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To Powerflow or not to Powerflow - That is the question


Bart Chilcott

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I have not heard much positive feedback on the J models and up.  I do know they seem to work really well on a lot of aircraft where the manufacturers did not refine their exhaust systems.  My guess is that if you added powerflow to a C, E, F, and electronic ignition with the sloped windshield you would have a really great performing aircraft. Pireps please!:D

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5 hours ago, m20kmooney said:

Which concepts of arithmetic give you the most trouble? Multiplication and percentages? The point is how poorly the PFS scavenges the spent exhaust gases when compared to stock in view of its cost.

 

What’s with all the negativity?

Attacking another MSer?

Attacking a product that other MSers use and support?

Then follow it up with an opinion that isn’t in line with the people that have bought it...

On 11/14/2018 at 12:24 PM, m20kmooney said:

Powerflow says a stock exhaust leaves behind about 20% of spent gases while their exhaust allows almost 95% intake of pure fuel air. Difference being about 15%.

So they are being removed because a 15% difference at best does not warrant a 222% in cost over stock.

 

Some people feel a bitterness when something they want costs more than they can afford... I get this feeling all the time...

 

leaving the the bitterness at home helps keep things interesting...

Continuing the bitterness has people clicking the ignore button...

Be a part of the community.

Best regards,

-a-

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1 hour ago, carusoam said:

What’s with all the negativity?

Attacking another MSer?

Attacking a product that other MSers use and support?

Then follow it up with an opinion that isn’t in line with the people that have bought it...

 

Some people feel a bitterness when something they want costs more than they can afford... I get this feeling all the time...

 

leaving the the bitterness at home helps keep things interesting...

Continuing the bitterness has people clicking the ignore button...

Be a part of the community.

Best regards,

-a-

The op posed a question and asked for input: “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 majorcomplaint)  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!”

In the interest of objectivity I was presenting to him powerflow’s own numbers which may in all probability explain why they are being returned. I regret that’s not good enough for you and you view it as negativity. I’d suggest you take it up with powerflow. Nevertheless thank you for your opinion. No apologies here however!

Edited by m20kmooney
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Powerflow says a stock exhaust leaves behind about 20% of spent gases while their exhaust allows almost 95% intake of pure fuel air. Difference being about 15%. So they are being removed because a 15% difference at best does not warrant a 222% in cost over stock.

 

15% more oxygen should result in 15% more fuel burned, which should result in 15% more horsepower...that would easily be worth the premium if true.

Of course if the 20% is the amount of air (exhaust gases) left when piston has completed it’s exhaust stroke, and the volume is 1/15th of cylinder volume, so on in intake you get 14/15ths fresh air and 80% vs 95%...the difference would only be about 1%.

And if you run LOP, there is some leftover oxygen in those exhaust gases, would make it less of difference.

I would like to an independent test.

Edit:

I did find a test done in a Mooney by :

https://www.planeandpilotmag.com/article/accelerating-a-mooney/

Upshot is to maximize gain, fly at 11,500’...5 knot gain, at 7500’ it was 3 knot gain.

 

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As usual in aviation there are trade-offs...

1) reducing exhaust pressure, aka back-flow, is great for increasing engine power...

  • some people have a nice filter to help here...
  • some people use an alternate air source... to gain about 1” of MP...
  • some people have a new cowl that comes with air flow improvements for the engine too...
  • at the end of the process, the improved flow of the muffler goes with the improvements up front...
  • One significant restriction up front, and the exhaust system won’t do very much... there is some balance involved...

2) The cost can be an increase in exhaust sound level...

3) There are two independent causes of sound being emitted from a Mooney...

  • Engine exhaust
  • Propellor tip, radius and speed effects... and materials of construction too...

4) The prop is about 10x the sound produced by the exhaust...

5] Where sound is a challenge, like Europe, prop design makes a difference... more, shorter, composite blades make a significant and measured difference.

6) with an IO550, I don’t hear the exhaust tone in the cabin at all, and the prop turning at 2700rpm is noticeably louder than 2500rpm.

7) externally, the 2700 rpm prop is a scream...

8) Since installation is going to be aircraft specific, and thus results are going to vary by aircraft...  it is great to have the input from other MS members.

9) To focus on marketing strategy of PF...

  • you are in the right place.  
  • Right thread...

10) Dig deeper with your shop...

  • How many have been returned?
  • Why?
  • Are these reasons related to Mooney installations?

11) When There is a promise of performance... these should be measurable. They are measurable.

12) What is valuable to one person, can be useless to the next...

13) One thing the PFS does differently... eliminates the internal seam in the construction that has a history of failing in Mooneys... Avoiding CO poisoning is important to many...

14) Engine performance is a pretty complex subject... a 10% increase in power may...

  • Improve T/O distance measurably 50%...
  • Improve Climb speed measurably the same magnitude...
  • Do very little in terms of going faster, without a great increase in FF...

15) Let’s get a copy of the What PF promises to see what they are saying technically... See if it matches what some customers are expecting... @m20kmooney, want to take the lead on that?

16) Everyone’s input is important... try extra hard to avoid getting in the way of other people’s opinions.

The bitterness on delivery, got in the way of YOUR important details.  

Not everyone is a great writer. It takes some people more effort than others...I’m still learning myself... :)

Best regards,

-a-

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47 minutes ago, carusoam said:

As usual in aviation there are trade-offs...

1) reducing exhaust pressure, aka back-flow, is great for increasing engine power...

2) The cost is an increase in exhaust sound level...

3) There are two independent causes of sound being emitted from a Mooney...

  • Engine exhaust
  • Propellor tip, radius and speed effects... and materials of construction too...

4) The prop is about 10x the sound produced by the exhaust...

5] Where sound is a challenge, like Europe, prop design makes a difference... more, shorter, composite blades make a significant and measured difference.

6) with an IO550, I don’t hear the exhaust tone in the cabin at all, and the prop turning at 2700rpm is noticeably louder than 2500rpm.

7) externally, the 2700 rpm prop is a scream...

8) Since installation is going to be aircraft specific, and thus results are going to vary by aircraft...  it is great to have the input from other MS members.

9) To focus on marketing strategy of PF...

  • you are in the right place.  
  • Right thread...

10) Dig deeper with your shop...

  • How many have been returned?
  • Why?
  • Are these reasons related to Mooney installations?

11) When There is a promise of performance... these should be measurable. They are measurable.

12) What is valuable to one person, can be useless to the next...

13) One thing the PFS does differently... eliminates the internal seam in the construction that has a history of failing in Mooneys... Avoiding CO poisoning is important to many...

14) Engine performance is a pretty complex subject... a 10% increase in power may...

  • Improve T/O distance measurably 50%...
  • Improve Climb speed measurably the same magnitude...
  • Do very little in terms of going faster, without a great increase in FF...

15) Let’s get a copy of the What PF promises to see what they are saying technically... See if it matches what some customers are expecting... @m20kmooney, want to take the lead on that?

16) Everyone’s input is important... try extra hard to avoid getting in the way of other people’s opinions.

The bitterness on delivery, got in the way of YOUR important details.  

Not everyone is a great writer. It takes some people more effort than others...I’m still learning myself... :)

Best regards,

-a-

Nah, I’ll pass. Thank you. May expose what you don’t want to hear and risk being called bitter. We all are capable to do our research and make our own decisions.

Edited by m20kmooney
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Sharing what you know is alway appreciated... holding back info you know and don’t want to share, may be considered self centered? Some times it may be Better to say nothing to protect your image...?

Sharing info...

1) It could be helpful for somebody else...

2) Helping somebody else, is a great way to get help in return, when you are having a bad day...

3) Some people call it paying it forwards...

4) Use the search, that term shows up a few times around here...

5) Some people prefer to not write anything... hard to pay anything forward using that technique... to each, his own...

6) There isn’t any news bad enough in aviation, that I wouldn’t keep an ear open to...

7) Bitterness... we are all too young for that...  :)

8) Looking up PF promises...  http://www.powerflowsystems.com/products.php?cat_id=5    not too hard really...

9) Too difficult to read through doc...?

This is their note related to hp increase... a 14% increase on a dyno... (I did the math in case there is an error...) yes, none of us are flying a dyno, so Mooney Pireps are important...

We had the privilege of visiting Ly-Con. Located in California, Ly-Con is leading the way in high performance engine overhauls. They own state of the art equipment, including an aircraft engine dyno. In order to prove what our system can do, and hopefully combat some skepticism, we installed a Power Flow Tuned Exhaust on one of their test stands, and compared the dyno numbers to the same engine with the OEM Cessna exhaust. The engine used was a Lycoming O-320 A1A, rated at 160hp.dyno rig

Here is what we found: 
Peak Horsepower Developed:
PFS Tuned Exhaust:157.1hp
OEM Cessna exhaust:133.3hp

That's a 23.8hp difference! Those extra horses really give you a dramatic pitch angle on Vx and Vy climbs. It is by far, the most impressive difference you will notice on your first flight after installation.

10) Mooney specific pireps can be found here... maybe it only works on O360s...?

http://www.powerflowsystems.com/products.php?cat_id=5&pid=26

 

11) So the Mooney IO360 pireps are here...

http://www.powerflowsystems.com/products.php?cat_id=5&pid=46

 

12) those pireps may have been hand picked by a marketing person at PF...  So getting a first hand pirep from an MSer may make more sense... the way to do that oftenrequires being nice.  Because that is how people interact in a self rewarding kind of way. There are a few threads of those around here as well...

13) The cost of a PF is a giant hurdle for Many MSers... leaving very few in the field to get a decent pirep from...

14) Getting before and after performance data is also hard to do accidently... or intentionally... by the time the need arises for a new exhaust system, the old one is broken and not AW...

 

Skip the bitterness, the laziness, the firing back... none of it looks good, or helps anyone... and that job has been taken by somebody else already...

Join MS in the open posting arena!  :)

PP thoughts only, I may have been a sales guy once... 

Best regards,

-a-

 

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2 hours ago, teejayevans said:

I did find a test done in a Mooney by :

https://www.planeandpilotmag.com/article/accelerating-a-mooney/

Upshot is to maximize gain, fly at 11,500’...5 knot gain, at 7500’ it was 3 knot gain.

 

Everyone interested in a Powerflow exhaust should read this.  Several interesting points: Cherokee and 172 exhausts were optimized for low altitude--where they normally fly.  PFS asked Mooney owners where they flew and optimized the exhaust for 11,500' and 2600 RPM rather than the 8 or 9,000' and 2500 RPM answer.  Bill Cox with Plane and Pilot appears to give a pretty good test.  First got a baseline with the stock exhaust then putting a PFS on his F.  Net result was 3 knots at 7500' and 2500 RPM, 5 knots at 11,500'.  He also time the climbs and found a 50 FPM improvement.  One horsepower will raise 33,000 pounds one foot in one minute.  Four horsepower will raise a 2500 pound weight roughly 50 feet in one minute.  So about 4 horsepower.  Doesn't come anywhere near what Ly-Con measured on their dyno. (Someone on another forum referred to it as California horsepower)  3-5 Knots at altitude, less down low.  No wonder people don't see the results.  I have spent many hours flight testing my airplane. It takes a determined effort to measure small changes.  

If, if I get another Mooney and it needs more than minor exhaust repairs, I would probably go with the PFS and enjoy a small benefit at higher altitudes.  Others might be better off saving about $2k.

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9 minutes ago, teejayevans said:

From the article:
“The price for the Power Flow exhaust system on any of the 200 hp Mooneys is $4,590”, I had my old exhaust rebuilt for about 1/4 of that FWIW.

T J, the upfront cost is not the whole story... why did your exhaust have t be rebuilt? Was the underlying reason(s) it had become unairworthy addressed by the re-builder? If the rebuilt exhaust is essentially the same as it was before how long will it be before you or the next owner will be facing the same choice again? If we prorate the value of the engine based upon the TBO should we prorate the value of an exhaust based upon its "TBO?

From http://www.powerflowsystems.com/products.php?cat_id=5&pid=46

#2) The Power Flow System has no service life limit. It is designed and built to last several thousand flight hours and will quite likely be the last exhaust system you need to buy for your aircraft. As with any high performance system however, it must be maintained properly. Every 500 flight hours or annually (whichever comes first) the four slip joints on the system must be cleaned and lubricated with high temperature anti-seize compound. Most Customers have this maintenance performed during the aircraft's annual inspection which adds about 2 hours of labor to the inspection. We have had several of our Tuned Exhaust Systems rack up over 4,000 flight hours of trouble free performance (7,000+ flight hours is the current record in a commercial operation) as long as this maintenance is performed as required.

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T J, the upfront cost is not the whole story... why did your exhaust have t be rebuilt? Was the underlying reason(s) it had become unairworthy addressed by the re-builder? If the rebuilt exhaust is essentially the same as it was before how long will it be before you or the next owner will be facing the same choice again? If we prorate the value of the engine based upon the TBO should we prorate the value of an exhaust based upon its "TBO?

AFAIK, it was the first time (3000+ hours) it needed work. I noticed I was getting exhaust when turned on the cabin heat. I’ve got 700 hours on it since. So I guess we’ll see.
I don’t understand why it has to stick like a sore thumb, has nobody ask PF why?
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32 minutes ago, teejayevans said:


AFAIK, it was the first time (3000+ hours) it needed work. I noticed I was getting exhaust when turned on the cabin heat. I’ve got 700 hours on it since. So I guess we’ll see.
I don’t understand why it has to stick like a sore thumb, has nobody ask PF why?

I'm not sure what you're referring to. Mine is swept back with the top of the tailpipe 4" from the belly. 

IMG_20180710_142512734_HDR.jpg

IMG_20180710_142537667_HDR.jpg

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48 minutes ago, teejayevans said:


AFAIK, it was the first time (3000+ hours) it needed work. I noticed I was getting exhaust when turned on the cabin heat. I’ve got 700 hours on it since. So I guess we’ll see.
I don’t understand why it has to stick like a sore thumb, has nobody ask PF why?

The shape and length of the collector is influenced by the RPM for which the system is optimized. It is my understanding that it is more important at the lower RPM ranges that our engines operate. I’m certain that PFS designed the collector and head pipe to be as attractive as the could within the parameters of the performance goals.

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33 minutes ago, teejayevans said:


Compare yours with this one (maybe the Js are different):

The close up is of an E that was just posted for sale here a day or two ago. Seems to stick out more than my PFS.

DSCN1110.JPG
7dcd2da3d605abd7afa53b4fc897504a.jpg

Yeah, I think you're right about the Js... I went looking for pics of conventional exhausts and found a pic of Marc Chula's beautiful '66E (which I used to own a long time ago).

Image may contain: airplane, sky and outdoor

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Acrimony not withstanding, I'm glad this thread came back to life. That Plane and Pilot article cited above is very informative.  Some observations:

-At least for us pre-J folks, the performance gains are likely legit, though maybe not at the level of 5-7kt increases, unless one is partial to flying slower at 12,000, which most of us are not.

-Fuel savings at given speed would help recoup a little of the extra cost over a standard exhaust.

-You can never have too much climb rate.  It's like being too rich, too in shape, or too good looking. 

-Greater durability might help recoup a lot of cost, if you're committed to keeping your plane for the long haul.  Is this durability aspect legit? If so, why are they more durable than a standard exhaust? This part is not obvious from the marketing. 

-The prospect of running cooler at a given power appeals greatly to us C model guys, who are cursed with high temps and frequent cylinder work.  Maybe a bit of cost savings there too?

My Knisley exhaust has about 2000hrs on it, and it cost me about $500 in the last year in parts plus labor to replace a disintegrating tail pipe. I'm not sure that was a wise investment, but I just needed to get back in the air.  I'd best be ready to replace the whole exhaust in the near future before I end up puffing on CO.  I'm very close to ordering a Powerflow system with the $700 discount that comes with ordering well before delivery.  It can sit in storage until next annual, or when the muffler tries to kill me, which ever comes first. 

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5 minutes ago, DXB said:

-Greater durability might help recoup a lot of cost, if you're committed to keeping your plane for the long haul.  Is this durability aspect legit? If so, why are they more durable than a standard exhaust? This part is not obvious from the marketing. 

I am pretty sure the PFS is heavier gauge steel. I don't know if the sheet steel is a different alloy though I suspect it is. Is a conventional muffler even ss? The PFS is.

As has been mentioned, the PFS does not have the baffles that in a conventional muffler are prone to rust out and break loose, sometimes partially block air flow. Based upon how many Mooneys come into @AGL Aviationfor annuals with un-airworthy mufflers I suspect that there are a lot of pilots whose mufflers are shot and they don't know it. In my case, a chunk of the tailpipe dropped off. On further inspection the muffler was shot. I'd had the plane a few months and had had an intentionally abbreviated PPI done. I think AGL is in the habit of boroscoping the muffler very early in the inspection just in case he needs to order a muffler.

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I am pretty sure the PFS is heavier gauge steel. I don't know if the sheet steel is a different alloy though I suspect it is. Is a conventional muffler even ss? The PFS is.
As has been mentioned, the PFS does not have the baffles that in a conventional muffler are prone to rust out and break loose, sometimes partially block air flow. Based upon how many Mooneys come into [mention=14357]AGL Aviation[/mention]for annuals with un-airworthy mufflers I suspect that there are a lot of pilots whose mufflers are shot and they don't know it. In my case, a chunk of the tailpipe dropped off. On further inspection the muffler was shot. I'd had the plane a few months and had had an intentionally abbreviated PPI done. I think AGL is in the habit of boroscoping the muffler very early in the inspection just in case he needs to order a muffler.

We do... typically we look at the “hot spots” first and try to keep downtime waiting on parts to a minimum


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On 4/10/2017 at 6:55 PM, Whiskey Charlie said:

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!

IMO Powerflow may give you the flexibility, depending on your engine, to increase your TAS by a couple of knots with the penalty of more fuel flow, or save that fuel and go your “normal” couple knots slower. But realistically flying a Mooney you may not do that. I know I probably wouldn’t. Of course you can increase fuel flow and RPM and gain those couple of knots without the expense and permanent weight gain of powerflow. It just doesn’t offer a significant speed increase and four grand buys a lot of fuel as does three grand or two. 

Edited by m20kmooney
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1 hour ago, m20kmooney said:

IMO Powerflow may give you the flexibility, depending on your engine, to increase your TAS by a couple of knots with the penalty of more fuel flow, or save that fuel and go your “normal” couple knots slower. But realistically flying a Mooney you may not do that. I know I probably wouldn’t. Of course you can increase fuel flow and RPM and gain those couple of knots without the expense and permanent weight gain of powerflow. It just doesn’t offer a significant speed increase and four grand buys a lot of fuel as does three grand or two. 

Does it really weigh more? It looks like the Powerflow exhaust for the C model weighs 17.5 lb- sounds pretty light though I cant find a weight for the stock exhaust.  I did note theres an STC that lets one increase the useful load of a 172N by 100lb after installing one.  

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43 minutes ago, DXB said:

Does it really weigh more? It looks like the Powerflow exhaust for the C model weighs 17.5 lb- sounds pretty light though I cant find a weight for the stock exhaust.  I did note theres an STC that lets one increase the useful load of a 172N by 100lb after installing one.  

It does weigh more. IDK exactly how much more. I have seen numbers ranging from 6 to 13 pounds more. 

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  • 3 months later...

After reading this thread it appears to me that some of you may not fully understand what an exhaust header is supposed to do and why.  Tuned exhaust headers are designed to use the explosive kinetic energy of the spent exhaust gasses to pull a vacuum on the exhaust port as the piston is approaching TDC on the exhaust stroke.  While the piston is moving through TDC and is very close to the top of its stroke, the exhaust valve is closing as the intake valve is opening.  Several degrees before TDC the intake valve begins to open, several degrees after TDC the exhaust valve becomes fully closed.  During this short time of valve overlap both valves are partly open and the piston is very close to the head, leaving the small exposed volume of the combustion chamber open to the “wind” formed by the moving intake and exhaust gasses.  This wind can move backwards through the engine if there is back pressure in the exhaust or vacuum in the intake manifold during the valve overlap period.   The diameter and length of the header tubes, collector, and output pipe work together to harness the momentum of the exhaust gasses and pull on the exhaust port as the piston nears TDC and the flow of gasses leaving the cylinder slows.  Depending on valve timing and other factors, these forces could be powerful enough to pull some intake mixture clean through the combustion chamber and into the exhaust manifold.

At first header pipes were designed mostly by trial and error.  Later a series of manometers were connected through a timed distributor to a sensing port close to the head.  12 Manometers tied to the engine at 5-degree intervals could show the port pressures from 30 degrees before to 30 degrees after TDC, giving the designer a better look at what affects the headers were actually providing.  These days modern computer programs can simulate the filling and emptying cycles of an engine with a high degree of accuracy, provided correct information about the various engine parameters are applied.  This includes bore, stroke, RPM, bearing friction, ring friction, parasitic loads, valve diameter, valve lift, timing and lift profile, intake runner length, diameter and type, exhaust runner length and type, carburetion, octane rating, fuel ratio, ignition timing, and atmospheric conditions including temp, altitude, and barometric pressure.  An engine designer or modifier with a computer now has a tremendous tool available to get most of the trial and error bugs worked out before welding up pipes and adding them to the engine.  I have experimented with these computer programs and they can be a lot of fun as well as enlightening as to how engines move air and produce usable power. 

There is another aspect to all of this to consider.  Engine and airplane manufactures have known for decades that intake and exhaust systems can improve or retard engine performance.  Therefore, lower performance machines will likely have quieter and more restrictive exhaust systems, whereas higher performance machines will likely have louder and less restrictive exhaust systems.  That means there is less potential for improvement on the higher performance machines with less restrictive exhaust systems than there is on the lower performance machines with more restrictive exhaust systems.  However, the lower performance engines are also likely to have less aggressive valve timing and lift profiles, thus limiting how much improvement can actually be realized.  This is one reason why performance increases are likely to be small.  If you are racing cars and a small improvement let's you beat the competition and win some races, then all the effort is worth the cost.  Not racing? Then maybe not.  Fortunately there are other tangible advantages like improved takeoff, initial climb, better climb at high altitude, and higher service ceiling. These other improvements are also likely to be small.  The components are of high quality and designed to last for the airplane's lifetime, so the PFE is and premium upgrade not just a replacement exhaust.  Is all this worth it to you?  Only you can decide that.  

Now let’s look at some of the performance numbers from Powerflow.  There is a link to the performance charts at the bottom of their web pages for the M20C 180HP and M20EFJ 200HP machines.  These files show stock TAS and fuel flow vs PFE modified TAS and fuel flow at 2500, 5000, 7500, and 11500 feet and at different RPM settings.   In nearly every case there is a slight speed gain and a slight fuel flow increase.  Most readings are taken from 50°F ROP and WOT or as specified, meaning that the data could be duplicated if necessary.   For example, M20E at 7500 MSL 2500 RPM WOT 50°F ROP tested 153 KTAS at 11.0 GPH with the stock exhaust.  With the PFE it tested 159 KTAS and 11.7 GPH.  What would the fuel burn be back at 153 KTAS with the PFE? By reducing RPM to get back to 153 KTAS the fuel burn would be 153 / 159 (Squared) x 11.7 = 10.83 GPH.  That number might not be perfect, but it is pretty close by my estimates.  I admit that is not a lot of fuel savings, but it takes the same HP to drive 153 KTAS with either system, so the PFE is actively improving engine efficiency by about 1.56%.  The 50°F ROP engine is thus more efficient at the same power output, and making that same amount of power at a lower RPM.  At 159 KTAS vs 153 KTAS the engine is producing about 8% more power to do so.  159/153 TAS (squared) = 1.07997.  11.70/10.83 = 1.080.  In a cruising airplane the fuel burn and HP required varies with the square in the change in true airspeed unless the drag profile is changed by adding weight or changing the configuration.  That means you can use your airspeed indicator to indicate fuel flow, like a poor man’s fuel flow meter. 

If you want to learn more about how engines and computer simulation software works, get a copy of Desktop Dynos from ebay.  It is old book but very informative.  If you want to learn how to use your ASI to indicate fuel flow then read my article in Air Facts Journal and apply that to the charts in your POH.   I made a quick reference chart that is easy to use while flying. 

https://airfactsjournal.com/2014/02/knowing-true-airspeed-fuel-management

Have FUN!  Fly Safe!!  Petehdgs

Powerflow M20C180.pdf Powerflow M20J200.pdf

Edited by Petehdgs
improve formating, correct typo
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