ecu voltage problem

Wed Apr 30 16:56:09 GMT 1997

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Someone on this list (or KitCar, I forgot which) said that auto electronics 
are evil :)

You might need to build your power supply a little differently, utilizing a 
choke based noise filter btw the EFI computer and the alternator.  Your 
alternator might need some reworking, and if your efi system doesn't draw 
that much current, just for a test, you could try one of those line-noise 
filters available from electronic hobby shops (which is nothing more than a 
choke coil and sometimes a capacitor), and see if you get any improvement.

I'd place an ocilloscope on the V+ in line on your computer and look for 
any funky ripples, then at least you have a solid direction to go in.  Its 
theoretically possible that something under the hood that rotates is 
creating electrical noise and your unshielded EFI computer is picking it 
up.  Could also be a weak ground.  The ocilloscope will be able to tell you 
more.

Fred

-----Original Message-----
From:	S. Lastuka [SMTP:kicker at u.washington.edu]
Sent:	Wednesday, April 30, 1997 11:33 AM
To:	diy_efi at coulomb.eng.ohio-state.edu
Subject:	ecu voltage problem

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,
Sean

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