The Wankel Rotary Engine was and still is an engine that is designed to offer maximum power and performance but it does have several drawbacks. Mazda has tried for several years to offer us the rotary engine as a power plant for their RX series vehicles that are some of the most impressive sports cars that we’ve ever seen. Because of the power that can be pushed from these smaller engines we tend to love them at first, but once we experience any of the drawbacks the engines present, the romance is pretty much gone. Here are some reasons this engine might not be used ever again.
Low Thermal Efficiency – As the rotation takes place inside the engine the flame has more fuel and air to attempt to ignite in order to create combustion. This continued increasing of the combustion space causes there to be air and fuel that isn’t burned inside the chamber during combustion which is why some rotary engine vehicles have produced flames out of their exhaust pipe. This causes wasted fuel and a lower efficiency rating for the heat and amount of fuel injected into the chamber thus causing lower fuel efficiency numbers and worse emissions than most vehicles.
Sealing is Difficult – Inside the chamber the combustion is constantly taking place on one side while intake is happening in the other. There are typically three seals in place to help prevent gases and air from mixing in one area to another, but the differentiation of heat one either side of the chamber can cause the expansion of the metal which leads to leaks, causing the sealing to be faulty even when oil is injected into the chamber to attempt to lubricate the walls of the chamber against wear on the rotating parts.
Burning Oil – With oil being injected directly into the chamber it’s being burned with the fuel. In addition to this injection, the oil is injected into the intake manifold just like a normal engine. Because of the burning of oil in the chamber you would have to constantly check your oil after a drive in a car with a rotary engine and make sure you have sufficient levels of oil for any driving you might do. Adding oil directly to the chamber also increases the emissions that are expelled from the vehicle, making it difficult for a rotary engine to pass an emissions test.
Terrible Emissions/Gas Mileage – With the first three reasons leading to this fourth it’s easy to see how the emissions can be so much higher than on a typical engine. The burning of excess gas during exhaust, a lack of sealing inside the engine and the burning of oil all lead to much higher emissions than would be acceptable on the market today. As for the gas mileage the numbers are horribly low considering the fact the engines are smaller than others. Looking at the comparison given in the video, the numbers are astounding as to what the rotary engine produces.
Will the rotary engine be used for the next line of the RX vehicles from Mazda? That’s hard to determine considering these engines have a difficult time selling themselves. If Mazda were able to counteract all the points above and offer us a rotary engine that is just as fuel efficient and emissions friendly as the engines we currently use it’s possible the Wankel could be used in the next line of RX models. I guess we will have to just wait and see what comes of the rotary engine and how Mazda intends to power the RX-Vision. Here’s a video explaining four reasons why the rotary engine is dead.
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