Pros And Cons Of The HEMI Engine
Known for its muscle, the HEMI engine has been popular ever since it debuted in Chrysler's vehicles in the early 1950s. The original model was a V-8 configuration that offered drivers 180 horsepower. Today, that kind of power hardly seems worth a second glance, but in 1951, it turned heads. It wasn’t long before Chrysler, aware there was a growing market for the HEMI, devoted their resources to further developing the engine. It offered 425 horsepower by 1965.
The main ingredient behind the HEMI's enormous power and efficiency was the design of the combustion chamber. Rather than relying upon a traditional flat design, the HEMI was curved at the top (similar to the top edge of a ball). This curvature eliminated much of the thermal inefficiencies suffered by the flat head engine.
In this article, we’ll take a closer look at the pros and cons of the HEMI engine. To be sure, it’s not the ideal design for every driver, but for some, it offers unparalleled performance.
Advantages Of A HEMI
There are two main advantages to a HEMI engine. The first advantage involves the amount of surface area within the combustion chamber. To understand why, it’s important to review how your vehicle’s engine generators power. During the 4-stroke process, the fuel within the chamber is ignited by the spark plug. It burns and produces energy. The hotter the fuel is, the more efficiently it burns. Because of its design, a HEMI has less surface area than a conventional flat head engine. That means the fuel within the chamber burns more efficiently because less heat is lost to the limited surface area.
The second advantage involves the valve size. In a regular flat head design, the size of the fuel and exhaust valves is limited due to their placement. In a spherical design, the size of the valves can be much larger. The larger the valves, the larger their corresponding openings during the 4-stroke combustion process. That translates into more airflow.
HEMI Drawbacks
There’s one main drawback to a HEMI: the number of valves it allows per cylinder. Because the top of the chamber is shaped like a ball, it can only fit two valves. Many of the performance vehicles that are rolling off the factory floor today are taking advantage of 4-valve cylinders. In the same way that larger valves offer more airflow, so too, do four valves offer more airflow than two valves.
There is a smaller reason HEMI has recently fallen out of favor with drivers who need immense power in their engines: the size of the combustion chamber. The design does not allow the chamber to be smaller. Meanwhile, automakers are trying to reduce the chamber’s size to further limit surface area and heat loss.
Most motorists will not have use for a traditional HEMI engine given their other options (for example, a newer pentroof design). That said, it’s impossible to ignore the impact the HEMI has had upon the automotive industry.