Exhaust Popping not from closed throttle??

[AndyRV7]

I was hoping to get some insight into what seems like a somewhat common exhaust popping problem. I read all the threads I could find but they all seem to relate to closing the throttle on final, and that being the cause. The problem I am speaking about occurs on downwind when the CS prop and mixture are pushed full forward, while still under some lower power setting (maybe 1500rpms??). The the exhaust will pop/rumble repeatedly for a good 10 seconds or so before it quiets down. I didn't notice any power issues but the plane was in a slowing configuration at the time.

The engine is an O-375 with a Hatzell prop and dual mags. The idle speed is around 800-850 rpm. I don't know the exhaust.

Thanks! Andy

[Kahuna]

This is exhaust scavenging. Normal. The RPM does not indicate your level of power. The "Popping" can happen at any RPM, but it comes with a closed throttle, or very nearly closed. Most common with an injected motor and cross over exhausts, but is found on most any type.

[AndyRV7]

Originally Posted by Kahuna

This is exhaust scavenging. Normal. The RPM does not indicate your level of power. The "Popping" can happen at any RPM, but it comes with a closed throttle, or very nearly closed. Most common with an injected motor and cross over exhausts, but is found on most any type.

OK, So it sounds like I might be in the same "closed throttle" categoy as everyone else, I just happened to trip that scenario earlier in the pattern?

That's comforting. Thanks!