VairHeads, I had an interesting glitch a couple of weeks ago with my Corvair. On takeoff with daughter Claire sitting next to me, about 1000' off the end of the runway, one cylinder dropped out completely. I swapped over to the other fuel/ignition/battery system and there was no change (so I'd just eliminated everything but mechanical difficulties, in less than 5 seconds). It did exactly the same thing as I was leaving my father's farm a few hours later. It's a good thing I had 5 more cylinders, so it really didn't hurt climb rate much, but not knowing what was going on, I didn't know if it was about to quit completely or what. Even my brother the Cessna pilot (who was watching the takeoff from the ground) got worried after hearing the engine sputtering. Now that I think back on it, this incident was very similar to some events last summer, where I thought maybe I had water in the fuel, but didn't find a drop on further examination.
Going back through the EIS data that I store on my laptop every time I fly, I can clearly see the CHT on #2 stabilize while all the rest continued to climb, and EGT #2 starts dropping while all the rest keep climbing. So number two croaked for about 30 seconds and then came back. At first I thought it was a sticking valve (hence the name of the chart you'll see), but other analysis (like the high fuel consumption rate) points to the number 2 spark plug fouling due to being too rich. Now that I know what's going on, I've been making takeoffs with the mixture pulled out about 3/4", which is still plenty rich, but not rich enough to foul anything. I'd readjust the cable at the carb, but for winter time use I'd have to move it back again, so this'll work for now. If I were real gung ho I'd make a stop collar that I could put around the knob, and maybe I'll do that eventually, for now it's been three weeks without a recurrence, so I think it's "solved". I guess my point is that the EIS (or something similar) is a pretty valuable troubleshooting tool, especially if you collect the data for trend analysis. See http://home.hiwaay.net/~langford/EIS/150_valve.gif (which has been "decluttered" down to CHTs and EGTs) and http://home.hiwaay.net/~langford/EIS/150_numbers.gif . The zeros in the tach column were where I switched out ignition systems, and I don't have a tach line going to the second coil (deliberate separation of the two systems). 267 Corvair hours and climbing... Mark Langford, Huntsville, Alabama see KR2S project N56ML at http://home.hiwaay.net/~langford email to N56ML "at" hiwaay.net
