PowerFlow Exhaust on a 170

[johneeb]

George,
I have an engine with either a fixed pitch or constant speed and the pitch is set at 51"s and it turns 2700 RPM, lets assume everything else is equal and we are running the engine at 7500' density altitude and max throttle.

To make an improvement in the volumetric efficiency of the combustion chamber, I add a tuned exhaust system which is designed to improve the intake and exhaust flow.

Now I set the pitch of the constant speed or fixed pitch prop to 53"s and the engine still turns 2700 RPM the Torque developed must have increased while the RPM is still 2700. Albeit more heat and higher fuel burn at that max power setting.

With the 53" pitch the airplane must be flying faster.
Johneb

[Bruce Fenstermacher]

John I think you missed George's point and that is that Powerflow says there will be no more fuel burn or heat created. I agree with George that these claims can't be true.

As for whether the Powerflow improving engine breathing over the stock system which I admit as George describes seems to be pretty good, I don't know.

Yes I'm sure a "magic exhaust" can through "pulse" "harmonic" trickery make an engine produce more HP. I've seen it on model airplane engines and the same thing can be applied to a C-145 but maybe not to the same degree of success.

And I agree 100% with Eric that unless the PowerFlow doubled my HP, I'd NEVER hang one of those ugly things on my plane.

[inman]

I was amazed when I had my exhaust system off of my O-360 that the tubes just dump into an empty can with no baffling or anything. I guess I always thought that it would look more like a glass pack or automotive style muffler. Since My Avcon Conversion does have the Hartzel prop. and My STC says to run it at 2400RPM at 21 inches, it seemed to me that if I could hold that manifold pressure up at higher altitudes instead of flattening out my prop like I have to do now, I would really get speedy. I know the effect of putting after market exhaust on some of the old 4 cylinder street bikes I used to have really generated a strong "power band" and being that I am targeting a certain RPM, an exhaust system that really "sucked" at 2400 RPM would be optimal. The factory exhaust looks like all they cared about was providing a place for a heat shroud and a way to exit the exhaust. Thanks for all the great discussion. As a relatively new A/C owner, this is incredibly valuable.

[GAHorn]

Of course, no exhaust systems actually "sucks" exhaust gases out of an engine. In every case when the piston is pushing those gases out there is a momentary increase in exhaust system pressure. There is never a negative pressure (because of valve overlap.*) I don't know how they installed "dozens of high speed sensors" equally inside two radically different exhaust systems in order to have an un-biased sales-graph, (*but OEMs all know about the effects of valve overlap and deliberately designed it in order to take advantage of the momentum of the exhausted gases.) I do not believe there is any "backflow" of exhaust at cruise rpms in an overlapped engine. That's the reason for the overlap. Anyone who's ever witnessed venturi effect will recognize that high pressure gases in movement will have significant momentum.
One of the Powerflow testimonials is: "My cruise before was 90 MPH indicated at 2,400 RPM after Power Flow was 110 MPH indicated. ... Robert D. Stager - Kanab, UT"
This is pretty good hype when you think about it. We all know that drag increases as the SQUARE of velocity. It's been said that for every knot of increase above 100 kts it requires a 4 hp increase in power. If that premise is correct, to gain the additional 20 mph Robert Stager claimed it would take 68 additional hp. Powerflow doesn't even make such an outrageous performance claim. (They let a "customer's testimonial" take that liabilty.)
Oh, well. If you like gadgets, I guess this is at least one that will be a visible clue that money was spent. (Looks like a donkey that needs viagra to me.)

Disclaimer: I have no financial interest in any aircraft exhaust sytem other than the one on my airplane.

[N1478D]

. . . (Looks like a donkey that needs viagra to me.)

Disclaimer: I have no financial interest in any aircraft exhaust sytem other than the one on my airplane.

Well, that just begs the question - Do you have any interest in a donkey that does not need viagra?

[GAHorn]

I'm not discussing politics any longer.

[BradW]

Of course, no exhaust systems actually "sucks" exhaust gases out of an engine......"

Just a point of comedy; way back a long time ago when I was working on a multi-engine rating, I was flying a Piper Apache 150. It was equipped with something Piper called 'Augmenters' if I remember correctly. Claim was that it actually produced measureable thrust using venturi affect from the exhaust nozzle!

[mvivion]

George,

There is no Power Flow exhaust for the O-300 engine, so your arguments that it wouldn't help that engine a bit are totally moot. It would appear that perhaps the Power Flow guys agree with you. Or not.

As to constant speed props, and your argument that that doesn't make any difference, I would point out that every engine is run in a test cell after it's built. They are run there with a test club, and not a constant speed test club. They have to make a minimum rpm and hp rating. If they make more than that, its gravy, if they make less than rated power, they go back to remanufacture, as does the whole batch of engines that test mule represents.

An example of engine hp ratings is available in the newest Continentals:

Continental historically rated engine hp via an old certification standard that said an engine could make + or - 5% of rated horsepower. So, a Continental IO 520 engine, rated at 300 hp for takeoff, could legally only make 285 hp in the test cell, and be installed.

Lycoming, on the other hand, has for many years, and with most of its engines, adopted the newer certification standard, which requires that an engine make + 5%, -0. So, an IO-540 Lycoming, rated at 300 hp, actually has to make 300 hp in the test cell. If it doesn't, they have to pull the whole batch of engines that this test sample represents, and remanufacture them. So, how does Lyc deal with this? Their engines are designed to produce 310 hp (or so) from the git go, so that in the event that a weakling gets picked off the line for the test mule, it'll still make rated hp, ie: 300.

The newest Continentals, specifically the IO 550s, are required to meet the same standard that Lyc has been using for some time. Get a pilot in an IO 550 equipped airplane, and they are amazed at the power that engine makes (by the way at 2700 rpm for takeoff, as opposed to 2850 in the 520), but golly, its still a 300 hp engine. Yeah, but the 550 is actually making 310 more than likely, while the 520 is probably making 290 or so.

Exhaust systems CAN improve the power output of an engine. Any shadetree mechanic knows that. It ain't rocket science, even a whole bunch a good ole southern boys have figured that out. Not straight pipes, mind you, but a tuned exhaust. They do make a difference even on an airplane engine. Good grief, Harley will tell you everything you need to know about exhaust systems, fer cryin out loud. LOUD, that is.

Now as to butt ugly, I couldn't agree more, and I wouldn't hang one of those puppies on my airplane for love nor money, either. Or even hp, I reckon.

Mike Vivion

[GAHorn]

George,

There is no Power Flow exhaust for the O-300 engine, so your arguments that it wouldn't help that engine a bit are totally moot. ...
Mike Vivion

The observations and opinions I've presented are not "moot" simply because that muffler company hasn't STC'd their product for a particlular engine, Mike. I believe they are applicable, appropriate, and accurate. Changing the nameplate or dataplate or brand of maker...of an engine....neither validates nor invalidates the principles discussed because ALL engines of ANY mfr are subject to the same laws of physics.
You didn't state your source for claims that TCM and LYC used different certification standards for engines. Any chance you can provide some source- documentation on that statement? I'm sure curious about it. It's always been my understanding the FAA required all mfr's to meet the SAME certification standards. I've witnessed numerous final test cell runs of new engines and all the engines I observed were required to meet the horsepower output specs claimed on the dataplates regardless of mfr.

[zero.one.victor]

Maybe Powerflow is mixing apples & oranges in their claims:
1) Fuel burn & heat is reduced *at cruise power*
2) Horsepower is increased *at full power*.
I can see how both claims could be true given the qualifiers. I know they don't make a powerflow for the 145, but hypothesize that they do for my example- I'm more familiar with the C-145 power settings & speeds.
Say your 76/55-propped 170 could only turn 2600 straight & level before,now with the powerflow it can turn 2700 due to increased efficiency-- same as if you ported & polished, added headers,etc with a souped-up car or motorcycle engine. 2700 versus 2600= more power.
You cruised at 120 mph before turning 2400 rpm, now you get that same 120 mph at the same 2400 rpm but with lower manifold pressure, again due to increased efficiency. 22 inches versus 23 inches= less fuel consumed & heat produced.
I'm not saying that Powerflow can meet those claims, just stating that I think it's possible.
But they're still ugly.......

Eric

[R COLLINS]

When it comes to motorcycles or performance 4 wheelers a muffler can boost power, but only in conjuntion with other modifications. When I soupped up the motor on my Yamaha Raptor (that somebody stole) I first opened up the airbox for more fresh air and then installed a performance muffler. These two mods did nothing for it because it messed up the fuel to air mixture and would bog down on the top end. So a new jet kit was ordered and the animal came alive. This is the same principal for your Continental or Lycoming, if want more power you have to get more fuel and airflow, the muffler can't do this alone. FWIW, Randal

[mvivion]

George,

The Continental and Lycoming factory reps verified the story I offered. Go fly an IO 550 some time in an airplane that was very recently equipped and flown by YOU with a 520, and you'll be a believer.

Everyone I have ever met who's flown a lot of both swears that Lycoming engines of comparable hp rating make more power than Continentals, till recently, with the IO 550.

My point in reference to the O300 wasn't that it couldn't make better power, but simply that they haven't done it, they haven't proven it on a dyno, and therefore your arguement is moot.

They have done it on a Lycoming 360, they have run it on a dyno, etc.

Now, whether the fuel flows are different, I wouldn't know.

I do know that with changes in the mixture control, one can significantly alter the fuel flow for an engine. If the engine's exhaust is more efficient, you SHOULD be able to more aggressively lean an engine, but you'd have to consult John Deaken about that. He's the guru on all that stuff.

The comment is somewhat correct that changing the exhaust won't change the power without changing the intake, but this statement ignores the fact that the intake may ALREADY be optimized, and is simply being held back by the exhaust.

I'm sorry, people, but it is a proven fact on thousands of engines that tuned exhausts can improve horsepower. Now, what that does to fuel flows is something else, but if you're arguing that you can't make more hp with a tuned exhaust, you need to go back to hot rod 101.

And, yes, a Lycoming is just that similar to a Harley Twin Cam, and I done just that a while back.

Mike

[zero.one.victor]

I have to agree with Mike about the exhaust may be the limiting factor-- a chain is only as strong as it's weakest link, and all that.
I thought about it, & want to add a third example/ possibility to my scenario:
you cruised at 2400rpm & 120 mph before, now with the powerflow you cruise at the same 2400 & 120, AND the same manifold pressure, BUT with a reduced throttle opening. Reduced throttle opening = less fuel consumed & less heat produced.
(But the powerflow is *still* ugly )

Eric

[blueldr]

Any airplane requires a certain HP for a given speed, all other things being equal.
There are three things, and three things ONLY, that make HP.:
Displacement--RPM--and BMEP(Brake mean effective pressure).
You MUST change one of these to change the HP.
On an engine with a fixed pitch prop(and a CS prop is a fixed pitch until it gets into the governed range), how do you determine that, at full throttle static, your engine with a tuned exhaust is giving you more power? Your ONLY indication is an increase in RPM.
If you are going faster in flight, you're using more power. If the engine is producing more power, it is using more fuel. There just aint no free lunch!

[28Charlie]

I recently witnessed a friends Lyc O-320 on a Cub go thru several props before they got the increased HP settled down to the legal max rpm at full throttle. The engines new Millenium jugs received porting, polishing and a valve seat angle change from a California speed shop who is legal to perform such matters on aircraft engines. It received a tuned exhaust manufactured in Anchorage that is also legal. My best friend who assembled the engine at his FAA repair station is building and installing a dyno for verification of power and to help insure proper break-in of his future engine rebuilds. The owner of the Cub who has 8000 hours in 160 HP and 180 HP Cubs said it was well worth it. Another O-320 received similar work and was dyno tested in California at the shop doing top end work. They witnessed 190 HP.