CorvAircraft> mixture problem

[jbfjr]

Mark,

Since leaning out your mixture control, have you noticed any 
difference in any EIS parameters?

John Franklin
GN-1 Aircamper
164cid Corvair
Richmond, TX

---------- Original Message ----------------------------------
From: "Mark Langford" <n56ml at hiwaay.net>
Reply-To: Corvair engines for homebuilt aircraft 
<corvaircraft at mylist.net>
Date: Thu, 6 Jul 2006 09:24:27 -0500

>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
>
>_________________________________________________________
>search the CorvAircraft archives at 
http://www.maddyhome.com/corvairsrch/index.jsp
>to UNsubscribe from CorvAircraft, send a message to CorvAircraft-
leave at mylist.net
>Other CorvAircraft list info is at 
http://www.krnet.org/corvaircraft_inst.html
>
 

________________________________________________________________
Sent via the EV1 webmail system at mail.ev1.net