0-200 continental max rpm low, top speed low

[dothetime]

I am flying a AMD Zodiac 601XLB powered by a Continental 0-200, Sensinich wood prop 68 inch diameter, 57 inch pitch.
Plane has 400 hours TT, I bought it about 6 month ago and I believe I was seeing higher max rpms, 2700, and higher max speed, about 128 MPH, engine spec is 2750 redline.
What I am seeing now is 2500 max rpm leaned out, at 7000 feet, and 118 mph
Static is 2300, take off 2340.
I have checked the throttle throw, carb heat, replaced the plugs, checked the timing, cleaned the fuel screen, air filter.
Next check will be a compression check.
I don't think the prop could have warped, the plane is tied down outside, but the prop has a cover. may have to find a way to check the prop specs.
The plane flies fine, no vibrations, fuel flow looks normal and cht and egt are all normal on the dynon D180, fuel is 100 LL
anyone experience something similar that could suggest a solution? It seems that something has changed, prior owner reports better numbers.
Dave

[rwanttaja]

Sounds like you're doing the right things. As a non-expert, I would start to examine the air induction system...you cleaned the air filter, but check and make sure there isn't any other kind of restriction. Ensure the carb heat is turning OFF.

You mention that you noticed it's different vs. six months ago. Did you buy it at the time of the cold weather? In a lot of parts of the country, the change in the density altitude over the past six months has been significant!

The Fly Baby engine Guru, Harry Fenton, would be a good guy to ask. Contact him via the Fly Baby Engine Page (http://www.bowersflybaby.com/tech/fenton.htm).

Ron Wanttaja

[dothetime]

Sounds like you're doing the right things. As a non-expert, I would start to examine the air induction system...you cleaned the air filter, but check and make sure there isn't any other kind of restriction. Ensure the carb heat is turning OFF.

You mention that you noticed it's different vs. six months ago. Did you buy it at the time of the cold weather? In a lot of parts of the country, the change in the density altitude over the past six months has been significant!

The Fly Baby engine Guru, Harry Fenton, would be a good guy to ask. Contact him via the Fly Baby Engine Page (http://www.bowersflybaby.com/tech/fenton.htm).

Ron Wanttaja
Thanks for your input Ron,
carb heat is working normally, I am in southern florida so density altitude not a problem
Dave

[dothetime]

Checked compressions all ok
will be looking at the prop next

[skyfixer8]

Good call on the induction system Ron. Saw something similar years ago on a Cessna 150. Decal on a newly installed starter came off and got sucked into the carb heat duct and partially blocked the venturri. Tool a while to find that one.

Bill Landry

[cub builder]

I believe I was seeing higher max rpms, 2700, and higher max speed, about 128 MPH, engine spec is 2750 redline.
What I am seeing now is 2500 max rpm leaned out, at 7000 feet, and 118 mph
Static is 2300, take off 2340.
Dave

Do you have a 4 point EGT on this engine? If so, has there been any significant change to what you saw previously with your EGTs? I would looks closely for induction leaks. Sometimes the boots simply get loose or crack. Also the intake tubes have been known to crack. Give your intake system, air filter, air box, carb controls and carb throat, intake tubes and intake boots up to the cylinders a good exam both inside and out for cracks, leaks, or obstructions. Also a check of mag timing may be in order.

You mention the loss of RPM and indicated air speed at 7000'. Are you comparing your previous numbers from a colder season and lower altitude? The change in air density (Density Altitude) from winter to summer and sea level to 7000' is significant. So make sure you are comparing apples to apples. My O-200 powered KR loses roughly 200 RPM and 25 mph IAS between sea level and 9500'.

-Cub Builder

[dothetime]

Hi cub builder
thanks for the input.
i have done all of the above, the plane is in Florida, so density altitude is pretty much the same all year.
i have a 4 cylinder egt and cht all normal.
i checked the tightness of the boot clamps, I can look more closely for cracks, but I am having no idle issues or lean issues
which should show up with intake leaks.
3000 feet, 5000 feet, 7000 feet, I can't seem to get more than 2500 rpm, take off 2340 rpm
max speed 100-105 mph, previously was getting 125-128 mph, and closer to 2750 rpm
other owners of 601xlb think I have too much prop pitch at 57 inches, but the aircraft was doing better than what I am seeing, and that's the prop that came with the plane from the manufacturer.
i even verified the tach is right on.
i would like to check the prop pitch and see if it changed by warping.
dave

[Eric Brown]

Check your exhaust system. A partial blockage of one or more cylinders will cause a power loss.

[67jwbruce]

valve throw (possible worn cam?).

[martymayes]

I am flying a AMD Zodiac 601XLB powered by a Continental 0-200, Sensinich wood prop 68 inch diameter, 57 inch pitch.
Plane has 400 hours TT, I bought it about 6 month ago and I believe I was seeing higher max rpms, 2700, and higher max speed, about 128 MPH, engine spec is 2750 redline.
What I am seeing now is 2500 max rpm leaned out, at 7000 feet, and 118 mph
Static is 2300, take off 2340.


I'm not sure what the problem is. Those numbers look normal. If you fly at sea level it's going to have more power.