Chrysler HEMI History

HEMI - as Chrysler calls its own internal combustion engine, which combustion chamber has the shape of a hemisphere. Over the past half century the acronym has become a kind of symbol of Chrysler, and just mention of it immediately evokes associations with the powerful American muscle-cars of past century.

The use of a hemispherical combustion chamber allowed to increase engine power, because of more complete combustion. In addition, such engines have significantly lower levels of noise and vibration.

Chrysler HEMI engine have obvious flaws also. First of all, they include the high cost of production (due to more complex structure), low reliability, relatively high weight (on average 25% more than a conventional engine), high toxicity and rather high fuel consumption. 

Chrysler HEMI history has, surprisingly, aerial roots. The first engine with hemispherical combustion chambers was created by Chrysler in the distant 1940, when the company decided to draw the attention of the militaries to their own products. It's about a little-known Chrysler IV-2220 - engine, intended for use in military aircraft. Actually, the shape of the combustion chamber was not its only distinguishing feature - 16 cylinders, inverted V-shaped layout and monstrous power of 2500 hp!

But what's even more amazing is the fact that despite the active promotion of the brand HEMI worldwide as its own design, it was not Chrysler to invent HEMI. And Chrysler wasn’t the first to use it in cars. About 30 years before early Chrysler HEMI similar engines was already used in Europe, by Peugeot and Alfa Romeo. In the 40's engines with hemispherical combustion chambers could be found on the racing Jaguars, during more than 30 years (from 1963 to 1999) such engines were used by Porsche. 

And yet, today HEMI associates with Chrysler only. Americans, like no other, paid special attention to this engine and achieved the most impressive results.

First HEMI appeared on Chrysler in 1951, it was the famous HEMI V8 331 Firepower. This engine brought the company a lot of big racing victories and made the Chryslers one of the most powerful and fastest cars in the world.

The very first appearance of HEMI on the racetrack plunged into shock all Chrysler’s competitors: in Daytona 500 race in 1964 Chryslers and Plymouths equipped with HEMI engines have won three victories in a row. Next, Chrysler stamped one victory after another during the season in 1964, and on the race track HEMI have no real competitors. Chryslers gained new victories and it seemed that no one could stop them.. But already in 1965 Nascar banned HEMI for use on race cars - these endless victories looked too suspiciously.

Naturally together with race HEMI Chrysler produced also civilian version, the so-called "Street HEMI". If the sports version of the engine had one carb with four chambers and aluminum cylinder heads, the easier road version had two carburetors, cylinder head made of cast iron and a lower compression ratio. The engine can be combined with mechanical and automatic transmission. Installing HEMI was quite expensive and cost about $ 1,000.

Year 1966 was the next round of development in Chrysler HEMI history, a new HEMI 426 was introduced. New engine was installed in legendary Dodge Challenger. Engine capacity of 7 l (number 426 denotes the engine’s volume in cubic inches), and power of 425 hp. The angle between the intake and exhaust valves - 58 degrees. Acceleration from 0 to 100 km/h with such a monster under the hood takes only 5-6 seconds (depending on model), but his appetite was to match the characteristics - 30-40 l per 100 km.

Oil crisis of the early 70-s stop Chrysler’s building muscles. High fuel prices cause decline in sales of powerful muscle-cars, and last 115 “pre-crisis” HEMI Chryslers were sold in 1971. For long period of time HEMI engines disappeared from company’s brochures. May be to resume with renewed vigor in early 2000-s.

At the moment there are 3 generation of HEMI: The first is the HEMI Firepower (1951), the second- HEMI 426 (1964), and finally, the third generation - the modern HEMI.

Thanks to MDS (Multi Displacement System) modern HEMI can boast relatively moderate appetite. This system was developed during the time of alliance with Daimler, and it works quite simple: the system just shut down "unnecessary" cylinders at a time when the car does not require maximum power. This system is used including 5.7 V8 HEMI engine under the hood of Chrysler 300C and programmed to work in two modes - the most economical and the most effective. In the first case, when the car moves at a low speed, MDS switches off 4 cylinders and thus reduces fuel consumption. Disconnection of cylinders going in no time - it takes only 40 milliseconds! When the car is accelerating increasing the engine system swithes on 4 "additional" cylinders and thus maximum efficiency is achieved.

In addition, the modern HEMI 5.7 V8 uses a system of two spark plugs per cylinder. It also contributes to a more complete combustion of the fuel mixture, resulting in increased power and reduced fuel consumption.

Interesting facts from Chrysler HEMI history:

• The first engines with hemispherical cylinder heads appeared over 100 years ago

• Cost of early Chrysler HEMI engine was a third of a cost of a car itself

• 1955. Chrysler 300 HEMI - the first car with engine power of over 300 hp!

• Chrysler HEMI engine is installed on the most powerful lawnmower in the world 

• In 1991, a car with a HEMI engine set an absolute speed record in Supercharged class, speeding up to 410 miles / h!

HEMI engines today can be found on the most powerful and expensive models of Chrysler and Dodge - executive sedans 300C, Dodge RAM pickup trucks, SUVs Dodge Durango and Jeep Commander, Dodge Viper and Challenger, etc.