Date:         Sat, 22 Jul 2000 21:46:37 EDT
Reply-To:     kenneth d lewis <kdlewis@juno.com>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         kenneth d lewis <kdlewis@juno.com>
Subject:      Re: Hand-held tach use with Digifant
Comments: To: johnpatt@warwick.net

John;
        The resistor are in series and form a voltage divider to reduce
the signal level. Evidently those values did not work for me either
because I used a potentiometer in it's place. This allowed me to "dial
in" the proper level for my test equipment.
        I just went outside with ohm meter in hand to measure it for
you(I left it hooked up) but I could not access it. I have the crew cab
loaded up for a canoeing/kayaking trip tomorrow. I will try again later,
remind me.

Drive Safely & Good Luck
Ken Lewis    <Kernersville,NC>
86 VW crewcab;60 356B Coupe
--------------------------------------------------

On Thu, 20 Jul 2000 23:23:53 -0400 John <johnpatt@warwick.net> writes:
>QUESTION FOR THE LIST:
>
>When working with 2.1L Digifant systems, what do you use to check
>engine
>speed at the engine compartment? (running to the front of the van to
>look at the tach doesn't qualify as an answer).
>
>The Digifant system has a unique primary ignition circuit control
>perhaps similar to the old capacitive discharge systems. While
>powerful
>and efficient for ignition performance, the Digifant system dynamics
>are
>such that conventional hand-held tachometers cannot read the RPM
>correctly. This limitation for hand-held tachs to read the Vanagon
>ignition RPM goes all the way back to the air cooled AFC Vanagons.
>
>There is a way to "buffer" the signal dynamics to allow a hand-held
>tach
>to read to the signal correctly. However this procedure only applies
>to
>AFC/California Vanagons. The simple modification is shown in the
>Bentley
>on page 24.11 using parallel resistors at the signal input.
>
>However this modification (for AFC systems) does not provide accurate
>RPM readings on Digifant systems presumbably because the resistor
>values
>must be changed to suit the dynamics of the Digifant ignition control.
>
>My question is has anyone determined how to adapt a hand-held tach to
>a
>Digifant system using this resistor-type modification shown on Bentley
>page 24.11? If not what are you using to read RPM at the engine
>compartment?
>
>Regards,    John

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