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Auto Adviser with Phil Hanson


Front, rear or mid-mounted engine - which is best?

For decades, cartoonists and comedians have made mileage out of cars that don’t have their engine at the front.

A hapless motorist looking under the bonnet of an original Volkswagen Beetle for the missing engine – everyone’s seen or heard them.

So why is it that some designers put the engine in the middle or the rear? They can’t all be relatives of joke-makers looking for material.

Engines have been in the front ever since horses and bullocks gave way to the powered vehicle, so why would you want it anywhere else?

Although some pioneers flirted with other locations, Ford’s Model T well and truly established the front-engine configuration.

That location has stood the test of time, its nose-heavy weight distribution being the only significant drawback. These days, we have engines in the front driving the front wheels, the rear wheels or all four wheels; a truly adaptable and universal arrangement.

But there has been an influential group of companies and designers that favoured rear-engined cars as a way of putting extra weight – and thus traction – over the driven wheels, and also as a way to cut costs.

Years ago, it was easier to get more traction this way than with the now ubiquitous front-wheel drive, which added the complication of having to also steer the wheels.

The configuration saved manufacturing costs as the entire engine/driveline could be assembled as one unit and slipped into the body.

The original Beetle is the enduring symbol of a rear-engine, rear-drive car, although others were developed around the same time.

The downfall of the rear-engine, rear-drive configuration was its oversteering handling characteristics.

In a corner, the rear end wants to swing wide, especially if the driver brakes or lifts the throttle.

Experienced drivers often enjoy this characteristic, but for many others it was a quick and easy way to a good crash.

Engineers and tyre designers were able to minimise, but never eliminate, oversteer.
Front-wheel drive cars have the opposite characteristic: understeer, which is regarded as more benign and able to be handled by the average driver.

You might think the rear-engined car would have faded away, but it didn’t. Porsche persisted in the 911 series, often teaming it with all-wheel drive. At the other end of the cost scale, the Indian Tata Nano, the world’s cheapest “real” car and currently one of the most talked-about on the planet, has also appeared with its little engine in the rear.

So, if a front-engine car understeers and a rear-engine car oversteers, a car with its engine in the middle would be just right, right?
You can certainly achieve perfect 50-50 weight distribution by putting the heaviest component in the middle, improving stability, and honing responsiveness by reducing the vehicle’s moment of inertia.

However, from any packaging perspective, the middle is a lousy place to put the engine, pretty much limiting the configuration to two seaters.

Engineers responsible for efficient cooling are presented with a challenge. It also limits access for maintenance, but no more than all the vans with their engine under the driver’s seat.

The mid configuration has proved popular on sports cars, from Italian exotics to affordables like Toyota’s MR2.

Although many mid-engine designs have the powerplant immediately behind the passenger compartment, it doesn’t have to be that way. Other designers have opted for a front mid-engine configuration in which the engine is placed well aft of the front wheels – Auto Adviser fondly remembers British TVRs of the 1970s that used this arrangement particularly well.

Mid-engine cars can be great fun to drive but they need to be watched on wet or slippery surfaces.

Although the configuration is said to offer some traction advantages, take it with a grain of salt; they may break away quite easily in the wet and be hard to get moving on snow or ice, should that be a problem in your area!

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