Jim Duda

During the past several Central Texas Club 40 races the TT muffler (#9209) for the TT Pro 40 (#9140) has appeared with a CONE style baffle as opposed to the familiar Wafer/Cyclonic type - so, does one have an advantage over the other? We compared them using a popular Club 40 prop (APC 10.5 X 4.5) and a popular AMA424 prop (APC 9 X 6). Not to worry: the performance is so close as to be a non-issue.

Date = 5/5/2010
Location: 30 Deg, 42', 57.07"
-97 Deg, 37' 40.39"
Altitude: 802 Feet ASL
Temp = 83F
Barometric Pressure = 29.92 in. HG
Humidity = 31%
Time = 11:30 a.m. CDT

Plug OS #8
Shim = .0165 (Stock)
Fuel = Ritch's Brew 15% nitro, 18% lube (ALL synthetic)
Tank = Non-Bubbless (Stock SRM II)

WEIGHT Muffler - Wafer/Cyclonic Baffle - 3.84 oz, 108.9 grams
Cone Baffle - 3.96 oz, 112.3 grams

RESULTS -

APC Sport 9 X 6 Wafer/Cyclonic Baffle = 16,891 RPM
9 X 6 Cone Baffle = 16,853 RPM

APC Sport 10.5 X 4.5 Wafer/Cyclonic Baffle = 15,380 RPM
10.5 X 4.5 Cone Baffle = 15,384 RPM

We used 3 different tachs - all 3 were very close but we used the data from the TNC tach.

A special THANK YOU to Bob Petrinec, Terry Large, and Dr. Barry Reade for lending the cone baffle style muffler for these tests!

dasintex

My Feedback: (10)

Jim; Thanks for doing these tests and posting the results, not a big difference, it would all come down to piloting skills, in which case the extra few rpm's may help, but overall pretty close.

dnrocc

My Feedback: (3)

Jim,

A big thanks to you and the GAMA guys for taking the time to perform these tests. Your attention to detail and recording of conditions make it a very valid test and I agree there is no significant difference. Learning to get around the pylons is the secret.

On another note, if you guys every feel like setting up your labratory and killing some more time, I would be curous about the difference between baffle and no baffle. Lots of different opinions on this subject with no documented facts to back it up. It won't change anything based on the rules, but I as well as others would be real curious about the true difference.

Again, thanks for the thorough test and well documented results.

Don

Jim Duda

I am VERY familiar with the Baffle - No Baffle controversy - since the boys were DQ'd at the Georgetown race for running without the baffle, I did some tests the following day. I took 3 bone-stock #9209 mufflers (with the wafer/cyclonic baffle) and ran them against the one without the baffle. Prop was an APC 10X5 on 15% race fuel. The results were surprising:

The NO BAFFLE muffler was 800 RPM slower than the best of the 3;
The NO BAFFLE muffler was 400 RPM slower than the next best;
The NO BAFFLE muffler was 250 RPM slower than the worst of the 3;

We learned our lesson! I also pinched the nose to match the current SR MII and that was the plane he flew in Waco. I guess we can thank the "legal" muffler for his 1:22 fast time in rather breezy conditions...(wink)

Bottom line: If you want to go slower, remove the baffle. My guess is the increased muffler pressure "tunes" the exhaust for increased performance.

Ken Erickson

A definite big "Thank you" for the effort and the reports.

Seems like, even with all the interest around the country, Texas is still the epicenter of Club 40 racing.

Now if I can just get started in central Indiana.

Ken Erickson

THRL-CKER

We can bost that we now have 9 club members flying SkyRaiders here in Waco, some have not attended a race yet, but they will.

gefisher

My Feedback: (2)

Hey Ken,
I'm headed to Kokomo Indiana on the 20th for my grandsons birthday, wish I had time to come down and fly with ya!

gary

scattermaster

Jim,
I know this is an old thread but I'm a newbie and just getting my research done. I was the new guy in Georgetown last week. I had a blast. (2nd B main !)
Anyway,
Thanks for posting this. I had heard from mmmm, (nameless is good!) that the old style mufflers ran faster and that I should open up the holes in my new style muffler.
Now, I won't bother.
Jim Plake