Rob Green (right), with happy customer Raghu Chetty.
Rob Green (right), with happy customer Raghu Chetty.
Picture shows clearly the Whipple twinscrew supercharger and its belt drive, as well as the specialised intake trunking. Picture: Rob Green
Picture shows clearly the Whipple twinscrew supercharger and its belt drive, as well as the specialised intake trunking. Picture: Rob Green

Johannesburg - The contraction 'Hemi' when applied to internal combustion engines indicates a hemispherical combustion chamber, with the valve stems at an angle to each other.

In the days before multivalve cylinder heads, it had the double advantage that the valves could be made much larger than those of a conventional 'flathead' engine, and the inlet and exhaust ports were much straighter, leading to better gas flow at high revs.

The principle goes back to 1901, but the biggest proponent of this rugged, high-torque architecture has always been Chrysler - so much so that it has actually trademarked the word Hemi as a brand name for the muscular big-bore V8s produced by its SRT performance division.

These were always naturally aspirated, until the advent in 2014 of the supercharged 6.2-litre Hellcat engine, rated at a fire-breathing 520kW and 883Nm - but it's only available in the two-door Charger and four-door Challenger models, neither of which is made in right-hand drive, so we can't get them here.

The hottest hemi you can buy in South Africa is the 6.4-litre naturally-aspirated V8 in the SRT8 derivatives of the Chrysler 300C and Jeep Grand Cherokee, good for a respectable 347kW and 631Nm - but it's not in the same league as the Hellcat.

UPPING THE ANTE

That's not fair, said the adrenalin junkies at RG Motorsport in Strydom Park - so they did something about it.

Their tuning programme for the Chrysler 300C SRT8 starts with the Supercharged Stage One package, featuring a Whipple twin-screw supercharger - chosen for its blend of response, spread of power and refinement.

That's bolted directly on to the standard intake manifold, with its own self-contained lubrication system, backed up by high capacity fuel-injectors and a bigger-than standard intercooler core, and using the existing exhaust system. It's good for 480kW at the flywheel - a 38 percent improvement on the original.

Stage Two adds a dual 76mm Techniflow exhaust system, liberating another 20kW, while the Big Bang version goes a step further with hand-built, ceramic coated 'branch' manifolds and an induction kit to unleash 530kW - 10 more than Chrysler's flagship Hellcat V8 - at 6500 revs (accompanied by a sound track with more than a hint of Nascar in it) and 852Nm at 3000rpm.

Perhaps even more impressive is RG Motorsport's claim that the Big Bang SRT8 delivers more torque at 1800rpm than the factory lump does at peak - and is still churning out 738Nm at 6500rpm.

That's good news for those with big mountains to climb, because the same supercharger conversion - give or take a nut and bolt or two - will also bolt straight into a Jeep Grand Cherokee SRT8.

Upgrades on the 300C SRT8 and Jeep Grand Cherokee SRT8 start from R190 000, including RGMotorsport's six month/20 000 km warranty.