Power Flow Exhaust: Owners Say Thumbs UP - Aviation Consumer (2022)

In the ongoing search for more speed and performance, aircraft designers have only two variables to manipulate: aerodynamics and power. But either option can cost real money. Hot-rodders and motorcyclists, among others, long have known the benefits of less-restrictive exhaust systems as a means of tweaking the engine equation.

Power Flow Systems figured that out a decade ago and applied it to its series of tuned exhausts for various airframes with small-displacement Lycoming (O-320 and O-360) engines. The company says one of its exhausts often can increase an airplanes performance for not too many dollars. And if you fly a lot, it might pay for itself through fuel savings. Are the results worth the expense? Are Power Flows customers seeing real-world improvements? To find out, we surveyed Power Flow customers for their real world results compared to our own data, collected when Power Flow first came on the market.

Airplane manufacturers rarely spend time optimizing the engine compartment. Instead, they just make sure everything fits, which can result in some Byzantine exhaust pipe routing. That means exhaust gases from each cylinder travel unequal distances before being dumped overboard. Power Flow likens the resulting increased back pressure in the system to a kinked garden hose. Improve the engines ability to breathe, according to theory, and youll improve performance without altering anything else. This something-for-nothing phenomenon only works if the engine and its exhaust are not working at top efficiency: Some combinations of carburetors/engines/airframes may not see any benefits, according to the company.

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Power Flow says its header pipes from each cylinder are of equal length, so when the negative pressure following one cylinders power stroke occurs, the lower pressure helps extract the exhaust from the next cylinder. Since the length of time each exhaust pulse needs to travel from the cylinder to the collector varies with engine speed, the company has optimized its systems for 2450 RPM. At that speed, Power Flow says more of the exhaust is scavenged from the cylinder and the incoming fuel/air charges volume is greater. Early Power Flow designs were fitted with a rather ungainly pipe assembly, extending below the cowling and supported by a rod. This rod usually extends through a hole cut in the cowling during installation. Later designs use a so-called short stack, which is about the length of a stock system, eliminating the support rod. Both the original design and the optional short stack are available in either stainless steel or ceramic-coated stainless. For some applications, only the short stack is available.

For a Grumman Traveler, Cheetah or Tiger, Power Flow says youll immediately notice a 30 to 130 RPM increase at full throttle, plus significant climb rate improvement. Similar claims exist for other engine/airframe combinations for which Power Flow offers an exhaust. (See the table at left.)

Since theres no free lunch, especially with airplanes and 100LL, more power means higher fuel burn than in an unmodified airplane. Power Flows fuel-savings claim comes from being able to cruise at the same speed as before the conversion, using less throttle and therefore less power. Many owners report their fixed-pitch propellers tended to turn too fast on takeoff or in cruise after the conversion and have re-pitched the prop, returning RPM to POH values while still seeing increased climb and cruise performance.

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Using the Grumman Traveler, Cheetah or Tiger as an example and choosing to cruise at the same airspeed as before, the company says youll save up to 2.2 gallons per hour. If so, and at $4 a gallon for 100LL, the math is easy. Thats about a $10/hour savings in fuel. Or you can go faster and get to your destination sooner.

System prices range from $2695 in polished stainless for an O-320- or O-360-powered Glastar/Sportsman 2+2 to $5600 for a ceramic-coated system to fit a Cessna Cardinal RG. Most installations are straightforward, although some Mooneys may require additional parts and Diamonds DA40 may require a prop change and/or a different engine baffling system. The companys products include an unconditional 60-day (from date of installation) money-back guarantee on the purchase price-you eat the shipping.

Installation should take about four or five hours at whatever rate your shop charges. Plan on that extra expense when factoring how long, if ever, youll recoup the acquisition and installation costs through reduced fuel consumption.

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If readers who responded to our feedback request are any indication, the majority of Power Flow customers are happy with their purchase. Several sent in detailed before and after results, including static RPM readings, fuel flow, time-to-climb and full-throttle cruise speeds. A few said they experienced no performance gains; others only noticed improved climb rates. Those who chose to return their system to Power Flow for a refund seemed happy with the companys response.

A typical report came from Greg Burnett of Dodge Center, Minnesota. “I bought one of the first Power Flow exhausts for my 1974 Cessna 172M with a Lycoming O-320-E2D. The installation was a simple remove/replace and the added strut was easy to install. I found that my static RPM had gone from the low end of the allowable range to the high end, an increase of 150 RPM. In flight, I gained about 150 FPM in climb and in level flight below 3000 MSL, I could exceed redline RPM. I also found I could now run lean of peak, which resulted in lower fuel burns and CHTs and very efficient flight.”

Stan Fetter is a fleet operator based in the Washington, D.C., area. His three O-320-H2AD-equipped 172N Skyhawks saw heavy use flying traffic reporters before being converted to Thielert diesels. He reports 150 FPM or so improvement in climb rate, with fuel savings a little over one GPH, depending on the airplane and pilot, “which added up pretty quickly when we were flying 325 hours or so per month across all three airplanes.”

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Fetters Power Flow systems held up well: “There was a bracket that cracked periodically; over the life of one system we probably had to weld it a couple of times and eventually replaced it. I only actually wore one of them out, and that was a first-generation system that went well over 7000 hours. In my case, they paid for themselves between longevity and reduced fuel burn,” Fetter said.

Morton Boyd installed a Power Flow on his 1970 Mooney M20F, with an IO-360. “Generally, I would summarize as follows: 15 percent faster climb, 4 to 6 knots faster cruise, .5 GPH lower fuel burn.” See the table above for Boyds detailed before-and-after numbers.

But not all Power Flow customers saw Boyds results. “After a few hours of us, one of the exhaust pipes separated from the cylinder head flange, in flight, causing a dangerous condition and resulting in an immediate precautionary landing,” wrote another Mooney M20F owner, Alex Melton. “In the months following, several different pipes were sent from Power Flow and installed to try and alleviate the cracking at this flange. The results were always the same: After about three to five hours, the pipe would crack near the flange. Melton got a refund and installed another aftermarket exhaust, which proved trouble-free.

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If we had an airplane for which one was available-and we either needed a new exhaust, flew the airplane a lot or wanted some extra performance-wed definitely consider a Power Flow exhaust. For around $4000, or maybe 10 percent of the airplanes value, most customers will see at least a small boost in performance, whether measured in improved climb rate, higher top speeds and/or reduced fuel consumption at the same cruise speed as before. Theres very little available on the aftermarket these days providing the same return rate on investment.

But ensuring the investment pays off requires us to, you know, actually fly the airplane. A lot. If most of your flying is in search of the $100 hamburger, whether you get there two minutes early or two minutes late isnt worth the acquisition and installation expense, in our view. Wed want such a purchase to break even for us after two or three years. Using Power Flows fuel-savings numbers (which might be a bit high for the real world), if we figure $4000 for the parts, plus another $500 for installation, wed need to fly about 450 hours at $4 a gallon before we broke even. At 150 hours a year and 2.2 GPH savings, it would take us about three years to get there.

Of course, if you just want the fastest Skyhawk or Cherokee out there or want a better designed exhaust, Power Flow is worth a look. Although owners report good results, even Power Flow says not all airplanes will benefit from one of its exhausts. But the companys money-back guarantee almost makes it a no-brainer to give it a try.

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What does a power flow exhaust do? ›

Depending on the make and model of your vehicle, a powerflow exhaust will increase the performance of the vehicle through the more efficient flow of exhaust gases through the system.

What is a flow through exhaust? ›

The exhaust gas traveling at a slower speed than the sound energy also passes through the entry cone

What is aircraft exhaust systems made of? ›

Aircraft exhaust systems are predominately constructed of stainless steel or, in some cases, an alloy called Inconel. Welding these components to make repairs rarely is effective or has a short useful life thanks to contamination from all the exhaust gases passing through.

What is aircraft muffler? ›

muffler, also called silencer, device through which the exhaust gases from an internal-combustion engine are passed to attenuate (reduce) the airborne noise of the engine.

Does a freeflow exhaust increase power? ›

In a free-flow exhaust system, the mufflers are removed or converted to “straight-through” units. These offer less resistance to the gasses passing through the exhaust pipe. In theory, the lower resistance will improve engine performance. This performance improvement will especially be noticeable at high engine speeds.

Does a powerflow exhaust use more fuel? ›

Increased Fuel Efficiency

With a POWERFLOW performance system increased power and up to 10% fuel efficiency can be experienced.

Does free flow exhaust damage engine? ›

No, it just means it has a small displacement. A lawnmower has a much lower exhaust flow rate than a car, but lawnmower engines are generally MUCH dirtier than car engines are.

What is free flow exhaust system? ›

A free flow exhaust, simply put, is an exhaust that decreases the amount of back pressure in the exhaust system and possibly also providing a smoother passage for the exhaust.

Does free flow exhaust save fuel? ›

Free flow exhaust system

fuel savings, but by removing the exhaust gas more efficiently, more torque is available sooner without significant changes to the power/torque curve. A proper exhaust system installation may also significantly reduce turbo lag due the increased efficiency of exhaust gas extraction.

What metal is used for jet exhaust? ›

Inconel – This material is perhaps the most common used to create a vehicle exhaust extraction system. With resistance to both extremely cold and hot temperatures, inconel is corrosion resistant and oxidation resistant.

What metal are aircraft exhaust pipes made of? ›

Inconel. One of the most commonly used materials for exhaust nozzles is the Inconel. Inconel is a nickel-chromium alloy and it is classified as a superalloy. The best part of this material is that it is resistant to extreme weather conditions and temperatures.

How does an aircraft exhaust system affect engine performance? ›

First, it vents exhaust gases away from the engine and fuselage while reducing noise. Secondly, the aircraft exhaust system indirectly supplies cabin and carburetor heat. Now, aircraft exhaust systems are constantly exposed to very high temperatures, sometimes in excess of 1200 to 1400 degrees Fahrenheit.

Why don't they put mufflers on planes? ›

The aircraft muffler's role is so significant that if they fail, it can lead to serious consequences that include carbon monoxide poisoning, serious injuries, fire, and total loss of the plane. Wear and tear in the metal and leaks in the muffler can also lead to partial or complete engine power loss.

What is the difference between muffler and exhaust? ›

So to put it simply, the exhaust controls the output of gas while the muffler controls the noise level of doing so. It might help to remember that another word for 'muffler' is 'silencer'.

Why are small planes so loud? ›

Why are small planes so loud? Small planes are loud for the same reason that its passengers are more likely to experience turbulence: There isn't as much space to absorb wind force and sound.

Which is better free flow or chambered muffler? ›

Free-flow mufflers basically mean there are no chambers that separate the pipes. However, a free-flow muffler is produces more noise than a chambered muffler. Additionally, Mr. Ang says it still depends on the amount of the material a muffler has for it to serve its purpose.

Does a straight pipe add horsepower? ›

You'll likely gain about ten hp with a straight pipe as compared with five hp or less by just taking off your muffler. Keep in mind that putting on a straight pipe also involves adjusting your fuel injection and otherwise tuning up the car.

What will make my exhaust louder? ›

You can increase the exhaust sound by drilling holes in it or by taking off the muffler. You can also remove the catalytic converter or install a cat-back exhaust. Consider putting on a performance muffler, cold air intake, turbocharger, straight pipe exhaust, or aftermarket exhaust if you have the money.

Are powerflow exhausts loud? ›

Can I get a good tone / How loud? Yes, Powerflow silencers are known to produce fantastic exhaust tone. From silent to very loud, our knowledgeable franchise managers and fitters will ensure you get the tone and noise levels you desire.

Does straight pipe waste more gas? ›

Both muffler delete and straight pipe do not improve gas mileage. In some cases, gas mileage becomes even worse because drivers unintentionally rev more because of the improved sound. If your main concern is gas mileage, then muffler delete and straight pipe are not for you.

Does exhaust affect gas mileage? ›

In short – no. Louder exhaust does not use more fuel. In fact- there's no correlation between them. A car engine creates combustion to deliver power – which generates a lot of noise.

Do I need a tune after new exhaust? ›

You need a tune – mainly to increase the amount of fuel injected into the combustion chamber. Otherwise, it will be a bottleneck to your HP gain – you only have extra air from the exhaust but not enough fuel to burn all of the air.

Are aftermarket exhaust bad for the engine? ›

Does an aftermarket exhaust affect the engine of a bike? A. Yes, changing the exhaust can affect the power of the engine.

Does slip on exhaust damage engine? ›

Yes, it can. It can lean out the air/fuel mixture to an extreme. This will result in a melted piston (or 2).

How much does it cost for a new exhaust system? ›

Custom exhaust systems are designed to replace the factory-issued components of your car. Depending on the desired result, you can expect to spend anywhere between $500 to $2,000. The price depends on the make and model of your vehicle and how many pieces of the exhaust system you want to change.

What is a high flow exhaust? ›

A high-flow catalytic converter has fewer restrictions than a normal catalytic converter so that exhaust gases flow at an increased rate. This modified exhaust system optimizes the flow of exhaust gases, and so all performance modifications.

What are the different types of exhaust systems? ›

The three main types of exhaust systems are header-back, cat-back, and axle-back. Depending on what type of system you choose, aftermarket systems will come with some combination of header or intermediate pipes, crossover pipe, catalytic converter, mufflers, and tailpipes.

Can you put a free flow exhaust on a diesel engine? ›

Yes, a free flow can be put in a diesel car as well.

What does an Akrapovic exhaust do? ›

Our exhaust systems are designed to provide you with higher levels of performance. We call it Pure Power. Reduced weight from the combination of the right materials and the best design to ensure optimum exhaust flow. The right catalytic converters and the best shapes.

How does the exhaust system affect performance? ›

Updating the exhaust system will mean that the engine essentially “breathes” better. Used up fuel and air exit will exit the combustion chambers faster. When the engine has a tight, functional exhaust system, more power is freed up, which means increased horsepower of the engine.

Why is titanium used in jet engines? ›

For aircraft engines, titanium alloys stronger than pure titanium are used for their light weight, high strength (high specific strength) and heat resistance properties.

What are jet engine combustors made of? ›

Combustor: partially Yttria stabilised zirconia, with a melting temperature between 2,700 and 2,850 °C. HP Turbine: single crystal nickel alloy, coated in ceramics. LP turbine: single crystal nickel alloy. Exhaust: single crystal nickel alloy.

What are jet engine blades made of? ›

Modern turbine blades often use nickel-based superalloys that incorporate chromium, cobalt, and rhenium. Aside from alloy improvements, a major breakthrough was the development of directional solidification (DS) and single crystal (SC) production methods.

What is ice in aviation? ›

CLEAR ICE. Clear ice or glaze ice is a heavy coating of glassy ice which forms when flying in areas with high concentration of large supercooled water droplets, such as cumuliform clouds and freezing rain. It spreads, often unevenly, over wing and tail surfaces, propeller blades, antennas, etc.

Can you use mild steel for exhaust? ›

Mild steel is the least expensive option for exhaust parts. It is also easier to work with than stainless steel. However, it does not resist corrosion at all. Mild steel exhaust parts can be painted with High Temp Paint.

What three things could be caused by an exhaust failure? ›

San Francisco Automotive Solutions
  • Check Engine Light. Obviously, your check engine light can come on for any number of reasons and a failing exhaust may be one of them. ...
  • Loud Acceleration. ...
  • Funny Smells. ...
  • Poor Fuel Efficiency. ...
  • Vibrations and Rattling Noises. ...
  • Car Losing Power.
7 Aug 2018

What are the two types of finishes on aircraft exhaust systems? ›

There are two general types of exhaust systems in use on reciprocating aircraft engines: the short stack (open) system and the collector system.

What are the possible hazards of exhaust system failure? ›

Depending on the location and type of failure, an exhaust system failure can result in carbon monoxide poisoning of crew and passengers, partial or complete loss of engine power, or an aircraft fire. Cracks in components, leaking gaskets, or complete failure can cause serious problems in flight.

Why are aircraft engines louder than car engines? ›

Prop powered general aviation aircraft are far louder than automobiles. No pilot flies without a headset because the noise makes it otherwise impossible to communicate with the ground or other pilots. Peak levels exceed 100db and the continuous average is around 85db, which is damaging to hearing without protection.

Do planes have silencers? ›

Single engine planes use a muffler shroud to heat air for the defrost and cabin heat. The muffler isn't nearly as large or effective as the ones on cars but a large part of the noise from an airplane is from the prop, so having a larger muffler would not eliminate the noise.

How loud is a Cessna 172? ›

One study compared a Cessna 172 (single engine) and a Piper Seminole (twin engine) and found that the average cabin noise was around 86 decibels, with no huge difference between the two aircraft.

Do mufflers increase horsepower? ›

A good muffler not only improves horsepower, but it also adds aesthetics to your car and gives your car a modified look. Great alternative to buying an exhaust system, and much less expensive. With a muffler you are essentially replacing one of the most restrictive areas of your exhaust for a fraction of the cost.

Do exhaust tips change sound? ›

Exhaust tips, since they are literally at the tailend of the exhaust system, will make a car have a more powerful sound. But a normal tip typically will have a small effect on the exhaust sound. A larger tip will give the engine a stronger, hearty sound, while a small tip will produce a raspy sound.

What is an exhaust tick? ›

Smells, or Ticking? Diagnose a Car or Truck Exhaust Manifold Leak

Do bigger planes feel less turbulence? ›

Although turbulence occurs in both large and small planes, it is typically worse in smaller planes because they weigh less, and so more likely to move in line with the air and thus feel turbulence more.

Is turbulence worse on a private jet? ›

Private jets are less likely to encounter turbulence than commercial aircraft, as they have a quicker climb and usually cruise above turbulence. But when private jets do experience turbulence, their smaller size means that it may feel more violent to passengers than it would in a larger commercial jet.

Why do planes not sound at night? ›

During the day, when the air is warmer than the ground, noise energy from an airplane staying in the air, so while you can still hear it, it seems quieter. Conversely, at night, when the ground is warmer than the air, the noise is drawn down, making it seem louder.

How do you check exhaust restrictions? ›

In most cases, exhaust restriction in speed-density systems can be diagnosed by looking for a significant loss of intake manifold vacuum at higher constant-throttle engine speeds. An alternative method is to directly measure exhaust gas pressure by removing the oxygen sensor and installing a backpressure sensing tool.

How is exhaust flow rate calculated? ›

The ratio of total carbon at the incinerator inlet and outlet is multiplied by the inlet volume to determine the exhaust volume flow rate.

What is the meaning of exhaust system? ›

An exhaust system is used to guide reaction exhaust gases away from a controlled combustion inside an engine or stove. The entire system conveys burnt gases from the engine and includes one or more exhaust pipes.

Which part of the exhaust section accelerates the gas flow? ›

Exhaust nozzle—accelerates the exhaust gases up to high velocity and low pressure.

What are the symptoms of a blocked exhaust? ›

Six Signs My Exhaust System Is Clogged or Leaking
  • Burning Odors. Burning odors coming from the engine bay suggest that your exhaust manifold is leaking. ...
  • Fuel Odors. A clogged exhaust system will send diesel fuel or gasoline odors into the passenger cabin. ...
  • Poor Gas Mileage. ...
  • Power Lag. ...
  • Too Much Noise. ...
  • Visible Damage.
15 Aug 2021

How do you tell if your exhaust is blocked? ›

Signs of a Plugged Exhaust - YouTube

What happens if you cover your exhaust pipe? ›

It will damage your vehicle forever and could potentially hurt you. If the object is under-marked or does not fit properly into the exhaust pipe, it will take nothing, it will in turn slide down from the exhaust pipe and will not affect the car's engine.

How do you calculate exhaust size? ›

Exhaust Diameter Formula

To calculate the exhaust diameter, multiply the RPM by pi and the cylinder, then divide by 88,200. Take this result and take the square root of it to get the exhaust diameter.

How do you calculate exhaust gas speed? ›

In order to determine, exhaust gas flow rate in mass or volume, the formula for total mass of exhaust gas is ma (mass of air)+ mf (mass of fuel). mass of air is determined by orifice meter at inlet connected to U- tube manometer.

What is exhaust gas pressure? ›

Definition. Engine exhaust back pressure is defined as the exhaust gas pressure that is produced by the engine to overcome the hydraulic resistance of the exhaust system in order to discharge the gases into the atmosphere.

What are the three 3 functions of the exhaust system? ›

Most people know that an exhaust system removes the harmful gases produced in your engine; however, exhaust systems do a lot more! Your vehicle's exhaust system has four main functions: control noise, carry away gases, improve engine performance and improve fuel consumption.

What is an example of exhaust? ›

The definition of exhaust is the release of used steam or gas. An example of exhaust is what comes out of a car's tail pipe. To exhaust is defined as to use up, tire out or discharge. An example of to exhaust is someone draining their savings account.

How much does exhaust system cost? ›

Custom exhaust systems are designed to replace the factory-issued components of your car. Depending on the desired result, you can expect to spend anywhere between $500 to $2,000. The price depends on the make and model of your vehicle and how many pieces of the exhaust system you want to change.

What are the 3 main components of gas turbine? ›

Gas turbines are composed of three main components: compressor, combustor and power turbine.

How fast does air leave a jet engine? ›

A typical speed for air molecules exiting the engine is 1,300 mph (2,092 kph). The bypass air generated by the fan - This bypass air moves at a slower speed than the exhaust from the turbine, but the fan moves a lot of air.

What are the two main factors which affect the performance of gas turbines? ›

Air temperature and site elevation

Since a gas turbine is an air-breathing engine, its performance is changed by anything that affects the density and/or mass flow of the air intake to the compressor.


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