This article describes another oddity of motoring - the 5 cylinder engine.
Most car engines are up to 6 cylinder in length – most larger engines are in a V formation – V8 and V12, which are 4 and 6 in length. There have been two and three cylinder engines in smaller post war cars but in the last 40 years, most engines have been 4, 6 or 8 cylinder motors with straight, flat and V formations.
So, 5 cylinder engines aren’t new – like many technologies or concepts in motoring, the 5 cylinder engine was first seen in aircraft engines before migrating to cars.
The 5 cylinder motor provides a nice mix of the benefits of the 4 and 6 motors – the fuel efficiency of the 4 and the power advantage of a 6. However, having an odd number means that the motor is unbalanced so needs to be designed to give a smoother delivery.
An interesting thing about engines is when the power stroke happens. On a 4 cylinder engine the crank receives a power stroke sequentially – i.e. when one cylinder finishes a power stroke, another is starting. On a 5 cylinder engine, there is a slight overlap and so the torque of the stroke causes low and high speed vibrations – the unbalancing I spoke of earlier. So like large capacity 4 pots, the engine needs a balancing shaft.
Interestingly, balancing shafts – invented by Frederick Lanchester, of the Lanchester car company. On large 4 cylinder motors, the engine needs 2 balancing shafts but on a 5 cylinder engine, only one is needed to counter the fact that the engine vibrates due to the firing order and where the pistons are at any time. However, the balancing shaft cannot be fitted in the same place as the 4 cylinder motor and it is slightly off-centre which reduces the efficiency of the counter weights.
5-cylinder engines have been built by GM, VW/Audi, Honda, Volvo, FIAT and Mercedes. Volvo and VW/Audi are the current users of this formation. The engines have been designed as a modular design, which means that they can be built on the same production lines as their related 4 or 6 cylinder versions.
For example, the VW/Audi V5 is essentially their V6 with one cylinder missing and it isn’t a true V formation, being at an angle of just 15˚ instead of the normal 60˚ and because of this the cylinders share the cylinder head rather than having two.
However, saying that only a handful of manufacturers build 5-cylinder motors doesn’t mean that only a few cars have them. VW shares it’s motors with Audi, SEAT and others, Volvo being part of Ford, shares the motor between the S40 and Focus models and GM use theirs in the Hummer and several Chevrolet models and many of the current motors are now being supplied with turbochargers to increase the power and efficiencies
And to finish off, the V5 really made it’s mark in MotoGP racing with the Honda RC211V that won many World Championships. This engine had three forward facing cylinders and two rear-ward at 75.5˚ and produced 220hp from 990cc.