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Exhaust upgrade

Hp/Torque.

Hi Steve. I'm sorry but I don't agree with your theory at all. To keep it short, I will say it this way. The Continental O-200 was certified by the factory as 100 HP. That was with 4 inch straight exhaust stacks. When Piper added their exhaust system to the engine it lost around 10HP. If you put the straight stacks back on the engine it will again produce 100 HORSEPOWER at 2750 rpm. Peak torque is far below that rpm. :-? Jerry.
 
Jerry, could you be a little more specific about "peak torqe" What cam do you use in the 0200?

Does the leading edge exhaust feed both "banks " into the oposite sides of the muffler? I kinda get the impression from you that these new exhaust systems aint that great.
 
Jerry,
You are correct in that the manufactures specify a particular hrsp at a specific rpm. That will not change at that rpm. However most engines will not produce rated hrsp (rpm) because of the exhaust system. Any improvement in flow through the exhaust will allow more rpm to regain the lost hrsp. As to the torqe (manifold pressure) the constant speed prop guys have the advantage in the gov. flattens the prop to reach rated rpm, but with a poor flowing exhaust system the available torque is lower and the prop pitch will increase only so much and still maintain rpm. With a good flowing exhaust, the manifold pressure increases allowing a higher pitch to the prop to maintain rated rpm. That is why those guys seem to get better performance increases with the improved system over the fixed pitch.
As for what I did on my Cub, I converted the inside of the muffler to flow like a glass pack muffler used on the hot rods. The current exhaust muffler is highly restrictive in it's design and a straight through flow made a big difference on the Lyc 290D2. It also lost 15 degrees average oil temp. The problem I ran into was the cost of testing equipment the FAA wanted me to have to prove the system. Couldn't afford it then.
Steve
 
Hp / Torque.

Hi Steve. OK, so much for keeping it short. We can look at the engine as a type of air pump. If we limit the escape of exhaust gas during the exhaust stroke, there will be an increase in residual pressure left in the cylinder when the intake valve opens. ( this also retains additional heat in the engine ) Therefore the intake stroke will not be able to create as much vacuum ie; causing a reduction in manifold pressure. Well and fine. The problem that I have is if this is more detrimental to torque or HP. We know that we will arrive at peak torque at a much lower rpm than peak HP. I don?t have the manual handy but let?s say that peak torque is 2100 rpm. We are pumping 2931 cu ft of air through our pump. At peak HP, or 2750 rpm we are pumping 3838 cu ft of air. I submit that any restriction in the airflow on the intake side ( dirty air cleaner ) or the exhaust side ( Piper exhaust system ) is going to be exponently more detrimental at the higher airflow.
When we were testing our four into one exhaust system, there was no (visible on our MP gage ) change in MP. There was however increased rpm ( time ) , increased thrust ( force ) which computed onto a 9 hp ( corrected for ambient conditions ) increase over the stock system.
Cobblemaster. I am not experimental. I have to keep a stock cam. :) Jerry.
 
Hi Arcticace---I must be missing something here. How did you increase cruise with your hp increase. You do have a fixed pitch?? Thanks
Click to expand...
AKPa/18,
I think you are right. Jerry's NOS example would apply to a dyno or a CS prop. A fixed pitch prop will produce the same amount of thrust at a set RPM and airspeed no matter what is turning it (rubber bands :wink: ). My cruise speed figures were at 8000' DA and full throttle. All other factors were the same for both flights. Sorry I should have stated that more clearly.
 
Thrust - RPM

Hi Artic Ace. I do not agree with your statement, ( A fixed pitch prop will produce the same thrust as long as the RPM remains constant). If you add either alcohol or NOX to an engine the thrust (torque) will increase and the RPM can remain constant. It has to do with the modified burning rate (cylinder pressure) on the burning (power stroke) of the cycle. It burns longer and therefore holds higher pressure longer on the power stroke allowing better angle on the crankshaft for a longer time. Which is why (at night) you see more flame coming out the stack of an alky burner than a gasser. :) Jerry.
 
Jerry, I was just wondering if you had the cam that C90s used to have that are no longer available. Somebody told me they had more torqe or power or something like that.
 
Cam.

Hi Cobblemaster. The C-90 cam has more overlap than the O-200 cam and works very well in the O-200. There are several flying in Waynes neck of the woods. Just have to use them Exp. Jerry
 
Hi Jerry,

I see that you are equating thrust and torque. When I used the term "thrust" I was refering to what the propeller delivered to the airframe. If you mean thrust with reference to the piston acting on the crankshaft I will have to scratch my head a bit longer before I really understand.
Perhaps these things we can agree on--Torque times RPM is proportional to power and increased power applied to a fixed pitch propeller will increase it's RPM. Then you will have to agree with my statement. If not please explain. Glen
 
Power/torque/hp.

Hi Articace. We still don't agree yet I'm afraid. Power (HP) is force times distance divided by time. Torque as such dosen't have an entry point. Let's try this. If you take an engine and run it flat out. It will have a peak HP and peak torque. If you reduce the bore and increase the stroke of the engine and re-run it, it will repeat the previous results except the torque rating will be higher. Cyl pressure on the extended crank throw for a longer time. Diesel vs Gas, same thing. Longer burn more torque same horsepower. So you can say that by adding NOX we are (chemically stroking ) the engine by creating a longer burn. If you really push the NOX it will affect everything, including gobs of horsepower. I am talking light loads. I guess I have gotten off subject. Bottom line is almost any free flowing exhaust will perform better than Piper's stock setup. A 4 into one will create a much better performing engine, at only a slight increase in noise. Not having a dyno, and needing comparisons, we tie the tail down and take thrust readings. Correct it for air density and that is what we go by. To do a worthwhile comparison in the air, you need (still) air. Then you have to run both systems (propellers or what ever ) at a constant pressure altitude, constant MP, constant weight, and then correct for temp. In testing 4 propellers it's a lot faster to do it on the ground. When talking to Continental about their correction factors, they just laughed. They simply take the test cell to sea level pressure and temp. They don't have to correct anything. Must be nice. :) Jerry.
 
O320-150

I can't tell for sure from all these posts. Is there an approved tuned exhaust available for the 150hp O320?
 
Exhaust.

Hi Guys. I hate to be the sticky wicket, but this is a equal length exhaust system. I don't know of ANY TUNED exaust systems on the market. Equal length, more free flowing than stock, a great system , Yes. Tuned, NO. Not even exhaust augmenters are tuned. For the cam timing and the RPM of the (non Reno) O-320 the primaries would have to be around 53" long. There is no way that much tube is going to fit under your cowl. If it would fit the power would only be available over a 150-200 RPM band. You don't want that in your Cub. Forget Tuned unless you are into Motocross. Even then they have to run at least 6 gears to stay in the power band. :) Jerry.
 
That's why "tuned" works so well on a snowmachine.....the clutching keeps the engine turning at the RPM YOU want it to.......

I suppose the same is true of a constant speed propeller, eh??

Okay........as I hand the microphone to FLAGOLD the HUSKY pusher, salesman, fanatic, whatever :D :crazyeyes:

Why don't we all just have individual straight pipes sticking right down out the side cowls???

Noise??

Straight pipes don't seem to bother the Harley guys.

'nuff.

Dave.
 
Noise

Hi Dave. I think anyone that has flown a J-2 (50hp) without proper ear protection will probably agree with the noise issue. :crazyeyes: Jerry.
 
After about a 3 year wait, the Lees exhaust is finally installed on my 160 HP Cub and signed off.

The weight difference was an additional 4.5 pounds over the Atlee Dodge exhaust that I was running.

The performance difference is significant. It definitely accelerates faster on the take off run and breaks ground quicker, maybe 35 feet or so with full tanks and no passenger or cargo. The noticeable difference is the climb rate at full throttle and 50 MPH (my normal climb out speed for bush work).

I can't quote you any numbers but the nose of the plane is noticeably higher on climb out at the same speed as before the installation.

This is second only to a Borer prop as far as a bolt on performance item.

It is second to nothing as far as bolt on horse power.
 
David M. Calkins said:
Why don't we all just have individual straight pipes sticking right down out the side cowls???

Noise??

Dave.
Click to expand...

I do... It's loud...
 
Sounds like he made the mistake of assuming he had no increased performance because he had no increase in RPM. Bad assumption.

You will notice in my description of improved performance, I never mention increased RPM.

The big difference is in the torque, just like when you put headers on a car. You wouldn't notice the difference unless you put the plane in a position to use the additional torque.

Now he has the additional RPM but has probably drastically reduced the additional torque. When you are slinging a flat Borer prop at extremely high tip speeds anyway, the last thing you need is more RPM.

He could have saved a lot of money and got about the same thing by gutting out a stock muffler.
 
I didn't mean to imply that I did not see any RPM difference, just that, that is not a total indication of increased HP. There was a significant increase in RPM but I haven't quite figured out how much yet. It was enough to screw up my tach.

On the first static run up I saw the tach go to 2650 and it normally went to 2400 with a cold engine (first flight of the day). Since then, the tach reads 100 RPM high. Incidentally (unrelated), I have noticed a consistent 50 RPM difference when running up a hot engine (after a flight long enough to get all the metal parts up to normal operating temperatures). Guess I will my next investment will be a new tach.

Anyway, after sifting through all the fuzzy data, I would say I gained 50 to 100 RPM at full throttle and breaks locked, engine cold (first flight of the day). By comparison, I gained 50 RPM when I upgraded from 150 HP to 160 HP.
 
On the Dodge mufflers, the baffle isn't even attached, so it does nothing structurally.

Some people say gutted mufflers reduce the carburetor and cabin heat availability. There is also a good chance that it would adversely affect the power curve of the engine and the sound is different enough to draw attention to it. I don't know any A.I. that would sign off a gutted muffler.
 
here tis

cubexhaust.JPG
 
EXHAUST AND OTHER TALK

THIS TALK GROUP IS SO INTERESTING AND SMART! i HAVE THE BEST TIME JUST READING ALL THE COMMENTS AND ZINGERS. I WOULD LIKE TO ADD ONE. I BELIEVE THE HOME BUILDERS( AND THE MODIFIERS) HAVE BECOME THE HEART AND SOUL OF AVIATION AND IT'S A GOOD THING.HISTORY(C-140 C-170 C-172 HANG GLIDER CHALLENGER CHAMP TAILWIND PA-28-151 AND NOW SPORTSMAN 2+2
THANKS JIM
 
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