Date:         Tue, 1 Jan 2002 22:55:38 -0600
Reply-To:     John Rodgers <jhrodgers@MINDSPRING.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         John Rodgers <jhrodgers@MINDSPRING.COM>
Subject:      Re: B. Bobs day at the dyno and the importance of fuel air
              ratioupdate
Comments: To: Robert Donalds <bostneng@FCL-US.NET>
Content-Type: text/plain; charset=iso-8859-1

Having read of Boston Bob's efforts to get a Dyno Grip on his big valve engine, and of Mark Ingalls efforts using the Boehler DigiTool, aircraft type exhaust gas temperature readouts came to mind.

I've been away from aviation for quite a number of  years but I remember using the EGT gages as a guide to manually setting  the fuel air mixture during various flight regimes for best performance. On those aircraft with engines equipped with an EGT probe mounted in each exhaust stack just outside the cylinder head, it was possible to  select through each cylinder and determine which cylinder was running the leanest. The leanest running cylinder then became the guide cylinder by which the mixture for the engine was set. That way one avoided burning up a valve or worse, burning up the engine. By watching the EGT gage, for any given throttle setting (manifold pressure setting) the mixture could be set for Rich Best Power, Peak Power, or Lean Best Power. Rich burned more fuel, but you got almost best power, but not quite. Peak Power, while the top performance, was no good because you also got maximum temperature and could induce detonation. Lean Best Power ran a little cooler, gave the
best fuel economy, but had to be run at reduced power settings, meaning your speed wasn't as great.

With the tendency of the "Boxer" engines, both aircooled or wassercooled, to burn up #3, it has always seemed to me that some sort of EGT system for  all four cylinders would be appropriate. The "Averaging" of all 4 of the exhaust gas mixtures on the Wasserboxer, and the Aircooled, has always seemed to be less than adequate, the way I see it, than  individual read outs from each cylinder. It would be very cool if the DigiFant ECU could identify the leanest cylinder, then use it to set the mixture for operation of all cylinders. At least the chance of having an overly  lean cylinder to burn out would be eliminated.

Comments?

John Rodgers
88 GL Driver who has experienced the burnout of #3 once already!