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Thread: powerflow exhaust

  1. #1
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    powerflow exhaust

    I thought I would post this on MM in addition to the
    Beechaeroclub site so a few more people might read it.
    I recently installed my power-flow exhaust system. The
    installation was straight forward and had no
    surprises. I did need to enlarge the cowl opening 1
    1/2 inches length wise to aid in clearance and add a
    doubler. The install makes working on the engine,oil
    changes etc very easy as the muffler is now out of the
    way. After doing the paperwork and double checking the
    install, I took it for its first flight. I obtained
    130 more RPM in static so, I was excited to see what
    that translated to in flight. I accelerated down the
    runway and the plane leaped into the air. I was
    lighter than usual so, I couldn't say at that time
    whether it was weight, power or both. I climbed to
    8500 feet with a DA of 11.4K and still saw a ROC of
    300 per minute -solid. That is an improvement as I
    have flown this profile before, solo, full fuel and
    hot.I know this flight was different. What I
    discovered was I reached altitude 20 miles sooner than
    my other flights. I thought this significant but, I
    wanted more info prior to a post. Today I took my wife
    along, full fuel and HOT . We took off at 97 degrees
    and again the plane leaped off the runway. My wife
    commented on quickly we were airborne.(She isn't a
    pilot and she noticed) I can't give a ROC as the
    thermal activity caused fluctuations in climb but I
    can Say we saw indications of 750 thru 1100 FPM as we
    climbed to 4500 feet for a DA of 7500. At 4500
    indicated I leveled off. The aircraft accelerated and
    the tach exceeded 2700 so I began throttling back. I
    pulled back 2" of throttle for a 2530 RPM,indicating
    125 for a true AS of 139 MPH (I wish it were knots but
    it is MPH). The verdict is still out on how much
    improvement I am seeing. The preliminary indications
    are I have a 5% increase in power for a usable 8 HP. I
    will keep posting as I get new figures. My next test
    is to throw my 300 lb friend into the cabin and see
    what the plane does. He will represent a additional
    180 LBS over what I have tested so far.


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  2. #2

    powerflow exhaust

    >I recently installed my power-flow exhaust system. The installation was
    >straight forward and had no surprises. I did need to enlarge the cowl
    >opening 1-1/2 inches length wise to aid in clearance and add a doubler.

    This is typical on PF installs. Some cowl mods are commonly needed,
    regardless of brand of the plane. They should all be spelled out in the
    STC, both drawings, and written instructions for any skin mods.

    >I obtained 130 more RPM in static so, I was excited to see what that
    >translated to in flight. I accelerated down the runway and the plane
    >leaped into the air. I was lighter than usual so, I couldn't say at that
    >time whether it was weight, power or both.

    Everyone has the same issues of being so excited by their new expensive
    purchase that they don't have solid back-to-back before and after
    data. The comparisons are all "it feels stronger" and "the ROC was better,
    though I was solo on this flight". There IS a difference. The amount of
    the difference in a real world situation has been difficult to nail down.

    >The aircraft accelerated and the tach exceeded 2700 so I began throttling
    >back. I pulled back 2" of throttle for a 2530 RPM,indicating 125 for a
    >true AS of 139 MPH (I wish it were knots but it is MPH). The verdict is
    >still out on how much
    >improvement I am seeing.

    Given that the aerodynamics of the plane and the pitch of the prop have not
    changed, the plane will fly at EXACTLY the same airspeed for the same RPM
    on the tach. The location of the throttle lever to achieve this RPM may
    change with improved engine breathing, but the relationship of airspeed and
    RPM will remain constant.

    Without previous data to compare with (manifold pressure reading would have
    been nice), one can only speculate that the amount the throttle was pulled
    back was different. If at 8000' of DA and full throttle, your engine will
    exceed 2700 RPM in level flight, then you should consider a prop pitch
    change. Otherwise you effectively have turned your $4000 muffler into a
    climb prop with the same change in T/O and climb performance that you could
    have gotten with a $150 prop pitch change.

    >The preliminary indications are I have a 5% increase in power for a usable
    >8 HP. I will keep posting as I get new figures. My next test is to throw
    >my 300 lb friend into the cabin and see what the plane does. He will
    >represent a additional
    >180 LBS over what I have tested so far.

    That is about right, based on wide experience with the PF product on
    several different brands. The "23 HP" number in their old ads was as
    generated on a test stand, and does not seem to compare in flight. Also
    the 2.2 GPH savings advertised was obtained by operating the engine above
    80% power and leaned to economy, compared to the stock-mufflered engine at
    full throttle and full rich. So one would NEVER reproduce the test method
    in the air and obtain any fuel savings while violating the Operating
    Limitations, as explained in the POH and the Lycoming Handbook for Engine
    Operators ($19 from Lycoming, available for each engine family).

    The way to look at the PF is that it provides a boost in T/O and climb, and
    that compared with the High Compression mod to the O-320-E series engine
    (150 HP), it gives about the same boost in performance and economy (if you
    can force yourself to throttle back). Combine the 2, and you have spent
    ~$10K and have really made a change to the performance of the A23-19 and
    siblings.

    Those with Sundowners and 160 HP model 23s, that don't have piston options
    for higher compression really don't have many other choices for T/O and
    climb performance improvement, except the PF exhaust.

    Each inch of prop pitch increase is about 2.5 mph in top speed at 2700 RPM,
    and about 50 RPM difference in engine speed at full throttle. The HC mod
    is good for about 2" of pitch change, without decreasing the climb, and the
    PF seems to be good for about the same. So after doing the High
    Compression mod, and adding a PF, one could expect to increase the prop
    pitch 3-4" and pick up 7-10 mph on the top end, without killing the T/O and
    climb.

    Or if you can stand it, you could throttle back at altitude and get a fuel
    savings of about 0.5 GPH from the piston change, and about the same from
    the PF. However I have YET to find a pilot with a PF and HC conversion
    that can fly X-C at the same airspeed as before and save the fuel. <G> If
    we wanted to save fuel and spend more time on the trips, we'd have bought
    Honda Insights or Toyota Prius' and been ground pounders amongst the 18
    wheelers on the interstate, and been getting 45-50 MPG instead of 15 MPG at
    110+ knots!

    Bob Steward, A&P IA
    Birmingham, AL

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  3. #3
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    powerflow exhaust

    Bob I believe that the extra horsepower you are now achieving can be
    translated into more speed. If your engine is now producing more power to get the
    extra cruise speed all you have to do is cruise at a higher altitude for your
    75% power setting. You should find that your cruise rpm at 75% will now be at
    a higher altitude since you are producing more horsepower. You will find all
    your 75% numbers are no longer a valid number at the full throttle settings
    in your poh. If you are flying at less that full throttle setting then
    everything you said is true. If you want better speed on a long cross country just
    climb to an altitude that is full throttle that gives you your cruise rpm. The
    air is thinner and you will be pulling 75% you will end up with your highest
    cruise numbers. I have a 23-24 any chance they would make a PF for my model?
    Alan

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  4. #4
    Orbiting Earth Heading to Pluto sjcote's Avatar
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    powerflow exhaust

    Hee Hee! Ain't it a hoot?

    I got to fly Robin's Sundowner prototype at BAC Fest last year. And I found
    the same type of changes. Of course it was entirely subjective, no chance to
    compare apples to apples, but we were rippin' along at 2600 RPM and 130 MPH
    on a staggeringly hot Wichita day.

    Steve Cote

    N1958L

  5. #5
    I have the 160 HC stc on my engine. I have the cruise prop. On my recent CC, I averaged 8.5 GPH, full throttle and leaned at 9500 and 10500. At lower altitudes leaned, I average 9.5 GPH. Yes, I could have changed the pitch in the prop, accepted a lower speed and come out a few dollars ahead. Now, I have the option of a faster speed, a better climb, reaching higher altitudes or a lower fuel burn. With an average of 93 Kts for my last trip to OSH, I didn't relish the thought of losing any speed with a pitch change. Also each inch of pitch reduces RPM by 50. Had I been able to achieve 50 more RPM on two occassions, this would have made the difference of achieving an altitude that placed me out of IMC smoke in Montana and being beat by thermals in NM. For those that can't afford the Powerflow, perhaps the pitch change would be more of an option. Personally I look at the pitch change as a compromise that I didn't wish to accept when then was another option(at this time). My Musketeer is my only hobby. You can say I didn't need the HC Stc, I didn't need the VG's, I didn't really need new glass, my engine could have gone possibly another 3-400 hours prior to rebuild, I really didn't need a prop overhaul etc. I like to experiment and see what things do. I have found my Musketeer an excellent platform to conduct these experiments. The powerflow cost me 4K the prop change would have been 650 bucks. If I'm still in need of more climb, I still have the pitch option. I guess to each his/her own. Musketeers forever-Bob

  6. #6
    DITTO Bob!

    The Powerflow exhaust has been everthing I expected and more on my 150 hp 74' Sport. I have a stc'd prop which is 1" larger in diameter than stock and climb suffered, but not anymore.

    Leo

  7. #7
    Today I loaded the plane with 300lbs of weights from my weight room and full fuel to get some apples to apples on figures. The OAT was 88 degrees in my area with 29. 83 on the alt setting. On the initial ground run, I indicated 2580 RPM and climbed out at 750 FPM. The length of the run is estimated at 1/3 less that before. I was off prior to a turn out that I measured previously and being off before that was an indication of better climb. The 2580 was an additional 100 RPM and I used 85 MPH on climbout. I transitioned to 100 MPH after 1000 Ft and climbed to 4500 feet for my first sample( RPMs increased as I shallowed the climb). The climb rate dropped to 600FPM at 100 MPH. Climbing at 2583 RPM at 4500 Feet yielded 400 FPM soild. The temp was 83 degrees, 29.83 for a DA of 7100 Feet. My CHT was 338 and EGT was at 1323. I continued the climb to 5500 feet and the climb rate droped to 300 FPM at 2665 RPM, CHT 336, EGT 1330 OAT 82 Degrees for a DA of 8250 Ft. I continued to 6K with still a 300 FPM climb at 2666 RPM still indicating 100 mph. The OAT was 82 degrees, CHT 338, EGT 1314, DA 8856 feet. Up to 7K the ROC dropped to 150 FPM with 2583 RPM, OAT 78, CHT 334 egt 1328, Alt 29.83 with a DA of 10065 Feet. on up to 8500 feet. At 8500 feet the DA was 11514 feet. My ROC was 100 FPM my RPMs were 2560 in climb. The oat was 74, chts 328, egt 1327 still indicating 100. I leveled out at 8500 and the airspeed indicated 110 MPH for a true AS of 113 kts or 130 MPH. Comparing apples to apples; In Sante Fe NM with a field elevation of 6400 plus and 96 degrees I had less than 50 FPM at the weight I was carrying. If you look at my figures for the 8500 feet, I am still obtaining 100 FPM. This would have saved me a few grey hairs during the trip. Level at 8500 feet, my RPMs were 2560 in climb and 2660 leveling out. Carrying this weight at this DA on the last flight prior to the powerflow would only yield 2500 RPMs. Would I like more? sure as would we all. I'm pleased as I know I can make most altitudes easily as I don't carry this much weight USUALLY !! ha ha. I will keep evaluating the performance but so far, I pleased. There is only one major thing lacking now-WHEEL PANTS -are you reading Robin? ha ha (Note the RPMs were taken from my Horizon Tach. Any change in pitch no matter how slight veries the reading)

  8. #8

    powerflow exhaust

    "I have a 23-24 any chance they would make a PF for my model?
    Alan "

    They've made kits for IO-360's, but rumor has it that Robin Thomas is
    still working with that, as the gain wasn't huge. I've seen them on
    Mooney J models IO-360-A3B6D, owners never report much change in the
    lower altitudes below 10,000 feet. I'm waiting, credit card in hand,
    for the wheel fairings that Mr. Thomas is creating.

    For a slight gain (using a hair less throttle for the same RPM) you
    might try the Challenger Aviation air filter which is an FAA legal,
    repackaged K&N filter. Its much better than trying to suck air through
    an inch of stick foam (Brackett)

    Joe, also A23-24

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