Author Archives: PFS

“Pick Your Price” Discount Program- How It Works

“It looks like Power Flow always has a “special” sale going on! What’s up with that?”

Very observant, Grasshopper, and quite true – we DO!

We call it our “Pick Your Price” program and here’s how it works:

Power Flow can ship a complete Tuned Exhaust System, any version, within two weeks or less. Back in the “Good ole’ (pre-2008) days” we used to sell every system at, or very close to, list price and then spend a lot of time “negotiating” with each Customer to arrive at a mutually acceptable ship date. To meet those ship dates we frequently had to pay a LOT of exorbitant “expedite” fees, overnight shipping charges and overtime rates for our own production team. Not particularly efficient and very stressful on our end because we often had no idea what (if anything) our shop crew would be doing from one week to the next.

When the good times got a little tougher we (along with all the other survivors in this industry) were forced to adapt. We eventually figured out that the further ahead we can plan our production activities, the lower the costs (and stress levels) for those operations become and we are happy to share the resulting savings with those Customers who are also able to plan ahead a little bit.

Our “Pick Your Price” program is designed to do that by offering discounts (usually anywhere from $300.00 to $1,000.00) based on the lead time you select. We review the amount of the discount(s) and the lead time required to get them every couple of weeks and make adjustments based on: #1.) Our current production backlog, and; #2.) How busy (or quiet) the sales phones and e-mailed inquiries have been.

Of course, not everybody has the luxury of waiting, and after some folks decide they want something, they want it right NOW! In those instances, we will drop everything else and focus on getting that particular system out the door ASAP – usually within a week or less, but we charge (and believe me, we earn) full list price for that extra effort.

Although most Customers seem to intuitively grasp the relationship between longer lead times and lower costs, we have had a few enterprising souls call us up wanting to place an order for delivery ASAP, but at the fully discounted price. Their rationale being something like: “Just send me the system that you built for one of those Customers who placed his order 6 – 8 weeks ago.” After congratulating them on their ability to “think outside the box”, I am compelled to point out that we would still be faced with dropping everything else and spending a lot of extra time and money to fabricate and ship a new system to replace the one we ship to them in time to meet the Ship By date we promised to our original Customer.

Another feature that the more perceptive observer might notice is what I refer to as our “Anti-Procrastination Device”. As it turns out, pilots are just as adept at that ubiquitous skill as the rest of the world. So, we give you a good reason to go ahead and take the plunge! It might be a significant discount on one of our optional upgrades, or it might be a limited time reduction in the lead time required to get the biggest discount. Whatever it is, our motivation is the same: we’d like to promote you from Perennial Prospect to Satisfied Customer as soon as possible.

If you can think of a better approach, or even if you can’t but just have an opinion you’d like to share – we’d love to hear from you.

Click here or paste this link in your browser to learn more: https://www.powerflowsystems.com/news.php?nid=65

-Jim

Power Flow in AOPA news – “Exhausting maintenance: Performance improvements”

Be sure to check out what Jeff Simon with AOPA had to say about the Power Flow Systems Tuned Exhaust by clicking here: Exhausting maintenance: Performance improvements – AOPA

Having trouble with the link, paste this URL into your browser: http://www.aopa.org/News-and-Video/All-News/2015/January/20/Exhausting-maintenance-Performance-improvements?WT.mc_id=150123epilot&WT.mc_sect=gear#.VMQhKCDlj_g.mailto

Does the PFS have a flame tube?

This was asked on another user group after a pilot experienced a large loss of power using a traditional exhaust.

In a traditional exhaust, gases are shot at each other and have to diffuse through a flame tube to exit. When that flame tube breaks down, it is hoped that the chunks are small enough to not block the exit from the muffler and thereby causing a potentially dangerous power loss or new hole in the muffler for your air pump (the engine) to relieve the pressure it created.

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Example of a stock exhaust system

One of the engineered “improvements” of the Power Flow over traditional Elano style (and other standard) exhaust systems is to allow an uninterrupted pathway for the exhaust gases in the muffler area. For all Exhaust systems except Cessna “short Stack” and our earliest Mooney 200 HP exhaust (PFS-16201 without the quiet pipe), the muffler consists of a 14 inch stainless steel perforated tube that has a 2.0 inch diameter. The gases exit the 4 to 1 collector, go down a 2.0 inch pipe and enter the muffler area and continue down the 2.0 inch inner diameter of the perforated tube. If you look at the PFS muffler, the outer area of the pipe has an expansion from a 2.0 inch area to a 3.5 diameter. On the inside of the muffler, the perforated tube (called a muffler insert) is inside the outer section creating a constant 2.0 inch pathway for the exhaust gas. This is muffler insert is based upon automotive type sound suppression, but adapted for aviation. The inner wrapping that is directly exposed to the exhaust gases is made up of INOX stainless steel fibers, with the outer layer a high density BASALT wrap. It looks a little like fiberglass, but it is brown in color.

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View looking down installed muffler insert inside tailpipe

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Uninstalled muffler insert

This high density wrap around the perforated tube is designed to be sacrificial. It will, over time, break down into very tiny hairs and blow out the tail pipe. The structure of the inner stainless steel tube is designed to stay intact and isn’t standing in the way of the gas pathway. On condition (we have seen between 400 and 800 hours) you remove the entire muffler insert, and replace it with another for about 15-30 minutes labor and $180.00 for the part (pricing correct as of December 2014, subject to change). This can be done in the field, while the exhaust is on the plane, if you want. No overhaul or sending the muffler out for rebuild.

To inspect the PFS muffler, you shine a light up the tailpipe. You are looking to make sure that the inner tube is intact and that you can see the light reflecting back from stainless steel hairs. I recommend that every PFS owner take 10 seconds and do this during pre-flight.

If you have a Cessna Short stack or the earliest 200 HP Mooney Power Flow exhaust, you don’t have a 14 inch muffler insert. The outer diameter of your tailpipe is 3.0 inches instead of 3.5 inches and what you have is a more rudimentary, sound suppressant cone inside the last 5 inches of the tailpipe.

General 472
PFS Short Stack Tailpipe

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Installed Muffler Insert

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Cessna Short Stack with a Silencer Cone

Because this cone doesn’t have any material on it, there isn’t anything to “wear out.” It is possible that over time the cone will deteriorate and when that happens, it can be easily replaced.

INSPECTION & PREFLIGHT

To inspect the PFS muffler, you shine a light up the tailpipe. If you have muffler insert, you are looking to make sure that the inner is intact and not deformed and that you can see the light reflecting back from stainless steel hairs. I recommend that every PFS owner take 10 seconds and do this during pre-flight. If you have a cone type (Cessna short stack and early 200 HP Mooneys), you want to make sure that the muffler cone is still intact.

Darren Tilman
General Manager

Edited 01/08/2015: Previous posting reflected outdated pricing and misstated some technical aspects. We apologize for any confusion.

Cessna Short Stack vs. Classic – difference?

The only measurable performance difference between the short stack vs our classic (long pipe) are found only on the Cessna 172 and 177. This does not apply to Grummans and Piper installations.

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Cessna 172 (Short Stack)

The performance differences are subtle and only seen in three areas, which the average customer/non test pilot may not even notice.

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Short Stack Ceramic tail pipe 

1) The RPM gain on the C172 with the classic we measured at 65 RPM on our test aircraft. The short stack showed 58 RPM. Slight loss in performance, but hard to see.
2) The classic exhaust system allowed aggressive leaning – lean of peak operations for fantastic fuel savings. The reality is that the vast majority of our customers don’t use lean of peak operations so this is an unrealized benefit.
3) We have a report from a customer who routinely flew their C172 at 15500 MSL Feet with the PFS classic. They converted to the Short stack and reported the loss of Lean of peak leaning and they were unable to get above 14000 MSL – so we have a reduction in the gain in service ceiling.

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Classic Kit

From an installation and maintenance aspect, the short stack for the Cessna models wins in most areas:

The short stack is: 1.5 pounds lighter, takes one hour less to install (average) and does not require you to remove the lower pipe to remove the cowling.

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172 with Classic Tailpipe

From a noise perspective:
The noise on the ground in the cabin with the short stack is a bit more “sharp”, but in flight our customers have told us the noise appears to be lower than with the classic system. This is likely because the short stack points down and is 2 feet forward of the cabin. The classic pipe is 2 feet closer to the cabin and pointed straight back (aft.)

Grumman and Piper short stacks are approximately the same length as the “classic” systems they replace, so there is no change in tuned length or performance. The Cessna Short stack is approximately 40% of the tuned length of the classic pipe, hence the slight drop in performance.
__________________
Darren Tilman
General Manager
Power Flow Systems, Inc.

Are you “Baffled” by high CHT’s?

Due to our years of experience dealing with all kinds of engine related issues, we frequently get calls from pilots (Power Flow Customers or not) seeking help and advice in dealing with a variety of problems. Chief among these problem areas is engines that run hotter than the owner/pilot feels they should. As fellow aviators, we like to lend a hand wherever / whenever we can, so we were very happy to run across this discussion of what is probably the leading culprit behind engine overheating in the GA fleet. In all honesty, I have never seen a more thorough, concise and understandable explanation of this extremely important topic.

Originally published in 2005, the article is reprinted in its entirety below with the kind permission of the Author, noted Aviation Maintenance guru, Mr. Mike Busch.

The Savvy Aviator #14: Engine Cooling — Less Is More

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If your CHTs are running warmer than you’d like, odds are that you’ve got leaky cooling baffles under your cowling. Fixing those leaks is usually simple — and the less air leaks, the more is available to cool the cylinders.

The Savvy Aviator

I recently had my engine rebuilt and had a new baffle kit installed,” a Cessna T210 owner recently emailed me. “The CHTs for cylinders #5 and #6 are always 20ºF to 30ºF hotter than the rest. During climb the difference gets even bigger. Cylinder #5 and #6 CHTs are very difficult to keep below 400ºF during a climb, even with the cowl flaps open and rich mixture.
“Should I consider giving them some air?” the owner asked, attaching some digital photos of what he had in mind. “On cylinder #6, why not cut one or more holes in the white aluminum baffle in front of the cylinder? On cylinder #5, why not drill one or more holes in the horizontal aluminum plate located behind the oil cooler?”

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The owner of this T210 suggested making some baffle modifications to improve cooling of cylinders #5 and #6 by “giving them more air.” This would not have been a good idea, and would almost certainly have made things worse instead of better. (Click all photos for larger versions.)

I replied that cutting holes in the baffles was definitely not a good idea, and that doing so would undoubtedly make the cooling problems worse, not better. It was apparent that the T210 owner didn’t understand how the powerplant cooling system in his aircraft works, or what the function of the baffles is. He’s not alone — I’ve observed that quite a few A&P mechanics don’t fully understand it, either!

Cooling: Then and Now

In the early days of aviation, aircraft designers took a simple approach to the problem of cooling aircraft engines. The engines were mounted with their finned cylinders out in the slipstream and cooled by the horizontal flow of ram air. This design is known as “velocity cooling” and was adequate for cooling the low-compression, single-row radial engines of the time.
As engines grew more powerful and multi-row radials and horizontally opposed engines went into service, it became obvious that simple velocity cooling wasn’t up to the job. For one thing, cooling was uneven — front cylinders got a lot more cooling airflow than rear cylinders. For another, sticking all those cylinders out in the breeze created horrendous cooling drag. A better scheme was obviously needed. That better system was known as “pressure cooling” and is the method used in all modern piston aircraft. Pressure cooling is accomplished by placing a cowling around the engine and using a system of baffles and seals to produce the volume and pattern of cooling airflow necessary to achieve even cooling with minimum drag.

spiritofstlouis

Early aircraft engines were “velocity cooled” by passing the slipstream over the finned cylinders. However, this simple approach to cooling is simply not practical for today’s high-performance engines and low-drag airframes.

What Do Baffles Do?

Our modern piston aircraft are powered by tightly cowled, horizontally opposed engines. Inside the cowling, a system of rigid aluminum baffles and flexible baffle seals divide the engine compartment into two chambers: a high-pressure area above the cylinders, and a low-pressure area below the cylinders and behind the engine. Cylinders are cooled by the vertical flow of air from the high-pressure above the engine to the low-pressure below it. Cooling airflow is top-to-bottom, not front-to-back.

engineflow

The heart of a modern ‘pressure-cooled’ powerplant installation is a set of rigid, sheet-metal baffles and flexible baffle seals that, together with the engine cowling, divide the engine compartment into two chambers: a high-pressure area above the engine and a low-pressure area below and behind the engine. Engine cooling depends upon the vertical airflow from the upper chamber to the lower one. Cowl flaps modulate the cooling by regulating the vacuum in the low-pressure chamber.

The volume of cooling airflow that passes across the cylinders is a function of the pressure differential between the upper (high-pressure) chamber and the lower (low-pressure) chamber of the engine compartment. This pressure differential is known as “delta-P.” Cowl flaps are often used to modulate the cooling airflow. Opening the cowl flaps reduces the air pressure in the lower chamber, thereby increasing delta-P and consequently the volume of cooling air that passes vertically across the cylinder fins.

It’s important to understand that the pressure differential between the upper and lower chambers is remarkably small: A typical, high-performance piston aircraft generally relies on a delta-P of just 6 or 7 inches of water — about 1/4 PSI! Aircraft designers try to keep this delta-P to an absolute minimum, because higher delta-P means higher cooling drag.

… And So What If They Don’t?

Because the pressure differential (delta-P) on which engine cooling depends is so very small, even small leaks in the system of baffles and seals can have a serious, adverse impact on engine cooling. Any missing, broken, or improperly positioned baffles or seals will degrade engine cooling by providing an alternative path for air to pass from the upper chamber to the lower chamber without flowing vertically across the cylinder cooling fins. (This is precisely what the effect would have been had the T210 owner cut holes in his baffles, which is why I strongly discouraged the idea.)

Probably the most trouble-prone part of the cooling system is the system of flexible baffle seals. These flexible strips (usually high-temp. silicone rubber) are used to seal up the gaps between the sheet metal baffles and the cowling. These gaps are necessary because the baffles move around inside the cowling as the engine rocks on its shock mounts.

cylinder

Flexible seals are used to prevent air from escaping through the gaps between the engine-mounted sheet-metal baffles and the cowling. To do their job, they must be oriented so as to curve toward the high-pressure chamber above the engine, so that air pressure pushes them tightly against the cowling

To do their job, the seals must curve up and forward into the high-pressure chamber, so that the air pressure differential (delta-P) presses the seals tightly against the cowling. If the seals are permitted to curve away from the high-pressure area — not hard to do when closing up the cowling if you’re not paying close attention — they can blow away from the cowling in-flight and permit large amounts of air to escape without doing any cooling.

I recall some years ago inspecting a Cessna TR182 whose pilots had complained of high CHTs. Upon removing the top engine cowling, I immediately spotted the problem: One of the ignition leads was mis-routed and became trapped between the baffle seal and the cowling, preventing the baffle seal from sealing against the cowling. The ignition lead had become severely chafed where it rubbed against the cowling, and an A&P had wrapped the chafed area with electrical tape, but failed to re-route the tape-wrapped lead to keep it away from the baffle seal. Clearly that A&P didn’t understand the importance of an air-tight seal between the baffle seals and the cowling. Repositioning the ignition lead solved both the cooling problem and the chafing problem.

Another common problem is that seals may develop wrinkles or creases when the cowling is installed, preventing them from sealing airtight against the cowling and allowing air to escape. It’s important to look carefully for such problems each time the cowling is removed and replaced, and especially important when new seals have been installed (as was the case with the T210).

cylinderblock

Inter-cylinder baffles are oddly-shaped pieces of sheet metal that mount beneath and between the cylinders, and force the down-flowing cooling air to wrap around and cool the bottom of the cylinders. (This photo was taken looking up from the bottom of the engine, with the exhaust and induction systems removed to make the baffle easier to see.)

Another trouble-prone part of the cooling system is the inter-cylinder baffles. These are small, oddly-shaped pieces of sheet metal mounted below and between the cylinders. Their purpose is to force the down-flowing cooling air to wrap around and cool the bottom of the cylinders, rather than just cooling the top and sides. These baffles are difficult to see unless you know exactly where to look for them, but they are absolutely critical for proper cooling. It’s not at all uncommon for them either to be left out during engine installation or to fall out during engine operation. Either way, the result is major cooling problems.

Recently, I noticed that the #3 cylinder of the right engine on my Cessna T310R was running noticeably hotter than its neighbors. I removed the top cowling from the right engine nacelle and carefully inspected all the aluminum baffles and rubber baffle seals, but couldn’t find anything awry. Frustrated, I removed the lower cowlings so that I could inspect the underside of the engine. Sure enough, I discovered that the intercylinder baffle between cylinders #1 and #3 had vibrated loose and shifted about 1/4 inch out of position, creating a significant air leak near the #3 cylinder. Repositioning the baffle properly and tightening its attach bolt to hold it securely in place against the cylinders and crankcase solved the problem.

Why The T210 Engine Ran Hot

With this as background, I emailed the T210 owner to discourage him from cutting holes in his baffles, and suggested instead that he examine his baffles and seals for existing holes and gaps that could be plugged up to improve cooling. A couple of days later, the owner emailed me back a series of digital photos showing a half-dozen air leaks that he found in his newly installed baffles.

leak

Close-up of a fairly significant cooling air leak due to a wrinkle in a flexible baffle seal. This problem was apparent only with the top cowl installed, and could be seen by inspecting through the front intake openings using a flashlight. It’s an excellent idea to look for such baffle seal problems during preflight inspection.

One of those photos revealed a fairly significant cooling air leak due to a wrinkle in a flexible baffle seal. This problem was apparent only with the top cowl installed, and could be seen by inspecting through the front intake openings using a flashlight. Savvy pilots who understand the importance of baffles and seals look for this sort of thing during pre-flight inspection. (Since mechanics do most of their inspecting with the cowlings removed, problems like this sometimes escape their detection.)

I studied the photos and continued my email dialog with the Cessna owner. Between the two of us, we managed to identify a dozen leaks in the T210’s new baffle system. Some were small, others more serious. Combined, they accounted for a significant loss of cooling efficiency. With a few well-placed dabs of high-temp RTV sealant and a little trimming of the flexible seal strips, the owner plugged the leaks in short order, and his engine began running noticeably cooler.

“Copyright 2005, Savvy Aviator, Inc. (www.savvyaviator.com). All rights reserved.”

About Mike Busch

Mike Busch is arguably the best-known A&P/IA in General Aviation. He has been a well-respected aviation writer, teacher, journalist, and crusading iconoclast for more than four decades. For the past 20 years, the primary focus of his writing and teaching has been aircraft maintenance. He is founder and CEO of Savvy Aircraft Maintenance Management, Inc., the world’s largest company providing professional maintenance management services for owner-flown aircraft, and of SavvyAnalysis.com providing engine monitor data analysis for piston aircraft. He also offers free maintenance webinars for aircraft owners on the first Wednesday of each month. Mike co-founded AVweb, the Internet’s premier aviation magazine and news service, in 1995, and served as its editor-in-chief for eight years. In 2008, the FAA Administrator honored Mike as “National Aviation Maintenance Technician of the Year.” His book “Manifesto: A Revolutionary Approach to General Aviation Maintenance” is available on Amazon.com.

Why do I have a “popping” sound?

A popping sound is not a normal occurrence with a Power Flow System. The following list should help you troubleshoot the problem:

1. Is there evidence of ‘blow by’ (exhaust leakage) where the tailpipe slides over the 4-to-1 collector or around any of the headers? If so it may be cause.

2. Check the muffler insert located in the tail pipe to be sure there is no partial or complete blockage.

3. Check your induction system for any leaks.

4. Are you leaning as much as the Power Flow will allow on the ground? The Power Flow will enrich the mixture so more aggressive leaning is needed during ground operations.

5. Check the idle mixture on the carburetor by doing a Lycoming idle rise. If it is set too rich it can lead to excess unburned fuel which is ignited by the hot exhaust pipes.

-Darren

Edit:

In addition to the above, a leaking primer can cause popping in the exhaust at low power settings. Simply block the line and test fly.

Ceramic vs. Non-Ceramic Tailpipes

Some information that might help you with your decision. Our “ceramic” option is designed only for aesthetics; that is: how nice the visible portion of the tailpipe looks. Except for the last part of the exhaust (the tailpipe) the rest of the exhaust system is made from the same 321 Stainless steel tubing.

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Above: Ceramic Coated Short Stack Tailpipe

In fact, ceramic coating the entire exhaust is a bad choice in both the FAA’s view and our view. Ceramic will act an insulator and change the heat profile in the exhaust tube, changing the exhaust’s ability to dissipate heat. However, most critically, the ceramic coating is like a very thick layer of paint. The FAA wants to ensure that you (or your technician) can easily inspect an exhaust tube and be able to see the signs of heat stress or fatigue before it reaches a critical point and leads to a big crack or failure in the tube. With a ceramic coating in place, you cannot easily see signs of impending problems until after they have occurred.

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Above: Polished Short Stack Tailpipe

So how did we get FAA approval to ceramic coat part of the exhaust? Lots of persuasion, and the fact that the only part we ceramic coat is the last part of the exhaust that primarily exits the cowling area. In a worse case scenario, if the exhaust were to crack in this area, you would not have a crack inside the cowling that could contribute to a possible safety hazard.

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Above: Complete Kit for Cessna 172 with Short Stack Tailpipe

We have not seen any evidence that LOP operations cause damage to PFS exhaust systems, and I haven’t seen that be the case with stock exhausts, either. Excessive vibration is a far greater concern – so get a dynamic balance and check that periodically. As to burn-through; we haven’t seen anything to support or contradict that thought. Ceramic coating acts to protect the base material, but brings with it other issues to be concerned about (above.)

In the end, my advice would be to get the ceramic coated tailpipe option to avoid the look of a brown pipe.

Darren Tilman

How do you Lean for best power?

Question: I want to evaluate the performance and improvement with a Power Flow exhaust as compared to the Standard exhaust. How do you lean for best power on my fixed pitch aircraft?

Answer: With the throttle at full (wide open), and the mixture initially at full rich, you should start to lean the mixture after passing through 3500 to 5000 feet MSL (reference your POH for specific recommendations).

Leaning gradually you are looking and listening for an increase in RPM. Generally, you should see an increase of at least 20 RPM during a climb from the full rich to peak RPM points. You know you are at the peak when further leaning reduces the RPM from its highest point. Move the mixture back in to achieve that Peak RPM. I recommend releaning every 2500 feet of additional altitude. If workload permits, you could be moving the mixture more often, but then you aren’t looking outside for traffic and that isn’t as safe as flying first, leaning second.

Question: I used the same EGT value for leaning for both the standard exhaust and the Power Flow. Is this ok?

Answer: Leaning of the engine done during the climb to a constant EGT is not as valid as leaning to peak RPM. Peak EGT changes with altitude and atmospherics as well as with the kind of Exhaust system used. It is typical to see a 50-75 degree higher “peak” with a PFS than the stock exhaust. If the stock peak was 1425 at 3500 feet, and you lean 75 rich of that (1350), you may likely be at or very near best power/peak RPM. However, the PFS peak may be 1475 or 1500 degrees at 3500 feet, so leaning to 1350 is actually a great deal cooler/richer – resulting in less than best power and therefore lower performance. This is the problem with the constant EGT method – it doesn’t reliably produce best power. You should lean to achieve the highest RPM, if you are looking for best power.

*Please note, the above pertains to fixed pitch.

Darren Tilman
General Manager

Design Point of the Cessna 172

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The following question has been asked recently by a customer who flys a Cessna 172: “…with the D2J, the best fuel efficiency seems to occur near 55% power, say 2350 RPM at 8000 ft. ‘Just wondering what your design point was?”

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The answer to this is, the PFS exhaust system for the Cessna 172 was technically optimized at 2450 RPM at sea level. In my flight testing experience, that RPM is the true “peak” point and it is still correct at altitudes as high as 8500 feet. I haven’t specifically tested the Electroair, but I understand how it works and it is the same ignition mapping as the much older LASAR ignition system which I did do some testing on. As the throttle is reduced (actually as the manifold pressure is reduced, but it is the same thing at lower altitudes) the ignition timing will advance as long as it is below 23 inches of manifold pressure. This ignition timing effect may alter the performance and therefore may affect where the peak RPM of the Power Flow is.

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Green line represents Power Flow. Notice during over lap, where the exhaust gas valve and intake valve are both open, Power Flow creates a negative pressure to suck out all the exhaust gases.

To figure out what the actual performance curve in your aircraft is for a given altitude (fixed pitch props):

In level flight, set the throttle to 2300 RPM in level flight with it leaned using the same leaning methodology each time. Ie: 50 rich of peak or 75 Rich of peak. Wait 3 minutes for everything to stabilize and record fuel flow, airspeed and engine EGTS and CHTS. Then repeat the test at 2350 RPM, releaning the engine using the same method each time, and after waiting 3 minutes for everything to stabilize, again record fuel flow, airspeed and engine EGTS and CHTS. Add another 50 RPM increment and incrementally go up to 2500 RPM. Then you can look at the data and see at what RPM the best “bang for the buck” occurred. My money is on 2400-2450, but we would love to see your data!

Darren Tilman

The Need For Inspection

Some customers have commented that after installing a PFS tuned exhaust on their aircraft that the inspection joint has passed without issue at each annual. It has been asked if we, PFS, can find a way to get rid of the need for the inspection and thus lower the yearly annual labor bill.

The purpose behind the detailed inspection (taking things apart) is FAA mandated to make sure that all exhaust systems are complete and don’t have any cracks developing in the cabin heating area. Unlike the original exhaust design, our exhaust system was designed to absorb/dissipate the stress from each cylinder’s movement from heating and cooling by allowing free movement at the slip joints which is where the headers go into the center section.

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Picture a trombone slide. These joints work great at absorbing the stress and vibration but they only do that when they are free to move. Once they bind-up, the stresses will still be there, but they will now go and “relieve” itself somewhere else and that could be in the form of a crack either in the header of the collector assembly. We know you can’t do a detailed inspection of the exhaust without taking the exhaust apart and so while it is apart that is the ideal time to lubricate the slip joints to keep them freely moving to give you the best safety and longevity.

Darren Tilman