M20C PowerFlow PIREP

[Jakes Simmons]

     During my last annual in August at Maxwell’s, had a PowerFlow exhaust installed on my ‘76 Ranger. Thought I would do a PIREP after 25 hours since install. 
     Short version, no regrets and plan to keep it but if I was starting from scratch would have waited until original exhaust had issues and needed replacement. I think the PowerFlow works best for owners who consistently fly long cross countries at 10k and higher. Lower flying and hamburger runs, probably unnecessary.

     Had money saved for a couple years waiting on TT/AeroCruze to be available for M20’s. Finally last year, and a month before Duncan announcement, decided to throw in the towel and put the money toward something else on the airplane. I had been aware of PowerFlow systems for a number of years and seen good performance gains on friends’ Cessna’s. I called the company after seeing one of their specials expire and asked if they could extend it if I had an eight month lead time. They said no problem and even added the ceramic coating since delivery would be so far out. 
    Just as scheduled, they sent the exhaust directly to Maxwell’s before my plane arrived. Normal install, I also added the Challenger air filter. Prop was dynamically balanced by the local wizard. THAT made a crazy difference. I had prop balanced 18 months before but the local Maxwell guy must have performed black magic. 2700 to 2300 no appreciable difference in vibe level, very smooth, or at least as smooth as a Lycoming four banger will go.

     Important note, my mixture control was repaired and adjusted during this annual. I had not realized there had been a significant problem. This plays out later.

     New exhaust added a couple pounds to front of airplane but was a wash because of previous removal of vacuum system. Looks cosmetically good and the coating stays clean. I seem to have lost a bit of speed down low. Previous multiple cardinal runs at 2000 AGL consistently showed 151 kt averages WOT. Did a few with new install, now consistently 148 kts. I haven’t noticed any measurable differences in TO distance or initial climb out. Butt says it’s a little reduced but that’s not quantitative. 
     The positive performance differences I have noticed are up high. Depending on OAT, I’m getting 20-21.5” MAP at 11k, before it was 19 or a hair higher. Coming back from Tupelo MAPA yesterday, the Ranger was still climbing 5-600 fpm at 100 kts indicated at 11000 ft. My airplane has most of the major speed mods and that with the PowerFlow, the Mooney is  getting original POH numbers. It was showing 145-147 TAS at 2450 rpm. I do not have an engine monitor so no real time fuel flow. My after flight fill up numbers haven’t changed. Maybe getting to altitude faster offsets any higher burn.

     The biggest operational difference is mixture control setting. Previous to this annual, I had two mixture settings, full rich and a spot well back, maybe 3/4 inch from cutoff. Engine ran smooth with rich all the way to cruise and smooth down to final with it pulled back. Now it’s a different story. Passing 5k in the climb, I need to start leaning or engine will stumble. It needs to be gently leaned throughout the entire climb. At cruise 10-12k, I pull it back to a spot physically forward of the original one, showing 100 ROP on the single point EGT gauge. On the way down same thing, mixture needs to be constantly attended to for the engine to stay in a sweet spot, smoothness wise. First time in a landing descent after install, engine was stumbling so bad, I thought it was going to quit. Called Lynn at Maxwell’s to see if something had been missed. He explained how much adjustment my control had needed. Now I have learned not to go full rich until short final. 
     Cabin heat is also better. No noticeable difference in noise level. I used to cruise at 2350 but now I do 2450. I had read they tuned this exhaust for 11k and 2450 and that is where it seems happiest.

     So, if you’ve got the O360 and consistently fly 3-4 hour legs above 10, AND could use a new exhaust, it’s worth it. Hamburger runs at 5k, 1 to 2 hour flights, probably repairing your current exhaust makes more sense, as always depending how much you’ve got squirreled away in the kitty. Since this all was done, the AeroCruze kit came in. Now I am “squirreling” away for the install price. Hope this helps…

[DXB]

30 minutes ago, Jakes Simmons said:

     During my last annual in August at Maxwell’s, had a PowerFlow exhaust installed on my ‘76 Ranger. Thought I would do a PIREP after 25 hours since install. 
     Short version, no regrets and plan to keep it but if I was starting from scratch would have waited until original exhaust had issues and needed replacement. I think the PowerFlow works best for owners who consistently fly long cross countries at 10k and higher. Lower flying and hamburger runs, probably unnecessary.

     Had money saved for a couple years waiting on TT/AeroCruze to be available for M20’s. Finally last year, and a month before Duncan announcement, decided to throw in the towel and put the money toward something else on the airplane. I had been aware of PowerFlow systems for a number of years and seen good performance gains on friends’ Cessna’s. I called the company after seeing one of their specials expire and asked if they could extend it if I had an eight month lead time. They said no problem and even added the ceramic coating since delivery would be so far out. 
    Just as scheduled, they sent the exhaust directly to Maxwell’s before my plane arrived. Normal install, I also added the Challenger air filter. Prop was dynamically balanced by the local wizard. THAT made a crazy difference. I had prop balanced 18 months before but the local Maxwell guy must have performed black magic. 2700 to 2300 no appreciable difference in vibe level, very smooth, or at least as smooth as a Lycoming four banger will go.

     Important note, my mixture control was repaired and adjusted during this annual. I had not realized there had been a significant problem. This plays out later.

     New exhaust added a couple pounds to front of airplane but was a wash because of previous removal of vacuum system. Looks cosmetically good and the coating stays clean. I seem to have lost a bit of speed down low. Previous multiple cardinal runs at 2000 AGL consistently showed 151 kt averages WOT. Did a few with new install, now consistently 148 kts. I haven’t noticed any measurable differences in TO distance or initial climb out. Butt says it’s a little reduced but that’s not quantitative. 
     The positive performance differences I have noticed are up high. Depending on OAT, I’m getting 20-21.5” MAP at 11k, before it was 19 or a hair higher. Coming back from Tupelo MAPA yesterday, the Ranger was still climbing 5-600 fpm at 100 kts indicated at 11000 ft. My airplane has most of the major speed mods and that with the PowerFlow, the Mooney is  getting original POH numbers. It was showing 145-147 TAS at 2450 rpm. I do not have an engine monitor so no real time fuel flow. My after flight fill up numbers haven’t changed. Maybe getting to altitude faster offsets any higher burn.

     The biggest operational difference is mixture control setting. Previous to this annual, I had two mixture settings, full rich and a spot well back, maybe 3/4 inch from cutoff. Engine ran smooth with rich all the way to cruise and smooth down to final with it pulled back. Now it’s a different story. Passing 5k in the climb, I need to start leaning or engine will stumble. It needs to be gently leaned throughout the entire climb. At cruise 10-12k, I pull it back to a spot physically forward of the original one, showing 100 ROP on the single point EGT gauge. On the way down same thing, mixture needs to be constantly attended to for the engine to stay in a sweet spot, smoothness wise. First time in a landing descent after install, engine was stumbling so bad, I thought it was going to quit. Called Lynn at Maxwell’s to see if something had been missed. He explained how much adjustment my control had needed. Now I have learned not to go full rich until short final. 
     Cabin heat is also better. No noticeable difference in noise level. I used to cruise at 2350 but now I do 2450. I had read they tuned this exhaust for 11k and 2450 and that is where it seems happiest.

     So, if you’ve got the O360 and consistently fly 3-4 hour legs above 10, AND could use a new exhaust, it’s worth it. Hamburger runs at 5k, 1 to 2 hour flights, probably repairing your current exhaust makes more sense, as always depending how much you’ve got squirreled away in the kitty. Since this all was done, the AeroCruze kit came in. Now I am “squirreling” away for the install price. Hope this helps…

Interesting PIREP.   When I did a Powerflow in my '68C the first thing I noticed was dramatically better takeoff power with a better climb rate.  However, I also noticed higher CHTs in climb, which I mitigated by very shallow climb until above 120mph, then stay at >120mph as long as practical to maintain a good climb rate.  I also got faster speeds (solidly >150kt TAS) and higher CHTs in cruise, but I added a variably timed Surefly so I'm not sure how much the Powerflow contributed there - it definitely contributed to power in initial climb as the Surefly stays in fixed timing until MP drops below 24.  I rarely cruise above 9k so I can't vouch for it up there - interesting regarding its tuning for 11k and 2450.  I'll have to try it sometime.  I don't see a bump in MP you describe - I imagine that's the Challenger filter?  I don't see how the exhaust would cause that. FWIW I did a Donaldson filter at the same time, which supposedly provides better filtration with comparable airflow to the Challenger.

[FlyboyKC]

I upgraded to the Powerflow last year in my 68G. I didn't see any noticeable increase in climb performance, however it did kind of seem that the climb was stronger and more consistent on hotter days.
My CHTs  and EGTs now are more equal to one another. I did see some minor increase in CHT temps, but they still run ~315 - 330 even on hot days. I also noticed an increase in MP at higher altitudes but haven't realized any fuel mileage benefit, which is probably not economizing my cruise. Airspeed wise I true out at 135knts consistently.

If I had to do it over again, would I? Probably although I might try the Surefly first to see what benefits that yields. Although that is on my list of things to buy when the mags need overhaul.

Neal 

[Jakes Simmons]

On 10/16/2023 at 10:48 AM, DXB said:

Interesting PIREP.   When I did a Powerflow in my '68C the first thing I noticed was dramatically better takeoff power with a better climb rate.  However, I also noticed higher CHTs in climb, which I mitigated by very shallow climb until above 120mph, then stay at >120mph as long as practical to maintain a good climb rate.  I also got faster speeds (solidly >150kt TAS) and higher CHTs in cruise, but I added a variably timed Surefly so I'm not sure how much the Powerflow contributed there - it definitely contributed to power in initial climb as the Surefly stays in fixed timing until MP drops below 24.  I rarely cruise above 9k so I can't vouch for it up there - interesting regarding its tuning for 11k and 2450.  I'll have to try it sometime.  I don't see a bump in MP you describe - I imagine that's the Challenger filter?  I don't see how the exhaust would cause that. FWIW I did a Donaldson filter at the same time, which supposedly provides better filtration with comparable airflow to the Challenger.

Hey, I appreciate the reply. I still have the original engine gauges, who knows what actual numbers they represent, but I haven't noticed any discernible changes even after long climbs. Were you deciding between Electroair and SureFly when going with an electronic ignition? If so, and if you get a minute, I am interested in why you chose SureFly and if you thought it worth it, plus does the change in timing work well with the MP drop? I already run fine wire plugs and was thinking about a mag replacement next yea

[Skates97]

I added a Powerflow a few months back and see better cruise speeds and an extra 1-200fpm in the climb above 8,000' than before. I typically cruise at 9,500-10,500 as you need to so you can clear the big rocks out west. In cruise up there with the same fuel flow settings I went from 166mph TAS to 170 mph TAS. (Everything in my old 1965 is in mph but translates to about a 3.5 knot gain). I am able to bring it back to 9.1-9.2 gph and still get the 166 mph TAS which used to take 9.8-10 gph to achieve.

[DXB]

1 hour ago, Jakes Simmons said:

Hey, I appreciate the reply. I still have the original engine gauges, who knows what actual numbers they represent, but I haven't noticed any discernible changes even after long climbs. Were you deciding between Electroair and SureFly when going with an electronic ignition? If so, and if you get a minute, I am interested in why you chose SureFly and if you thought it worth it, plus does the change in timing work well with the MP drop? I already run fine wire plugs and was thinking about a mag replacement next yea

Surefly is a quicker simpler cheaper and more modular install over Electroair - I think most folks have been going in that direction for certified electronic ignition since it came out. Durability and reliability seem to far exceed that of a regular mag, with lower long term cost since no 500 hr IRAN/overhaul. Much easier starts, particularly in cold. Clearly greater leaning ability despite the sloppy mixture distribution of the C. Only question is whether to use fixed timing setting vs. variable timing setting, with latter providing greater power and efficiency -  I've been thinking of going back to fixed timing setting due higher CHTs in cruise.  Unfortunately you have to remove the Surefly to change the timing setting switches,

[jetdriven]

The powerflow does 3 things.  All related.  It burns more fuel.  Makes more power. Runs hotter.  We’ve got 3 clients with powerflow systems and all three require a LOT more fuel flow at takeoff power to stay below 415 CHT. 400 usually isn’t achievable.  The cardinal guy had his carb rebuilt then re-jetted three times.  To the OP I would put some real instrumentation  in that plane because you are likely busting redline CHT at 1000’ after takeoff.