Date: Thu, 23 Nov 2000 15:14:11 -0800
Reply-To: Stuart MacMillan <macmillan@HOME.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Stuart MacMillan <macmillan@HOME.COM>
Subject: Rev limits, definitive answer
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Nothing is in the Bentley regarding this for the Digijet (there is a
5600 RPM cut out noted for the Digifant), but I found this in the book
"Bosch Fuel Injection and Engine Management" by Charles Probst,
published by Robert Bentley, 1989, p. 14:
"Precise control of fuel delivery allows the fuel system to be used to
limit engine RPM and prevent damage from overrevving. Before the days
of catalytic converters, RPM was limited by simply cutting out the
ignition when RPM got too high. Cutting the ignition, however, still
allows unburned fuel into the catalytic converter and causes it to
overheat; sometimes dangerously. Since the mid 1970's and the advent of
catalytic converters, RPM limitation has been accomplished by the fuel
injection system cutting back on fuel delivery. The goal is to keep the
engine running at its limitation without dumping unburned fuel into the
catalytic converter."
I can attest to this. As I was attempting to overtake a vehicle in
third gear once I hit this limit. The engine lost power but kept trying,
as my speed dropped I realized what was going on and dropped back.
You are right Rich, it is much simpler and cheaper to program a chip
than make a mechanical device, and as this paragraph states, that would
cause problems with the CAT anyway.
I'm enjoying the aroma of turkey cooking in the oven right now, it's
almost time to eat. Happy Thanksgiving to Rico and all other listees!
" RPM Limitation?
Rico Sapolich wrote:
>
> << The Digijet has a limit too >>
>
> The rev limiter on the 1.9L of which I have knowledge is in the form of a
> centrifugal switch built into the distributor rotor specified for this engine.
>
> Stuart,
>
> The more I think about this, bolstered by some cursory research, the more I
> feel that I have been propagating some misinformation and all you have said
> is correct. My reasons are: 1) It would be a real feat of engineering to
> design a reliable, high voltage, automatic disconnect to fit within the
> confines of the distributor rotor and which costs less than $10; 2) The
> engine would probably backfire once the revs dropped below the limit
> setpoint. I wish I still had my '84 1.9L so that I could dissect that rotor.
>
> I hope this day of thanks finds you with many blessings.
>
> Rich
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