Friday, June 03, 2011

Corvette and the downsizing: time for a change?

This post is dedicated to some of the Truck Mod Central guys.

Well-known worldwide as an American institution, the Corvette is portrayed as a legend, comparable to famous European high-end sports cars such as some Ferrari and Porsche models, among others.
It's also known to spot another America's #1, the Chevrolet small-block V8, currently in its 4th generation but still relying on a traditional OHV layout while its opponents from Europe and Japan usually have DOHC cylinder heads. However, some hoaxes about a possible engine downsizing are getting some space in the media and already generating some discussion. OK, it's a possibility in these days of EPA and CAFE witch-hunting, but would it be really a change so enormous in the Corvette's basic concept? Maybe not...

Currently powered by either a 6.2L (430HP @ 5900RPM/424lb.ft. @ 4600RPM - also available with a supercharger for 638HP @ 6500RPM/604lb.ft. @ 3800RPM in the ZR-1 version that is "cheaper", has a close performance and is not so gas-guzzler as a Ferrari 599 GTB Fiorano with its hi-revving normally-aspirated DOHC 6.0L V12) or a 7.0L V8 engine (505HP @ 6300RPM/470lb.ft. @ 4800RPM). But, instead of its European counterparts with specially developed engines, the Corvette relies essentially in the same engines used by the large pickups and body-on-frame SUV's from Chevrolet and GMC, with a smoothier throttle response, preferred by a lot of American customers.

Rumors about a smaller engine have gained force since the GT2-class C6-R Corvette appeared with a 5.5L version of the V8, with 500HP. For a street-legal version, reported to be released in a 440HP rating, a feature that would be expected is direct injection, already found on some of its opponents such as Ferrari 458 Italia. But either hi-revving or a DOHC head still find some resistance from the most traditional Corvette customers and enthusiasts. Then forced induction comes as a reasonable option to manage the lower displacement issue without sacrifice the power but, again, different concepts have been shown as the way to go: turbo or supercharger?

While some people are still worried about the turbo-lag, and then considering the engine-driven supercharger as the most cost-effective option, there are those who would prefer to enjoy the kinetic energy thrown away by the exhaust pipes to drive a turbo. Nowadays, with the advances on engine management achieved with the electronics, a turbo setup seems to be the most reasonable. Advancing the ignition point at the engine startup has been reported to "wake up" the turbo earlier, for example, and also more modern turbo designs such as VGT have become helpful to manage this issue. And obviously, a properly-sized turbo is essential to have the most suitable boost ratio according to the engine revving.

As far as a lower displacement goes, considering FIA's current standards considering each liter in a forced-induction (most notably turbocharged) engine equal to 1.7L in a normally-aspirated, I wouldn't expect anything above 3.6L to replace the 6.2L in the entry-level Corvettes, retaining its current power/torque ratio or improving it. Maybe now that Ford, GM's archi-rival, is having some success with its Ecoboost range even in the F150 pickup, could be an incentive for a downsizing attempt. And it's perfectly viable for GM, since a 3.6L DOHC V6 engine is already available in its range and some aftermarket turbo setups have been successful, specially in Australia. However, a loyal Corvette enthusiast would still desire the V8 layout. Then, even the DOHC Northstar engine in its supercharged 4.4L version, rated at 469HP @ 6400RPM/439lb.ft. @ 3900RPM from the STS-V is often pointed as a reasonable option for an entry-level model to meet both EPA newer regulations and the enthusiasts.

Anyway, one thing is certain: even with some changes, the Corvette must retain its essentially American soul, and this is a hard challenge for the engineering team...

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