Performance Mods: More Power Up Front

You’re normal. You’ve owned your airplane for a few years, done those little things to make it really “yours,” and you intend on keeping it for some time. But you have this nagging feeling in your gut that “if only it … were faster … climbed better … could take off and land shorter … then it would really be the perfect airplane for me.” 

Every aircraft owner goes through the “if onlies” multiple times during ownership. It used to be that the “if onlies” made aircraft salespeople very happy because owners would gladly trade up for a more capable airplane that came closer to the owner’s vision of ideal.

With the prices of new (and used) airplanes leaving the rate of inflation in the dust, trading up isn’t the attractive option that it once was. That combined with the aggressive development of aftermarket aircraft modifications means that owners have some very attractive options when it comes to adding a mod to their aircraft with the odds that the change produced will be worth the price. As part of our series on aircraft upgrades, here we’ll look at some top-pick choices for adding more power. Use it as a general guide for shopping.

What Kind of Mods?

For this three-part series, we’re going to look at modifications designed to increase cruise speed, increase rate of climb, and/or reduce stall speed (STOL). Put simply, to increase performance it’s necessary to increase thrust (via engine horsepower and/or propeller efficiency) and/or reduce airframe drag. To decrease stall speed to turn the airplane into a STOL bird it’s necessary to change the shape of the wing’s airfoil and/or change the flow of the air over the wing. We’re breaking up the series into three parts: one on adding power, one on reducing drag, and one on STOL mods. 

While this part will be devoted to more power for the airplane, we’ll explore the regulatory environment common to all three parts of our series, the required STC (Supplemental Type Certificate). We’ve seen unapproved engine upgrades in all kinds of airplanes over the years, and in the eyes of the FAA, these alterations deviating from the original type design ultimately make for an unairworthy airplane.

Let’s Look at STCs

Most of the modifications we looked at meet the FAA’s definition of “major alteration” in FAR Part 1. That includes the phrase “might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness …” A company that develops a modification that meets the FAA’s major alteration definition must go through a development and testing process and be awarded an STC by the FAA before it can sell the product and it may be installed on a production airplane. Bluntly, the mod designer must prove that the mod does not adversely affect or diminish the performance or handling characteristics of the original design that received an FAA Type Certificate issued to the manufacturer. That means that any mod you buy will come with STC paperwork, a requirement to follow the installation instructions, make the appropriate logbook entry, and file a Form 337 for the major alteration with the FAA. 

To obtain an STC, an applicant does not need to demonstrate any increase in performance of the airplane—just that it doesn’t have an adverse effect—the FAA doesn’t care if it makes the airplane better, it just can’t make it worse. That explains why virtually no mod shop offers new performance data on the airplane as modified. You’re usually on your own to see if the mod really makes the airplane go faster, climb higher, or stall slower than before the mod. 

Over the years we’ve reviewed many of the modifications offered and can say that almost all of them do at least some of what it is they are advertised to do—and the feedback from owners attesting to desired performance changes have helped the mod shops continue to sell their wares. 

I Wanna Go Faster … Give Me More Noise up Front

No matter how we wrap our desire for speed in euphemisms to try and justify spending money on an aftermarket mod, it is always about speed. That’s why most of us fly.

There are two ways to increase speed, reducing drag and increasing thrust—known since air racing in the 1930s where huge engines were bolted to the smallest airframes possible, making many of the racers look like a flat-headed bug. They often flew as they looked—scary, but they were fast. A look at racing speed records for the era show a hard aerodynamic reality—airspeed increase is proportional to the cube root of the horsepower increase. In other words, if you want to go 10% faster, you’ve got to increase horsepower by 33%. For example, the miserably handling Gee Bee series set records based on power and a primitive idea of streamlining (the fuselage got even wider aft of the engine). In 1931 the Gee Bee Z, with a 535-hp radial up front, set a speed record of 267 mph. After dropping in a 750-hp radial, its top speed was 281 mph, or 14 mph gained for an additional 215 hp.

The next year, Dr. Jimmy Doolittle (Ph.D. in aeronautics from MIT and of WWII carrier bombing attack on Japan fame) took a successor Gee Bee, the Model R, powered by an 800-hp radial, to 294 mph. Even with the cleaned-up airframe, it took 50 more hp to get 13 more mph. After that race Dr. Doolittle quit racing saying that the risk was too high for the marginal increase in knowledge gained. It would take a few more years until we learned enough about stability and control as well as flutter to make airframes that could safely handle very high speeds.

Howard Hughes flew his beautifully streamlined, retractable gear H-1 Racer to a land plane speed record of 352 mph in 1935. However, the Brits made the folks in the U.S. look like pikers. Competing for the Schneider Cup Trophy for speed in seaplanes, Supermarine’s genius engineer, R.J. Mitchell, married a Rolls-Royce RV-12 engine developing 2,350 hp with his elliptical-wing, sleek airframe and a pair of floats (not retractable) to create the S6B racer, which set a seaplane speed record of 407 mph in 1931—take that Howard Hughes. However, the state of the art in metallurgy (always the driving factor in engine development) meant that the RV-12 essentially melted by the end of a race. The marriage of Rolls-Royce, Supermarine, and Mitchell later resulted in another offspring, the Supermarine Spitfire of World War II fame. 

What’s Available Now

In the general aviation world, there are a number of STC holders that will drop a larger piston engine—or in some cases a turboprop—into your airplane. It’s never cheap and one needs to keep in mind that it means increased fuel consumption in an airplane with fuel tanks designed for smaller engines, a potentially limiting factor. Adding fuel tanks cuts into useful load and going turbine means using heavier jet fuel, also negatively affecting useful load. 

We think that the best way to increase speed via the increasing power route is to go with an STC-approved higher horsepower engine. It will provide the happy side effect of greatly increased rate of climb. Climb is a function of horsepower available above power required to fly level at Vy. If it takes 50 hp to fly level at Vy—leaving 50 hp to pull you upward—in a Cessna 150, the 150-hp conversion means 100 hp available horsepower, an increase of 100%, dramatically increasing rate of climb. We spent some time towing gliders in a 180-hp Cessna 150. It could get up and climb in a hurry, although we were less impressed with its speed and handling in level flight—as well as the fuel burn. 

In smaller GA aircraft such as the Cessna 150, the purveyors of big-engine STCs seem to come and go. Our search for an engine swap STC for the Cessna 150/152 series came up empty. We recommend inquiring though the type club for your aircraft. In the Cessna 150/152 world, it appears that it’s more economical for a stock 150 owner to sell it and buy an already modified airplane than to try to find an STC and buy a new or used engine (and possibly propeller) and pay for the installation.

In the slightly larger airplane world, we found several shops that hold STCs for installing larger engines. In no particular order, this is a select list of shops we like.

Wipaire

Known and respected for building floats for airplanes, Wipaire has a lot of experience with the difficulty of getting a seaplane off of the water in high and hot conditions. Wipaire came up with what we think is a stunning upgrade to the Cessna 182—the Boss 182 for the S and T models. It installs a Lycoming IO-580 engine with 315-hp stock, or—after tuning by Ly-Con—340 hp. A new prop is required, and gross weight increases are available. The full conversion includes engine and prop as well as rudder extension, new engine mount, new interior, and upgraded instrument panel. 

The conversion can be done for wheels or floats. Wipaire does not publish prices on its website, but given the extent of the modifications expect the cost to start at $600,000 and continue north. In years of talking with mod shops, they are reluctant to give exact pricing because, when they open up the airplane, they too often find gremlins or something ugly that must be repaired before even starting on the mod. OK, that’s putting it mildly, you would not believe the crap they find—improper repairs, unauthorized parts, parts held on with zip ties and duct tape—don’t be surprised if your prized airplane has some ugly secrets in its guts.

Wipaire also offers performance enhancing mods to the Cessna 206, starting with installation of a Continental IO-550 (300 hp continuous) and a McCauley or Hartzell “Power Prop.” Given that the price of a new IO-550 is in the high $60,000 range, the performance gain for someone looking for speed may not be worth it. If looking for increased capability, rate of climb and shorter takeoffs, especially for commercial 206 operators, it could be a no-brainer.

Air Plains for Cessnas

Based in Wellington, Kansas, it’s always seemed to us that Air Plains has been offering engine upgrades so long that they were doing them for the late 1920s Cessnas as Clyde rolled them out of the door. It turns out that they started work in 1977, hold 31 STCs, and have done 3,018 engine upgrades. They specialize in Cessna singles. Here’s a quick summary:

• Cessna 172 Models B through P, power to 180 hp
• Cessna 17 Model R, power to 180 hp
• Cessna 180 through model K, power to 300 hp
• Cessna 182 through model R, power to 300 hp
• Cessna 182RG, all models, power to 300 hp
• Cessna 182 Models S and T, power to 260 hp
• Cessna 182 RG, all models, power to 260 hp

Air Plains also offer propeller upgrades for all models. As an aside, propeller upgrades usually generate some increase in rate of climb, and possibly in cruise speed. For singles with engines below 230 hp, going from a two- to three-bladed prop may result in a slight decrease in cruise speed.

D’Shannon for Beechcraft

D’Shannon Aviation is long the big dog in upgrading Beech aircraft with bigger engines, scimitar props, performance exhaust, gross weight increases as well as gap seals, VGs, and engine baffling. The upgrades are available for Bonanzas, Debonairs, and Barons. Engine upgrades are to the 260-hp IO-470C and N, 285-hp IO-520, and 300-hp IO-550B. Performance exhaust systems upgrade to system to maximize power output and are available on Bonanzas and Barons. 

Fortunately, D’Shannon provides an upgrade matrix on its website so owners can quickly find what is available for their airplane.

Mike Jones Aircraft/Lock&Key

Tennessee-based Mike Jones Aircraft continues doing engine-plus-other-upgrade Colemill conversions for Cessna 310 models I-R, Piper PA31-310, PA31-325 and PA31-350 Chieftain, Beech A-55, B-55, C-55, D-55, E-55 and 58 Baron as well as Bonanza models A-36, S-35, V35, E-33A and F33A. We like that the website includes a price sheet for each conversion. The company has also developed winglets for most of the Beech Baron and Piper Navajo lines. 

In addition, Mike Jones offers two attractive Lock&Key refurbishment programs for twins that start with the company buying a carefully vetted Piper Navajo or Beech Baron and spending three-quarters of a million dollars upgrading it to what might be considered nearly new condition—which may include an engine upgrade—fly it 15-30 hours, give it a final inspection and turn it over to the new owner. The company says that all you have to do is insert your key, unlock the door, and fly it home. Price for the Navajo starts at $1,400,000 plus options, and Jones says Lock&Key planes appraise at full value.

But it isn’t only about Navajos and Barons. Jones is also looking for other models to put in the Lock&Key program, including Cessna singles—contact the company if you have a clean one to hand over.

Texas Skyways

Texas Skyways has been offering engine and propeller upgrades for Cessna singles for over 40 years. Its 250-hp Continental O-470-U/TS engine conversion is available for Cessna 180s and 182s. The website does not specify if all models of each series are included.

Continental 280-hp IO-520-F, O-520-F/TS, and O-520-U/TS are available to upgrade power on certain models in the following Cessna lines: 180, 182, 205, 206 and 210. 

A 285-hp Continental IO-5500F or O-550-F/TS can be hung on select models in the following Cessna series: 180, 182, 205, 206 and 210. 

All of the above engines come with a 2,500-hour TBO. The 300-hp IO-550-lD is offered to upgrade the Cessna 185 series.

RAM Aircraft

Since 1976 RAM Aircraft has been a full-service engine overhaul, airframe upgrade, and aviation support center in Waco, Texas, specializing in Beechcraft, Cessna, and Cirrus airplanes, although it only offers engine power upgrades for twin Cessnas.

For the Cessna T310 series RAM offers two power upgrades, the Series I, boosting power output to 300 hp per side, and the Series IV that cranks things up to 325 hp on each wing. 

For the Cessna 340 and 340A, RAM offers its 325-hp Series IV mod, advertised to increase the twin-engine rate of climb from 1,650 FPM to 1,815 FPM and bumps cruise speeds by about five%. At 75% power at 20,000 feet, the Series IV mod ups cruise speed to 225 KTAS—that will run with an early King Air 90.

For the Cessna 414 (tip tank model), RAM’s Series IV mod boosts power from 310 hp to 325 hp per side, bumping rate of climb over 10% and cruise speeds about 5%. As we said, power increases do more for climb rate than speed.

The Cessna 414A (no tip tanks) can be upgraded with the Series IV mod, also boosting power to 325 hp per side. All-engine climb goes up by about 5% while the cruise speed delta is less than 5%.

For the C-model Cessna Golden Eagle—421C—RAM offers two mods, the 421C and the 421CW. The later includes installation of winglets. The advertised 325 hp is kept for both mods, but other cleanups boost the rate of climb from 1,210 FPM to 1,290 FPM for the RAM 421C and 1,450 for the winglet version. Cruise stays the same for the RAM 421C but increases by five to 10 knots with winglets, depending on power settings. 

John Jewell Aircraft

John Jewell Aircraft offers power upgrades for legacy Cessna 182s (through 1986 model year) and Cessna 210s and T210s models K, L, M, and N. 

The Cessna 182 STC installs an O-470U engine modified to produce 252 hp with a 2,00-hour TBO and offers a choice of propellers. The company advertises a rate of climb increase up to 400 FPM and a five to eight knot cruise speed bump. 

For normally aspirated Cessna 210s, the STC upgrades to the 300-hp IO550L with a choice of a three-bladed Hartzell or McCauley prop. 

Interestingly, John Jewell “de-turbos” the T210 by installing a normally aspirated 300-hp IO-550L engine. The company advertises up to a 20% increase in rate of climb and 10% increase in cruise speed at gross weight. The de-turbo mod also increases TBO and advertises more economical performance up to about 10,000 feet (where we expect the crossover from a normally aspirated engine to a turbocharged one). Removing the turbo increases useful load. 

Bold-Warrior

Locust Grove, Georgia-based Bold-Warrior offers 180-hp upgrades for most Piper Warriors, Cherokees, and 7 Series Citabrias. Pricing as this is being written is $66,900 for an installed engine and propeller at Bold-Warrior’s shop. The company schedules two days for the upgrade, making it the fastest of any of the mods we’ve experienced. 

Bold-Warrior’s website indicates that on its test aircraft the Piper performance increased rate of climb by 200 FPM, cruise speed by six to 10 knots, depending on propeller, and service ceiling by 3,000 feet, with a slight increase in range. On the Citabria 7GCBC test aircraft they recorded an 800 FPM rate of climb increase and 16-knot cruise speed increase. 

Penn Yan Aero

Penn Yan Aero has been offering its SuperHawk conversion/overhaul boosting 150-hp and 160-hp Lycoming engines in Cessna 172s to 180 hp for over 40 years. The company will either overhaul and convert the O-320 engine to an O-360-A4M SuperHawk engine (at its facility or will ship all parts and replacement propeller to your shop for free) or swap out your existing engine for a new (zero-timed) O-360-A4M engine. It also offers an owner the option of providing the engine and buying the kit, STC, instructions, hardware, and Sensenich propeller—and pay for shipping. 

Penn Yan will also do the RAM 160 conversion to Piper PA-28-140 and PA-28-141 and Cessna 172 model I, J, K, L, and M—all having 150-hp Lycoming engines—upping the horsepower to 160. 

While it is not a power increase for the Cessna 172N, Penn Yan will install a Lycoming O-320-D2J or O-320-D2G engine in place of the original O-320-H2AD, which does not enjoy a great reputation. (Why would anyone put the letters “AD” in the name of anything related to airplanes?) There is a capability/performance increase; however, a 100-pound gross weight bump.

Northpoint Aviation

After taking over the P Ponk XP470 engine power upgrade STC for the Cessna 182, Northpoint Aviation has not looked back. The upgrade is also available for all models of the Cessna 180; plus Northpoint acquired Soloy Aviation Solutions three years ago, buying all of the STCs, intellectual property, and product lines. Soloy has been known for decades for its turbine conversions of helicopters, Cessna 206s and 207s, as well as Beech Bonanzas. On the piston end, The XP470 engine conversion can be done at Northpoint or your shop—it takes a stock Continental O-470 engine, modifies it with larger cylinders and 7.5 to 1 compression pistons, turning it into essentially a carbureted O-520, and adds a two- or three-bladed McCauley prop, keeping the existing engine mount, baffling and cowling, thus only adding four pounds to the empty weight of the airplane. Horsepower increase with the mod is advertised to be from 35 to 45. 

Northpoint does not advertise prices as it says it does not control pricing or warranty of the shops it has authorized to do the conversions. Based on what we’ve been able to observe, figure the price to start at about $50,000 and go north depending on the condition of the engine being modified and what’s found once the shop gets into the guts of the airplane. Nevertheless, over the years we’ve felt the P Ponk/XP470 engine conversion for a 180 or 182 that is based where rate of climb might really matter is good bang for the buck, especially given the modest weight increase.

Northpoint currently advertises the Soloy MkI and MkII turboprop conversions for the Cessna 206. The MkI mod is applicable to the 206G and H. It installs a Rolls-Royce/Allison 250-C2 turboshaft engine rated at 417 hp while reducing the empty weight of the airplane by 150-170 pounds, which goes a long way to offsetting the effects of the heavier fuel and greater fuel consumption. The cowling is redesigned to dramatically reduce drag, new engine mounts are installed, and the electrical system is upgraded. 

The MkII mod for the 206H and T206H goes with the -B17F version of the engine, which develops 510 hp but is derated to 417 hp, allowing more power in higher density altitudes.

We’ve seen the Soloy 206 mods operating for years, mostly in countries where avgas is hard to obtain, and we’ve been impressed with their performance carrying heavy loads. Northpoint does not advertise the price for the mods, but our best estimate is that a new engine would run on the order of $500,000 (overhauled can be had for less), plus installation; the cost would probably start at $750,000 if you supply the airplane, at least $1,000,000 if you need to buy an airplane to be modified. 

In our opinion, given that a person could probably buy a decent used Cessna 208 for not much over $1 million or a used Kodiak for as low as $1.5 million, we’re not convinced that the Soloy Cessna 206 conversion is financially wise currently.

Vitatoe Aviation

Based in Chillicothe, Ohio, Vitatoe Aviation’s current upgrades of the Cessna T210 and P210 grew out of work former drag racer Larry Vitatoe did with Tornado Alley Turbo’s engine experts, Tim Roehl and George Braly. The TSIO-520 engine is replaced with an IO-550 that is connected to the airplane’s original turbocharger in a manner to turbonormalize the system—maintaining 31 inches of manifold pressure and 310 hp up to 23,000 feet and increase cruise speed to over 200 knots. 

We flew the P210 mod some years ago and noted that in a climb to 22,000 feet at 120 KIAS, the climb rate never dropped below 900 FPM—roughly twice what we were used to in the stock P210 over the years, especially when trying to keep CHTs from skyrocketing. The conversion is done at Vitatoe’s facility and includes a remanufactured engine, new Hartzell prop, engine mounts, and accessories. We like pressurized piston singles, and feel this mod gives the kind of performance the P210 should have had originally, plus the airframe accommodates tall pilots easily. If you have a P210 that you truly like, we think that the odds of this mod being right for you are pretty good. Completion time can be 12 to 16 weeks. Vitatoe’s website has pricing effective March 2025. 

Bolt-On Power: Exhaust

The auto racing world discovered the idea of fine-tuning an engine exhaust system by making the length of each exhaust tube so that the low pressure traveling down the tube behind each exhaust puff would reach the collector in time to suck out the exhaust from the next cylinder, creating a low pressure at each exhaust port when it opens to improve scavenging the products of combustion while decreasing back-pressure on the cylinder. Less back-pressure, more power output. Power Flow Systems successfully applied the concept to aircraft engines, gaining on the order of 10% more power per installation, a decrease in brake specific fuel consumption, and an increase in torque.

We’ve flown behind the systems in several aircraft and compared the before and after with a Cessna Skyhawk. Short answer—it works. Power Flow stresses the increase in climb performance, which is what we’ve observed. It says cruise speeds will increase about five mph. 

Power Flow’s website includes pricing for the system (installation varies but shops we’ve spoken with say that it’s fast) and starts at $6,900. The highest price we saw was $10,450. Rather than try to list all the aircraft for which the system is STC’d, we’ll state that if you are flying a single, there’s a high probability that there is a Power Flow system for it. 

For on the order of $10,000 installed, and a 10% increase in rate of climb, we think the odds of this mod being right for you are high—especially when you’ve watched the trees on the end of a runway get taller on warm days.

Electronic Ignition: SureFly, Electroair, Hartzell E-MAG

In the automotive world the benefits of electronic ignition are well known; variable timing provides more power, stronger spark, makes starting easier and, in the aircraft world, it does away with pulling and inspecting magnetos every 500 hours. 

For aircraft, most of the benefits are obtained by replacing just one mag—there’s no need to pay the freight for replacing two.

SureFly offers electronic mags (which it refers to as SureFly Ignition Module—SIM) for both four- and six-cylinder engines. For a four-cylinder engine, the SIM is priced at $2,095; for a six-cylinder engine the cost is $2,295. The system advances ignition timing only in cruise, so there is no benefit in climb. However, the increase is measurable and goes up with altitude. Sticking with the old cruise speeds, an owner can expect a 10-15% reduction in fuel burn in cruise. 

Electroair offers a more sophisticated electronic ignition as it varies ignition timing during all phases of flight. That gives increased cruise speeds or a 1-2 GPH reduction when flying at pre-electronic ignition speeds and an increase in rate of climb and service ceiling by up to 10%. The price for a four-cylinder engine kit is $2,960; six-cylinder kits star at $3,735. Installation is more complex than just replacing a magneto, so a prospective buyer would be wise to talk with a shop that has installed many of them, and call Electroair directly—they have very experienced techs answering customer calls, and in our experience, love to talk electronic ignition.

Hartzell acquired E-MAG, a manufacturer of electronic ignition systems, in 2025. It recently announced a drop-in magneto replacement solid state electronic ignition system, which is going through the certification process for installation in Part 23 (and CAR 3) factory-built aircraft. Pricing and capabilities have not been announced as of this writing. We’ll be watching to see what develops. 

Wrap It Up

We think that owners who need better climb rates and shorter takeoff rolls in the areas they fly, especially in summer weather, can potentially find a mod that increases engine power output. The amount of increase tends to be proportional to price, but at the lower cost end, we think the odds for a mod that does what you want at a reasonable price are a Power Flow Exhaust and/or replacing one mag with electronic ignition.