Conventional Otto Cycle Engines:
Beating a dead horse

Comparing the DRE to today's engine

We will not compare the DRE to conventional engines quantitatively until we have tested a running version exhaustively. Performance numbers from computational models are some what useful but they always have a factor of doubt surrounding them. This is why we will stick to qualitative comparisons between the DRE and modern engines.

We believe our engine is better than conventional engines and other engine concepts but we also understand that the proof will only come from studying a running prototype.

What makes the Doyle Rotary better?

(Click an advantage to read it's description)

• Split cycle

  One row of pistons performs the intake and compression (IC) strokes while the other row performs the power and exhaust (PE) strokes. The central combustion chamber separates these two rows. This layout is advantageous because it opens up many options that a conventional engine does not have:

  • IC pistons and cylinders can be designed differently than the PE side
  • There is no need to fire before top dead center
  • Fuel can burn for a longer duration and more completely in the combustion chamber
  • Pre-ignition air-fuel mixture temperatures are lower

  

• All of the parts have history

  Many new engine concepts rely on new, complex or exotic parts to run. This can range from more complicated valve assemblies to sealing technologies that haven't even been invented yet.

  The DRE uses off the shelf components. From the piston and cylinder technologies that have been in use for hundreds of years in steam and combustion engines, to the apex, side and corner seals that were first used in production vehicles in 1967 (and still in use in the 2011 Mazda RX-8), the components of the Doyle Rotary have been constantly tested by the public for at least 40 years.

  So unlike other concept engines, asking whether the Doyle Rotary will work does not involve questioning the components. The parts within the DRE will function just like they have for years.

  

• Overall easier to manufacture parts

  As today's engine has increased in efficiency, it has also dramatically increased in complexity. This complexity not only requires more parts to be manufactured and assembled, but also forces the manufacturing process to have tighter tolerances. All of this adds up to increases in manufacturing time and costs.

  The DRE is simpler and cheaper to manufacture because several portions of the engine perform with less parts. Consider the 200+ parts a conventional four cylinder uses to manage port timing. Not only does the Doyle Rotary control ports with much less parts (58), these parts do not open and close or move at all. Less parts leads to lower costs and inserting seals is much easier than assembling the entire valvetrain.

  Cycle Timing

  The cylinder head on a late model four cylinder Otto cycle	Doyle Rotary
  1 head casting with 10 machined cam journals, 65+ tapped holes, 16 seat pockets, 16 guide holes, machined head surface, machined valve cover surface, 20 cam cap seat surfaces, 4 seal surfaces, oil passages and 4 sparkplug holes. 16 valves 16 guides 16 guide seals 16 springs 16 retainers 32 keepers 16 spring buckets 24 studs 20 cam cap bolts 16 valve seats 2 camshafts 2 sprockets 2 VVT assemblies(not sure how many parts are in them)	28 corner seals assemblies 14 apex seal assemblies 14 side seal assemblies 1 intake port block 1 exhaust port block
  195 or more parts 14 unique parts	58 total parts 5 unique parts

  Connecting Rods

  Otto	Doyle
  1 rod with two tapped holes six machined surfaces and one close tolerance bore with oiling holes. 1 rod cap with four machined surfaces and two machined holes. 2 rod bolts that use the torque angle method to stretch the bolt during installation. They also align the cap with the rod. 1 wrist pin bushing to be pressed in to the rod, oiling holes drilled and then honed to size. 2 rod bearing halves made from a steel base metal and then plated with a very soft low galling material.	1 Rod with oiling holes, four machined surfaces and and two honed holes.
  The rod components are then cleaned and assembled, honed on the big end, disassembled and re-cleaned to prepare for engine assembly. The rod is design from very strong heat treated steel and made as light as possible to be able to move the piston up and down as many as 117 times a second.	The rods are attached to the outer housing on one end and to the piston on the other. They travel around with the outer housing making a circular motion, there is no reciprocation in the Doyle Rotary.

• Easier to assemble

  The Doyle Rotary has four man sub assemblies.

  The Cylinder block assembly has five components that slide in place and two end caps.

  

  The stationary port/crank assembly has seals that slide into place and its four sections are bolted together.

  

  Piston Rod assembly has three components that are attached to each other using wrist pins.

  

  Outer Housing assembly has two end caps

  

  The rotating cylinder block is positioned over the stationary port/crank assembly.

  The rods and pistons are installed into the cylinder block.

  The outer housing is assembled around the cylinder block and port/crank assembly

  Finally the piston rods are pulled out and attached to each rod mount and then the rod mounts are attached to the outer housing.

• One combustion chamber

  In a conventional engine each combustion chamber burns slightly different from the others. This is because of differences in operating temperatures and intake and exhaust lengths. In the Doyle Rotary each cylinder uses the same combustion chamber. This increases the consistency in power between each cylinder leading to an engine that runs smoother and has consistent wear characteristics for each component.

  

  In this view you can see the Intake Port, the Combustion Chamber and the Exhaust Port.

  You can also see the direct injector and spark plug.

• No valvetrain

  Eliminating the valvetrain provides many advantages. Less energy will be lost due to friction and manufacturing and assembly will be cheaper and simpler. The two biggest advantages to removing the valvetrain are a higher fluid efficiency and a lower chance of failure.

  Unlike valves, the ports in the DRE open and close instantly. This allows the port to remain open longer and to remain at full flow much longer than in a conventional valvetrain. This will be very noticeable at higher RPMs when the fluid efficiency of conventional valvetrains begins to drop. Also, at higher RPMs valves begin to float. The stationary seals will not have issues at higher RPMs.

  The valvetrain in today's engines is the root of many engine failures. The following common failures can not occur in the Doyle Rotary:

  • Blown Head Gaskets
  • Cracked Heads
  • Flat Cams
  • Bent Valves
  • Dropped Valves
  • Timing Belt Breakage

  

• Fewer moving parts

  Eliminating the valve train not only gets rid of 100 or so moving parts, it also gets rid of the cam drive mechanism and simplifies the oiling system.

  The Cylinder block assembly has five components that slide in place and two end caps.

  

  Piston rod assembly has three components that are attached to each other using wrist pins.

  

  Outer Housing assembly has two end caps

  

• Fewer overall parts

  Approximately 135 fewer parts not counting fasteners. That's 135 parts that the consumer does not have to buy, 135 parts that the consumer does not have to pay to have installed and 135 parts that are not going to break and need replacing.

• Less oil windage

  In conventional engines the crankshaft creates a dense vortex of oil within the crankcase. This vortex induces drag as the crankshaft collides with the oil suspended in the vortex. This also shortens the life of the oil. Windage trays and scrapers have decreased the effect of windage but preventing the drag is impossible to do when the crankshaft is spinning at thousands of RPMs inches away from the oil pan.

  In the Doyle Rotary, windage is almost negligble. The cylinder block, pistons, rods and outer housing all rotate at the same speed. The oil exiting the cylinder block is slung out to the outer housing. A suspended oil vortex can not form and the spinning portions of the engine do not have to cut through a dense fluid.

  Also, in conventional engines, as the piston moves up and down within the cylinder, the height of the column of air below it changes. This means that as the piston moves toward top dead center, a low pressure area is formed underneath it. This creates drag on the piston. The piston must pull the oil filled air along with it. Then when the piston begins its downward stroke it is resisted by the oil filled air compressing against it.

  In the Doyle Rotary, the height of the column of air under the piston never changes because the piston is at a constant distance from the outer housing.

• Smaller and lighter per unit of displacement

  The Doyle Rotary saves space and weight for many reasons. First, eliminating the valvetrain is a big reduction. Secondly, because the cylinder block and outer housing are innately balanced, dead weight does not need to be added for balancing. Finally, because the cylinders are tightly nested, space and material are both saved.

  

• Lower NOx and hydrocarbon emissions

  NOx results from the combustion temperatures remaining at a very high temperature for a long duration. Attempts to keep the combustion temperatures low in conventional engines are hindered by a couple of factors:

  The pre-ignition temperatures are high because the fresh air being pulled in during the intake stroke enter a cylinder that has just exhausted extremely hot gases.

  The peak temperatures are increased as the ignition timing is advanced. Firing before top dead center results in the piston compressing the mixture that has just been ignited. Compressing the air adds to the combustion temperature.

  In the Doyle Rotary fresh air is introduced to a relatively cool cylinder. This leads to lower pre-ignition temperatures. The fresh air is then compressed and transferred to the central combustion chamber. Fuel is then injected and ignited. Firing after top dead center decreases the peak combustion temperatures.

  Hydrocarbons arise from unburned fuel leaving the engine via the exhaust. The Doyle Rotary allows the fuel to burn within the combustion chamber and then in the power cylinders. Allowing a longer burn duration will decrease the amount of fuel exiting the engine.

Possible disadvantages of the DRE

(Click a disadvantage to read it's description)

• Oil injection for seals

  Just like in the Mazda Rotary engine, the seals in the DRE will require oil from an oil injector. This oil will inevitably be burned in the combustion process. This will lead to an increase in hydrocarbon emissions. The 2011 Mazda RX-8 currently injects a small enough amount of oil to pass emissions regulations. This means the DRE will at least meet the required level.

  However, the DRE should require less oil to lube the seals than the Mazda Rotary. The seals in the Mazda engine travel across large distances in many directions in a figure-eight pattern. The seals in the Doyle Rotary slide in one direction and traverse a smaller area per cycle of the engine. This should allow us to inject less oil than the Mazda engine.

  The oil injection problem could be rememdied by making the seals out of a better material. We use the Mazda seals because they are easily available and proven by time.

• Power pistons temperatures

  Because of the near constant combustion, the power pistons will remain very hot. This can be remedied in the same way used in newer engines: oil sprayed under the pistons.

• Selling the engine to automotive manufacturers

  Selling any new technology is tough. Selling new engine technologies is even tougher. Asking an auto manufacturer to abandon the engine they have been using for 100 years is the toughest.

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