Throughout the middle 1950’s until the late 1960’s, General Motors (GM) made several attempts to mate its “Whirlwind” gas turbine engine to its motor coach line – these test models were labeled “Turbo Cruiser I, II, and III.” However, despite all its engineering prowess, GM never could overcome some of the design’s inherent deficiencies. But they continued trying – and in 1969 when Greyhound and its subsidiary MCI came forward requesting an alternative to diesel power that was smoother, quieter, and with reduced maintenance costs, GM offered up its Allison GT-404 turbine.
Gas turbine engines always displayed some unique advantages as an over-the-road powerplant. They were significantly lighter than an equivalent diesel engine – the GT-404 weighed approximately 1700-1750 lbs compared to 2300-2500 for the DD 8V-71 diesel. Further, they had much less vibration and a smoother ride. Lastly, fewer moving parts and simpler operation had the potential for lower maintenance costs.
The GT-404 was a two-shaft, regenerative gas turbine developed by the Allison Engine Division of General Motors – it was nicknamed the “VIP” (Versatile Industrial Powerplant). It made 325 hp and 580 lbs-ft of torque (for comparison, an 8V-71 made 318 hp and 863 lbs-ft). In 1969, Greyhound provided a lightly used MC-7 to Allison – out came the 8V-71 and in went the 404, mated to an Allison automatic transmission. For two years Greyhound put it through a testing regime. Several more buses (MC-8s) were converted in the early 70’s and joined the tests. Results were generally positive, though engine throttle lag, a problem never fully resolved, was noted.
This initiative caught the attention of the government and in 1978 the Department of Energy joined the program, bringing additional federal funds for more extensive testing and evaluation. In turn, four turbine-engine MC-8s were placed in Greyhound revenue service beginning in Jan 1980. To ensure a rigorous evaluation, several high-demand routes were chosen (Washington DC to Philadelphia, Los Angeles to San Francisco, etc.). The testing period lasted until Sep 1981.
Pictures of these turbine buses are hard to find, but they were similar in appearance to the diesel engine models, except in the rear. Rather than a rear bumper exhaust outlet, they had a large vertical stack that exited near the roof, to keep the hot exhaust gases away from traffic and pedestrians. Because the exhaust ducting and bulkier recuperator/regenerator systems, the rear window glass was omitted, creating a solid rear cap. In addition, the rear engine doors and side ventilation grilles were redesigned and expanded compared to the standard doors found on the diesel model, as the turbine required a much higher volume of airflow for combustion and cooling.
What were the evaluation results? Passengers expressed overall favorable views, noting the quiet and vibration-free ride, though they did mention that standing outside the bus smelled like an airport parking apron. Drivers had mixed feelings; they liked the turbine’s power and torque, but had to significantly adjust their driving style due to the initial throttle lag and lack of engine braking. Management was clearly unimpressed – fuel consumption was 25% worse than with the diesel and the lower maintenance costs failed to appear as the buses were also off the road more often for repairs. Failing to achieve its most important objective of lowering costs, the program ended in 1982. Out came the 404’s, and the 8V-71s were re-installed.
As we’ve seen with other examples, new innovations can be technically successful but not commercially viable. Unfortunately none of these turbine-engine buses were saved – one would have made a nice addition to Greyhound’s historical fleet or the Greyhound Bus Museum.
Fun Fact 1: Though it failed as a vehicle powerplant, the GT-404 did find later success as an auxiliary power generator for the Patriot missile system.
Fun Fact 2: Ford and Continental Trailways tried a similar turbine engine swap into a Silver Eagle in 1969, which lasted less than a year with similar results.
Fascinating!
Buses aren’t glamorous, but they’re essential transport for millions of intrastate road warriors. Your posting accurately describes the reality every organization must address: cost. The benefits gained couldn’t justify the costs. We can marvel at the technological advances this engine offered at that time, but reality beckoned.
I believe it is possible that the additional fuel consumption was a huge problem. Federal funding couldn’t continue during this era for transportation that consumed more fuel. Someone in GM however, changed the funding priorities so that the engines were sold to the Feds, under the Department of War. SMART.
Thanks for this posting!
Turbines are more efficient at high airflows, like aircraft or marine use where high percentage to maximum power is required most of the time. Piston engines are much better at lower airflows, where vehicle engines spend much of their time.
Turbines never proved effecient in road vehicles. If diesel fuel stays at today’s high price, it will be interesting to see how that shapes the automotive future.
There have been a number of attempts to mate turbine technology with large vehicles over the years. None of them seem to have worked out.
In the early ’50s Boeing developed a turbine engine and worked with Kenworth. One or two were built and put into service with an over the road trucking company. A later version of the engine was apparently installed in a couple of American LaFrance fire engines and tried in Seattle and San Francisco. The BC Department of Highways had a couple of Pacific 4×4 snowplows powered by a Pratt and Whitney turbine engine in the early ’60s in a quest for more speed when plowing mountain passes.
When I was an apprentice with Highways 40 odd years ago I worked with an older guy who had been involved in the snowplow project, and he said the trucks were thirsty, used up brakes at an alarming rate and were useless for anything but plowing snow, at which they excelled. The engines were apparently replaced by 6 cylinder Cummins diesels after a few years.
I didn’t know about these Greyhounds, interesting article.
Syracuse NY had one or two turbine powered fire trucks in 1967. International Harvester owned Solar Turbines and built a cabover 4000 series called the Turbostar in 1968 for testing. Ford and GM both experimented with turbine powered trucks from the mid 50’s until 1970 or so and Chrysler fooled around with the turbine cars over about 10 years. Even Union Pacific tried them for locomotive use. They were called the “Big Blows”.
The military uses them in the Abrams and the Navy hovercraft. They seem to work well in anything that requires high power most of the time.
I knew about the attempts to bring turbine power to cars, particularly at Chrysler and Rover, but never knew about these turbine bus experiments, after turbine cars were abandoned. Interesting.
Close but no cigar!
Moving right along to battery power now high fuel cost seem to have helped proliferate EV anything now, $30 bought 10 litres of diesel last week on discount day and even less of 91, but it has slowed traffic down as people try to eek out mpgs from their chosen ride,
M1A tank uses gas turbines engine for Honeywell. I believe some of Russian tanks use turbine engine. So I assume it’s a reliable engine
In the military it’s ok for a more powerful engine option to be used despite it basically drinking much more fuel. The Abrams is crazy fast, and silent for something so big and heavy. Like aircraft gas turbines, they can go many more hours than a diesel piston engine before rebuild time, but this cost would bankrupt a transit company, along with the fuel bill.
We could have possibly seen a gas turbine supercar, but engineering costs plus emission regs killed that dream, and likely would have done the same to a coach or heavy truck that made it to fleet production.
The article I found here says that the higher fuel use IS important, for the amount of tank “under armour”, and for supply-chain logistics. It also says the turbine is inherently more expensive/harder to maintain because it is aerospace tech: it doesn’t mention longevity, but the high tech specialist part does suggest higher expense when necessary.
It’s actually an interesting article in relation to turbine use generally, doubtless including buses.
https://www.eit.global/comparison-of-diesel-vs-gas-turbine-engines-in-combat-vehicles/
For now.
The new M1E3 prototype apparently uses a hybridized CAT C13D.
Seems a bit weedy though at only 13 liters.
Interesting info Jim, never heard of these Detroit ‘Diesel’ Allisons before. Love the classic Greyhound coaches, regardless their power unit.
I wonder what they ran on? Kerosene?
They used Diesel No. 1 and 2 during testing Justy, though I did read that aviation fuel or kerosene would have worked also.
Looks like the publicity tour covered a lot of territory.
The first picture was taken in front of the Queen Elizabeth Fairmont Hotel in Montreal. It’s the building on the right, but only a small portion of the building can be seen. The left-most building has been re-clad in glass. Place Ville-Marie would be behind the photographer.
(What got my attention was the ad for McGregor socks (Bas McGregor) on the other bus. My favorite socks for decades, until production moved to China…)
Google Street View image below.
An old friend of mine worked for the Hound at the old Los Angeles terminal. He once told me one of these turbine powered MCI’s left L.A. with much fanfare and a bunch of Greyhound exec’s on board. A wrecker drug it back to the station a short time later…
Interesting idea, too bad (?) it didn’t work out .
When I was younger I often rode the hound to go fetch vehicles I’d purchased far away .
I spent many days riding second tier busses all over New England in the 1960’s .
-Nate