POWERTRAIN MAGIC MID-ENGINED
How the exhaust design challenges were overcome in the 2020 Corvette Stingray
W
hen it comes to designing a high- performance sportscar or supercar, a mid-
engine arrangement offers the ultimate chassis performance in terms of weight distribution, handling, braking and dynamic response. For this reason, most racing cars switched to the mid- engine layout in the 1960s; some, such as the famous Auto Union ‘silver arrows’ used the format as far back as the 1930s. However, although positioning
the powerplant in the middle of the car, directly behind the occupants, is best practice for optimising driving dynamics, such a design presents engineering challenges for road- going vehicles in terms of packaging, noise, vibration and harshness
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(NVH), and heat management. For the exhaust system, these issues must be addressed without compromising engine performance, exhaust emissions or sound characteristics – all essential factors for a sportscar. In its recent collaboration
with General Motors on the exhaust system for the new high- performance, mid-engine Corvette, Tenneco had to tackle all these challenges. The company employed several technical solutions to accommodate the packaging and thermal requirements of the emissions system while optimising efficiency and retaining the characteristic exhaust note that is synonymous with the V8 Corvette. This was achieved by using a
combination of active and passive exhaust valve technology, and
advanced heat shielding techniques. The valves vary system backpressure and shape the exhaust sound to provide the right balance of performance, sound characteristics and regulatory compliance, while the heat shielding protects vulnerable items from excessive temperatures within the tight packaging constraints.
THE LURE OF THE MID-ENGINE DESIGN With so many hurdles to overcome, one might question why a manufacturer would go to the trouble of engineering a mid-engine installation, especially when it has a heritage of charismatic front engine/ rear drive cars, such as the previous Corvette models. The choice of engine location plays
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