EFI system by placing a 10,000uF cap accross the supply, 
after a diaode.  Originally this was to protect agains brownouts during 
cranking, but I haven't had any problems.

  Iw ould be interested in hearing some of the details of your system... 
Mine is a MAP based system with lookup tables for delta-throttle, ECT, 
and others, but it seems to be very difficult to tune properly (I am 
strictly an EE, and have little/no car experience).

Any pointers?

                Thor Johnson
          johnsont at falcon.cs.mercer.edu
     http://falcon.cs.mercer.edu/~johnsont
                                                    
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