istrumit
Well Known Member
Hello all -
A few minutes from landing on a flight a few weeks ago, I felt a very, very subtle change in engine vibration, so I had a quick look and noticed the CHT on #3 cylinder (IO540) had risen about 15 degrees and was suddenly the hottest cylinder (I was descending at medium power).
I fiddled with mixture and nothing improved (or got worse).
And i watched as the temperature continued to gradually rise by about 5 degrees until I was within range to reduce power and land, at which time it fell back in line with the rest of the cylinders.
At no time did the cylinder actually fail to fire, but it did seem 'unhealthy'.
I pulled the data from my monitor and I found that, just after beginning my descent, #3 started to rise and #4 started to fall, both abnormally (compared to data from other flights).
I inspected the injectors for #3 and #4 and saw nothing obviously wrong. I used cleaner on them anyway.
Test run was good. And I test flew it again today.
Everything seemed normal during test, until I saw that #4 had gotten unusually cool again.
Landed..ran it up....tested the leaning process...all normal.
Took off again...all normal, but I decided to postpone my 1.5 hour trip until I figure this out.
So, currently, I have a normal running engine that seems to have fluctuating temperature previously in 3 and 4, but now, just #4.
I also tightened the intake on all cylinders (to account for induction leaks).
Bottom line...I'm stumped.
The engine runs fine. Starts fine.
But, I want to understand this anomaly.
Ideas ?
Thanks,
Scott
A few minutes from landing on a flight a few weeks ago, I felt a very, very subtle change in engine vibration, so I had a quick look and noticed the CHT on #3 cylinder (IO540) had risen about 15 degrees and was suddenly the hottest cylinder (I was descending at medium power).
I fiddled with mixture and nothing improved (or got worse).
And i watched as the temperature continued to gradually rise by about 5 degrees until I was within range to reduce power and land, at which time it fell back in line with the rest of the cylinders.
At no time did the cylinder actually fail to fire, but it did seem 'unhealthy'.
I pulled the data from my monitor and I found that, just after beginning my descent, #3 started to rise and #4 started to fall, both abnormally (compared to data from other flights).
I inspected the injectors for #3 and #4 and saw nothing obviously wrong. I used cleaner on them anyway.
Test run was good. And I test flew it again today.
Everything seemed normal during test, until I saw that #4 had gotten unusually cool again.
Landed..ran it up....tested the leaning process...all normal.
Took off again...all normal, but I decided to postpone my 1.5 hour trip until I figure this out.
So, currently, I have a normal running engine that seems to have fluctuating temperature previously in 3 and 4, but now, just #4.
I also tightened the intake on all cylinders (to account for induction leaks).
Bottom line...I'm stumped.
The engine runs fine. Starts fine.
But, I want to understand this anomaly.
Ideas ?
Thanks,
Scott