Path: utzoo!utgpu!attcan!uunet!husc6!think!bloom-beacon!bu-cs!purdue!decwrl!labrea!glacier!jbn
From: jbn@glacier.STANFORD.EDU (John B. Nagle)
Newsgroups: sci.electronics
Subject: Re: ??: computer-controlled engines
Message-ID: <17608@glacier.STANFORD.EDU>
Date: 3 Aug 88 22:46:47 GMT
References: <7200006@silver>
Reply-To: jbn@glacier.UUCP (John B. Nagle)
Organization: Stanford University
Lines: 75

In article <7200006@silver> commgrp@silver.bacs.indiana.edu writes:
>What experiences have people had with car engines controlled by 
>digital computers?  Are they a mature technology, or are they like 
>color television in the 1950's?  Most car problems are electrical in 
>nature; electronic engine control would seem to decrease reliability.  
>
>I've heard the following rumors about digital engine-control 
>computers:
>
>1. They contain a register which records the highest speed at which 
>the car has been driven. This can be read by dealers, who will refuse 
>to repair engines under warranty if the number is too high.

      Somebody put that in a Cadillac engine control program a few
years back.  A bit was set in non-volatile memory if a speed of 85mph
was exceeded.  Apparently this was just something some programmer stuck
in, and there was a minor flap about the "invasion of privacy" thus
represented.

      I did some work involving Ford engine control programs in the early
1980s, and at that time, there was no long-term storage in Ford's system,
based on a custom chip later sold as the Intel 8061.  There were vague
dreams of storing info about, say, the last five or so times the engine
had done something unreasonable, such as stall or miss.  But nothing was
implemented along those lines through '83, when I lost touch with that
effort.

>2.  A new car's computer assumes default parameters, and sets new ones 
>as it "learns" the car's performance over 50 miles of driving.  If the 
>car battery is disconnected, the computer forgets the learned values, 
>and the engine runs less well for 50 miles while the computer retunes 
>itself.  (Is the highest-speed memory erased by disconnecting the 
>battery?)

      There was some question at one time as to whether such a setup
would consititute a "defeat device" under the terms of the Clean Air
Act.  The problem is that any mechanism not exercised by the "city" and
"highway" test cycles that affects engine performance that affects
emissions can be illegal.  So there are regulatory obstacles to
long-term adjustment.

>3.  The federal government has funded research (thusfar unsuccessful) 
>to discover a ray like Batman's which stops car engines, for law-
>enforcement purposes.  Big Brother plans to require a remote-disable 
>feature on engine computers.

      The California Highway Patrol actually funded research in this area
shortly after World War II.  But I hadn't heard anything recently, not
that I would be likely to.  Comments?

>4.  Radio-frequency interference can jam the computer, causing various 
>effects like engine stop or full throttle.  This definitely happens 
>with radio transmitters mounted in the car; there was a long 
>discussion of it on rec.ham-radio last year.  Manufacturer's 
>recommendation: Don't install any 2-way radios. What happens when you 
>are next to a semi with a 100-watt CB "linear" amplifier??

      I know that at Ford, they had some trouble with this, but overcame
it.  One of their tests involved driving by some huge radionavigation
site in Michigan.  The Ford systems circa '83 deliberately had limited
authority, in that they could only tweak the throttle about 20%, for
example (this was a bellcrank arrangement, and you could feel the
throttle servo pushing back at you.).  There was also a hardware backup
system (referred to as "limp-home mode") which allowed driving with the
computer down.  In this mode, spark timing was fixed, so speed was
limited, hence the name.

      Generally the vehicle electronics were designed to operate with up
to a 30 watt radio transmitter on board, this being about as large as
police or business band gear gets.  Hams have special problems.  If
you want to run a few hundred watts in a car, this comes under the heading
of "vehicle modification" and some engineering work on the vehicle electronics 
will probably be needed. 

					John Nagle