lml@lancaironline.net Mailing List Archive

Matt,

Excellent. That is, in my opinion, the most likely cause of the change. And I wouldn't be surprised if there were no telltale exhaust stains on the outside of the pipe. It is entirely possible and maybe likely that there will be little or no leakage of exhaust out the crack, but it is very likely that cold air will be sucked into the crack, easily creating a low exhaust temperature reading. The high pressure exhaust pulse lasts for only a few crank degrees and for the rest of the cycle there is no pressure in the exhaust pipe. And even though the pressure is high for an instant the high velocity of the exhaust can create a local low pressure area.

Gary

From: mmcmanus@grandecom.net
Date: November 11, 2007 4:03:45 PM PST
To: lml@lancaironline.net
Subject: Re: [LML] #4 cylinder EGT

I was crossing New Mexico in August in my 360. In the middle of nowhere (of
course) I suddenly got a slight noise increase, and lost 200-300 degrees on the
EGT of one cylinder. No change in speed. Diverted to Double Eagle in
Albuquerque. They cleaned the injector for that cylinder - no change. Next we
pulled the lower cowl to get to the bottom plugs and whalla, the exhaust
manifold had a huge crack just below the flange allowing exhaust gases to
escape so the probe for the EGT wasn't getting as hot. They welded it back up
and I was on my way.

So the obvious (the injector) wasn't the problem at all.

Matt McManus
LNC2 360

Quoting Dan Reagan <dreagan@fuse.net>:

About 10 flight hours ago my #4 EGT dicided to start running about 150
degrees less than the others. This is a FADEC engine so there is a
possibility of injector problems but other than that please give me some
ideas what has changed. The temp shows approximate correct ambient temp when
shut down overnight.

Any help would be greatly appreciated.

Thanks,
Dan Reagan
IVP TSIO550 450+hours