R4 in-line engine - what is its design and on which cars was it used?

The R4 engine is installed in motorcycles, cars and racing cars. The most common is the so-called variety of a simple four with a vertical structure, but among the designs used there is also a flat type of engine - a flat four. If you want to know more about individual types of motorcycles and check out key information, we invite you to the next part of the article.

Basic information about the power unit

The engine has four cylinders in a row. The most commonly used variety is from 1,3 to 2,5 liters. Their application includes both cars made today and cars made earlier, such as Bentley with a 4,5-liter tank of the period 1927-1931.

Powerful in-line units were also produced by Mitsubishi. These were 3,2-liter engines from Pajero, Shogun and Montero SUV models. In turn, Toyota released a 3,0-liter unit. R4 engines are also used in trucks weighing between 7,5 and 18 tons. They are equipped with diesel models with a working volume of 5 liters. Larger engines are used, for example. in locomotives, ships and stationary installations.

Interestingly, R4 engines are also installed on smaller cars, the so-called. kay truck. The 660cc units were manufactured by Subaru from 1961 to 2012 and distributed by Daihatsu since 2012. 

Characteristics of the in-line engine 

The unit uses a crankshaft with very good primary balancing. This is due to the fact that the pistons move in pairs in parallel - when one goes up, the other moves down. However, this does not happen in the case of a self-ignition engine.

In this case, a phenomenon called secondary imbalance occurs. It works so that the speed of the pistons in the top half of the crankshaft rotation is greater than the acceleration of the pistons in the bottom half of the rotation.

This causes strong vibrations, and this is mainly affected by the ratio of the mass of the piston to the length of the connecting rod and the stroke of the piston, as well as its peak speed. To reduce this phenomenon, lighter pistons are used in standard cars, and longer connecting rods are used in race cars.

The most popular R4 engines are Pontiac, Porsche and Honda

Among the largest powertrain models that were installed in widely produced cars was the 1961 Pontiac Tempest 3188 cc. Another big displacement engine is 2990 cc. cm installed on Porsche 3. 

The units were also used in racing cars and light trucks. This group includes a diesel engine up to 4,5 liters, installed by the manufacturer Mercedes-Benz MBE 904 with a capacity of 170 hp. at 2300 rpm. In turn, the small R4 engine was installed in the 360 Mazda P1961 Carol. It was a conventional 358cc overhead valve pushrod. 

Other popular R4 engine models were the Ford T, the Austin A-series subcompact unit, and the Honda ED, which pioneered CVCC technology. This group also includes the GM Quad-4 model, which was the first multi-valve American engine, and the powerful Honda F20C with 240 hp. at a volume of 2,0 liters.

Application of the motor in racing sports

The R4 engine was used in racing sports. It was the car with this engine, driven by Jules Gu, that won the Indianapolis 500. Important information is that for the first time double overhead camshafts (DOHC) and 4 valves per cylinder were used. 

Another innovative project was a motorcycle created for Ferrari by Aurelio Lampredi. It was the first four in a row in the history of Formula 1 from the Italian Scuderia. The 2,5-liter unit was installed first on the 625 and then on the 860 Monza with a displacement of 3,4 liters.