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Stinging sensation

The automobile may be more than a hundred years old, but in some areas it’s difficult to spot the 100-plus years of progress. The Scorpio Hybrid does what few other cars can: it combines a diesel engine and an electric motor and batteries. Shapur Kotwal finds out.

entertainment Updated: Apr 29, 2008 21:22 IST

The automobile may be more than a hundred years old, but in some areas it’s difficult to spot the 100-plus years of progress. Look under the column of efficiency and you’ll be flabbergasted.

Petrol engines have dismal efficiency levels of 25 per cent with diesels doing slightly better at 30 per cent, depending on whom you ask. Now compare those figures to 90-95 per cent quoted for electric cars.

However, while electric cars have no tailpipe emissions, storing the electric energy (in batteries) and charging them poses major problems. Batteries hold very little energy and make electric cars heavy. The perfect compromise would thus be a little bit of both — the hybrid. By combining an internal combustion engine with electrical motors and batteries, they offer more efficiency on the one hand and not much weight or range penalty on the other. Tailpipe emissions are better, too.

First look

Mahindra and Mahindra has been paying attention to the potential of hybrids, and had put up their diesel-electric Scorpio hybrid on display at the Auto Expo in Delhi in January. Up and running, the Scorpio Hybrid is among the first functional diesel hybrids in the world, right alongside the C-Class diesel hybrid Merc.

Nosing around, I found a large Bosch Motor Control Unit and orange high-voltage three-phase wiring, the bits that mark it out as hybrid. A few months and a mini-miracle later I got to steer it through the gates of M&M’s R&D facility at Nashik. To start the Scorpio Hybrid, you turn the key. There’s a moment's pause, an eerie silence, with no frenzied whirring of the starter motor audible. That’s because there isn’t one.

Then, as if there’s a ghost in the machine, Mahindra’s hi-tech common-rail mHawk diesel unobtrusively comes alive with its familiar soft pitter- patter. It’s an automatic, so I place the ‘box in ‘D’ and squeeze the right pedal. Not much is noticeably different. There’s that strong tug as I accelerate, maybe a touch more than normal, and it moves forward smartly on just a dab from the throttle.

Initially, I pay more attention to how well the automatic gearbox gels with the torquey nature of the Scorpio. It gathers pace effortlessly and keeps the momentum going even when you upshift. I head out from Nashik down a well-paved state highway. There’s a central console-mounted screen that has a couple of active display diagrams and I select the one that shows the flow of power. It tells you how much electric power the Scorpio is using, whether its motor is topping up the batteries or if power is being supplied to the car via only the 2.2 mHawk engine.

Alchemy at work

I start driving with one eye on the screen, watching to see if the Scorpio is being provided an electrical assist or not. On small throttle openings, the assistance can be detected. The mHawk common-rail diesel is one of the most impressive motors of its kind, with minimum turbo lag and a large wedge of torque available from a low speed. But the disdain with which the Hybrid is pulls and the total lack of any lag from the motor tells me there is some alchemy at work here. And the display proves it.

The E-machine bar on the display is showing activity and arrows lead from the battery to the motor through to the gearbox. So it is the electric motor assistance that’s been helping the Scorpio move so effortlessly. Time to use more of the electric boost. I flatten the throttle on an open stretch from a cruising speed of around 40 kph and I’m pleasantly surprised by the instant shove from the back seat. The electrical assistance from the motor feels very impressive and the Scorpio positively scoots forwards like it is being powered by a 3-litre motor.

It feels almost 10-15 per cent faster than the regular Scorpio and the crisp throttle responses are fantastic. The whole car feels lighter and more lithe, although in reality it is 180 kg heavier (because of the heavy batteries and motor of the hybrid drive system). The extra performance is positively invigorating and soon I’m seeking out gaps in highway traffic so I can flex my right foot.

The nuts and bolts

Dr Arun Jaura, who heads the project for M&M, has been involved in alternate energy projects from his days at Concordia University, Montreal. But M&M needed outside assistance for such a hi-tech venture. The Hybrid Scorpio has been designed and engineered with the help of FEV, a German company that provides technology solutions and engineering services.

Here’s a quick tech map of the Scorpio Hybrid: The basic components include a circular electrical motor that’s fused to the flywheel of the mHawk motor, an automatic gearbox and a suitcase-sized set of NiMH batteries that is placed at the rear. Four computers or electronic controllers that are integrated by a master Vehicle System Controller (VSC) run the combined power train. This is not a plug-in hybrid, so you can’t plug it into the wall socket in your garage. The Scorpio Hybrid uses the greater efficiency of the electric motor to augment the diesel motor.

Despite being called a hybrid, energy comes from the diesel engine. The VSC allows the engine to charge the batteries during times of partial load, when much of this power would otherwise have been wasted. The batteries also get some amount of energy from regenerative braking, where the electric motor is made to act as a generator. The charge now gets “wound back” to the battery pack. The energy stored in the batteries is then returned to the car via the motor much more efficiently.

Start-stop mechanism

On the return leg of our long drive, I steer towards some of Nashik’s sparse traffic, to test the start-stop system. I’m greeted by silence and a stopped motor a few seconds after I’ve put my foot on the brake. The air-conditioner blower stays on, but the compressor is switched off.

M&M says it will also install a manual override, so if you’re stuck in traffic, you can keep the AC going. The instant I take my foot off the brake, the engine springs back to life allowing me to pull cleanly away from the lights.

Start-stop makes the hybrid 20 per cent more efficient. Yes, you read that right.

But don’t rush out to buy the Scorpio Hybrid; it won’t hit showrooms for a couple of years yet. Though this prototype may have performed well and displayed massive potential, putting the car into production at the right price will be a big challenge.

M&M is in the process of localising the components that make up the hybrid system; engineering reliability and a high degree of robustness into these is likely to take a fair amount of time. Still, M&M’s technological prowess and efforts in the area deserve to be applauded.

Autocar India