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 great."

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 all.

FMI: www.powerflowsystems.com