Power Flow Systems, Inc.
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Frequently Asked Questions

» Which aircraft are FAA approved (STC) with the Power Flow Exhaust?
» What about experimental (homebuilt/amateur) built aircraft?
» If your aircraft model is not listed, and you have a Lycoming four cylinder engine
» Can I get an FAA Field approval for my aircraft?
» What type of performance gains can I expect?
» Will I get climb or cruise performance?
» Will it increase my RPM?
» Will I go over RPM Redline?
» Will I get Altitude or Service ceiling increases?
» Will my EGT probe fit in your exhaust?
» What type of fuel saving should I expect?
» Does the tube have to stick out of the cowl?
» Does this tube increase drag?


» Which aircraft are FAA Approved (STC) with the Power Flow Exhaust?     back to top

Cessna 172: 172, 172A-P with Lycoming O-320
Cessna 172: 172, 172A-Q with Lycoming O-360
Cessna 175: 175, 175 A-C with Lycoming O-360
Cessna 177: 177 B with Lycoming O-360
Cessna 177: 177, 177A with Lycoming O-360
Cessna 177: 177 with Lycoming O-320
Grumman AA5: AA5, AA5-A with Lycoming O-320 (s/n above 641)
Grumman AA5: AA5 with Lycoming O-320 (s/n below 641)
Grumman AA5: AA5-B, AG5-B with Lycoming O-360
Mooney M20: M20 B,C,D,G with Lycoming O-360
Mooney M20: M20 E,F,J (201) with Lycoming IO-360
Piper PA28: PA28-150, 160, 180 (under s/n 1761) with Lycoming O-360
Piper PA28: PA28-150, 160 (under s/n 1761) with Lycoming O-320
Piper PA28: PA28-140 with Lycoming O-360
Piper PA28: PA28-140 with Lycoming O-320

» Experimental or Field Approval required for the following.     back to top
Sportsman: Sportsman 2+2 with either Lycoming O-320 or O-360
Glastar: Glastar with either Lycoming O-320 or O-360
Cessna 170: 170 with Lycoming O360 (Field approval required)

» If your aircraft type is not listed and you have a Lycoming engine:     back to top
Our engineering and R&D resources are limited. We are developing and certifying the aircraft models that are the most popular. Currently our exhaust design has been proven on 4 cylinder, Lycoming engines. As resources permit, the smaller aircraft markets will be entered into the certification process. You can let us know that your are interested in an exhaust system for your aircraft by filling out our information request.

» Can I get an FAA Field Approval for my aircraft?     back to top
Power Flow Systems does not do field approvals here at the facility. There are limited instances of people being able to do field approvals on their own with their mechanics. Please contact us if you have further questions.

» What type of performance gains can I expect?     back to top

Each aircraft will experience different results in a real world application. Please go to the aircraft product page that corresponds to your aircraft to see results that are based on your aircraft test results and customer experiences.

» Will I get an increase in climb or cruise performance?     back to top
The types and amount of improvement that you will see depend on the aircraft and the type of propeller configuration (fixed or constant). Please refer to the individual product pages for the specific ranges for each individual aircraft. Below is a general explanation between constant speed and fixed pitch improvements. The numbers stated may not be valid for all aircraft.

For a constant speed prop application, the Power Flow exhaust will allow you to generate the same amount of power as before, using less throttle and lower Manifold Pressure. As compared to the stock exhaust system, if you set the same power settings with manifold pressure, mixture, RPM and Fuel flow, you will ultimately generate more power and higher cruise airspeed. Constant speed equipped aircraft report a top airspeed gain of between 3 and 11 miles per hour when measured with the throttle set at wide open (full). Your fuel flow may be higher than you are used to because your engine is generating more power than it ever did before. As a result of greater power available to the engine, your aircraft will climb at a greater rate than stock. An O-360, constant speed aircraft reports an average 200 FPM increase in rate of climb at the same airspeeds.

For a fixed pitch prop, at cruise, airspeed is directly related to RPM. During each rotation of a fixed pitch prop, the prop can only pull the aircraft forward as far as its effective pitch. If you generally cruise at a specific engine RPM, say 2300, the prop turns at 2300RPM and still provides the same airspeed. You will note that it doesn .t take as much throttle to achieve that 2300 RPM. You can utilize the extra RPM our exhaust provides to increase airspeed, but you would have to allow the RPM to increase. To boost your ultimate top speed, your only possible alternative is to consider "re-pitching" your propeller. In climbs, your engine turns at a faster rate and therefore you climb at a faster rate. The typical fixed pitch C172 customer reports an average 150-225 FPM improvement in rate of climb.

» Will it increase my RPM?     back to top
Yes, on a fixed pitch aircraft the PFS exhaust will increase your available RPM for Static (ground run), takeoff, climb and cruise. The typical range that people have seen an increase is from 30-130. The average fixed pitch aircraft has seen 60-70 RPM increase.

On a constant speed prop, the PFS exhaust will not increase your available RPM. If you set 2500 RPM with your prop control, the engine will regulate at 2500 RPM. As your engine may be making more power than before, the blades will be driven to a higher pitch resulting in higher rates of climb or faster forward airspeed than you saw with the stock exhaust.

» Will I go over RPM Redline?     back to top
No, on a constant speed equipped aircraft you won .t go over redline unless you have a pre-existing problem that allowed you to go over redline before the PFS exhaust installation.

On aircraft equipped with a fixed-pitch prop, it is more likely that you may exceed redline at full throttle at lower altitudes. Power Flow recommends that you do notexceed redline. You should reduce throttle accordingly to match your manufacturers . recommendations. Some of ourcustomers have reported that experienced prop shops have re-pitched their propeller to obtain a better cruise performance by sacrificing some of the improved climb performance from installing a Power Flow Systems Tuned Exhaust.

» Will I get Altitude or Service ceiling increases?     back to top
Yes. Most of our customers have reported an effective increase in service ceiling by up to 5000 feet. The average gain is 2500 feet, depending on how big of a gain the PFS exhaust provided you. Power Flow Systems, Inc. does not guarantee a specific increase in the aircraft service ceiling and it is highly recommended that you evaluate and test your aircraft .s performance prior to .counting on . a particular gain or service ceiling.

» Will my EGT probe fit in your exhaust?     back to top
Our exhaust is manufactured with thicker stainless steel tubing that stock, but EGT probes can be mounted in the exact same manner as they were in your previous exhaust and will operate normally. We recommend that you install the same distance as before or to the probe manufacturers recommended distance. All probes should be installed the same distance; otherwise temperatures may not be accurate. If the probes are installed in a different location than with the stock exhaust, a different reading may occur.
Power Flow recommends the use of engine monitors. Drilling holes for the EGT does not void the warranty or money back guarantee.

» What type of fuel saving should I expect?     back to top
The Power Flow, when leaned correctly has been able to save up to 2.5 gallons per hour. If you fly faster or climb faster than before, you may burn more fuel. With the Power Flow you can fly the same speeds, but it requires less throttle, therefore saving fuel. Many flight schools and clubs use our system and have successfully saved 1.12 to 1.9 gallons per hour. Refer to individual product pages for a more accurate fuel savings numbers.

» Does the tail pipe have to stick out of the cowl?     back to top
Yes and No. There are several reasons behind the distinctive exhaust . performance, heat concerns, durability, etc. In April 2005 we announced a revolutionary new look to our product . the .short stack. .
The Short Stack exhaust is available for all Pipers, Grumman .s, & Cessna .s. The Cessna short stack comes out of the cowling at exactly the same angle, length and diameter as the stock exhaust. As it is a shorter length than the ideal tuned length, the average Cessna sees only about 80% of the improved benefits as compared to the .Classic . original exhaust. If the look of the exhaust was a concern and you don .t want to squeeze every ounce of power out of the exhaust, then we recommend the short stack. If, on the other
hand, you want to have maximum gain for the exhaust, then the classic is the only way to go.

For Piper .s and Grumman .s, there is no performance loss from the use of the .short stack . as that system .s design is of the same length as the original .classic. . We were able to find an engineering solution to routing as much of that tubing inside the aircraft cowling as possible.

The Classic System style is available at a lower price than our new Short Stack.

» Does this tube increase drag?     back to top
We have accomplished flight-testing and found that drag caused by the tailpipe is overcome by thrust coming out of it. During testing we have also examined the use of fairings. Our testing indicates improvements in cruise speeds as well as engine temperatures from the use of exhaust fairings. We have an exhaust fairing available for the Classic C172 exhaust. Cessna C177 (Cardinal) and Grumman owners can also use the existing fairings on the market with our products . some realignment may be required.

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