Rear Engines Return?
November 2005
The arrival of Mitsubishi i (or iCar for European market) reminds me the trend of rear engines might return - and I will be glad to see that. You might remember many of the world's best selling car in the past were driven by rear-mounted engines, such as Volkswagen Beetle, Fiat 500 and Fiat 126. But the rear-engine era was ended by Sir Issigonis's Mini, whose transversely-mounted front engine and front-wheel drive layout was even more space efficient. Moreover, placing more weight to the front instead of the rear can make the car "safer" to handle, because it is more likely to understeer rather than oversteer. Since the 70s, the automotive world has been dominated by FF cars.

There were some exceptions, however. In 1998, Honda released a Kei car called Z in Japan. It was powered by a rear-midship engine placed under the rear seat. In the same year, Smart's city car (renamed to Fortwo later) also brought back the rear engine. Then comes Mitsubishi i. Now Fiat is also studying the possibility of its future small car. So why are car makers bringing back an outdated concept?

The reason is to satisfy the increasingly high crash protection standard while retaining interior space. Today's tough requirements for crash protection eat into the space a small car can provide. Most mini cars now employ longer front overhang than those of a decade ago (see the new Fiat Grande Punto and you will know). This gain weight, hamper performance and fuel consumption. It also make the already nose-heavy FF car even more unbalanced, hence deteriorate handling. To a small car with restricted dimensions, most notably the Japanese kei car, the crash protection structure could eat into cabin space. Every car needs to have an adequate crumple zone at its nose to absorb the crash energy. The effectiveness of crumple zone depends on structural design as well as space available - there should be sufficient clearance between the bumper and the internal hard points like engine and battery. The higher the crash standard, the longer the crumple zone will be necessary and the less space available to passengers.

In the view of this negative future, returning to rear-mounted engine could be an answer. Look at the Mitsubishi i: its front overhang is virtually non-existent, allowing a super-long wheelbase at 2550 mm. That's a massive 130 mm longer than the previous kei-car record set by Honda Life. Despite of the lack of front overhang, the empty space in front of the cabin provides a huge crumple zone. On the other hand, the engine is mounted at a tilt angle under the rear seat, so it occupies no cabin space and it matches perfectly with the fashion of high seating position.

Concerning the oversteer drawback of rear-engined layout, nowaday's suspension design can easily handle that. Finally, returning to rear-wheel drive and a slight rear-biased weight distribution could help making our small cars more entertaining to drive. Car makers can also develop sports cars cost efficiently from those RR platforms, just like what Smart did to the Roadster.

For all these reasons, I am eagerly awaiting the return of the rear engine era.

Mark Wan

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