

| Subject: | Re: Addendum: Boston Bob Big Valve Engine Update |
| From: | John Bange |
| Date: | Thu, 30 Jun 2005 13:15:53 -0700 |
> Someone a while back posted about work on adapting a "hot" type AFM unit > for use on a Vanagon. I believe those Bostig Engineering guys are working on that one. They did a dyno test not too long ago, but I haven't heard anything since. Their web site is refusing connection, so I dunno what's up recently. > Also there was some discussion about > re-engineering the Idle Stabilizer Control box (in front of the right > tail light) into a solid state unit less susceptable to failure. Heh. That was me. I won't go so far as to call it a pipe dream, but progress is definitely slow on that project. So far all I've done is trace out about a quarter of the circuit diagram for the standard analog unit (thanks to Frank Condelli for providing me with a couple no-go units to bash on). It's a remarkably complex hand-tuned analog computer. Being mostly a digital electronics kind of guy, analog control systems like this are black magic to me. I'm thinking that the way to really approach this is from the other end: monitor the various inputs in conjunction with the air bypass valve output in a running vehicle in order to get the operating parameters. I'm under the impression/delusion that a digital idle control unit would be unbelievably easy to implement compared to the analog one, as there's one thing digital can do that analog can't, and that's COUNT! There are obviously only a few variations in optimum RPM depending on whether the AC compressor is on, the engine is warming up, etc. A digital controller need only count the R's Per M and adjust the idle stabilizer valve if the number is too high or too low to match the current "mode". I hope to have the engine into my vehicle soon (it's been dead since Dec 25, though, so "soon" is very relative) and then I can start working on "improvements". If my Idle Stabilizer Controller experiment works, I may even feel bold enough to design an ODB II-compliant digifant ECU replacement! OK, maybe not. Probably just a Zemco-style engine monitoring system...
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