Bolt-On Exhaust Systems Tout Better Power, Economy
by ANN Correspondent Franklin Porath
It sounds like something from the back pages of popular
newsstand magazines... like "run your car on water", or "magnetize
your fuel line", but surprise! There actually are real systems that
deliver both higher power (read, better rate-of-climb) and better
fuel economy to boot. And its devotees are almost religious in
their fervor to spread the word.
Powerflow Systems, Inc. makes bolt-on exhaust systems for some
10 popular piston aircraft. Their performance claims seem too good
to be true, but the reality is that their customers are very happy.
Morten Boyd says his Mooney M20F goes faster and, at the same time,
burns less fuel. He gains an additional 4 to 6 knots but uses at
least 1/2 gallon less an hour. He also says it runs an average of
10 degrees cooler cylinder head temperature during climb. He gloats
that also faster than his friends with M20E models and "it sounds
Perhaps by virtue of its location in Daytona Beach, FL,
Powerflow Systems took the NASCAR route... tuning and scavenging
bolt-on exhaust systems for General Aviation and experimental
aircraft. They are able to cut, bend, and weld some 14 feet of
tubing to squeeze under the cowl, which adds, on average, about 10%
more usable horsepower.
The General manager, Darren Tilman explains, "Because of
scavenging, the engine doesn't have to make the power. On a
constant speed propeller it doesn't take as much manifold pressure
to go the same airspeed you're used to." The exhaust is tuned just
like a race car, using the resonance of the tube length and the low
pressure power impulses. (The company mantra is "Suck, squeeze,
bang, blow, make it go with Powerflow...")
How much fuel can you save? The figure seems to be a real 15%.
One customer from Germany brought his computer graphs and print
outs to Oshkosh to show Tilman that for the same speed he had
improved fuel flow by 5 litres, or 1.5 gallons per hour.
What is the downside? Apparently, not much. Some aircraft, such
as Piper or Grumman may require minor cowl mods. Powerflow Systems
also strongly recommends that the propeller be dynamically
balanced. If done within the first 25 hours they will double the
year warranty. Powerflow is so confident in its product that they
offer a 60 day money-back guarantee for skeptics.
Although they have 135 dealers, and sell direct, their marketing
has been very much by word-off mouth when the experience gets
circulated through type-clubs. This often creates demand for
additional products. As an example, after the Cessna Cardinal Fixed
Gear exhaust system was released they had so many requests for the
Cardinal retractable that they engineered and certified a new
system for that model. In the nine years since their first system
for the Cessna 172, they have delivered 3,300 units.
So, it seems that for about $200 per horsepower, you can get
something for almost nothing. Perhaps there is a Santa Claus after