Power Flow Exhaust and O-320 PIREP

AKBill

AKBill

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AKBill
Thinking about getting a Power Flow Exhaust for the Sport. O-320-E-3D, wondering what to realistically expect for a performance increase.

From what I have read it's an increase of 23hp. I was considering installing and O-360 into the Sport, the cost of that upgrade would be equal to the selling price of the plane. Fun to think about but I don't think I could get my money back on sale of the Sport.

So my next thought was a power flow exhaust. $4000 for an exhaust system is not chump change, is it worth it and does it really increase HP by 23hp?

Thanks
Bill B
 
I have no personal experience Bill but from what I've heard, 23 hp on an O-320 is greatly exaggerated; this from my A&P and two IA's that I know.
 
Timbeck2 said:
I have no personal experience Bill but from what I've heard, 23 hp on an O-320 is greatly exaggerated; this from my A&P and two IA's that I know.
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Thanks, just trying to get a realistic outlook of the system. As I said $4000 is not chump change to me...:)
 
I'd ask the PowerFlow folks how that's measured, and how you'd see it in engine parameters (rpm, I would think, for a fixed pitch prop).
 
I've heard it's closer to 2-5hp. That being said I had a buddy (well known for exhaggerating) that everytime I spoke to him his powerflow exhaust gained more power. Before long his 160hp 172 was "basically a high performance plane with the 45hp from the powerflow" :lol:
 
My PA28-140 has lots of mods: gap seals, wheel pants, wing tips, and a powerflow. The only mod that made any noticeable difference at all is the powerflow. My friend has a nearly identical PA28-140, except instead of a powerflow, he has the 160 hp cylinders (mine still has the 150 hp cylinders). When he and I fly together, we are dead even...same climb, same cruise, etc....so, from that, I'd say the powerflow adds about 10 hp. One other thing the powerflow does is it changes the exhaust note, so nearly everyone used to a stock o-320 notices "something is different".
 
Mtns2Skies said:
I've heard it's closer to 2-5hp. That being said I had a buddy (well known for exhaggerating) that everytime I spoke to him his powerflow exhaust gained more power. Before long his 160hp 172 was "basically a high performance plane with the 45hp from the powerflow" :lol:
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Sounds like the folks who buy 10 bolt-ons for their muscle car or diesel truck, then claim they are +100hp because each one “adds 10hp”...
 
If the PowerFlow exhaust had been available for my Maule, I’d have done it...the O-300 probably wasn’t making more than 100 hp due to the cruise prop. Any bump would be significant.
 
My Cherokee 140 makes 107kts @2500' zero wind. When looking at speed gains it appears wheel pants would add another 2-3kts, what does the PowerFlow provide?
 
When we installed the powerFlow on our Cherokee 140. We had to re-pitch the prop, to prevent exceeding max static rpm. And would routinely see 115kts in cruise at 8gph. You could also land, full stop, and takeoff, in under 1000'. So, the powerflow does something positive for performance.
 
IIRC, speed increases as the cube root of horsepower, so 8% power increase would be a 2% speed increase. There are better ways to increase speed.

As @bluerooster alluded, horsepower will show up in takeoff and climb numbers.
 
Mooney Fan said:
My Cherokee 140 makes 107kts @2500' zero wind. When looking at speed gains it appears wheel pants would add another 2-3kts, what does the PowerFlow provide?
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Don't count on it with the wheel pants...as it was explained to me, anything under 150 kts, wheel pants are for looks only (especially true with a fixed-pitch prop). My Cherokee sees no difference, pants on / pants off. I've tested it.
 
I’d look into a acorn or something
 
I had on installed on my Cherokee 140 and thought there was some improvement. I have a Warrior II now and unless there is real, objective data, I don't think that the so-so improvement is worth the cost.
 
I have one on my 91 Tiger with an 0-360. My rate of climb is significantly better in the warmer months, and I am able to lean to low 9’s at 2450 RPM without excessive EGT/CHTs if I want to fly slow at maximum economy and range. I repitched my prop from 61” to 63” when installing the PF and my top speed hasn’t really increased. I installed the PF because I live out west and anything that will help with DA is something I am interested. I was told by PF to expect a 15 hp increase. I don’t know if that’s true but the engine does seems to perform better. Finally, PF has Oshkosh specials each year - I think my exhaust was like $3600 and I had it installed during the next annual.
 
Jumpmaster said:
I have one on my 91 Tiger with an 0-360. My rate of climb is significantly better in the warmer months, and I am able to lean to low 9’s at 2450 RPM without excessive EGT/CHTs if I want to fly slow at maximum economy and range. I repitched my prop from 61” to 63” when installing the PF and my top speed hasn’t really increased. I installed the PF because I live out west and anything that will help with DA is something I am interested. I was told by PF to expect a 15 hp increase. I don’t know if that’s true but the engine does seems to perform better. Finally, PF has Oshkosh specials each year - I think my exhaust was like $3600 and I had it installed during the next annual.
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Thanks for the input. What did the prop cost?
 
I think something like $300 and that included a static balance. After the prop was remounted and the PF installed, I had the prop dynamically balanced. Got to say it runs pretty smooth.
 
I believe you should consider the tried-and-true performance increase. One with solid scientific evidence.

Experience with high-performance motorcycles has proven that each sticker you add gives 2.6hp. You apply as many as possible from suspension manufacturers, engine and brake parts manufacturers, etc.

Considering the surface area of a Cherokee 140, should you apply this method of performance improvement, you can virtually have a Dakota with minimal effort!!!
 
We have a 172, with the Pearce STC to bring the 150 hp to 160. Added to that, it has a Powerflo, and one mag replaced with an electronic ignition.

I came to the club from flying 172s with the 180 hp Great Plains conversion.

Subjectively, I see no diffrence in performance, so I do believe/buy the 20+ hp increase, though mabe the EIS has some impact.

Bottom line, it doesn't pull like the 210 hp T-41s I was flying, but it matches the 180 hp.
 
Sundancer said:
We have a 172, with the Pearce STC to bring the 150 hp to 160. Added to that, it has a Powerflo, and one mag replaced with an electronic ignition.

I came to the club from flying 172s with the 180 hp Great Plains conversion.

Subjectively, I see no diffrence in performance, so I do believe/buy the 20+ hp increase, though mabe the EIS has some impact.

Bottom line, it doesn't pull like the 210 hp T-41s I was flying, but it matches the 180 hp.
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Thanks for your comments.
 
I’d factor in the age of the current exhaust. The STC that could make a noticeable difference is the 360 engine upgrade, if your SN allows. Of course you’ll never get a good portion of your $$$ back, evaluate the rest of your plane and how you have it setup for long term.

I’ll freely admit I’m ‘underwater’ with plane ownership, I’ve learned to accept that fact.
 
Sundancer said:
We have a 172, with the Pearce STC to bring the 150 hp to 160. Added to that, it has a Powerflo, and one mag replaced with an electronic ignition.

I came to the club from flying 172s with the 180 hp Great Plains conversion.

Subjectively, I see no diffrence in performance, so I do believe/buy the 20+ hp increase, though mabe the EIS has some impact.

Bottom line, it doesn't pull like the 210 hp T-41s I was flying, but it matches the 180 hp.
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I had a similar experience, I used to rent a 172K with a "RAM 160" conversion and Powerflow exhaust, it performed very close to a 180hp conversion. However, after changing owners a few times the Powerflow has been removed, no idea why.
 
My club has two 172N models that are nearly identical except that one has Powerflow and one doesn’t. I haven’t done any measuring or calculations but the one with powerflow seems like it might climb just a little bit better. A couple of other members swear that it climbs and cruises a lot faster but a couple others say it doesn’t. I haven’t tried to scientifically confirm.
 
Our Cherokee 140 has the Powerflow, but no 160 STC. It came with the Powerflow already installed, so I have no benchmark to compare. I will, however, say that I can outrun my friend in his standard exhaust equipped Cherokee. Also, one important point that nobody here has mentioned: Powerflows don't actually ADD any horsepower--they simply re-designed the stock exhaust to be more efficient, thereby unlocking horsepower that was previously untapped. A small distinction, but I feel it's important.
 
Yes, you could say The PF exhausts suck, and you'd be right. They are tuned, such that a pulse of low pressure travels backward from the exhaust opening to the exhaust valve, arriving just in time to suck hot exhaust gases out just as the exhaust valve opens, so the downward moving piston needs to exert less force exhausting the cylinder, thus more force is available to turn the propeller.
 
I have a 1969 Cessna 172K and it would go about 115 mph IAS or 120 mph TAS at about 2500 feet, 2550 rpm. Probably average.

I added PowerFlow at about $4500 with installation, then the RAM conversion to 160 hp, about $5000 with labor and parts.
However, the plane won't go faster without repitching the prop or buying a new prop with more pitch.
Stock is a McCauley 53" pitch. I bought a 172N prop (which is permitted by the RAM STC) Sensenich STC cruise prop, 63" pitch, $4000.

I now do 135 mph IAS, and 145 mph TAS (125 kts) at 3000 feet 2550 rpm.

My weekly flights are between HNL and MKK, in Hawaii, about 49 nm.
I probably don't save but a few minutes, and it took $15,000 to move that airspeed indicator up near the top of the green.

From a practical standpoint, I can now do the ILS at HNL at 130 knots TAS, 2600 rpm, and makes me less of a nuisance to ATC in between all the jet traffic. That's about the approach speed of the Cessna 208 commuter turbo props and the Hawaiian Air ATR turbo prop. I don't get routed here and there by ATC anymore on an instrument approach.
 
Absolute waste of money. Any difference anyone claims is because they don't want to admit how much money they've wasted.

I've flown multiple different types with and without Power Flow exhausts....I'm not kidding when I say that I wouldn't spend $100 upgrading to one.
 
jesse said:
Absolute waste of money. Any difference anyone claims is because they don't want to admit how much money they've wasted.

I've flown multiple different types with and without Power Flow exhausts....I'm not kidding when I say that I wouldn't spend $100 upgrading to one.
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Nah, I bought into the plane well after the Pearce, EIS, and PF were installed. No dog in the fight; it does perform substantially equivalent to the 180 hp conversions I came directly from. I'm sure the Pearce and EIS contribute substantially, so I can't say what percent is due to the PF, though. Climb impact is most notable; we were pegging the VSI with two guys and full fuel yesterday, on a cool day - the comments tegarding the prop are accurate - easy to exceed redline in full power climb, unless you get the nose up smartly.
 
MauleSkinner said:
IIRC, speed increases as the cube root of horsepower, so 8% power increase would be a 2% speed increase. There are better ways to increase speed.

As @bluerooster alluded, horsepower will show up in takeoff and climb numbers.
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Yeah, this. Top speed isn't the best way to compare. Load to full gross, climb full power at Vy, see what you get on the VSI. That will make a far greater difference and an easier number to compare. The speed gain will be mostly getting to altitude faster where you can get the best TAS.
 
jesse said:
Absolute waste of money. Any difference anyone claims is because they don't want to admit how much money they've wasted.

I've flown multiple different types with and without Power Flow exhausts....I'm not kidding when I say that I wouldn't spend $100 upgrading to one.
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You would think simple before/after dynomometer runs would settle this argument. Cars have rollers, why can't we attach a strain gauge to the tail of our airplanes?
 
asicer said:
You would think simple before/after dynomometer runs would settle this argument. Cars have rollers, why can't we attach a strain gauge to the tail of our airplanes?
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Because increase in hp may not equate to increase in speed given the amount of drag that big ole pipe hanging int the airstream might cause.
 
unsafervguy said:
Because increase in hp may not equate to increase in speed given the amount of drag that big ole pipe hanging int the airstream might cause.
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I wasn't talking about speed. I was talking about testing Power Flow claims of HP gains. And even if you don't see a speed benefit, you'll see a climb benefit if the claims are real.

Also, some Power Flow installations are "short stack" so no aerodynamic penalty there either.
 
asicer said:
I wasn't talking about speed. I was talking about testing Power Flow claims of HP gains. And even if you don't see a speed benefit, you'll see a climb benefit if the claims are real.

Also, some Power Flow installations are "short stack" so no aerodynamic penalty there either.
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A tethered prop is going to be operating in dirty air. Not sure that would tell you what you want to know. You’re also not going to want to run the engine at full power on the ground. Will suck in crap and overheat the engine.
 
Has anyone noticed that the PF exhausts sticks out,? Any HP improvement will be eliminated by extra drag.


Tom
 
MooneyDriver78 said:
Has anyone noticed that the PF exhausts sticks out,? Any HP improvement will be eliminated by extra drag.


Tom
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Just curious. Would you mind sharing your calculations of drag from the exhaust pipe vs. extra HP from the PF Exhaust? There are plenty of testimonials refuting your claim, some here on POA.
 
MooneyDriver78 said:
Has anyone noticed that the PF exhausts sticks out,? Any HP improvement will be eliminated by extra drag.
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They come in 2 different sizes. The short stack version doesn't stick out that much.
 
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