Cold wx starting quirks

zatatime wrote:


Question: What's with the extra long exhaust pipe on your bird?


It looks like a PowerFlow tuned exhaust. See :
http://www.powerflowsystems.com/

John Galban=====N4BQ (PA28-180)

zatatime wrote:

Sure, here are a couple of photos of it:
http://www.burningserver.net/rosinsk...ex.html#HEATER

Question: What's with the extra long exhaust pipe on your bird?

It's a "Powerflow exhaust" (tuned exhaust) I had put in about 4 years
ago. The big part of the extended tube shown in the picture is actually
the muffler.

I forget the company's name, but I think they're out of Florida. They
advertise up to 23 extra horsepower. I'd say I'm getting at least 10 on
top of the 160 sea level horses the engine's rated at. Very noticeable,
and welcome when flying in the local mountains, some of which exceed
14,000 feet.

Not a cheap add-on at almost $3K, but worth it IMHO. It's a real PIA to
take apart at annual time though.

Jim Rosinski

[use caution for thread drift]

Jim Rosinski wrote:

I forget the company's name, but I think they're out of Florida. They
advertise up to 23 extra horsepower. I'd say I'm getting at least 10 on
top of the 160 sea level horses the engine's rated at. Very noticeable,
and welcome when flying in the local mountains, some of which exceed
14,000 feet.

Don't konw, but I wonder. Doesn't that 160 hp rating come from the engine (not
airframe) manufacturer and doesn't it represent the maximum hp output in ideal
conditions?

Then, after the engine is rated by the engine manufacturer, the airframe
manufacturer decides what kind of exhaust system, etc it will have, and the
choice will determine how close the engine-in-the-airframe will come to
producing the theoretical power advertised by the engine manufacturer?

So would it be more accurate to say that with the modified exhaust, you might be
closer to actually producing the advertised 160 hp, rather than saying the power
is greater than 160 hp?

Notice each sentence above ends with a '?'. I'm not saying anyone is wrong, just
wondering how this horsepower rating game works, given that both the engine mfr
and the airframe mfr are making design decisions that probably affect the actual
power produced.

Dave

Dave Butler wrote:

I'd say I'm getting at least 10 on
top of the 160 sea level horses the engine's rated at.

So would it be more accurate to say that with the modified exhaust,
you might be closer to actually producing the advertised 160 hp,
rather than saying the power is greater than 160 hp?

Your description is probably more accurate than mine was. Aviation
Consumer did an excellent review of the Powerflow system in their May,
1999 edition. Here's a snippet from their analysis:

"When aircraft engines are certified by the factory to their claimed
horsepower, the tests are normally done in a dyno chamber with what's
called a 'neutral' exhaust. These are essentially straight pipes that
extend the exhaust manifold only far enough to direct heat away from
the engine during testing. Neutral exhaust systems aren't perfect, from
a volumetric efficiency standpoint, but for certification purposes, no
one cares."

My interpretation of this is that it might actually be possible to get
more than rated horsepower. Specifically, if the "tuned" system does a
better job than straight pipes. How likely is this? Dunno.

Jim Rosinski

It's an STC, so it's FAA approved. Whatever the power.

Karl

"Dave Butler" wrote in message
news:1104329653.980269@sj-nntpcache-3...
[use caution for thread drift]

Jim Rosinski wrote:

I forget the company's name, but I think they're out of Florida. They
advertise up to 23 extra horsepower. I'd say I'm getting at least 10 on
top of the 160 sea level horses the engine's rated at. Very noticeable,
and welcome when flying in the local mountains, some of which exceed
14,000 feet.

Don't konw, but I wonder. Doesn't that 160 hp rating come from the engine
(not airframe) manufacturer and doesn't it represent the maximum hp output
in ideal conditions?

Then, after the engine is rated by the engine manufacturer, the airframe
manufacturer decides what kind of exhaust system, etc it will have, and
the choice will determine how close the engine-in-the-airframe will come
to producing the theoretical power advertised by the engine manufacturer?

So would it be more accurate to say that with the modified exhaust, you
might be closer to actually producing the advertised 160 hp, rather than
saying the power is greater than 160 hp?

Notice each sentence above ends with a '?'. I'm not saying anyone is
wrong, just wondering how this horsepower rating game works, given that
both the engine mfr and the airframe mfr are making design decisions that
probably affect the actual power produced.

Dave

Jim Rosinski wrote:

My interpretation of this is that it might actually be possible to
get
more than rated horsepower. Specifically, if the "tuned" system does
a
better job than straight pipes. How likely is this? Dunno.


Not very likely. The tuned system is making up for huge
inefficiencies in the factory exhaust system. The straight stacks used
for testing are pretty close to ideal. The tuned pipes are designed
to reduce backpressure by having the exhaust pulse from one cylinder
lower the pipe pressure as the next cylinder opens it's exhaust valve.
With short stacks, backpressure is not much of a factor.

In order for a Powerflow to show gains in horsepower, you need to
start with a restrictive exhaust system. For example, they showed
excellent progress with the exhaust system that was fitted to the early
Cherokees. When they were developing a system for the later model
Cherokee 180s, they found that the factory system was pretty good
already and that they couldn't really improve performance significantly
by installing their tuned system.

John Galban=====N4BQ (PA28-180)