Hear The Banshee Wail Of A Porsche 928 With A Gas Turbine Helicopter Engine Swap

Turbine Powered Porsche 928 Topshot
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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.

Turboshaft Porsche 928 1

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.

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.

Porsche 928 Timing Belt Diagram

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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43 thoughts on “Hear The Banshee Wail Of A Porsche 928 With A Gas Turbine Helicopter Engine Swap”

  1. I dunno whether “17 MPG” is city, highway, or an average, but if it’s city, that’s still 1 MPG better than my old Volvo XC90 musters around town.

    Extreme kudos to the builders/owners/drivers of both cars: the 928 is a worthy subject for such inspired lunacy. IMO, it looks better with the stock wheels on the second/single outlet car. The Porsche ‘phone dial’ wheels are my faves for the 928 and most 944s too. Love ’em! 😀

    I wonder if some sort of over-the-counter noise cancelling audio tech could be used to reduce the noise somewhat? Through the stereo speakers in the cabin, and maybe squeeze a megaphone fed by the same cancellation signal under the body someplace where it won’t get melted? To try to reduce the noise for bystanders I mean.

    I always wanted/loved the 928, even if a pal of mine who worked at a Porsche dealership considers it to be a ‘ladies’ Porsche.’ It’s still sexy as hell IMO: the big hatch, the bubble butt, those fab headlights. I gather it’s pricey to buy and hard to find a lot of the little bits for the interior and exterior on these… not that that’s the only thing keeping me from buying one of course. 😉

    If I could maybe find an otherwise pristine example that was cheap due to a bad engine… maybe I could rationalize buying it and storing it in the alley behind my house until such time as EV conversion kits are available/affordable. Ah, fantasy…

  2. I wonder how long will the paint on the roof and rubber weatherstrips on the front windscreen last before they are degraded by the intense heat from the afterburner exhaust.

    By the way, a four brownie points scored for using the ECE headlamps and headlamp washers!

  3. OMG helicopter turbine! Compressor surge! That’s my jam!

    I’ve got to try and convince David to let me write about that! I could cram so much thermodynamics and aerodynamics in a single article!

  9. I guess it’s neat but a turbine engine is just not really great for the kind of power and RPM variation you need for powering a car.

    1. I remember Jaguar had a concept that was supposed to use a pair of turbines to generate electricity to power electric motors, which makes slightly more sense (you can keep the turbines in an efficient rev-range and don’t need sudden changes as long as there’s some kind of battery to buffer the output).
      Not that much sense mind you, but cool.

  13. Looks like a good candidate for hybrid; let the turboshaft engine power the generator, electric motors power the wheels.
    Or is the RPM of this beast too fast for a generator?
    Asking for a friend.

    1. I’m sure it is already geared down for helicopter use. If it needs further gearing, I wouldn’t think that would be a problem. I believe the original Jaguar CX-75(?) was a turbine hybrid, so the idea has definitely been presented before and has benefits, as well as drawbacks.

    2. The Chinook helicopter (and probably plenty of others, but this one I have experience with) uses a small turbine to power a generator as an auxiliary power unit. There are also trailerable units for ramp power that use small turbines to produce voltages needed on an aircraft without starting the engines. I can definitely see that being adapted to hybrid use, but I think there’s a chance you might lose any environmental benefits gained from any traditional hybrid setup. Let’s ask Toyota!

    2. If I’m not mistaken, brake torquing was heavily recommended in the Turbine Car, as it had a bit of lag. Also, wild-ass non-engineer guess, but smaller, less powerful Turbine that was quicker to spool up and more flexible?

  16. This would be good in Post-apocalyptic Australia. No stops and a long, straight road to oblivion. Mutants on your tail…

    Absolutely bonkers. And I love it.

    1. Sadly, in both Boeing-swapped 928s, the vehicles were destroyed when the Boeing ECUs took over the cruise control, braking system and power steering and drove the vehicles into brick walls.

  18. 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.

    Actually, the factory recommended interval is 30,000 miles. The 928 expert I know recommends a complete timing kit be done every 5 oil changes or 15,000 miles. At $900 in parts and I believe it’s 6 hours of labor, doing your own turbine swap is cheaper than 928 maintenance.

    1. Hmm. $900 in parts plus six hours of labor every 30K miles for a belt replacement? Over a relatively short time, it would be cheaper to do a SBC swap.

    2. It’s not quite _that_ bad. The $900 kits include a new water pump. The belt, pulleys and tensioners are a lot less.

      I’ve got a 944… which has the same timing belt changing recommendations as the 928. Tensioning it is a bit of a headache… but it’s really not that bad. The 928 may be worse… but it only take 6 hours if you are doing it on a lazy Sunday with too much beer).

      What’s bad is the guy (Arnworx) who made a tensioning tool that was a fraction of the cost of the Porsche tool… seems to no longer make them. Glad I have mine.

    3. Porsche’s TB-9103 for my 1992 model shows that the inspection of the camshaft drive belt be checked every 30K miles and replaced every 60K miles

      1. My (back-in-the-day) 928 had a timing belt wear sensor & warning.
        ..which I kept ignoring and ended up with about 20 bent valves in Hungary, quite far from my home at the time in far-western Germany 🙂

        good times..

  22. Sounds like an autocross wouldn’t go well. Well, then, we need footage of this wonder on a track.

    I love silly crap like this. Its basically the current iteration of those pre-war cars with the RR Merlin engine

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