Why is a rotary engine better

Combustion is what powers most engines. Both rotary and piston engines are powered by a four-stroke cycle. The four-stroke refers to the intake stroke, the compression stroke, the power stroke, and the exhaust stroke. Both engines need air, fuel, and spark to operate. Both are four-stroke engines. The rotor spins around an eccentric shaft inside a housing. The air is compressed along with the fuel, then spark is introduced, and finally exhaust escapes through the exhaust port.

For each complete rotor, two times as many power pulses as a one cylinder recip is produced. This means that the 1. This has some good and some bad consequences. Assuming that both engines have similar maximum RPMs, it means that the rotary has 1.

They also have more time for the power stroke — a real plus to get the most out of the combustion gas, especially at high RPM. Now the bad part. The rotary also has 1. This is one reason why rotaries waste more heat in the process of staying cool. Take a moment to study Figures 2 and 3 and soak it all in.

The bottom line is that a 1. Put another way, a 2-rotor rotary has the same number of firing pulses as a 4-cylinder recip, but because the duration of each firing pulse is degrees, the engine runs smoother due to the overlap of the firing pulses. So, what is the point of all this math?

Well, the point is to get a better understanding of WHY certain things are so important to a rotary — especially heat transfer. Remember, heat is potential power, so keeping heat in the combustion mixture makes more horsepower you can use. On to the next item: In comparison to a recip, the intake charge once it is inside the engine actually travels a long, tortured path. The figures above show it in detail. In a recip, the center of gravity of the intake charge only moves an inch or two as the piston moves back and forth between top dead center TDC and bottom dead center BDC.

One bad result is that there are a lot of square inches of surface through which to transfer heat, reducing thermal efficiency. However, here is the big point: The entire mass of the intake charge must pass through the narrow area between the rotor housing and the rotor as each rotor flank passes through TDC. For this reason and others, the shape of the rotor depression is quite important. Actually, this points out a weak point in the rotary—the maximum PRACTICAL compression ratio is not determined by detonation as is common in recips but by the ability of the burning charge to pass through the rotor depression.

This can reduce power, overheat the trailing spark plug, and substantially increase the heat dumped into the oil and water. Therefore, the shape of the rotor depression is a cut-and-try balancing act to find the best compromise. The engine makes no vibration during operation. A Wankel engine is not prone to engine knock or knocking. Since the engine consists of only a few parts, a Wankel engine is cheaper to manufacture and mass-produce.

The range of speed is wider. That would allow for a multiplication effect to occur with the gyroscopic precession as the entire engine mass rotates. The outcome of this increase resulted in control problems for aircraft that included stability issues.

If an inexperienced pilot was at the helm of the craft, then there was a greater risk that the vehicle would be unable to maintain is flight trajectory. You will go through more fuel with a rotary engine. Rotary engines produce a low compression ratio, even though you can rev it like crazy to get some tremendous power for it. There is a significant amount of fuel that remains unburned at the end of a combustion cycle with this technology.

There are also more emissions that come from this design, which can make it difficult to have a vehicle make it through carbon testing in areas where it is necessary. It goes through an incredible amount of oil to function correctly.

The design of the rotary engine, especially the ones invented by Wankel, is to burn oil during operation. It is a disadvantage that enhances the issues with fuel consumption and carbon emission problems that exist with this engine. Using the Mazda RX-7 as a real-world example of what to expect with a rotary engine, owners average about 18 miles per gallon with its fuel.

Some were only receiving eight MPG with their vehicle. Fuelly took the information from RX-7 owners over , miles driven to measure the fuel economy. The highest number recorded in their information collection was only 24 mpg. Rotary engines require more maintenance than their counterparts.

It can be expensive to fix a rotary engine. The simplicity of a Wankel engine often makes people think that they are relatively cheap to fix. That means your repair or regularly scheduled maintenance is likely to be a lot more expensive than what your mechanic would charge normally.

Seals can be a significant problem for rotary engines in cold climates. A rotary engine tends to produce about the same amount of torque as you will find in a screwdriver. This problem can lead to flooding when trying to make a cold start. The older 13B engines have more issues with this disadvantage than the modern ones, but it is still a good idea to let your motor warm to operating temperature before you decide to start driving.

We are not using this technology as often as we once did, but there are still specific applications where having it equipped to a vehicle makes sense. If you are thinking about the purchase of a Mazda or another make and model equipped with this technology, managing the disadvantages must be your top priority. The pros and cons of rotary engines can also point you in the opposite direction by showing you that alternative products are better for your needs.

At the end of the day, the decision is yours as to whether or not you are going to take advantage of what this technology provides.