If you’ve been on the internet recently, you may have noticed a set of recently-viral pictures of a Porsche 928 with two enormous hood-exit exhaust pipes. Is this a case of massive turbos? Not quite. Under the hood sits a Boeing T50 Turboshaft engine primarily used in the Gyrodyne QH-50C DASH helicopter drone. Yep, a turbine-powered 928. Pictures are all well and good, but did you know that actual video of the car running exists? Unsurprisingly, it’s as glorious as you’d expect.
This isn’t the first time this unusual Porsche 928 has gone around the internet. It was last up for sale in 2010 on eBay, and Autoblog reported that the seller wanted $20,000 for this strange contraption. The Boeing-swapped 928 reportedly gets 17 miles per gallon, still featured working air-conditioning at the time of its listing, and came with freaking afterburners.
Interestingly enough, the QH-50 DASH that the engine came out of has a Porsche connection of its own, as the original prototype was powered by a Porsche YO-95-6 flat-four making 72 horsepower. However, that wasn’t quite enough juice, so Gyrodyne eventually settled on turboshaft power. Output of turboshaft engines is somewhat oddly-rated due to the need for a reduction gearbox. See, the T50-BO-8A found in later QH-50C DASH helicopter drones makes peak power at 28,380 rpm, which is far too high to be useful in shaft-driven applications. As such, a series of cogs drop output RPM down to sensible levels, with the end result being 300 shaft horsepower at an output RPM of 5,950. That seems like it could be usable in a road car, but it’s worth noting that turboshaft engines have other quirks that affect driveability.
Check out this 350-horsepower turbine from a Vietnam-War-era QH50 helicopter drone crammed in the engine bay of a 1982 Porsche 928!!???? 17 mpg… on jet fuel.???????? pic.twitter.com/zSroFXKIo9
— Pro-Billet Torque Converters™ (@ProConverters) May 28, 2023
Because a turboshaft engine is sort-of like a big turbocharger, acceleration lag may hamper driveability. Depressing the throttle dumps fuel into the combustion chamber and ignites it, which spins up both the output shaft and the compressor, letting more air into the combustion chamber. The problem with that is you don’t have much control over air, so it’s possible to experience compressor surge if fuel is added too quickly. Compressor surge is a pretty nasty beast with the potential for serious blade damage, so fuel is metered gradually, slowing acceleration of the engine. This is fine when you’re trying to take off in an airplane, but it’s not optimal when, say, turning left onto a four-lane road.
Then there are the matters of noise and exhaust gas temperature. The spent fuel-air mixture exits a gas turbine at a temperature of several hundred degrees, promising to barbecue low-flying pigeons. At the same time, this car is said to pump out 130 decibels of sound while simply idling, which can cause serious hearing damage. Let’s just say, if you want to own a turbine-powered car, your neighbors better really like you.
Despite driveability compromises, a turboshaft engine does offer one benefit over the water-cooled V8 typically found in a Porsche 928 – no abominably-long timing belt to deal with. The timing belt on a Porsche 928 is 82.5-inches long, or in other words, longer than Lebron James is tall. Slice this timing belt across its width, lay it out, give it a pair of Jordans, and it’ll have a D-league contract by lunchtime. Pair that with a factory-recommended replacement interval of 60,000 miles, and you might be able to see a scenario in which the cost of jet fuel breaks even with typical maintenance.
Weirdly, this isn’t the only Boeing T50-swapped Porsche 928 in the world. At least one other example of this highly-concentrated lunacy exists, for a 1984 car with a single exhaust outlet that likely also makes a sound like the apocalypse came up for sale around the turn of the 2010s. That can’t be a coincidence, can it? I mean, how improbable would it be for two unrelated people to both conjure up the idea of putting a turboshaft engine in a 928 and then execute it? Whatever their origin, I’m thankful that these absurd 928s exist, because they prove the rationale of “because I can” is sometimes good enough.
(Photo credits: eBay seller, Porsche)
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