I have flown my J over 900 hrs the last 100 with the Powerflow.
The first takeoff with the Powerflow felt totally different, I actually said wow out loud, climb has improved.
I always climb at a cruise climb of 600 ft. A minute, on a 80 deg. Day I would see 115 knts, although not a perfect test
After the exhaust back to back tests showed an increase to 121 with the 600 ft. A min climb.
Cruise is about the same unless everything is fire walled, where my J was a bit of a dog at 158, now 163.
This all is affected by weight and temp, lean of peak at 9 to 10 thou I see 150 to 153 at 8.2, roughly .3 gallons saving.
Negatives: louder, more maintenance
Jed-Aire maintains my aircraft up here in cold Minnesota, Jason has 4 other customers with Powerflows. In conversations with them they have about the same results.
Disclaimer, after spending 4 grand on the exhaust I may be jaded.
However a friend has an 84 J with factory rebuild ( 100 hrs. On it ) we flew my J to OSH, in cruise we were B essing and he said it must be the exhaust, I said what you talking about, this thing climbs better than mine and really sets you back in the seat on takeoff. My engine has over 1800 hrs. On it
I have found after all these hours that lycoming has intake gaskets prone to leaking at the head, so if your egts seem different over time
Change them, I replace mine roughly every 100 hrs. Which seems to bring everything back in line. The gaskets are normally brittle ever time I change them. If you haven't done this for a while you may find you have lost a bit of power.
Ok, long winded post is over, I guess I wouldn't give my exhaust up, or my J.
Now all I need is polished and ported cylinders--yep, I'm addicted to speed!
