Leno’s Howmet TX drive reminds us why we love turbine cars

Jay Leno's Garage

Car enthusiasts are a strange, persnickety bunch. We’re cliquey, too. It leads to enclaves of supercar fans arguing (erroneously) that a V-10’s sound is superior to a V-8’s. Then there are Mazda RX-7 fans defending the fact that they’re beta testers for an engine that is advertised as being experimental. It’s right there in the emblem, guys. Like we said, strange. No, there isn’t much that we car enthusiasts can agree on, but maybe we can all come together and decide that while they might have only a few practical automotive applications, turbines are undeniably cool powerplants.

Jay Leno recently drove the Howmet TX, a turbine-powered experimental car—hence the TX moniker—developed in the 1960s by Bob McKee with backing by Howmet, an American aerospace corporation. The car is gorgeous, festooned with NACA ducts, and features a low hood in front of its center cockpit framed by tall, curvy, fenders that look like they came straight from a Can Am car. It’s everything we love about ’60s race car design. Then there’s the turbine.

The sound of a turbine firing up—a high-pitched whine interrupted by a booming baritone note as the fuel ignites—is like no other automotive powerplant. Turbines idle at speeds higher than most engines can withstand, and this one tops out at more than 50,000 rpm, speeds that would make even an F1 engine scatter its rods and window its block in an oily, violent cataclysm.

Bob McKee joins Jay along with the TX’s owner, Phillip Sarofim, to go over the car’s highlights. This one appears to be the third of four Howmet TXs built, and it’s powered by an Allison 250-C18 turbine like the one you’d find in a small helicopter or an MTT Y2K Turbine Motorcycle, which Jay happens to own.

McKee explains one of the turbine’s drawbacks: “There’s a hesitation a little bit, like spooling up a turbo.” That doesn’t bode well for a road course car, where carefully balancing steering and throttle input is crucial. Also, turbines don’t offer engine braking like a gasoline engine with a throttle plate, meaning brakes have to be oversized. Its single-speed gearbox didn’t include a reverse gear, so an electric motor adds that critical function. Finally, there’s another major hurdle to overcome. “They’re thirsty,” McKee admits, with fuel economy in mpg measured in the low, single-digit range.

Turbinator-II-Speed-Week-2018 turbine racer
Turbinator II, a turbine-powered land speed car, has recorded a flying mile speed of 493.037 mph. Credit: Brandan Gillogly

Those drawbacks come with some major advantages, however. When turbines are under constant throttle, fuel economy is improved and they are very power-dense, with the Allison 250-C18 producing 317 hp with an engine weight of around 150 pounds. Other variants of the Allison 250 produce in excess of 700 hp. Unlike a piston engine that requires piston rings to provide compression, the rotors of a turbine don’t contact the housing, which reduces wear and extends major overhaul intervals. For that reason, both GM and Ford considered turbines for semi-truck use. GM even put turbine-powered buses into a competition with AM General and Flxible for a government contract for a nationwide bus fleet that eventually fizzled and resulted in none of the companies offering up bids.

The Howmet TX is proof that turbine power is a viable option for race cars, and it makes a great argument as one of the best-sounding cars ever, not that that debate will ever be settled.




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    It sounds like a Jet plane at an airport idling and taxi-ing around. It must be loud as heck to be in but it looks and sounds cool.

    Bob McKee is a humble genius who deserves waaaaayy more recognition than he has received. He is 88 years old and still as quick witted as he was 50 year ago. One of the best engineers ever to meet a design target. In addition he was as kind and helpful to me when I had car trouble in his neck of the woods and a friend suggested Bob might have some suggestions on what to do. He couldn’t get me fixed, but he made sure a supplier of his would take care of me and he didn’t know me from Adam!!

    I have photographs that I took of the Howmet in the paddock at the 1968 Oulton Park 1 hour sports car race on April 12. The car attracted a lot of attention and was fairly competitive, although it didn’t finish the race. The Howmet raced for one season in the UK and then disappeared. An interesting development but not really a viable alternative to piston engined cars.

    No Jay, I did not enjoy that as much as you did….! How many YouTube creators get to drive a jet car around an active airport? Only one I can think of!

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