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I thought about the Powerflow exhaust but after reading reviews about it I opted for a new original exhaust. Knisely Welding makes one for about half of what a Powerflow runs. Still putting the engine together but this spring will find out how well the system works.

Cessna has a SB to remove them due to possibly breaking loose and clogging the muffler. I pulled my exhaust during o/h and after 900 hours they are intact. There are plenty of articles about why they are there so I won't go into that. I would suggest having the muffler pressure checked for leaks. I'm getting a whole new system from Knisely.

Roughly… For the older Mooneys…. Their intake and exhaust system were not as perfect as the newer Mooneys… room for improvement! If it is a forever-plane… there are some additional benefits… just not a lot… looks pretty… less likely to rust/fail/generate CO in the heater… For any plane… if you are relying on the speed numbers given… to improve your efficiency…. Expect those numbers are derived during flaming dragon mode flights…. Not LOP at 65%bhp… Older versions of the PowerFlow have a giant exhaust pipe sticking out in the wind… an obvious aero-goof up…. Make sure you are getting the newer aero-dynamic version… Somewhere… read up on the efficiency vs. heat output… less restrictive exhaust may have slightly less heat output… Looks like… if you have the dough for a forever-plane, and your exhaust system is worn out, for a few bucks more your steed gets a nicer exhaust system… CBs May prefer… an OH’d exhaust system from a company like knisely… comes back brand new like…works like original system did back before engine monitors were around…. Fuzzy PP memories only, stuff I have only read about around here… Best regards, -a-

When I replaced my turbo transition I believe Knisely welding sold me the gaskets. You may want to give them a call.

As a reference point when looking at overhaul costs, a new exhaust from Knisely is about $2.5k.

Not too many exhaust pictures around... Often there is a discussion regarding how long the tail pipes are for the PowerFlow exhaust... and what angle they came out... and what version was the most aerodynamic for Mooneys... A brief search, not too many details to sift through.... Best regards, -a- https://mooneyspace.com/search/?q=Knisely&quick=1

So I have an idea that's probably wrong, but may be worth mentioning. In addition to the two vents that blow on the mags, there's the large hole in the back of the doghouse that ducts air to the muffler shroud for cabin and carb heat. When those are off, there's a bypass to dump all the heated air overboard, and so there's always a substantial leak from the doghouse in flight regardless. Is it possible that the Powerflow allows much higher flow of air through that heat exchanger shroud than my old Knisely exhaust did? The difference in design suggests that might be the case. The only other time I've seen this same pattern of CHTs during operation was when the spark plug cover door on the right side of my doghouse partly came off in flight. That leak may have caused a similar airflow redistribution.

Over the last year I noticed some increased pitting on my turbo transition exhaust piece (see pictures below). I was keeping an eye on it but recently another A&P suggested that I take action as it was getting a little worse. As many of you know, there's no good way to tell exactly when this piece is going to go, but when/if it does it will be pretty catastrophic. Unfortunately, none of the traditional welding companies (Acorn, Knisely, ect…) are willing to repair it since it's cast. I wanted to share this experience because we found a tear in the slip joint after removal. This separation would have been nearly impossible to spot without removal since it's obscured on the backside of the v-band clamp. We also put oil on the outside of the transition piece to see if any of this pitting had resulted in actual holes. Sure enough, we got some staining on the inside (see photo). As I flew my plane to the shop this morning and it performed perfectly I started second guess my decision to change the part since it's fairly invasive. However, now I'm very glad that I did! The transition piece was the original from the factory so I'm not trying to scare anyone, but it may be good to have yours removed and checked if it has been a while. Below are some pics including the before picture, tear, inside staining, and final replacement installed.

While repair can be less than new, but isn't an all-new factory style exhaust around $2000 from knisely and only in the $3000 range for power flow?

knisely has changed policy...believe it or not it was cheaper to buy new exaust sections from AirPower (lycoming factory)Than the quote I got to repair plus they wanted 3 weeks.

pseudo summary.... 1) AWI aerospace welding inc... 2) Knisely... 3) Dawley... 4) PowerFlow... OH of muffler systems... often comes completely rebuilt with nothing left of the old system... a technicality that seems to work... Thinning of tubes that far from the exhaust valve is a strong sign that things upstream have some high heat experience as well... This is why inspection of the flame tubes and inner surface of the muffler is so important.... Check on the health of the flame tubes to see they are still there.... in their original shape.... Got a CO monitor with all that? Best regards, -a-

I have replaced the original exhaust off my 1983 M20J with new. This was a proactive step as part of my preventive maintenance philosophy for a plane I intend to keep a long time. No leaks or specific problems found, but that said, the exhaust is a wear item and original, about 2400 hours and 32 years, and the price reflects this. For someone who wants to put off a new exhaust a little longer in order to coordinate with their TBO or major annual, this may be for you. Only what is seen here is included: 4 risers, muffler/collector, and tailpipe. Specifically, the heater shroud and tailpipe hardware are not included. It is drilled for EGT probes on all 4 stacks. The #2 cylinder swage fit area was repaired once as part of my pre-purchase squawks. That was over 400 hours ago. Some of you are bound to wonder, so I'll add that I went with a new Knisely exhaust. Powerflow was more than I could afford/justify during this annual, but was surely tempted. Feel free to discuss the merits of my decisions amongst yourselves. I'll add that it was only flown ROP except when it was flown LOP, unless the moon was full, in which case I used camguard. :-) $300 plus shipping costs. Or pick it up at KFUL (other SoCal airports possible if we can coordinate schedules and you buy lunch) Reply or PM with any questions. thanks, -dan

I replaced mine a few years ago with one from Knisely Welding. Theirs was a complete replacement, risers and all, but it was shipped immediately whereas noone else in the country had a muffler on the shelf and I didn't have time for an overhaul.

I recently replaced the entire exhaust system on my C..... I ended up ordering one "off the shelf" from Knisely Welding (800) 522-6990. Just under $2200. A rebuild might have been a bit cheaper, but Knisely shipped it right away. The only issue was the heater shroud did not fit due to variations in Mooney exhaust systems. Knisely took care of it, but I had to pay the return shipping. Once that was taken care of, the system fit perfectly and has been trouble free.

There are a couple of welding shops mentioned around here. I think I recall knisely being one. Good or bad, I don't recall. If you are hands on, do some reading regarding CO and heat exchangers. As in carbon monoxide, poisoning, and detectors... Do a search on oil cooler overhaul. See what falls out of That as well... it has been done before... Best regards, -a-

I don't have Powerflow experience, but I replaced my muffler a few annuals ago. The old one was essentially hollowed out - all the internal baffles were shot and MIA. I needed back in the air ASAP and I could not find a single muffler on a shelf in the entire country - everybody wanted me to send them my core and they'd rebuild it. Didn't have that much time. Ended up talking to Knisely Welding in California. They had a brand new, built in-house, exhaust system in stock. Only catch was, theirs comes with new risers, muffler, and exhaust pipe - the only thing reused was the cabin heater shroud. It was was a simple bolt-on replacement, but it uses different pipe sizes or something that makes replacing the whole system necessary (or maybe it was the slip fittings that were different; I can't remember). Anyway, the tail pipe was noticeably longer than stock, similar to a Powerflow. When it came out of annual with nothing else done to the powerplant that would affect performance, I (almost) swear I picked up 5 or more knots of speed. I called Knisely to see if their muffler was responsible for my speed increase, and their response was along the lines of "we didn't test for that during certification and therefore can't claim a performance increase over stock". I swear I heard a wink and a nod over the phone. That's been 3 or 4 annuals ago and l'm still pleased with the purchase and performance. Also, instead of the muffler being ribbed like a coffee can as the original was, they use rows of threaded bolt shafts (I'm sure they have a technical name) for shroud standoffs, which I assume work much better for heat dissipation. Another advantage over the ribs is that now I can loosen the shroud and run my wireless proctologist-style camera up and down the rows, looking for exhaust leaks. Can't remember the price, but I'm thinking it was $1,500-$1,600 for the entire setup.Labor took maybe an hour.

Knisely called last night. My exhaust system is ready earlier than promised. It's in transit now. So far, so good.

Thank you. After spending a lot of time comparing, I ordered from Knisely. They thought they'd have a system ready to ship by Wed before Thanksgiving. I found out some of the shops I contacted were supplied by Knisely. Why not go to the source? Knisely wasn't the cheapest, so my CB credentials are in jeopardy.

I went with Knisely on my A&P's recommendation and after some comparison shopping. -dan

My #2 was also cracked at prebuy....welded by knisely welding and no futher problems 350 hrs later.I also change my oil but for the reverse reason John Green suggusts...you have your mechanic change the oil...and they know they can probably charge out for 200 or 300 bucks...but they are human and get busy...they will give the engine a once over...BUT..the Bravo really needs a detailed inspection ( I requently take an hour alone on exaust and hose inspection...I do the air filter at that time...it is so easy to remove and than you have direct access to turbo charger impeller and can spin the turbine for signs of roughness.I also give all exaust slip joints a shot of mouse milk and lube the wastegate pivot point with same...probably does no good...but I have had very little problems with exaust system with no changes in condition...an oil change takes me 4 hrs...from runup to runup..k

I've read that the PowerFlow does indeed increase performance on the carburated Mooney's. Not heard anything positive for injected models. I can attest to increased performance after PowerFlow installation on our 172. We purchased a new exhaust from aircraft exhaust.com last year when we overhauled our IO-360A1A. In hindsight it would have been less expensive to have the original overhauled. (As I understand it, an overhauled exhaust is essentially new anyway). We had to modify the old heat shroud as Aircraft Exhaust did not yet have PMA authority to provide new one. Something else needed modification, but I can't recall what it was. Knisely (sp.?) builds the exhausts in California for Aircraft Exhaust.com. They are very high quality units. No performance increases were expected or observed.