Narrative:

We were flying back to home base. I was going to drop my [passenger] off & go on for an overnight w/some friends. I was flying an SR22T. Had a pop up IFR fpl and noticed; after calling out the dash info; my airspeed was off a bit. Had made a slight turn; so my initial thought was it was wind change. But then it seemed too low for that (was around 140-150 versus 150 to 160); so I nosed up the throttle. Looked at the mp and it was like 26 or so. Pushed the throttle to get back to about 29-30 (where I normally run); but w/full throttle it would not hold 25. Airspeed deteriorating about 1k/2 min. Gauges all green. Tit cht & egt just fine. Enriched the mix. No joy. Started running a bit; not a lot but a bit; rough. Changed tanks (left to right). That was better. But speed still dropping; just more slowly & nothing getting better for the mp. Told ATC I had an engine problem & needed to divert. ZZZ was closest acceptable and behind us. They gave me vectors; then came back & said the airport was at 800 ceilings. Got flustered inserting ZZZ in the fpl but I was on heading; so I did it over & realized my mistake. Chose the GPS approach. Got it loaded. Never had time to pull the chart up on the ipad or the mfd to brief it. We were in pretty solid soup when we turned to ZZZ; and I was watching the gauges & listening to the engine. And flying the plane. No time to punch buttons or look down.I asked my [passenger] to dial in the CTAF for ZZZ. [Passenger] is not a pilot & does not like to do entry except the fpl on the ground. I pointed at the navigation instead of the communication so [passenger] was having a tough time. I realized that mistake; put it in the communication and announced my presence & the problem. ATC said I was still w/them. Had failed to flip the radio. Clearly I was frazzled. But I was flying the plane. Got set up for the GPS approach; ATC gave me vectors to the FAF to keep my distance shorter. They let me go to CTAF after asking us to write down a # & call from the ground to say we were ok. Got settled in on the approach; broke out about 1000-1500 feet AGL and [landed]. Never even had a chance to pull up the chart & brief it. Just too busy. Just hand flew it on the pfd. The last 1-2000 feet or so the engine got real rough & was backfiring noisily. Quite disconcerting! Tried to hold my altitude above 1500 until I saw the runway; less than 2 miles out; I guess (maybe 800 maybe 900; maybe 1000); as I knew I would not get a 2nd chance. As I worked thru the incident; I considered caps (the parachute) a couple of times; but decided not yet each time. On short final; I decided that if I did not see the runway at 1.5 m out; I would pull the chute. But we broke out & there it was. The local guys told me to taxi down to a hangar well past the FBO; where there was a mechanic. But by the time we shut down; the guy had driven over & said they had no idea where the mechanic was. Then another guy drove up from FBO & said ATC had just called saying there was company traffic (I am a fractional owner) nearby that could come by to help! I said; yes; please ask him to come if it was a solo person. Waiting on him to come; I was on the phone w/the company mechanic. I cranked the plane & did some stuff (checked the mags; full throttle; changed mix; etc.) for our mechanic; but he could not diagnose the problem just listening. Post mortem; I can't remember if [I] declared an emergency or not! Maybe not; since neither my [passenger] nor I remember them asking souls on board or fuel on board! When I first recognized there was a problem; I grabbed the poh; intending to see if I could find something. Never even opened it. Had no warnings on the dash or gauge alerts. My preflight was thorough with no fuel stuff. Had flown down w/92g; so I could make it back w/o a fuel stop. Took off w/62g. Sumped fuel was clean as a whistle. Everything was fine until I noticed the speed erosion. I was doing my normal callouts each time anything changed; and the engine stuff was all green. I was surprised how slow I was pulling up nearest; getting to a good airport (3rd one down; others had short runways or such). My [passenger] pulled up the frequencies for ZZZ on the old 496 he uses for identifying towns. I went to ipad airport page to check the runways. I felt slow choosing which approach I wanted; after ATC gave me the winds.we found that on the pilot's side of the engine that the middle section of the exhaust pipe (manifold section) that connects to the cylinder had burned through and created a 1' hole. That caused lack of exhaust pressure to the left turbo charger and manifold pressure dropped as a result. Lack of power and speed and backfire was due to this. Location of the hole was just above the intake air cleaner for the left turbo charger. The heat then burned thru the intake housing & damaged the air cleaner. Guy reporting all this to me remarked that I was quite lucky there was no fire. What caused the problem? Hot air blowing on the same spot evidently weakened it.I could have asked ATC for the da. I could have set IAS on the autopilot at 90 to extend glide. But I wanted to control the descent so that I had plenty of altitude in reserve to pull the chute if necessary. I am not certain that I could have identified the potential problem unless I had pulled the cowl off before flight & inspected the pipes and saw a bulge. But I am not a mechanic and would not be comfortable doing that. All in all; I think I handled the situation well; with the help of my [passenger] and ATC. I did not panic; but did get frazzled. I flew the plane the entire time. I did not feel out of control; but I did not feel I fully knew what the problem was. I think if I had tried to fly on to where I knew there was a cirrus service center; I likely would not have made it & would have had to pull the chute. And I may have lost the engine and had a fire. Glad none of that happened. The fraction's training requirements (flight review every 6 months instead of every other year) I am sure contributed to my satisfactory outcome.

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Original NASA ASRS Text

Title: SR22 pilot experienced a gradual loss of airspeed and MAP at 7000 feet and elected to divert. A suitable airport was chosen and a successful GPS approach was flown with the engine rough and backfiring noisily. Post flight revealed a hole burned in the number 4 exhaust manifold; reducing exhaust pressure to the turbo and impinging on the intake air box.

Narrative: We were flying back to home base. I was going to drop my [passenger] off & go on for an overnight w/some friends. I was flying an SR22T. Had a pop up IFR FPL and noticed; after calling out the dash info; my airspeed was off a bit. Had made a slight turn; so my initial thought was it was wind change. But then it seemed too low for that (was around 140-150 versus 150 to 160); so I nosed up the throttle. Looked at the MP and it was like 26 or so. Pushed the throttle to get back to about 29-30 (where I normally run); but w/full throttle it would not hold 25. Airspeed deteriorating about 1k/2 min. Gauges all green. TIT CHT & EGT just fine. Enriched the mix. No joy. Started running a bit; not a lot but a bit; rough. Changed tanks (L to R). That was better. But speed still dropping; just more slowly & nothing getting better for the MP. Told ATC I had an engine problem & needed to divert. ZZZ was closest acceptable and behind us. They gave me vectors; then came back & said the airport was at 800 ceilings. Got flustered inserting ZZZ in the FPL but I was on HDG; so I did it over & realized my mistake. Chose the GPS approach. Got it loaded. Never had time to pull the chart up on the iPad or the MFD to brief it. We were in pretty solid soup when we turned to ZZZ; and I was watching the gauges & listening to the engine. And flying the plane. No time to punch buttons or look down.I asked my [passenger] to dial in the CTAF for ZZZ. [Passenger] is not a pilot & does not like to do entry except the FPL on the ground. I pointed at the NAV instead of the COM so [passenger] was having a tough time. I realized that mistake; put it in the COM and announced my presence & the problem. ATC said I was still w/them. Had failed to flip the radio. Clearly I was frazzled. But I was flying the plane. Got set up for the GPS approach; ATC gave me vectors to the FAF to keep my distance shorter. They let me go to CTAF after asking us to write down a # & call from the ground to say we were ok. Got settled in on the approach; broke out about 1000-1500 feet AGL and [landed]. Never even had a chance to pull up the chart & brief it. Just too busy. Just hand flew it on the PFD. The last 1-2000 feet or so the engine got real rough & was backfiring noisily. Quite disconcerting! Tried to hold my altitude above 1500 until I saw the runway; less than 2 miles out; I guess (maybe 800 maybe 900; maybe 1000); as I knew I would not get a 2nd chance. As I worked thru the incident; I considered CAPS (the parachute) a couple of times; but decided not yet each time. On short final; I decided that if I did not see the runway at 1.5 m out; I would pull the chute. But we broke out & there it was. The local guys told me to taxi down to a hangar well past the FBO; where there was a mechanic. But by the time we shut down; the guy had driven over & said they had no idea where the mechanic was. Then another guy drove up from FBO & said ATC had just called saying there was company traffic (I am a fractional owner) nearby that could come by to help! I said; yes; please ask him to come if it was a solo person. Waiting on him to come; I was on the phone w/the company mechanic. I cranked the plane & did some stuff (checked the mags; full throttle; changed mix; etc.) for our mechanic; but he could not diagnose the problem just listening. Post mortem; I can't remember if [I] declared an emergency or not! Maybe not; since neither my [passenger] nor I remember them asking souls on board or fuel on board! When I first recognized there was a problem; I grabbed the POH; intending to see if I could find something. Never even opened it. Had NO warnings on the dash or gauge alerts. My preflight was thorough with no fuel stuff. Had flown down w/92g; so I could make it back w/o a fuel stop. Took off w/62g. Sumped fuel was clean as a whistle. Everything was fine until I noticed the speed erosion. I was doing my normal callouts each time anything changed; and the engine stuff was all green. I was surprised how slow I was pulling up nearest; getting to a good airport (3rd one down; others had short runways or such). My [passenger] pulled up the frequencies for ZZZ on the old 496 he uses for identifying towns. I went to iPad airport page to check the runways. I felt slow choosing which approach I wanted; after ATC gave me the winds.We found that on the pilot's side of the engine that the middle section of the exhaust pipe (manifold section) that connects to the cylinder had burned through and created a 1' hole. That caused lack of exhaust pressure to the left turbo charger and manifold pressure dropped as a result. Lack of power and speed and backfire was due to this. Location of the hole was just above the intake air cleaner for the left turbo charger. The heat then burned thru the intake housing & damaged the air cleaner. Guy reporting all this to me remarked that I was quite lucky there was no fire. What caused the problem? Hot air blowing on the same spot evidently weakened it.I could have asked ATC for the DA. I could have set IAS on the autopilot at 90 to extend glide. But I wanted to control the descent so that I had plenty of altitude in reserve to pull the chute if necessary. I am not certain that I could have identified the potential problem unless I had pulled the cowl off before flight & inspected the pipes and saw a bulge. But I am not a mechanic and would not be comfortable doing that. All in all; I think I handled the situation well; with the help of my [passenger] and ATC. I did not panic; but did get frazzled. I flew the plane the entire time. I did not feel out of control; but I did not feel I fully knew what the problem was. I think if I had tried to fly on to where I knew there was a Cirrus Service Center; I likely would not have made it & would have had to pull the chute. And I may have lost the engine and had a fire. Glad none of that happened. The Fraction's training requirements (flight review every 6 months instead of every other year) I am sure contributed to my satisfactory outcome.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.