How does engine placement affect performance?

author

Joel Ilton

Friday, 9 August 2019

There's been a lot of talk recently about the new C8 Chevrolet Corvette and the fact that the traditional front-engine, rear-wheel drive configuration that has been a staple of the Corvette since the late ‘50s has been changed to a mid-engine, rear-wheel drive, supercar-style layout. The new, sharp-looking Corvette is sticking to tradition with a V8 engine, but it will now be mounted directly behind the occupants instead of under the bonnet.

Why the change after half a century of using the same layout? Chevrolet says that moving the engine to the middle will improve the car’s handling and performance and that they had reached the limits of grip with the traditional front-engine, rear-wheel drive layout.

While this may come as a surprise to many, Chevrolet has considered using a mid-engine layout for the Corvette many times over the 50-year history of the model, and a number of concepts were developed, although never got off the ground due to mechanical or financial issues.

So, what’s so special about mounting the engine in the middle of the car anyway?

Actually, there are plenty of benefits to mounting the engine behind the passenger compartment. However, like most things, there are certain drawbacks to the design as well.

In a high-performance vehicle, optimising the vehicles handling characteristics is a priority and having supercar performance in a straight line but SUV handling during cornering would ruin the vehicle dynamics. Fitting the engine in the middle of the vehicle brings the weight distribution close to, or even exactly to, a 50/50 split between front and rear. That’s a good thing as too much weight at the front or rear can cause either understeer (the car does not turn enough into a corner) or oversteer (the car turns too sharply and may spin), both of which reduce the handling balance of the vehicle.

Going hand in hand with 50/50 weight distribution is the vehicle’s centre of gravity. A vehicle with a high centre of gravity - an SUV for example - will have less desirable handling characteristics due to the load transfer associated with the weight being located higher up. This is known as ‘body roll’ which, in extreme circumstances, can cause a vehicle to roll over. Having the engine mounted low down and in the centre of the vehicle shifts this centre of gravity, limiting body roll and improving handling balance.

Another benefit to a mid-mounted engine is an increase of tyre grip under acceleration. When accelerating, the weight of the vehicle shifts rearward through the suspension and onto the rear tyres, forcing them into the tarmac. This increases the drive of the car as the tyres provide more grip.

article image

The brand new C8 Corvette, now with a mid-mounted V8 engine

The most obvious drawback to the mid-engine layout is the reduction of interior cabin space. Fitting the engine behind the driver limits the vehicle to a strict two-seat layout. There’s a limit on cargo carrying room too as there can’t be a full-size boot. Most manufacturers will utilise the space in front of the cabin as a small cargo carrying space, but these are only suitable for small bags.

The main drawbacks however, are the safety aspects and the packaging issues that arise from stuffing a V8 engine and transmission behind the driver. With the engine in the middle, if the vehicle breaks traction and begins to spin it can happen suddenly. Unless you have lightning reflexes, or safety features such as traction control enabled, you could be in a bit of trouble.

Keeping the engine cool and fitting in all the necessary components that make an engine run in a small confined space is a difficult task. In a traditional front-engine vehicle, the radiator and other cooling components are located behind the front bumper and have access to clear airflow to keep temperatures in check. With the engine in the middle, these radiators tend to be mounted off to the side and fed air through specially designed ducting. This is not as efficient, as there is less surface area to provide cooling. Additional fans and other cooling system are used to keep temperatures within set parameters.

With all these new changes coming to the Corvette, Chevrolet seems to have the European supercars from Ferrari, Porsche, Lamborghini and others in its sights. With the standard model Corvette equipped with the 6.2L LT2 V8 engine producing 470 horsepower, it may be down on power compared to some it’s aimed at tackling, but there will be higher performance models announced closer to the full release of the vehicle in 2020.

Pricing starts from $US60,000 ($AU89,000 as of August 2019) and production is slated to start at the end of 2019. Word is they are producing the new Corvette in both left-hand drive and right-hand drive configurations and Holden - General Motors’ Australian arm - has already confirmed the Corvette will be coming our way.

 

author

WRITTEN BY

Joel Ilton

Finding a passion for cars from a young age, Joel carried out work experience as a mechanic whilst at school before starting an apprenticeship after finishing year 12.

After almost 10 years on the tools and in customer service, he moved into the IT realm as a Data Analyst and In-House mechanic at AutoGuru.

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