The Rolls-Royce Wankel Engine: A Revolutionary Military Powerplant

In the 1970s, Rolls-Royce embarked on an ambitious project to create a high-power, high-efficiency engine for military use. The goal was to design an engine that would be compact and powerful, with a focus on diesel technology. To achieve this, they turned to the Wankel engine, also known as the rotary engine, which had several benefits including small size and power density.

One of the challenges faced by Rolls-Royce was designing a high-compression ratio Wankel engine. To overcome this, they decided to use a supercharger or compressor to boost the air compression ratio. They achieved this by adding a second, smaller Wankel engine, which was used solely as a positive displacement compressor to force more air into the combustion chamber of the main rotor.

The design of the two-stage Wankel engine was crucial to achieving high power and efficiency. The lower stage had a displacement of 3250cc, while the upper stage had a displacement of 1265cc. By dividing these displacements, Rolls-Royce effectively multiplied their compression ratio by 2.57. This meant that they could achieve much higher compression ratios than would have been possible with a single-stage Wankel engine.

However, using two stages also presented some challenges. The size and weight of the engine were significant concerns, particularly since it was intended for military use. To mitigate this, Rolls-Royce looked into the possibility of designing a single rotor with a high compression ratio, but realized that this would require an impractically large footprint.

To overcome these challenges, Rolls-Royce turned to direct injection technology, which they had not extensively researched at the time. They experimented with 30 different combustion chamber designs and injector positions before settling on one configuration that worked well for their Wankel engine.

Direct injection was a significant improvement over traditional piston cylinder designs, where fuel was injected at a relatively fixed position. In contrast, Rolls-Royce's design used direct injection to perfectly distribute the fuel as it swept past the combustion chamber. This resulted in a more efficient and powerful engine.

The inner workings of the two-stage Wankel engine are fascinating. The lower stage, driven by the blue eccentric shaft, compresses air into the main rotor. As this rotor rotates, it compresses the air further before injecting fuel into the combustion chamber. Meanwhile, the upper stage, driven by its own eccentric shaft, uses the exhaust gases to drive a separate compressor that forces more air into the combustion chamber.

This cycle of compression and expansion continues in both rotors, with the result being a compact and powerful engine that produces 350 horsepower at 4500 rpm. Despite its size and weight, the Rolls-Royce Wankel engine was remarkably light for its output, weighing just 939 pounds.

In retrospect, it is clear that the project was ambitious but ultimately limited by funding and investment in research and development. As a result, we do not see many of these engines in use today. However, the concept remains fascinating, and it will be interesting to see if Mazda or other companies can develop similar technology in the future.

The Rolls-Royce Wankel engine is an example of innovation and risk-taking in the pursuit of engineering excellence. Despite its limitations, it represents a significant achievement in terms of power density and efficiency, and it remains a testament to the ingenuity of Rolls-Royce engineers.

"WEBVTTKind: captionsLanguage: enhello everyone and welcome i recently saw a jalopnik article about an auto car article from the 1970s that was talking about a rolls-royce wankel diesel engine and this was so fascinating that i thought i had to make a video about it so that's what we're going to be talking about here and basically uh this engine the goal of it was back in the 1970s rolls-royce wanted to make this as a military engine for use in the military and their goal was high power high efficiency in a very compact size wankel engines of course have the benefit of being small and power dense diesel engines have the benefit of being efficient so kind of combining all of that into this one amazing engine well the challenge that they ran into is that wankel engines are hard to design with a high compression ratio and their solution you could supercharge it you could turbo charge it they decided to add a whole nother wankel engine rotary in there basically in order to use that as a supercharger or as a compressor this is just a positive displacement compressor that forces more air into this combustion chamber right here so this one is just for transferring air this one is actually where combustion is occurring and so basically how this works is the ratio of the displacement of this rotary right here versus this one right here is going to give you your increase a multiplier for your compression ratio so this lower stage is 3250cc cubic centimeters versus this upper stage is 1265cc you divide those two and that means your compression ratio is effectively being multiplied by 2.57 now you may be thinking wow this is huge why would they use something so big to compress air for that other stage but actually they looked into just doing a single rotor with a high compression ratio simply by using the geometry of how it's designed and in order to do that it requires a really large footprint so a single rotor with a high compression ratio would be very similar in size to these two rotors using this to increase your effective compression ratio so overall the size is actually pretty compact even though it looks like it's basically enormous now another challenge they ran into is they decided to use direct injection but there wasn't too much research out there on using direct injection in diesel ankle engines so they ended up trying 30 different combinations for combustion chambers they tried six different injector positions uh basically over a hundred different combinations that they tried out and settled on one that worked best you know much easier in a piston cylinder device to just have that injector directly on top as that piston comes up right in the middle of that circle perfectly distributes the fuel versus you know having that winkle sweep by is much more challenging in order to have that perfect air fuel mixture and then have that ignite when you inject that fuel so how does this thing work well basically you have your air intake down here at the bottom so this bottom rotor rotates about this blue eccentric shaft right here as that rotates it compresses that air into this stage right here so then this rotor then rotates and compresses that air then you inject that fuel you have combustion occur the rotor continues to rotate about that separate its centric shaft right there in blue as it rotates uh the exhaust is then pushed out you know the that's the power stroke right there is rotating that then the exhaust is then pushed out and actually continues to do useful work rotating that second compressor with that exhaust and then finally dumped out this exhaust right here so that cycle just basically continues and you know both of these are rotating about and you're creating a good power within a pretty good footprint so the rolls engine is the 2-r6 engine and basically it was set up with two banks on two stages uh so overall this was basically a four rotor engine uh you know sorry rob dom they were doing this back in the 1970s producing 350 horsepower at 4 500 rpm and only weighing 939 pounds now 939 certainly sounds like a lot but remember this is a diesel engine and this is back in the 70s at the time it was way smaller and way lighter than similar diesel v8s that had similar output so the v8 you know diesels were much bigger similar much more weight a similar output you know but of course that drawback of their size and weight so they did actually achieve their goal of having something that you you know was powerful efficient and in a much more compact size it's unfortunate you know that ultimately uh the research kind of died out and so we don't have cool ankle engines running around today perhaps you know if more companies invested in it we could have them but hopefully mazda does come up with something in the near future so that would be cool to see you know this engine kind of live on but really neat concept you know it was it was fascinating to hear about this using a separate basically rotary engine just as an air compressor for the main rotor so very cool to see if you guys have any questions or comments feel free to leave them below thanks for watching should they keep watching more videos bucket they should probably keep what oh god hey that's all right it's not okay huh okay i'll let you get back to your nap youhello everyone and welcome i recently saw a jalopnik article about an auto car article from the 1970s that was talking about a rolls-royce wankel diesel engine and this was so fascinating that i thought i had to make a video about it so that's what we're going to be talking about here and basically uh this engine the goal of it was back in the 1970s rolls-royce wanted to make this as a military engine for use in the military and their goal was high power high efficiency in a very compact size wankel engines of course have the benefit of being small and power dense diesel engines have the benefit of being efficient so kind of combining all of that into this one amazing engine well the challenge that they ran into is that wankel engines are hard to design with a high compression ratio and their solution you could supercharge it you could turbo charge it they decided to add a whole nother wankel engine rotary in there basically in order to use that as a supercharger or as a compressor this is just a positive displacement compressor that forces more air into this combustion chamber right here so this one is just for transferring air this one is actually where combustion is occurring and so basically how this works is the ratio of the displacement of this rotary right here versus this one right here is going to give you your increase a multiplier for your compression ratio so this lower stage is 3250cc cubic centimeters versus this upper stage is 1265cc you divide those two and that means your compression ratio is effectively being multiplied by 2.57 now you may be thinking wow this is huge why would they use something so big to compress air for that other stage but actually they looked into just doing a single rotor with a high compression ratio simply by using the geometry of how it's designed and in order to do that it requires a really large footprint so a single rotor with a high compression ratio would be very similar in size to these two rotors using this to increase your effective compression ratio so overall the size is actually pretty compact even though it looks like it's basically enormous now another challenge they ran into is they decided to use direct injection but there wasn't too much research out there on using direct injection in diesel ankle engines so they ended up trying 30 different combinations for combustion chambers they tried six different injector positions uh basically over a hundred different combinations that they tried out and settled on one that worked best you know much easier in a piston cylinder device to just have that injector directly on top as that piston comes up right in the middle of that circle perfectly distributes the fuel versus you know having that winkle sweep by is much more challenging in order to have that perfect air fuel mixture and then have that ignite when you inject that fuel so how does this thing work well basically you have your air intake down here at the bottom so this bottom rotor rotates about this blue eccentric shaft right here as that rotates it compresses that air into this stage right here so then this rotor then rotates and compresses that air then you inject that fuel you have combustion occur the rotor continues to rotate about that separate its centric shaft right there in blue as it rotates uh the exhaust is then pushed out you know the that's the power stroke right there is rotating that then the exhaust is then pushed out and actually continues to do useful work rotating that second compressor with that exhaust and then finally dumped out this exhaust right here so that cycle just basically continues and you know both of these are rotating about and you're creating a good power within a pretty good footprint so the rolls engine is the 2-r6 engine and basically it was set up with two banks on two stages uh so overall this was basically a four rotor engine uh you know sorry rob dom they were doing this back in the 1970s producing 350 horsepower at 4 500 rpm and only weighing 939 pounds now 939 certainly sounds like a lot but remember this is a diesel engine and this is back in the 70s at the time it was way smaller and way lighter than similar diesel v8s that had similar output so the v8 you know diesels were much bigger similar much more weight a similar output you know but of course that drawback of their size and weight so they did actually achieve their goal of having something that you you know was powerful efficient and in a much more compact size it's unfortunate you know that ultimately uh the research kind of died out and so we don't have cool ankle engines running around today perhaps you know if more companies invested in it we could have them but hopefully mazda does come up with something in the near future so that would be cool to see you know this engine kind of live on but really neat concept you know it was it was fascinating to hear about this using a separate basically rotary engine just as an air compressor for the main rotor so very cool to see if you guys have any questions or comments feel free to leave them below thanks for watching should they keep watching more videos bucket they should probably keep what oh god hey that's all right it's not okay huh okay i'll let you get back to your nap you\n"