Understanding Chainsaw Power

Why Airflow, Torque, RPM, Chain Speed and Filtration Capacity Must Be Considered as One System

For more than 40 years, MaxFlow® has focused on one basic requirement: a chainsaw engine must receive enough clean air to maintain performance under real working conditions. That sounds simple, but chainsaw performance is not determined by any single number. Horsepower, torque, RPM, airflow and filtration capacity, chain speed, sprocket size, bar length, chain geometry, sharpening, operator technique all interact. Change one variable and several others can change with it. That is why a peak dyno horsepower number can be perfectly real and still fail to tell us which saw will perform better in the wood. A dyno tells us how an engine performed under a defined test condition but also requires us to ask why it made that number and whether the graph depiction remains under the load, gearing, bar, chain and operating conditions the saw will actually see.

A Chainsaw Has a Theoretical Airflow Maximum

A two-stroke chainsaw has an induction event every crankshaft revolution, so its theoretical geometric airflow can be calculated from displacement and RPM. Consider a 70 cc chainsaw operating at 13,000 RPM, a representative wide-open-throttle no-load speed used here only to illustrate the relationship:

70 cc × 13,000 = 910,000 cc per minute, or approximately 32.1 CFM.

That does not mean the engine actually consumes 32.1 CFM. It means that if every displacement cycle could be completely replenished with a fresh charge at atmospheric density, the engine would theoretically move about 32.1 cubic feet of air per minute.

A real chainsaw cannot do that, it does not have 100% airflow perfection. At 13,000 RPM, one complete crankshaft revolution takes only about 4.62 milliseconds, and the intake system has only a portion of that time available to move fresh air through the filter, intake tract and into the engine, a measurable process called volumetric efficiency

The 13,000 RPM figure is not intended to represent normal cutting speed. A chainsaw under load operates at a substantially lower RPM, often closer to the portion of the power curve where useful torque is being produced. The higher no-load RPM is used here simply because it makes the relationship between engine speed, available filling time and theoretical airflow easy to see.

As RPM increases, the available filling time becomes shorter. The engine must create the pressure differential necessary for atmospheric pressure to move the fresh charge through the filter and intake system in progressively less time. Eventually, the amount of useful fresh charge trapped per revolution begins to decrease even though RPM can continue increasing. The important point is simple: Increasing RPM does not indefinitely increase useful airflow and cylinder filling in direct proportion and torque, which is a function of airflow can fall off dramatically.

Measuring Chainsaw Airflow

Airflow and Pressure Are Not the Same Thing

This distinction is important. Air can be moving around the intake area without creating meaningful positive pressure at the filter. A naturally aspirated chainsaw does not have pressurized combustion air waiting to enter the engine. The engine creates the demand by producing a lower-pressure condition downstream, and atmospheric pressure moves air through the filter and intake toward that lower pressure. The filter’s job is to satisfy that demand while removing contamination and creating as little harmful pressure loss as practical.

Airflow theory is useful, but actual testing is essential. It is important to be able to distinguish between the different airflow dynamics affecting the filtration system. Chainsaw manufacturers do not claim that their centrifugal pre-cleaning systems supply compressed or meaningfully pressurized combustion air to the intake tract, yet the airflow those systems produce can be visible or easily felt and therefore confused with intake pressurization.

Our running-saw testing allows us to separate that measurable pre-cleaning airflow from the engine’s normal intake demand by using purpose-built fixtures and sensitive air-velocity instrumentation.

One instrument we use is a Taylor anemometer. For running-saw testing, it is mounted in a fixture that requires the engine to draw its combustion air through the instrument and then through the intake throat. We can also reconfigure the fixture so the engine’s combustion-air demand is supplied independently from atmosphere, allowing the excess air velocity provided by the flywheel system to be measured separately. That same intake throat can then be removed and tested independently on our SuperFlow SF-600 flowbench under a controlled pressure differential.

This gives us three different views of the same airflow system: the Taylor can measure the engine’s running intake demand, it can separately quantify the excess airflow supplied by the flywheel system, and the SuperFlow can measure the intake component’s airflow characteristics under a controlled pressure differential.

Through repeated back-to-back testing on several saw models, the Taylor measurements have shown a consistent relationship with our controlled airflow testing. Because the Taylor is being used in a high-vibration, pulsating chainsaw environment far outside its normal handheld application, we do not treat the raw reading as an absolute airflow measurement. Instead, we use the instrument comparatively and apply an empirical correction derived from the repeatable relationship established through our fixtures, engine measurements and controlled airflow testing.

The result is a repeatable measurement method using the same instruments, geometry and test procedures across the chainsaws and components being evaluated.

We intend to show these fixtures because we want the testing to be understandable and reproducible. We encourage others to test it themselves: control the geometry, use the same intake components, record the operating conditions, compare components back to back and, whenever possible, correlate running-saw measurements with a calibrated flowbench.

The purpose is not to ask anyone to accept a MaxFlow® number simply because we published it.

The purpose is to show how the number was obtained so others can test it for themselves.

Why Horsepower Can Increase While Torque Falls

The Chainsaw Is a Complete Cutting System

Torque is strongly influenced by how much useful fresh charge is trapped and burned during each combustion event. If increasing RPM causes less useful charge to be trapped per revolution, torque can begin to decline.

Horsepower can still increase because horsepower is calculated from both torque and RPM:

Horsepower = Torque × RPM ÷ 5252

For example:

Engine Speed 10,000 RPM 12,500 RPM

Torque 4.0 lb-ft 3.5 lb-ft

Horsepower 7.62 HP 8.33 HP

That makes the point immediately clear: torque dropped from 4.0 to 3.5 lb-ft, while horsepower still increased because RPM increased. Horsepower increased, but torque fell 12.5%. Both numbers are real.

The question is which one matters for the work being done. In brushing, limbing or smaller wood, a saw may remain near its higher-RPM range, where greater engine and chain speed can significantly increase production. Bury a long bar in large timber and the operating condition changes. Load increases, RPM falls, and the shape of the torque curve becomes increasingly important because it determines how much rotational force remains available as engine speed is pulled down.

A saw optimized for very high RPM may be exceptionally fast in light cutting, while a broader torque curve may perform better under sustained heavy load. Neither is automatically better. They are optimized for different work.

Engine RPM alone does not determine cutting speed. Bar length changes load, while sprocket size changes the relationship between engine speed, mechanical advantage and chain speed. Chain type, cutter geometry and depth-gauge setting determine how aggressively each cutter engages the wood.

Sharpening can be as important as an engine modification. A professional faller may adjust cutter angles, side-plate geometry, top-plate angle and depth gauges for the wood, bar length, engine characteristics and personal cutting technique. Two experienced fallers can prefer different setups on the same powerhead because they load and control the saw differently.

That is why professional users can often recognize relatively small changes in torque, throttle response, RPM recovery and chain speed that may be almost invisible to a recreational operator.

A professional faller develops something remarkably close to a Dyno in his elbow.

That does not make instrumentation unnecessary. It means controlled measurements and experienced field testing answer different questions.

Modified Saws Still Depend on Airflow

Why Filter Capacity Matters More Than a Clean-Filter CFM Number

MaxFlow® does not claim that a filter, by itself, creates horsepower. The engine determines how much air it can use. Porting, exhaust changes and other modifications may increase an engine's ability to move air or produce power over part of its operating range. MaxFlow® takes no position on whether a particular modification is worthwhile.

But if you choose to modify an engine to use more air, the filtration system must still be capable of supplying it. If the filter becomes the restriction, the engine cannot fully use the capability built into the modification. The principle is simple: A performance modification cannot use air the filtration system cannot supply.

MaxFlow® does not create that additional power. Our objective is to help make sure clean-air capacity does not become the limitation preventing the engine from using it.

If an engine requires 30 CFM, installing a filter capable of flowing 90 or 100 CFM does not make the engine consume 90 or 100 CFM. The additional capability serves another purpose, it provides reserve capacity.

As contamination accumulates, resistance and pressure drop across the media increase. A high-capacity filter can lose a substantial portion of its original clean-filter airflow and still remain comfortably above the engine's requirement. A smaller filter begins much closer to that requirement, so its margin disappears sooner. This is why clean-filter CFM tells only part of the story.

The more important question is, how long can the filter continue supplying the clean airflow the engine requires? That is sustained performance number MaxFlow offers.

Filtration Is More Than a Media Name

Paper, synthetic media, nylon mesh and oiled foam can all be engineered to different levels of airflow and particle capture. It is therefore misleading to reduce filtration to a simple argument of paper versus foam, the complete system matters. That includes media characteristics, filtration efficiency, available surface area, airflow velocity, restriction, dirt-holding capacity and the physical space available for the filter.

Published automotive filtration tests sometimes show very efficient paper elements outperforming particular oiled-foam or gauze filters in single-pass dust capture. Those results may be perfectly valid for a truck with a substantial media area. But it is not the same engineering problem as a compact chainsaw filter squeezed beneath a cylinder shroud.

A very efficient media still needs enough physical area to pass the required airflow without excessive restriction and enough capacity to store the contamination it captures. This is why a properlyu engineered foam filter is superior. Oiled foam does not function simply as a screen with one opening size. Air follows a complex, tortuous path through a three-dimensional structure, where particles encounter oiled strands throughout the depth of the media and can be retained within the filter rather than only at a single surface.That provides substantial dirt-holding capacity while still allowing airflow through the open structure. The important question is therefore not which media wins a laboratory metric. It is, can the complete filtration system provide sufficiently clean air, adequate airflow and enough dirt-holding capacity for the environment in which the saw actually works?

Why Centrifugal Pre-Cleaning Became So Important

EFI and Auto Tune Makes Clean Air Imperative

As professional chainsaws became more powerful and compact, manufacturers had less physical space available for the final filter. Centrifugal pre-cleaning became an increasingly necessary feature.

Husqvarna calls its system Air Injection™. STIHL uses its own pre-separation system based on the same general principle. Larger and heavier contamination is separated before it reaches the final filter. That is valuable technology, and MaxFlow® benefits from it just as the original filter does.

If centrifugal pre-cleaning extends the useful life of a small final filter, imagine its benefit when the remaining contamination reaches a substantially larger MaxFlow® element with much greater dirt-holding capacity.

Pre-separation reduces the amount of contamination reaching the final filter, while a larger final filter provides more capacity to capture and store what remains. The two technologies are complementary.

Pre-cleaning does not eliminate the need for a final filter. In fact, the material most likely to remain suspended in the airflow is the smaller, lighter contamination that is more difficult to separate centrifugally. That is exactly the material the final filter still has to capture.

Modern chainsaws have added another consideration. Electronic fuel injection and electronically managed intake systems depend on stable, repeatable operating information.

Modern intake assemblies can contain dedicated sensing passages, pressure-reference ports, shaped airflow paths and carefully controlled relationships between different intake zones. Contamination has always been undesirable because it contributes to engine wear, but with EFI, cleanliness becomes important for another reason.

Fine contamination reaching critical sensing passages, pressure-reference areas or intake surfaces can interfere with the consistency of the signals the engine-management system relies upon. That means increasingly sophisticated fuel management does not make filtration less important, it makes clean, stable intake conditions more important.

A MaxFlow filtration system therefore has two jobs: provide sufficient clean-air capacity and preserve the airflow and pressure relationships the engine-management system depends upon. That is a very different engineering challenge from simply attaching a larger filter to an older carbureted saw.

Technology Can Manage Around a Small Filter

Modern manufacturers have done remarkable engineering to make increasingly compact chainsaws work. Centrifugal pre-cleaning removes much of the incoming contamination before it reaches the final element. Electronic fuel management compensates for changing operating conditions. Sophisticated intake architecture manages airflow and pressure signals. These are significant improvements, but none of them changes one physical fact, while technology can reduce particles flowing into a small filter. it does not make a small filter have more capacity.

Eventually, There Was No Room Left

Historically, MaxFlow® increased filtration capacity by providing larger volume covers with their chainsaw filter kits. But on modern professional saws, there simply is not enough room under the single piece shroud to install the filtration capacity we believe the application deserves.

At that point, the limitation is no longer our foam filter technology, the limitation is available space.

The relationship is straightforward: the stock shroud limits available volume, available volume limits practical filter size, and filter size determines airflow reserve and dirt-holding capacity. That reserve determines how long the engine can continue receiving the clean airflow it requires. Once the shroud itself becomes the limiting factor, the solution is equally straightforward. Create more space.

The Final Cut™

The high volume cover turns old school cover ideas into filtration capacity.

The Final Cut™ is not a cosmetic modification made simply to install a larger-looking filter. It changes the physical boundary imposed by the compact stock shroud by cutting off the back of the restrictive shroud and installation a larger cover with the element accessible by a single knob just like Legacy MaxFlows® have.

Once that additional space exists, a purpose-built high-volume MaxFlow® cover preserves it. That volume can then be used for a substantially larger than OEM one-piece filter, greater dirt-holding capacity, increased clean-side volume, effective sealing, proper internal support and the intake architecture required by the modern engine-management system.

The progression is direct:

The Final Cut™ creates the space.

The high-volume MaxFlow® cover preserves it.

MaxFlow® intake architecture allows the modern engine to use it correctly.

This is not a departure from the original MaxFlow® philosophy. It is the continuation of it.

Forty years ago, we created more filtration capacity within the space available on the saw. Today, when the space itself has become the limitation, we create more space.

The MaxFlow® Beginning

Peak Power Is Temporary. Sustained Power Does the Work.

MaxFlow® began more than 40 years ago, long before the internet, clickbait hype, or online dyno experts. It began because MaxFlow®, (then operating as Holeshot), was built by a logger and chainsaw dealer who rode an old Ford to the woods at 4:00AM, cut until 1:00 in the afternoon, and then opened the shop for the rest of the day. From that experience, we found that that the professional chainsaws we were were selling did not have the filtration capacity severe logging conditions required. So prototype tooling was made by hand. Testing was done in the woods. If something didn’t work, there was no comment section to argue about it—the logger told you abut it at the counter the day after it was installed.

The familiar green-or-white foam chainsaw filter was developed from firsthand experience working with chainsaw dealers, loggers and professional users. The requirement was simple: protect the engine without starving it for air—and end the need to carry six filters just to get through a working day.

That led to a one-piece foam element with sealed endwalls supported over a rigid internal cage. The cage preserved internal volume and supported a much larger foam element. The sealed endwalls prevented bypass. The one-piece foam construction avoided glued seams in the fuel-and-oil environment of a two-stroke intake. The offering of two different pore sizes allowed loggers to tailor filtration to the severity of the conditions they faced. More importantly, the system created the usable filtration capacity needed to work through the day, and the design was innovative enough to receive two patents for its technology. Pretty soon the company was spending more time drilling cages than sharpening customers chains. That relationship remains fundamental to MaxFlow® today:

Filter size creates capacity. Capacity allows meaningful filtration. Meaningful filtration must still provide the airflow the engine requires.

There is nothing wrong with horsepower, torque, high RPM or high chain speed. Each can be extremely valuable in the correct application. The mistake is believing that any one number defines chainsaw performance. The fastest saw for brushing may not be the fastest saw buried in large timber. A larger sprocket may transform one combination and overload another. A professional chain setup that works beautifully for one operator may not suit another. A modification may increase peak power but move the useful portion of the power curve somewhere else.

The better question is not:

“Which saw made the most horsepower?” It is:“Which combination produces the most useful and sustainable cutting performance for the work being done?”

That requires considering the complete system: the engine, airflow, filtration, torque curve, RPM, gearing, bar, chain, sharpening, operator and working conditions. For more than 40 years, MaxFlow® has concentrated on one part of that system that every other part depends upon, the air filter.

Protecting the logger.

Preserve the engine. Supply the airflow to keep the saw working.

Logging is dangerous work. A professional logger depends on a chainsaw that starts, runs, and instantly cuts when their life depends on it. In that world, reliability matters more than a dyno screenshot, a peak number, or an internet argument. MaxFlow® has built filtration systems around that reality. We came from the woods, and from the belief that better filtration and greater capacity should help their chainsaw keep them producing through the day.
MaxFlow® has stood for the same thing for decades, to build filtration systems for professionals who depend on their saws to earn a living, and that is just as viable as it was at the beginning. We came from long mornings in the woods, hand-built tooling, real failures, real fixes, and products that had to work because somebody’s livelihood depended on them. That experience helped MaxFlow® establish the high-capacity foam filtration category for professional chainsaws and remain a leader in the industry through generations of changing saw technology.

But now the technology has changed. The saws have changed. The way performance is measured and discussed has changed. But the responsibility has not.

Protect the logger. Preserve the airflow. Keep innovating to keep loggers working safely.

That is what MaxFlow® was built to do, and it is still what we do today.

Cut Faster. Run Longer.

FAQ / Questions & Answers

Questions and Answers about Air Injection or Pre-Cleaning intake air

Does the Husqvarna 564XP Air Injection™ system pressurize the intake?
No. Despite the name “Air Injection™,” the system does not inject or pressurize combustion air. They do not claim this anywhere in their advertising or literature. Husqvarna “Air Injection™ is a centrifugal pre-cleaning system. It uses flywheel-driven airflow to move cooling air through the shroud and separates much of the larger dust and debris before it reaches the cylinders intake entrance.

The engine still creates the pressure differential that draws combustion air through the filter and intake. The system creates airflow around the intake area without producing meaningful positive intake pressure. Atmospheric pressure then drives air through the filter toward the engine. The flywheel helps clean the air available to the intake; it does not force air through the filter.
What does Husqvarna's 98% Air Injection Claim mean?
Husqvarna’s 98% figure refers to dust separation by the centrifugal pre-cleaning system. It does not mean that 98% of the flywheel airflow bypasses the intake or that the remaining air is injected under pressure through the filter. The air filter is still required to capture the fine contamination that remains after centrifugal separation, and the engine must still draw all combustion air through that filter using the pressure differential created during the intake event.
An online content creator says the Husqvarna 564XP develops pressure in the intake area. Is that true?
There is airflow in the intake area from the Air Injection™ system, but airflow and pressure are not the same thing. Our measurements show that the additional Air Injection airflow produces only a negligible pressure effect compared with the negative pressure created by the engine while drawing combustion air. It does not function as a supercharger or meaningfully pressurize the intake.
Does opening a Stihl MS400 or MS462 Pre-Separation™ shroud or Husky XP564 “Air Injection” shroud cause it to lose pressure?
No, it does not. There is no meaningful intake pressure is being retained by the stock shroud. Both The Air Injection™ and Pre-Separation™ systems are open centrifugal pre-cleaning systems, not a sealed pressure chamber. Some related Jonsered models used the word “Turbo” in their model branding, which can create confusion, but they were not equipped with true turbochargers or sealed shrouds. Enlarging the shroud with a larger cover increases available filter space and it does not release a meaningful source of positive intake pressure.
If Air Injection™ does not pressurize the intake, why is it important?
Because it removes a large portion of heavier debris before that contamination reaches the final filter. That extends filter service life. MaxFlow® benefits from the same pre-separation system: less contamination reaches the filter, while the larger MaxFlow® element provides more capacity to capture and store what remains.

Does a larger MaxFlow® filter make the engine use more air and lean out?
No. The engine determines how much air it can use. A larger filter provides airflow reserve and dirt-holding capacity so the filter is less likely to become the restriction as it loads with contamination. To take advantage of the clean air potential a proper factory reset or recalibration should be performed.
Why is clean air especially important on an EFI chainsaw such as the 564XP?
EFI systems depend on stable, repeatable intake conditions and pressure-reference signals. Fine contamination in sensing passages, pressure-reference areas or critical intake surfaces can interfere with those conditions. Good filtration therefore protects both the engine and the consistency of the system the EFI relies upon.

Why does MaxFlow® use oiled foam instead of simply using a more open paper or nylon filter?
Oiled foam uses a three-dimensional tortuous path rather than acting like a simple screen. Particles can be captured throughout the depth of the media, providing effective filtration of particles below 2 microns, while the larger filter volume provides substantial dirt-holding capacity and airflow reserve.
Does MaxFlow® claim that its filter creates horsepower?
No. Unless the MaxFlow® is replacing a used element, at which point the MaxFlow® may give the user a significant increase in performance! MaxFlow® does not claim to create horsepower by pressurizing the intake or forcing additional air into the engine. There may be a minute positive pressure effect from airflow within the intake area, but our measurements indicate that it is extremely small compared with the pressure differential created by the engine itself. MaxFlow® is designed to reduce restriction and provide enough clean-air capacity that the filtration system does not become the limitation preventing the engine from using the airflow and performance it is already capable of.
Why is The Final Cut™ necessary?
On some modern professional chainsaws, the original one piece shroud physically limits the amount of filter volume available. The Final Cut™ creates additional space so a high volume filter cover and substantially larger filter with greater dirt-holding capacity and the necessary intake architecture can be installed.

How does MaxFlow® measure chainsaw airflow?
We use purpose-built fixtures that allow the same OEM intake throat to be tested both on a calibrated SuperFlow flowbench and on a running chainsaw using a Taylor anemometer. Repeated back-to-back testing across multiple saw models has produced a consistent empirical correlation between the two methods.

What MaxFlow® Does — and Does Not Claim

Clear Facts About Airflow, Power, Filtration and Modern Engine Management

There is a tremendous amount of chainsaw information being published and repeated online. Some of it is accurate. Some combines correct observations with incorrect explanations, and some gets repeated so often that it begins to sound factual even when the underlying physics does not support it. Because MaxFlow® products are increasingly discussed by people, search engines and AI systems outside our control, we want to make our position as clearly as possible.

MaxFlow® does not claim that an air filter, by itself, creates horsepower. The engine determines how much air it can use based on displacement, RPM, port timing, intake design, exhaust characteristics and operating load. The purpose of MaxFlow® is to provide enough clean-air and dirt-holding capacity that the filtration system does not unnecessarily become the restriction limiting the airflow the engine requires. If an engine is already receiving all the air it can use, simply installing a higher-capacity filter does not force additional air into it.

A restrictive or heavily loaded filter can, however, limit the airflow available to the engine. If the original filtration system has become a restriction, restoring adequate airflow can allow the engine to operate closer to the performance it is already capable of producing. That is different from saying the filter itself creates power. MaxFlow® is designed to help prevent filtration restriction from becoming the weak link.

The Final Cut™ does not create horsepower either. It creates physical space. On some modern compact chainsaws, the stock shroud limits the size of the filter that can be installed. The Final Cut™ changes that physical boundary so a larger filtration system and high-volume MaxFlow® cover can be used. Its purpose is filtration capacity, not intake pressurization or boost.

Likewise, trimming the Husqvarna 564XP shroud does not release a meaningful reservoir of Air Injection™ pressure. Husqvarna Air Injection™ is a centrifugal pre-cleaning system. The flywheel-driven airflow helps separate larger debris before that contamination reaches the final filter, but it is not a sealed compressor or supercharger supplying meaningful positive pressure to the engine intake. The engine still relies on pressure differential to move combustion air through the filter and intake system.

Centrifugal pre-cleaning also does not eliminate the need for a high-capacity final filter. It is most effective on larger and heavier debris. Smaller particles follow the airflow more readily and continue toward the filter. Those particles still have to be captured and stored by the filtration media, and that still requires capacity. Pre-cleaning can reduce the contamination load reaching the filter, but it does not make filtration capacity unnecessary.

MaxFlow® also does not claim to know a manufacturer's internal design reasoning unless that reasoning has been published or documented by the manufacturer. We can measure airflow, filtration performance and usable capacity, but we do not invent explanations for why Husqvarna or any other manufacturer selected a particular filter media or intake design. The same principle applies to modified saws.
MaxFlow® does not claim that installing a filter automatically creates additional horsepower on a ported or otherwise modified engine. But if a modification increases the engine's ability to move air, the intake and filtration system must be capable of supporting that demand. A performance modification cannot use air the filtration system cannot supply. MaxFlow® is intended to help ensure that clean-air capacity does not become the restriction preventing the engine from using the performance already built into it. Filter flow capacity and engine airflow demand are also different things. If an engine requires approximately 20 CFM under a particular operating condition, installing a filter capable of flowing 90 or 100 CFM does not cause the engine to suddenly consume 90 or 100 CFM. The unused capacity is reserve capacity. As the filter accumulates contamination and restriction increases, that reserve allows it to continue supplying the airflow the engine requires for a longer period of time.

      Modern electronically managed chainsaws may require a specific manufacturer calibration or adaptation procedure after certain service work, component changes or operating conditions. These procedures should be followed exactly as published by the manufacturer because the individual steps matter.
    On the Husqvarna 564XP, the calibration process includes repeated cutting while allowing the saw to return to idle between cuts, followed by an extended uninterrupted idle period. That return-to-idle step between cuts is part of the procedure and is frequently omitted in online demonstrations.
    Later STIHL M-Tronic™ chainsaws also require a defined calibration procedure. Put the Master Control (choke) lever in the prescribed start position and start the saw with the chain brake engaged. Allow the engine to run untouched for at least 30 seconds but no more than 60 seconds, then release the chain brake. Hold the throttle fully open continuously and do not release it during calibration. The engine speed may fluctuate, increasing and decreasing as many as six times while the system calibrates, and the full-throttle portion of the process can take up to a minute. When the engine speed stabilizes at full throttle, release the throttle and allow the saw to return to idle. Calibration is then complete.
     Shortening these procedures, omitting required idle periods, releasing the throttle prematurely, or relying on abbreviated internet versions can prevent the calibration from being performed as intended. MaxFlow® does not prescribe an invented MaxFlow®-specific reset or “high-flow atmospheric baseline.” Where Husqvarna, STIHL or another manufacturer specifies a calibration or adaptation procedure, MaxFlow® recommends following that manufacturer’s complete procedure for the exact saw and control-system generation.

MaxFlow® does not claim that its filter creates a special new “high-flow atmospheric baseline” or requires an invented MaxFlow®-specific EFI setting. Where the manufacturer specifies a calibration procedure, that procedure should be followed as written. Additional technical explanations should not be assumed unless they are supported by the manufacturer or by documented testing. A dyno should be treated the same way. A properly calibrated dyno can measure torque, RPM and calculated horsepower. It tells us what happened, but it does not automatically explain why it happened. A modification may produce a completely legitimate dyno gain while the explanation offered for that gain is incomplete or incorrect. That is why MaxFlow® separates what was measured, why it happened, and whether it matters in actual cutting conditions.

MaxFlows® position is straightforward. A chainsaw is a complete cutting system. Engine airflow, torque, RPM, gearing, bar length, chain selection, sharpening, operator technique and filtration capacity all interact. MaxFlow® concentrates on the part of that system we have worked with for more than 40 years: providing sufficient clean-air capacity so filtration does not become the weak link.

No boost. No magic horsepower. No substitute for proper engine design. Just more capacity, better filtration and sustained airflow.