Hello,

I have a TF P-40 with an inverted O.S. 91 engine and I need some help selecting a muffler. Are there any in-cowl mufflers made for this engine with respect to it being mounted inverted? I searched Tower and I found several from Bisson, Slimline, Pitts, etc., but I can't determine if any of these would be appropriate for this plane. It looks like the ones on Tower would send the exhaust out the top of the cowl. I tried the Bisson muffler made for the .91 when mounted inverted, but it wouldn't fit.

Any recommendations or maybe some links to some mufflers that may suffice would be appreciated.



Thanks - Randy

check the Top flight web page for there P40 ,l they make a muffler with header

I used J-tec mufflers on my OS .91.
It may be best to call to get exactly what you want.

http://www.jtecrc.com/incowlmufflers60-129.htm

I have a hanger 9 p-40 with an inverted .61 fx with a slimline inverted muffler. It has 2 exhaust pipes that points straight down. It works fine but it did not fit completely in the cowl but close. I am sure they make that same muffler for the .91. Good luck, Erik

look Ma , no exits hole , great pressure and very easy to do ,
simply call Macs products , tell them your engine , he will sell you a 90 degree bend , flex pipe ect and you simply screw it on , its that simple ,

Randy if your going with a 2st 91 then your pipe selection is pretty limited to the Pits or slimline mufflers with a 4str theres alot more flexability as LDM pointed out.
there is a few threads on the TF P-40 the one by Richard Lee has some good Photos of his plane as well as some video.
here's what I did for my Hangar-9 P-40 the only thing you see is the little rubber deflector out the back,I am using a OS91 surpass.

yep that is what mine looks like with the 4 strokes , the nice thing is that you can still pressurize your tank from your standard muffler , the slimline versions on the two stroked require you to drill and tap the pressure valve , no big deal just more work

I'm assuming he has a 2-stroke, not 4-stroke. I'm sure J-tec, slimline or bisson will make a muffler that will work. The cowl is very narrow and you may have to do some carving out to make it work. It would bolt on the side of the motor with two tubes pointed down out of the side of the cowl. The TF in-cowl won't work with a .91 size. Good luck.

I know that Tower sells the muffler made
1)Just for the P40
2)for the OS Max ,
3)its on there website