What Is A Hemi Engine? Here’s The Full Scoop
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Hemi engines have quite the reputation behind them, and not just on the racing track. With a long history of power, performance, and success, the hemi engine is popular with a lot of different kinds of drivers and car owners.
But, when you’re first getting into cars and running in gearhead circles it can be confusing to hear people talking about hemis. It’s even less likely for average vehicle consumers to know what it means if they’re looking at a vehicle and see Hemi engine listed in the specs.
So, what is a Hemi engine, and what do they do for the people who have them? We’ll cover everything you need to know so you’re prepared the next time you’re buying, or can impress your friends with your new knowledge.
What Is A Hemi Engine?
Hemi engines are called Hemi because of the hemisphere shape of their combustion chambers. The round shape offers a lot of efficiency advantages and can make for a more powerful engine compared with alternative designs of the same size.
However, for all the added efficiency of a Hemi engine, they are more sensitive to octane ratings. The hemispherical combustion chambers make it a little easier for the pistons to cause premature combustion, so you need higher quality fuel to help reduce the chances.
Running low octane fuel in a Hemi engine can cause severe efficiency loss, and, over time, can even cause damage to the engine and fuel injection systems.
That said, for a lot of people the ability to use more efficient air intake systems, better spark plug positioning, and more complete fuel consumption are worth the slightly pickier system.
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How Long Have Hemi Engines Been Around?
If you want to know what is a Hemi engine you probably also want to know something about the history and how these engines got to be famous.
A lot of people think that Hemi engines are the creation of Chrysler, because the car manufacturer was the first to make Hemi engines famous, and did a lot of work promoting Hemi engines as a marketing feature.
The truth is a little different. For one thing, Hemi engines have been around since the turn of the 20th century and were used in European vehicles and even boats long before Chrysler used their first Hemi engine.
There is a little nugget of truth in the idea that Chrysler made the Hemi engine – and it’s an important truth to understand if you what to know what a Hemi engine is today. Chrysler’s hemi engines are where a lot of their popularity and reputation come from, and Chrysler trademarked the hemi name.
In a very real sense, Hemi engines wouldn’t be what they are today if Chrysler hadn’t adopted them and used them as a way to stand out from the crowd.
Even today, Chrysler is still one of the biggest manufacturers and users of the Hemi engine design, and they’re included in some Dodge, Ram, and Jeep models.
Do Hemi Engines Deserve The Hype?
One of the first things people ask when it comes to Hemi engines is if they’re really as good as their reputation would have you believe. After all, if the Hemi engine really is a miracle of efficiency and performance, wouldn’t Chrysler use them in more of their vehicles? Wouldn’t other car manufacturers have adopted them or come up with their own Hemi engine designs?
If a Hemi engine is really all that, why do so many people need to ask what is a Hemi engine, instead of just knowing?
Well, there are a few reasons the Hemi doesn’t have more mainstream popularity.
For one thing, the hemi engine is deeply connected to racing and race cars. Chrysler was required to come up with a street-legal version of the Hemi engine by racing organizations, to make the engine legal for their organizations.
While the Hemi engine gained more mainstream popularity in the 60s and 70s, it was a racing engine even at the height of its mainstream popularity and good reputation. No one who wasn’t looking for a fast and high-performance engine needed one, and the efficiency of the Hemi engine wasn’t needed for your average vehicle.
Modern Hemi engines are used for a wider range of vehicles, but at least some of those vehicles have a Hemi engine more in name than in practice. Chrysler’s Hemi engine has much flatter combustion chambers than it used to and has the efficiency loss and consistency increase to come with the altered design.
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Do Hemi Engines Have Problems?
The truth is that the Hemi engine, nowadays, doesn’t have the same kind of performance advantage that it used to hold over other engine types.
Don’t get us wrong, the improved efficiency is still there and is very real. Better gas mileage is one of the advantages of a Hemi engine.
That said, not everyone is convinced that the fuel savings and increased performance justify the extra work and maintenance needed to make sure a Hemi engine is working properly. Hemi engines don’t handle slight timing problems, inconsistent fuel amounts, or lower octane fuel as well as standard combustion engines do.
That’s less of a problem in some markets, where gas has higher octane ratings all the time. But in the United States, which is a large part of the market for today’s Hemi-equipped vehicles, it is a problem. U.S. fuel octane requirements are lower than the requirements in European markets, and even premium high-octane fuel here is only average compared to European fuel.
Put it together and Hemi engines are picky about octane and need more maintenance and tuning than other vehicles, which means that owners need to pay more for gas and may pay more at the mechanic as well.
It’s not so much that there are problems with Hemi engines as it is that there are practical barriers to making them a good option.
So long as traditional combustion engines work well enough, it’s unlikely that Chrysler will redesign their existing Hemi engines or make them a more common component in their vehicles. And with the rise of the electric vehicle and the hybrid model, more research dollars are being spent on better sustainable vehicle designs instead of improving on gas-powered engines of all types.
So, the heyday of the Hemi engine is likely behind it, but that doesn’t make the existing Hemi engines any less interesting or effective. And if fuel efficiency and performance are your goals, few engines will serve you better than a Hemi out of one of Chrysler’s classic muscle cars.
Comparison with Other Engine Types
You’ll notice significant differences when comparing Hemi engines with other types, such as flathead and overhead cam (OHC) engines. Hemi engines are famous for their hemispherical combustion chambers, which improve combustion and power. On the other hand, flathead engines feature a more straightforward design, resulting in lower efficiency and power due to less optimal airflow.
Hemi engines offer better power output than flathead engines but require more maintenance due to their complexity and higher cost. Unlike OHC engines with a camshaft placed directly above the valves to ensure accurate timing, Hemi engines achieve performance using a different method. OHC engines with advanced features, such as variable valve timing, can improve efficiency and power across a wider RPM range. However, they can be more intricate and expensive to manufacture and maintain, mainly due to their complexity.
While you’ll find that Hemi engines boast superior power output, you might appreciate the efficiency and precision that OHC engines bring to the table. Meanwhile, if you’re drawn to simplicity and ease of maintenance, flathead engines might catch your interest despite being less efficient. Each engine type has its own strengths, designed to meet various preferences and needs within the automotive world.
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