jim mosur wrote:

Hi Paul

I finally got hold of a sound meter to check the readings on my exhaust. I
removed my new gun type muffler that you saw at Osh. and replaced it with my
old system that basically consisted of 2, 2" dia. pipes dumping into a 5"
sch. 10 SS pipe x 15" long, This 5" pipe contained a internal 2 " dia pipe
perporated with !/2" holes feeding a single 2" dia. exhaust pipe just
pocking out bottom of cowl.
.
Ground Run.

OAT  25F
RPM 5000
POS.   30' to the rear of A/C 107 DB
            30' to the side of A/C 112 DB
            30' to the front of A/C 120 DB   (Prop .?)
Cockpit                                    113 DB

Flying.

Takeoff & climb    4980 RPM     105 D/B
                               5400 RPM     105 D/B
                               5300 RPM     108 D/B
                               4800 RPM     111 D/B  ( strange, must be
resonance)

I have not done readings from the ground with A/C overhead yet, maybe I will
get this done this week and then take these readings over again with my gun
type system.

Jim Mosur
C-GAPF
RV6 13B

Thanks for the data Jim. I will dig up those DB readings we took at Tracy's last year
for comparison. Here is a picture of Jim's muffler at OSH for background info.

Paul Lamar
 
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