Date: Mon, 8 Jan 2007 07:28:17 -0500
Reply-To: ------------- <VW4X4@VERIZON.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: ------------- <VW4X4@VERIZON.NET>
Subject: Re: Idle Stabilizer Control Unit Reverse Engineering
In-Reply-To: <Pine.LNX.4.58.0701071946070.20124@kenneke.com>
Content-Type: text/plain; charset=us-ascii; format=flowed
I have the ability the layout PCB's. If there is a circuit design
(schematic)
available for a new IS, or even an ECU, I can produce a professionl designed
PC board for free and the board for a very reasonable cost.
JOE. w
jon wrote:
>John,
>
>I'd be interested in an untouched malfunctioning unit. I want to drill
>down to the exact reason why it failed.
>
>I used to do "fiddly" analog design for oceanoprghic instruments, so
>op-amp wierdness used to be a daily chore. On one instrument, we hand
>tuned everything. It was a PITA. Every time we had a new tech., I had to
>spend almost a week training them how to select the tuning components
>based on components tolerances.
>
>At first look, the counting seems to be accomplished with a F to V
>converter. Wow.
>
>It would be very interesting to know why in the waterboxer application a
>seperate IS unit was needed. There are Digifant cars that don't have them.
>
>That also raises the question: How do megasquirt equipped WBXs idle? Given
>they use a whole different air intake scheme, that might be the answer.
>
>I've got an o'scope, so it has been in my plans to take a look at the ISV
>waveform. I'll let you know.
>
>Thank you!
>
>Jon Kenneke
>829 Washington SW
>Albany, OR 97321
>
>
>On Sun, 7 Jan 2007, John Bange wrote:
>
>
>
>>>How many folks out there have a *bad* IS control unit? I'd love one to
>>>verify if it's the transistor that went south.
>>>
>>>
>>I have a couple toasted ones Frank Condelli was nice enough to send me last
>>year for similar purposes. My initial plan was to desolder the parts off one
>>of 'em and map the PC board traces, then add in the components to get a full
>>circuit diagram. After a little poking around, though, I figured out that
>>it's actually a very touchy hand-tuned analog computer. Outstanding design
>>for its time (mid 80's), but seriously yesterday's news. What takes a bunch
>>of tense interwoven op-amps to do in analog, only takes a 25 cent
>>microcontroller to do digitally. The engineer that designed this circuit was
>>a genius, figuring out a way to "count" revolutions per minute and keep it
>>steady without actually having anything capable of COUNTING. I have a
>>partly done design for a PIC based replacement, but employment issues have
>>conspired to keep me away from completing it. The big missing piece was the
>>valve itself and how it's operated. I have no scope to hook up to it to see
>>how the idle controller opens and closes it. It reads constant voltage on a
>>meter, so I assume it's using some sort of pulse width modulation, but I
>>don't know. Perhaps someday I'll have the time and the oscilloscope I need
>>to look into it.
>>
>>Anyway, if you want a dead idle controller, I can dig one up and mail it to
>>you, if you like. Just email me your address and I'll try to find it in my
>>garage. I'm supposed to send Steve Sandlin four big boxes of foreign car key
>>blanks I don't need (USPS will be sorry they made those $4.85 flat rate
>>boxes!), so I'll be at the post office anyway and I'd probably be able to
>>get it out this week.
>>
>>--
>>John Bange
>>'90 Vanagon - "Geldsauger"
>>"Staubkess bolt? I have one of those?"
>>
>>
>>
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