Running hotter than normal

[Mikey]

Hello all. Over the last 4 or 5 months, I have noticed my CHT's have been steadily rising and the spread from the hottest to the coolest is increasing as well. (Used to be 30 degrees, now it varies between 35 & 40) It is to the point where I can't fully close the cowl flaps. This hasn't been an issue for the last 250+ hours on the plane over the past year and a half. This is when I started running LOP. I have an M20K/231. Inner-cooler and 'automatic' wastegate & GAMI injectors. I took the first picture this morning while flying from Phoenix to San Diego. LOP, 12k, Cowl flaps in tow (Fully closed and CHT's go over 400) The second pic is almost a year ago to date.  LOP, Cowl flaps closed, not sure altitude but probably pretty close to 12k. I know It was running about 45 degrees more LOP a year ago, but the CHT's are much cooler with the cowl flaps closed than they are now. What could/would have changed over the last year? (Compression check 2 weeks ago showed about same as annual in Nov. Any help would be appreciated!

 

Edited October 3, 2017 by Mikey

[Bob - S50]

Looks to me like what changed is the fuel flow.  You are now pushing an extra 2 GPH through the engine which is making more power which is heating up the CHT's.  I'll bet that if you lean it back to the same 10.3 GPH you had last year, you'll find nothing has really changed.

[LANCECASPER]

Check your baffle seals. The owner of this K model couldn't figure out why his engine was running so hot.

[Mikey]

I am going up again in the morning and I'll check the temps with the same fuel flow. Do you think running it at that fuel flow and TIT is too far LOP?

[Mikey]

Just now, Mikey said:

I am going up again in the morning and I'll check the temps with the same fuel flow. Do you think running it at that fuel flow and TIT is too far LOP?

I thought the same thing but they seem to seal pretty well and they are only about 2 years old.

[Bob - S50]

2 hours ago, Mikey said:

I am going up again in the morning and I'll check the temps with the same fuel flow. Do you think running it at that fuel flow and TIT is too far LOP?

I don't have a turbo, but there are 3 ways to reduce fuel flow:  RPM, MP, or Mixture.

[jackn]

You might want to check your plugs and/or mags. Weak sparks could prevent you from going further lop on the latest flights. 

[231LV]

5 hours ago, Mikey said:

I am going up again in the morning and I'll check the temps with the same fuel flow. Do you think running it at that fuel flow and TIT is too far LOP?

The only way you will go too far LOP is when the engine stumbles.....I have experienced what you are describing...sometimes I can run with the cowl flaps fully closed but usually fly with them in trail...the added 1 or 2 knots isn't worth the engine going up above 380 degrees as far as I am concerned.

[Shadrach]

 

On 10/3/2017 at 1:00 AM, Mikey said:

Hello all. Over the last 4 or 5 months, I have noticed my CHT's have been steadily rising and the spread from the hottest to the coolest is increasing as well. (Used to be 30 degrees, now it varies between 35 & 40) It is to the point where I can't fully close the cowl flaps. This hasn't been an issue for the last 250+ hours on the plane over the past year and a half. This is when I started running LOP. I have an M20K/231. Inner-cooler and 'automatic' wastegate & GAMI injectors. I took the first picture this morning while flying from Phoenix to San Diego. LOP, 12k, Cowl flaps in tow (Fully closed and CHT's go over 400) The second pic is almost a year ago to date.  LOP, Cowl flaps closed, not sure altitude but probably pretty close to 12k. I know It was running about 45 degrees more LOP a year ago, but the CHT's are much cooler with the cowl flaps closed than they are now. What could/would have changed over the last year? (Compression check 2 weeks ago showed about same as annual in Nov. Any help would be appreciated!

 

Comparing LOP from a year ago to ROP today is completely useless comparison.  Of course it was running cooler LOP,  that's one of the advantages to running LOP.  Collect some hard data over time or at the very least, compare the same power setting that you used last year...

Edited October 4, 2017 by Shadrach