# Roswell's thin air made a T-6 crew chief start his tuning over

By MarketScale Newsroom · Published 2026-10-27 · Sports & Entertainment on MarketScale
Canonical: https://www.marketscale.com/industries/sports-entertainment/roswell-s-thin-air-made-a-t-6-crew-chief-start-his-tuning-over-1277331

> Crew chief Charlie Duffy is relearning race 90's engine tuning for Roswell's thinner air after years of Reno data stopped working.

## Key points

- Race 90's engine runs at 2,400 rpm burning 70 gallons an hour, against the 450 hp at 2,100 rpm the Smithsonian lists for a stock R-1340 Wasp.
- The National Championship Air Races left Reno-Stead after the 2023 event and started at Roswell in 2025, so no T-6 crew has more than two Septembers of Roswell data.
- Duffy saved no telemetry from the first Roswell year; this season he is logging cylinder-head temperature, fuel flow and pressure to set the plane up for 2027.

Charlie Duffy has a new engine on race 90 and a file of numbers that no longer apply to it. The old engine, he says, liked running hot at Reno, and the crew learned over years exactly where it wanted to sit. In Roswell, with pilot Greg McNeely waiting on a setup, those numbers do not work.

Duffy explained the problem in a recent interview for Concorde Battery's Pilots in Winnebagos Talking Shop series, a MarketScale-produced segment recorded during race week with the show's host from Concorde Battery. The host reminded viewers that Duffy is the same man who drove a Factory Five Daytona in a Cannonball Run in early May to raise money for Tango 31. This week he is running a T-6 trainer the two date to the late 1940s, with a radial engine burning 70 gallons of fuel an hour.

The timing is tight. In a July 2026 roster announcement, the Reno Air Racing Association (RARA) listed McNeely, of Port Orange, Florida, in the T-6 class for the September 16 to 20, 2026 National Championship Air Races at Roswell Air Center, flying a T6-G named Undecided as race number 90. It is only the second year the races have run in Roswell, which means Duffy's Roswell file holds one season at most, and by his own account he did not save last year's data.

## The job is keeping hands off the airplane

Duffy's first rule for race week is that nothing comes off race 90 or goes on it without his permission. Most pilots are not mechanics, he says, so the crew keeps them off the airplane. McNeely is proficient, Duffy adds, but the plan is to keep him being a pilot this week.

Tech inspection is the reason. Duffy says the crew has to get through the sanctioning body's inspection with everything in top racing order before the races, and the crew chief is the one organizing who touches what. A volunteer with a screwdriver and good intentions is a risk to that order.

The crew sorts into two groups. One or two people know round engines, the radial layout in which the cylinders sit in a circle around the crankshaft, nine of them cooled by air rather than liquid in the Pratt & Whitney Wasp the Smithsonian National Air and Space Museum describes in its catalog. The rest, including the host, who volunteers on the crew, wax the plane, look it over for loose screws and bring anything they find to the mechanics.

## A tighter cowling buys speed and costs cooling

For race week, race 90 swaps its everyday cowling for a necked-down race cowling and tapes every ugly seam. The cowling is the sheet-metal shell around the engine, and the gap at its rear edge is where air that has cooled the cylinders leaves the airplane. Close the gap and the airplane gets slicker.

Speed tape is adhesive aluminum tape laid over seams so passing air slides instead of catching, and Duffy says it is there to make the airplane go fast. The crew also fits rubber under the wheels so the gear wells seal when the gear comes up. Duffy wants the silicone-based baffling with fiber reinforcement in the middle, because the plain version gets torn up by the retraction mechanism; the crew bought some that did not hold and is hunting for a stiffer kind.

The cost of all that sealing is heat. Less gap means less air leaving the cowling at the moment the engine is working hardest.

> In full race mode, we can reach up to 75 gallons an hour. Full race on, full hard, 2,400 plus RPM. And so you have to balance the trade off of heat, and the way you get rid of heat is more fuel, actually. — Charlie Duffy, Crew Chief for Greg McNeely, Race 90

Fuel as a coolant sounds backward, but AVStar Fuel Systems, a fuel systems company, lays out the mechanism in a product explainer on its site. In the company's description, a mixture that is too lean at high power raises thermal stress and the risk of detonation, while a mixture richer than the air can burn costs some power and burns more fuel. Duffy's extra fuel is buying thermal margin with horsepower, on an engine that gets less cooling air than it did under the stock cowling.

## Roswell's thin air put the Reno numbers out the window

Density altitude is the altitude the engine behaves as if it is flying at once temperature is added to the pressure reading. AVStar's explainer defines it as pressure altitude corrected for nonstandard temperature, pushed up by heat, elevation, low pressure and humidity, and notes it can sit several thousand feet above a field's published elevation on a hot day.

Roswell's airport sits lower above sea level than Reno-Stead did, the host observed, and Duffy agreed. Yet the air the engine breathes on race days is thinner, which is why the crew talks in DA, density altitude, rather than field elevation.

> The DA here is flying, like, between 7,000, 8,000 feet versus, Reno was a little bit less. — Charlie Duffy, Crew Chief for Greg McNeely, Race 90

The engine swap complicates it further. Duffy cannot carry even the old engine's Roswell habits forward, because the engine that formed them is gone.

Duffy's crew now reads three things off race 90's telemetry: cylinder-head temperature, fuel flow and pressure. Cylinder-head temperature, CHT, is the metal temperature at the cylinder itself, the fastest sign that cooling has fallen behind. Exhaust gas temperature, EGT, reads the heat leaving the combustion chamber and is the usual guide for setting mixture, but Duffy says EGT is going to be whatever it is, and CHTs, fuel flow and pressures are the only things he really cares about.

The host likened the week to automobile racing, where every track brings its own altitude and surface, and Duffy agreed that all of the data from years at Reno is out the window. He describes the current state as throwing darts and trying to find the bullseye, with more practice days ahead before he can tweak the setup again.

## Why there is no Roswell baseline to borrow

Reno gave T-6 crews almost six decades of the same course; Roswell has given them two Septembers. RARA said in a March 9, 2023 press release that it had agreed with the Reno Tahoe Airport Authority to make that year's event, September 13 to 17, 2023, the last at Reno-Stead Airport, closing a run that began in 1964. The airport authority's stated concerns, in the same release, included rapid area development, public safety and the impact on the airport, and RARA said it was already talking to other venues.

Texas Public Radio reported in June 2024 that the association had settled on Roswell, New Mexico, with racing to begin in 2025. RARA chief operating officer Tony Logoteta told the station the move followed a year-long relocation process, and that the association had long expected to lose Stead eventually as development pressed in around the airport, just not this quickly.

The course changed with the city. RARA's T-6 class page gives the fastest T-6 race speeds as 220 to 230 mph on the 5.06-mile Reno course, while its July 2026 roster post describes the Roswell racing at speeds exceeding 225 mph. For a crew chief, every one of those laps at Reno was a data point in the same air, and every lap at Roswell is a data point in different air.

## What thinner air does inside a 22-liter radial

Each intake stroke carries less oxygen as density altitude rises, AVStar explains on its site, so a mixture set for denser air is now richer than the air can burn. The company lists the results: less power, more fuel burned, fouled spark plugs and rough running. Push the other way at high power, it warns, and thermal stress rises along with the risk of detonation, the fuel charge exploding instead of burning in a controlled front, or preignition.

That is the box Duffy is working in. Every gallon he adds for cooling is a gallon the thin air cannot fully burn; every gallon he pulls back for power is thermal margin given away. The old Reno setting sat somewhere in that box for an engine that no longer exists, in air that no longer applies.

AVStar's leaning guidance is written for normally aspirated Lycoming engines, which it says may be leaned at roughly 5,000 feet density altitude and above, and the company states plainly that supercharged engines need separate procedures from the manufacturer. A 1940s radial in race trim is not what the explainer has in mind. Its advice for constant-speed propeller installations, set mixture from fuel flow, manifold pressure, rpm and temperature limits as the aircraft handbook directs, is close to what Duffy is doing with telemetry, minus the EGT he has chosen to ignore.

Neither Duffy nor RARA has published a Roswell target for cylinder-head temperature or fuel flow in the T-6 class, so the specific shift from Reno stays inside each crew's own data. Duffy's version of the answer is a direction, richer to cool, leaner to recover power, and a week of readings to find where the lines cross.

## A 1940s engine run past its catalog rating

The Smithsonian catalogs a stock R-1340 Wasp at 450 horsepower and 2,100 rpm; Duffy races his at 2,400. The museum's entry for the Pratt & Whitney Wasp R-1340 SC1 describes a nine-cylinder, air-cooled radial of 22.2 liters and 650 pounds, built around 1932 to 1936. The Wasp is the engine family that powers the T-6.

The catalog figure is a floor, not a late-1940s rating. The museum notes the Wasp stayed in production until 1960 and that later models produced up to 600 shaft horsepower, so race 90's engine almost certainly started life stronger than the museum's example. Even so, 2,400 rpm sits above the only speed the Smithsonian lists.

Pratt & Whitney's stock fuel-flow figure for the engine is not something the class publishes, so the 70 gallons an hour Duffy runs can be read only against the museum's horsepower and speed, not against a factory flow. What the comparison shows is that race tuning already pushed this engine past its catalog long before the venue changed, which leaves less margin for guessing when the air does.

## A class built on matched performance

RARA runs the T-6 class as match racing between stock aircraft, the North American T-6 Texan, the Canadian-built Harvard and the Navy's SNJ, according to its class page, which puts the emphasis on strategy and pilot skill rather than raw horsepower. The July 2026 roster post goes further, saying winning in the class does not come down to mechanical modifications because the airplanes have matched performance.

Set that against Duffy's week, which is almost entirely mechanical: a race cowling, taped seams, sealed gear wells, a new engine and a fuel-flow setup still being found. None of it adds horsepower. In a class where engines are equal by rule, cowling gap and gear-well rubber are where a crew chief finds speed, and Duffy's own description of the taped seams is that they make the airplane go fast.

RARA's July 2026 roster lists McNeely alongside Lee Oman, Vitaly Pecherskyy, Vic McMann and Virgil Tatman, with Ben York III's SNJ-5 flying as pace plane. Every one of those crews arrived in Roswell with the same shortage of local data, which makes the T-6 pits this September a contest of who learns the air fastest.

## Keep the data this year, set the plane up next year

Duffy is candid that he did not collect any data from last year. This year he is keeping all of it, so the crew can set the plane up when it arrives next year, and as the years go on the file grows into something like the Reno book he lost.

The signal to watch is Duffy's own: whether race 90 shows up in Roswell in 2027 with a baseline instead of darts. RARA's 2026 racing runs through September 20, and whatever CHT, fuel flow and pressure readings the crew logs in those days are the first pages of that baseline.

## Sources

- [2023 to Mark Final Year for National Championship Air Races at Reno-Stead Airport](https://airrace.org/2023-to-mark-final-year-for-national-championship-air-races-at-reno-stead-airport/) (Reno Air Racing Association (Airrace.org))
- [T6 Class - National Championship Air Races](https://airrace.org/air-racing/race-class-info/t6-class/) (Reno Air Racing Association (Airrace.org))
- [What Pilots Need to Know About Density Altitude and Mixture](https://avstardirect.com/what-pilots-need-to-know-about-density-altitude-and-mixture/) (AVStar Fuel Systems)
- [A Contrast in the Skies: The 2026 T-6 and STOL Drag Class Rosters Are Officially Locked In!](https://airrace.org/a-contrast-in-the-skies-the-2026-t-6-and-stol-drag-class-rosters-are-officially-locked-in/) (Reno Air Racing Association (Airrace.org))
- [Pratt & Whitney Wasp R-1340 SC1, Radial 9 Engine](https://airandspace.si.edu/collection-objects/pratt-whitney-wasp-r-1340-sc1-radial-9-engine/nasm_A19761915000) (Smithsonian National Air and Space Museum)

Tags: Concorde Battery, air racing, T-6 class, National Championship Air Races, crew chief, engine tuning

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