I have a 91 FX with a Top Flite in Cowl muffler set up and a 15 x 6 APC

My question is with the TF muffler it has 1/2 the volume of the stock muffler, will the engine run much different?

I am using it in the 1/7 TF p-47

Any help would be great!!

Thanks

Most likely the Top Flite muffler was intended for a 60 size engine. The resulting low volume for a 90 size engine will cause the 91FX to have high combustion temperatures.

You will most like noticed this as your plane flies by and the engine seems to be missing like the ignition is being interrupted. You will not be able to tune this miss out of the engine.

Bisson makes a nice Pitts style muffler with adequate volume.

Enjoy,

Jim

I would stay away from that muffler.As Jim says it is designed for the 60.
I tried it and had overheating troubles.

Thanks guys.

I have 5 flites so far and is still breaking in so plenty o power flying at 1/2 throttle.

I will look at changing that out.

Is it due to the smaller volume can vs the larger volume stock muffler?

Correct.

Both Slim Line and Bisson make pitts mufflers for the 61 and the 91 so be sure you use the one for the 91.

Tatone and J'tec make a contraption that can be plumbed up as a in-cowl muffler but they have even less volume than your present muffler.

One of the problems is that the 61 mufflers will bolt right up to a 91 and appear to fit perfectly.

Anymore, no one buys the 61 engines, everyone uses the 91's.

Enjoy,

Jim