Let me begin by apologizing for the length of this post but I am really hoping I can tap into the vast knowledge pool in the Van's community to help me with a very perplexing problem. Basically, sudden overheating with a cylinder during break-in.
in a nutshell, I am running an IO-360 in my RV-7 of 700 hours. I recently had to have Cy #1 and #3 re-honed due to vanishing. That's another story. Anyway yesterday I was finally able to go flying (cold, rain and snow for over a week). After preheating the engine I launched into a brilliantly clear cool day.
As I had been advised by a great many people, websites, books and a popular YouTube channel, I started flying a circular pattern around home airport at 26 in MP/2600 RPM (90% pwr according to Dynon Skyview EMS) at 3500 feet ASL. All was well for the first 1.5 hour with no surprises and very steady engine readings. Suddenly seemingly out of nowhere, the CHT of Cyl#1 quickly climbed over 400F and was rapidly going through 410-420-nearing 440 when I pulled the power back and pushed the nose over to get more air through the engine. The cylinder cooled and stabilized around 360 F so I slowly added power and was close to 90% again when second time, the CHT went through the roof. Again I pulled power and go it back under 400F. As the power was quite low, I added power and turned back towards the airport which was about 2 miles away. A third time the CHT climbed above 400F but I was quickly joining the circuit, called in "engine issue" and successfully landed. I ran fine during the landing circuit.
For those who might be asking, here's the engine readings for the first 1.5 hrs of break-in flight time., they were very steady.....MP 26.2 in/RMP 2600, HP-90%;CHT's-#1-357, #2-328, #3-343, #4-321 (remember #1 and #3 are the two cleaned and re-honed cylinders) EGT's 1153,1213,1125,1270 respectively; OAT 1C (33F) altitude 3500 FT, Baro setting 30.40; Oil PSI 83;Oil Temp 192F Fuel Pres 23; Amps 2, volts 14.1. Fuel Flow 15.9---full rich for the entire flight.
My local mechanic went over the engine and found NO induction leaks, a clean injection nozzle and no oil leaks. A few hours after landing on the advice of my local mechanic I switched the CHT's between Cyl 1 & 3 and went up for another flight, Again #1 CHT spiked, showing on CHT 3 after swapping with #1. I was anticipating it quickly landed.
So..question is...why would the CHT suddenly JUMP way over 400 F into the danger zone afterrunning for 1 1/2 hours when CHT temps are suppose to DROP during break in..and do it several times.?The other "newly reworked" cylinder behaved as expected.
I called the engine shop that performed the cleaning and re-honing work but had not heard back from them before end of business day yesterday.
Any thoughts? Ideas? Is my newly reworked cylinder pooched?
Thanks for your patience and taking the time to read all this.
Dave C
RV-7 C-GCPD
in a nutshell, I am running an IO-360 in my RV-7 of 700 hours. I recently had to have Cy #1 and #3 re-honed due to vanishing. That's another story. Anyway yesterday I was finally able to go flying (cold, rain and snow for over a week). After preheating the engine I launched into a brilliantly clear cool day.
As I had been advised by a great many people, websites, books and a popular YouTube channel, I started flying a circular pattern around home airport at 26 in MP/2600 RPM (90% pwr according to Dynon Skyview EMS) at 3500 feet ASL. All was well for the first 1.5 hour with no surprises and very steady engine readings. Suddenly seemingly out of nowhere, the CHT of Cyl#1 quickly climbed over 400F and was rapidly going through 410-420-nearing 440 when I pulled the power back and pushed the nose over to get more air through the engine. The cylinder cooled and stabilized around 360 F so I slowly added power and was close to 90% again when second time, the CHT went through the roof. Again I pulled power and go it back under 400F. As the power was quite low, I added power and turned back towards the airport which was about 2 miles away. A third time the CHT climbed above 400F but I was quickly joining the circuit, called in "engine issue" and successfully landed. I ran fine during the landing circuit.
For those who might be asking, here's the engine readings for the first 1.5 hrs of break-in flight time., they were very steady.....MP 26.2 in/RMP 2600, HP-90%;CHT's-#1-357, #2-328, #3-343, #4-321 (remember #1 and #3 are the two cleaned and re-honed cylinders) EGT's 1153,1213,1125,1270 respectively; OAT 1C (33F) altitude 3500 FT, Baro setting 30.40; Oil PSI 83;Oil Temp 192F Fuel Pres 23; Amps 2, volts 14.1. Fuel Flow 15.9---full rich for the entire flight.
My local mechanic went over the engine and found NO induction leaks, a clean injection nozzle and no oil leaks. A few hours after landing on the advice of my local mechanic I switched the CHT's between Cyl 1 & 3 and went up for another flight, Again #1 CHT spiked, showing on CHT 3 after swapping with #1. I was anticipating it quickly landed.
So..question is...why would the CHT suddenly JUMP way over 400 F into the danger zone afterrunning for 1 1/2 hours when CHT temps are suppose to DROP during break in..and do it several times.?The other "newly reworked" cylinder behaved as expected.
I called the engine shop that performed the cleaning and re-honing work but had not heard back from them before end of business day yesterday.
Any thoughts? Ideas? Is my newly reworked cylinder pooched?
Thanks for your patience and taking the time to read all this.
Dave C
RV-7 C-GCPD