GM’s all-new 6.2 V8 is no dinosaur

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IOL mot pic oct25 GM LT1 V8 1

David Kimble

A beautifully ghosted view of the new, 6.2-litre GM LT1 V8 engine.

American engine design has always been conservative, relying on huge cast-iron V8 lumps with big, lazy pistons and pushrod-operated valves to get the job done - and that worked fine in an era of cheap fuel.

More recently, European manufacturers (German ones in particular) have built all-aluminium, high-revving DOHC V8s that make Detroit iron look like the dinosaurs they are and US government fuel-consumption guidelines have all but condemned them to extinction.

So, when the 2014 Chevrolet Corvette arrives in US showrooms late next year, it will have an all-new (by American standards, anyway) 6.2-litre V8 delivering an estimated 335kw and 610Nm - which should take GM's fibre-glass roadster from 0-100 in less than four seconds.

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The new Corvette LT1 engine is the first of what GM is calling the Gen 5 family of small-block engines, and the first Bowtie Blaster to combine direct fuel-injection, continuously variable valve timing and the ability to run on four cylinders under light load.

Not only will the new 'Vette be the quickest ever away from the lights, it'll be the lightest on fuel, with GM's development engineers confident of averaging less than nine litres per 100km.

THIS IS HOW IT WORKS

Variable valve timing also contributes to a broader power band, they say; below 4000rpm, the torque of the Corvette LT1 is comparable to that of the seven-litre lump in the current Corvette Z06.

It's also the first big-inch GM engine with direct fuel-injection, which ensures more complete combustion by precisely controlling the mixture motion and fuel-injection spray pattern.

Spraying raw fuel into the combustion chamber also keeps it cooler, allowing for a higher compression ratio, even on the feline urine that passes for petrol in the US, and reduces emissions, particularly under cold-start conditions.

THIS IS HOW IT'S MADE

The LT1 head has smaller combustion chambers to match the specially-shaped piston crowns - giving it an 11.5:1 compression ratio - and large, straight, rectangular intake ports with a slight twist to enhance mixture swirl, while the spark plug angle and depth have been revised to protrude farther into the cylinder, closer to the centre of fuel burn.

The direct-injection fuel pump, delivering up to 150 bar, is mounted between cylinder heads under the intake manifold and driven off the rear end of the camshaft.

They're fed by an intake manifold with individual runners that feed a plenum, over a single 87mm throttle body. Breathing out is handled by "four-into-one" short-header, cast-alloy exhaust manifolds, leading straight into "wide mouth" catalytic converters.

While none of the technology is ground-braking by European standards, packaging all of it into a 6.2-litre V8 is a big step forward for GM's domestic engine division - we can only hope that GM Australia drop the LT1 engine in the next iteration of the Lumina so we can get a chance to try it.

TESTING THE NEW LT1 ON THE DYNO


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