To Powerflow or not to Powerflow - That is the question

[Bart Chilcott]

D Max has informed me that my stock exhaust on my 65 M20E has passed away.  In considering a replacement or repair, I've looked into a complete rebuild ($1800.00) or a Powerflow system ($4,000.00).  I've been told by my shop that he has have removed as many of the Powerflow systems as he has installed (excessive noise seems to be a major complaint)  I've read about the advantages of the Powerflow but I'd also like to hear from anyone who has had theirs removed and gone back to stock and why.  I figure if the shops are removing 50% of the sysytems, someone will surely be able to chime in.  Thanks in advance for your input!

[Guest]

A complete new system from www.aircraftexhaust.com is about half of a Power Flow.  I've installed a number of them.

Clarence

[Nokomis449]

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.

[DXB]

2 hours ago, Nokomis449 said:

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.

Now THAT is an interesting post.  I don't know much about tuned exhaust but I wonder how the two designs compare.  Did you also notice the cht drop others see  with the powerflow?  

Anyone else here with experience with this supplier? 

[Nokomis449]

No engine monitor, so no idea about CHT drop.  I'll try to find a pic of the longer tailpipe, but not sure I have one.

EDIT: Here's a parts breakdown and photo of my Knisley (I misspilled it in my original post) exhaust system, showing the longer tailpipe:

http://knisleyexhaust.com/mooney-m-20-180-hp-catalog

Here's a breakdown of the 200hp version:

http://knisleyexhaust.com/mooney-m-20-200-hp-catalog

Edited April 18, 2017 by Nokomis449
Corrected Knisley spelling and added links

[Nokomis449]

This zoomed and cropped pic is the best I can do tonight... but it shows how long the tailpipe is.

[Oscar Avalle]

I installed a powerflow system. I like it, the engine seems to run smoother and I feel (may be it is just a wishful thinking) that the plane has more power...

 

 

[Bob_Belville]

I've had a PFS on my '66E for almost 5 years. I like it. I bought it shortly after acquiring the plane when the old system failed so I had no objective "before" performance data. I think there is a power improvement and I think the design should last longer than a stock system. There are 2 versions of the tail pipe, one is louder than the other. Maxwell just installed one on 201DF and I think Lee had him change the tailpipe.

[Bob_Belville]

32 minutes ago, bluehighwayflyer said:

...It definitely makes more power but also increases fuel flow.  

ISTM, fuel flow is controlled by the big red knob. Here's 8.2 GPH going to KOSH last year when I needed to optimize range.

 

[M20F]

On 4/17/2017 at 11:00 PM, Nokomis449 said:

This zoomed and cropped pic is the best I can do tonight... but it shows how long the tailpipe is.

Sweet retractable step. 

[Bolter]

When faced with the same dilemma 2 annuals ago, I opted for the Knisley.  It was purely a cost decision, in my case.  I was happy with the Knisley assembly and have no regrets. This was an '83 M20J.  From my reading on the interwebs and MS, I think the modern Mooneys gain less from the PFS than vintage models.    

[M20D6607U]

I have a PF exhaust system on my M20D. Anything that makes the flow smoother adds horsepower. Power Flow says my engine has the sweet spot set at 2450 RPM. They also said they don't add more power, they just free up power that's lost in stock systems.  The slip joints have to be lubed with anti-seize at annual. Well worth the cost. I know Curtis at Knisley Welding and have used them for our customer airplane needs. They are great! But for my own Mooney, this system make my Lycoming run like a thoroughbred. 

 

[Godfather]

3 hours ago, nosky2high said:

Having flown nearly 1300 hours in the past six years, I've had to overhaul the entire exhaust system once(2012), overall the muffler again 400 hours later(2014), and now my muffler is showing wear inside and is in need of an overhaul again...

I've had it.

Powerflow on order. PIREP to follow.

Nice to have a Mooney collecting so many hours. 400 hrs seems a little fast to need an overhaul. The system on mine lasted a lot longer and I would think 1000 hrs would be attainable. I'm interested to hear how the PW holds up. 

[MyNameIsNobody]

NOPE.

[Bennett]

Just got my Mooney back from her annual at LASAR. the annual was held up by PowerFlow for a while although ultimately they came through and shipped an upgraded system at a very reasonable cost. The system has been on the airplane for many years, and needed an overhaul. I have the LoPresti cowl which needs a bit of a different system, and they didn't have all the parts in stock. Robert Brown at LASAR did a great job of negotiating a fair resolution to the situation.

 

 

Sent from my iPhone using Tapatalk

 

[steingar]

If my exhaust goes Powerflow will be high on my list.  Small price to pay for knots. If the damn thing's noisy I'll get better headsets.

[MyNameIsNobody]

Burn some gas, if you want to go fast...

[N6758N]

26 minutes ago, nosky2high said:

New exhaust arrives next week, anyone out there want a very serviceable M20C exhaust as a spare?

@Raptor05121 was looking for one, not sure if he ordered one yet. 

[Raptor05121]

37 minutes ago, nosky2high said:

New exhaust arrives next week, anyone out there want a very serviceable M20C exhaust as a spare?

What condition is it in? Slip tube ribbed?

[orionflt]

 

2 hours ago, nosky2high said:

New exhaust arrives next week, anyone out there want a very serviceable M20C exhaust as a spare?

Let me know how you like it, still debating what to do with my C when it needs a new exhaust, mine has been on since 2001

Brian

[pbarge]

My "E" model came with a power flow and was a 160 kt tas bird.  On flying my "F" home it was 150 kts tas.  I know the F's are slower than E's, but immediately ordered a power flow for it....

[Bob_Belville]

1 hour ago, pbarge said:

My "E" model came with a power flow and was a 160 kt tas bird.  On flying my "F" home it was 150 kts tas.  I know the F's are slower than E's, but immediately ordered a power flow for it....

160 ktas is pretty strong. All the mods? I see 160 now and then but I'd say 158 ktas is closer to what I see 70% power and not at gross. I have PFS, 201 w/s, cowl, etc. I need @Sabremech cowl to get to 160.

[Raptor05121]

15 hours ago, nosky2high said:

serviceable when removed, muffler is getting worn, slip joints, ribbed design.

PM sent

[Urs_Wildermuth]

I've had the powerflow system on my Mooney C ever since I bought the plane and I would not want to be without one.

Basically that is why. My C will do 150 kts at 6500 ft with 2500RPM/25". I understand that this is quite high for a C and has to do with the powerflow exhaust. The previous owner who installed it wrote that he would need 1" less MP to achieve the performance wanted.