Steve Foley wrote:
: For the PA28 with -160 or -180, there is a lot to it, and exhaust
: was an important reason why
: some are applicable and some are not.
:
: -Cory

: What I found interesting is that when I overhauled my engine, I upgraded
: from a 150HP to 160HP. It involved different pistons and wrist pins.
: Everything else stayed the same, including fuel burn.

: This upgrade invalidated my autogas STC. I called Petersen, and they said I
: needed the one with the fuel pump. I think that's a little strange, as the
: fuel system did not change.

Don't even get me going on that. It's a bull**** rule that basically stems from the fact the
Piper's PA-28 fuel system was marginal to begin with. Before we bought the STC, I talked with Petersen
directly about octane, why the STC was the way it was, etc. He said that the problem was "inadequate
fuel flow," with the stock Piper pump and it wouldn't pass what he called the "ditch test." Full-power,
with the plane in a very nose-high attitude (i.e. tail in a ditch) and the fuel pump didn't maintain
enough pressure. Also, on his test plane, the right tank flowed a little better than the left, so the
autofuel STC requires takeoff and landing on the right tank.

It was exactly my point that swapping pistons to make a -150 a -160 doesn't change the fuel flow
at all... yet by some magic, the pump is no longer adequate. It's bull****, but unfortunately that's
the way the legality of the system requires.

-Cory

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