ORIGINAL: hllywdb
I have to agree with you on the AX 40 for the small, fast planes. Light weight and high rpm. I use it where I used to use a 32 or 28 and really haul.
Do you know which tuned pipe header fits it? I have 3 for my 25 NVs that work great (got them off fleabay from an ex-racer) I know the 40 responds like the OS with the increased exhaust volume. I played around by making a 1'' extension to fit between the front and rear of the stock muffler using a longer bolt and picked up another 1200 rpm with the small props, so thinking it would do well with a tuned pipe too.
hllywdb, I am actually in that state right now. I put the AX-40 in a Hangar 9 Sundowner 36 in a 45 degrees off vertical. The tilt-down stock muffler still rubs agains the cowl cheeks. So, I would have to fabricate a spacer about 1/4 inch thick. I found a muffler at the Toledo Show last year and I tried to install it. The seller claimed it fits an OS 40 FSR, but is only slightly wider bolt spacing than the NV 40. But because I was trying to torque the muffler bolt at an angle, I ended up stripping the threads on the muffler mounting hole. I plan on drilling and tapping it to a 6-32 soon. I then will shop around for a tuned muffler. I don't think I want to do a tuned pipe, I am not such a dedicated speed flier. I will check with Jett Engineering for their tuned muffler. If not, I will get a MAC's one-piece muffler with an adapter.
If anyone has any other possible muffler solutions, it help me a lot.