Cherokee exhaust repair?

On Aug 23, 7:51 pm, wrote:
150flivver wrote:

: On Aug 22, 10:03 pm, wrote:
: ... Besides, I'm pretty sure that if we changed exhaust, we'd lose our
: autogas STC.
:
: -Cory
: ************************************************** ***********************
: * Cory Papenfuss, Ph.D., PPSEL-IA *
: * Electrical Engineering *
: * Virginia Polytechnic Institute and State University *
: ************************************************** ***********************

: I don't see how installing a Powerflow exhaust will invalidate an
: autofuel STC.

The autofuel STC is very complicated for -160 and -180 hp PA-28's. Unlike for 150 hp -140's or -150's, the Petersen
PA-28 high-compression STC is more than just a sticker for the fuel filler on the tank. Basically, the ones that are even
applicable must have the dual exhausts. If they have the aluminum, flip-up cowling they are not applicable due to vapor-lock
issues with the muffler near the firewall. Even the ones applicable require replacement of the electric fuel pump with dual
(redundant) electric fuel pumps and some re-plumbing.

Bottom line is that with a different exhaust, the autofuel STC would most likely have to be re-approved, which would
amount to doing a whole 'nother autofuel STC certification.

-Cory

--

************************************************** ***********************
* Cory Papenfuss, Ph.D., PPSEL-IA *
* Electrical Engineering *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

The autofuel STCs I've seen are for airframe and engines with no
reference to the type of exhaust system. In general, higher
compression engines don't have an STC for autofuel because of the
increased chance of detonation. Still don't see how a different
exhaust would increase the likelihood for detonation in a low
compression engine.