Perfromance/Altitude and CHT/EGT question

[bnicolette]

Hi all,

 

Well we had a great trip to Niagara Falls on Saturday.  Our first family adventure in the Mooney, weather was perfect and everybody had a blast.

 

Question #1:

I have been flying the Mooney (J model) since February.  I have noticed a lot of talk about the red box when reading about the engine monitors and the leaning process.  Most of my flying is point to point and usually a minimum of 170nm.  I almost always file IFR (habit I suppose and lonely without it) and minimum altitudes of 7000’ usually.  It appears to me that the red box doesn’t really come into play when at this altitude and really just wondering why one might fly lower than that when on a point to point trip?  I am just wondering if I might be missing something?  Is there an advantage to flying lower?  I must admit that I haven’t spent much time in the POH when it comes to performance charts, but I would think that the optimum altitudes would be somewhere around 7 to 8 thousand feet?

 

Question #2:

I have posed this before but just about the CHT values.  My #2 CHT is generally 50 degrees colder than the hottest CHT and the #2 EGT is about 60 degrees hotter than the coldest EGT?  What do you guys think this could be due to?  The spark plugs are brand new and the mag checks are normal so it’s not a plug issue?  I had a compression check done before this trip and they were 75, 75, 79, 75.  The engine has right around 600 hours SMOH.  I have about 30 hours on the airplane now since I have owned it and the values have not changed, so possibly it’s just the way this engine is?  I put the engine monitor in so the previous owner would not be of help?  Any input?

 

Thanks guys and blue skies to all.

 

Brett

[scottfromiowa]

Hey Brett.  Glad trip to Niagra Falls was good.  I think there is an impressive collection of WWII aircraft just north in Canada.  (Spitfire, Hurricane, ME-109, P-51, P-47 etc.) Might want to check that out some time.  My #2 CHT is about 50 degrees hotter (consistently).  I attribute this to probe position.  I had an OEM probe so multi-probe was  positioned differently.  The key is consistency, as you know.  If that is norm...all is good...if you notice a change time to inspect, right?  EGT really doesn't matter accept for leaning/mag check.  It's all about the cylinders temp.  #'s on EGT will vary and aren't an issue.  IF an EGT is wildly different (from group) may be a sign of a clogged injector, but a 50 degree difference not an issue (so I have read as they are just values).  I am a VFR pilot and I fly at 6500-7,500 (or higher depending on winds), but if I have a cloud ceiling lower...I can't get on top...or if possible for ceiling below at destination...I might also have to stay lower...This happens more than you would think in the summer in Mid West for a VFR pilot.  I agree that you shouldn't be at 70-75% of HP at those altitudes (in a J) and shouldn't be in the "red box".  I don't run above 25 inches of manifold pressure down low and lean to 10-10.5GPH.  Up high I lean to 30-50 LOP and firewall throttle with ram air open in my M20E.  There are some really good engine management articles that can be found on other links that discuss the "red box" in detail.  Some other links discuss in detail on Mooney Space.

[danb35]

Differences in EGTs from cylinder to cylinder are meaningless.  Significant differences in CHTs could mean something, but it could be anything from slight changes in baffling to a different type of CHT probe to...

[Parker_Woodruff]

my best TAS in my M20J was always between 6,000 and 9,000 depending on the day.  I would be interested to know where your #2 cylinder is in relation to its peak EGT.

[bnicolette]

Parker,

 Here is the LF Report from EZ trends for one of yesterdays legs. 

 

TIME	FF	E1	C1	E2	C2	E3	C3	E4	C4
4/30/2011 11:36	10.7	1408	351	1472	321	1434	348	1415	353
4/30/2011 11:36	10.7	1410	352	1474	322	1435	350	1413	354
4/30/2011 11:36	10.7	1415	352	1473	319	1436	350	1416	353
4/30/2011 11:36	10.7	1417	352	1479	320	1440	350	1425	352
4/30/2011 11:36	10.7	1422	352	1482	322	1443	350	1426	351
4/30/2011 11:36	10.7	1426	352	1487	322	1447	351	1431	351
4/30/2011 11:36	10.6	1431	352	1492	320	1450	351	1437	351
4/30/2011 11:36	10.5	1438	353	1494	320	1453	351	1436	351
4/30/2011 11:36	10.7	1440	353	1499	320	1455	351	1439	351
4/30/2011 11:36	10.7	1441	353	1498	319	1459	350	1444	351
4/30/2011 11:36	10.7	1441	353	1501	319	1460	350	1444	351
4/30/2011 11:36	10.7	1444	353	1502	319	1460	350	1442	352
4/30/2011 11:36	10.7	1445	353	1505	321	1460	349	1444	353
4/30/2011 11:36	10.7	1445	353	1503	322	1454	349	1438	353
4/30/2011 11:36	10.7	1445	353	1502	322	1453	349	1441	353

[Parker_Woodruff]

Need to know the EGT where the cylinder peaked and how many degrees it was rich or lean in relation to peak.  353 dF is nothing to be owrried about.

[bnicolette]

Quote: Parker_Woodruff

Need to know the EGT where the cylinder peaked and how many degrees it was rich or lean in relation to peak.  353 dF is nothing to be owrried about.

[Barry]

Well, you've the information on the engine. One reason for flying low is to get out of the way of high winds on the nose. A 40 knot wind at 7000 may only be a 15 knot wind at 3500.