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Date:         Mon, 12 Sep 1994 09:29:35 EDT
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         cchubb@ida.org (Chris Chubb)
Subject:      Re:Computers on Board

/I wonder if there exists some sort of device that you could plug in /between the engine (maybe the fuel injection) and the PC and then some /software allowing you to monitor/analyze the engine. I know that --at /least for the early fuel injected engines-- VW had a computer they used /for diagnostics and which plugged right into some receptacle in the engine /compartment. That might be a starting point.

I built as part of a student project oh, many moons ago, a diagnostic program that worked on the old, OLD, Timex-Sinclair 1000's. I might even have my write up around somewhere.

The program gave a decent approximation of RPMs, Dwell, and some other functions I cant remember. It used a 'black box' that hooked onto the expantion connector and the points wire of the distributor. It did not have enough memory for me to implement the diagnostic functions that I had envisioned, nor was the timing accurate enough. It ran off of 12 volts, was rigged as hell and impervious to water and grime, and used a small 12 volt TV for output.

If I were to to it again today, I would try to use a cheapo 8086 portable and implement the following functions:

Tach Dwell degrees between firing of successive cylinders degrees between firing of same cylinder (timing fluctuation) Inductive pickups on all four spark plugs. These could be cross referenced with the points to indicate no-fires TDC sensor with firing informaton to indicate advance. Reports advance curve under various driving conditions. Oxygen sensor, mabye to indicate mixture under various conditins.

If you have any suggestions, send them my way, or post them. As the list stands right now, the black box would not be very expensive. All it would have to do is read the various sensors, digitize the results, and serially send them to the host PC. The host PC would be able to do all the analysis of the data in real time, giving you information as you drive, or in the shop.

All of the sensors, (esp. the four inductive pickups) would be more expensive than the 'black box' reading equipment. The pickups, O2 sensor, TDC sensor, and some mounting brackets would cost about $100.00. I cant cost the rest of the system, and the computer would be up to you. The hardest part would be making all the logic operate reliably on 12 volts for long periods.

I have always been intrigued by the big computers at service bays, but I realized that the snesing hardware is trivial. All of the cost of these machines, mostly leased, is the vehicle tune-up database that they carry.

So, any ideas?

--- Chris Chubb (cchubb@ida.org) __________________________________________________________________________ \All opinions expressed or implied may not reflect those of the Institute \ \for Defense Analyses, the US Government, or anyone else. \ --------------------------------------------------------------------------


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