Max Power at high altitude

[jetdriven]

CHTs over 500 degrees usually are indicative of detonation. Mike Busch of Savvy has some webinars that explain it but basically high CHT are conducive to detonation, and detonation causes high CHTs. This can leasd ot thermal runaway and engine failure in something like 90 seconds.  I would definately borescope the cylinders and pistons and examine the plugs.

Regarding leaning, you can lean for best power like in a 172 you can hear the engine sound change pitch and pull harder right before peak. Then richen it a healthy amount from there.  The J with the McCauley prop only makes 2400~ RPM static so you can lean for peak RPM without an engine monitor.

Cylinders for a parallel valve Lycoming are around a grand each and maybe twice that installed. Given the cost of these repairs an engine monitor may pay for itself in one avoided event like this.  Might want to consider installing one.

Quote: crxcte

Thanks Swingin, I definitely did not have the mixture set right from the get go.  My high cht was near instantaneous do to excessive leaning.   I don't get to high DA very often but will add your procedure to a check list in the future and give it a try. 

[crxcte]

Yes Jetdriven, I discussed this with a CFI friend of mine and he said the same thing that it would cause detonation.  He also discussed how to recover from detonation from experience (full rich mixture, level out, pull some power back).  I think my OEM gauge is not all that accurate on chts.  I will definitely check out the plugs and cylinders.  thanks

[AlexR]

What year is your F?  Based on your avatar picture, it seems to me you should have a doghouse.  Perhaps that is the problem; some previous owner changed out the doghouse to a baffle system that is not up to snuff...  My doghouse 'seemed' fine but with just a little high temp RTV I was able to drop my CHTs by about 20-30 degrees. 

[Shadrach]

Verify temp on gauge... then check mag timing. 450 is too hot! Just because the gauge shows it to be in the green does not mean it's a good place to be.  Even the POH suggest 400df as a max continuous temp...

[crxcte]

68 M20F

[danb35]

Shouldn't have a doghouse on any F; the F was introduced after Mooney changed to a baffle design.

[Shadrach]

No doghouse... If this engine is detonating then something else is wrong. It is next to impossible to get a standard Lyc IO360 to detonate if it's properly set up...

[danb35]

An engine monitor would make it a lot easier to find out what's going on...

[fantom]

Quote: crxcte

68 M20F

[robert14]

Make sure that you have Mooey SB 182 installed. From a look at your photo ID, you do not have this mod. It will significantly reduce your CHTs and oil temps.

[Jerry 5TJ]

Just came back from Truckee last evening in the M20C.  Density altitude at 6 pm departure was 8900' so I elected to use their longer, 7000 foot runway even though the wind favored the other 4400 foot pavement.  I went to full power and set the mixture -- fairly rapidly -- to peak EGT then about 150 to 200 degrees richer, and rolled.  Manifold pressure was 21" as I recall.   I got about 500 fpm with the aircraft weight around 2100 pounds. 

 

 

 

[Shadrach]

Quote: robert14

Make sure that you have Mooey SB 182 installed. From a look at your photo ID, you do not have this mod. It will significantly reduce your CHTs and oil temps.

[crxcte]

I checked with Dogosh last week and told me about the 182 but said they didn't think Mooney would have it.  If anyone has a picture of it on their plane I would like to see it.  The pictures on the SB are not very good.