Firing on all (two) cylinders

The race for small diesel engines has been on for a while now and the Holy Grail has been the sub-litre class oil burner. Almost all the major car manufacturers have been toiling away trying to come up with that one engine which would satisfy their expectations for refinement, driveability and a disproportionate improvement in efficiency. Why ‘disproportionate’, you ask?

Somewhere along the way, it did seem like the engineering challenge of producing a sub-one-litre class diesel engine had overtaken the fundamental logic behind seeking a small diesel. The real reason for its development has to be substantial fuel savings. The prospect of the fuel price differential (compared to petrol) and a super efficient, small diesel engine is a tantalising combination.

For years, Maruti Suzuki has sourced its diesel engines from Fiat (as part of the alliance it has with the Italian company and GM). But, by late 2010, the Suzuki Japan had set the ball rolling on a new small diesel engine and the target size was 800cc. Last month Maruti Suzuki launched the two-cylinder engine in the Celerio. This is the first such engine worldwide, and the first in-house diesel in Suzuki’s history. So, does the Celerio with the new DDiS 125 engine deliver on the promise of disproportionate improvement in efficiency? We drove the new model to find out.

The new Celerio DDiS 125 is almost like a new variant introduction on the existing Celerio petrol model. To that extent it is just another engine option for this still relatively fresh passenger car model. So, the design of the DDiS 125 is exactly the same as that of the existing Celerios.

The car is clearly a Suzuki world strategic model. Essentially a tall-boy design, the Celerio is still a fairly proportionate and pleasing to look at hatchback from the front. The large headlamps, two-slat grille and the fog lamps integrated into a tightly wrapped front fender give this car a practical, but clean front. On the front wings, the DDiS logo is an addition on either side. At the rear, the upright hatch door and the tail-lamps remain the same. Again, the ‘nomenclature’ identification that it is a Maruti diesel is there in the form of the variant name – in the case of our test mule it was ZDi. Some of the kit you see in these pictures are optional additions.

The cabin of the Celerio DDiS 125 is again pretty much a carryover from the petrol siblings. The dashboard layout is a simple affair, with dual toned plastics layered over. Suzuki calls it the sweeping wave layout. Our test mule featured LED backlit scuff plates and fake wood inserts for the gear stick housing and centre stack. The most likeable features of the Celerio were always the multi-function steering wheel and the convenient gearshift stick position.

We would have liked a slightly lower seating position – even at its lowest setting the seat feels over-tall. There is also a lot of plastic all around, though the quality of fit and finish is much better than most of the older Marutis.

The heart of the Celerio DDiS 125 is the 793cc, two-cylinder diesel engine. The mill has many firsts to it and considered even on paper is quite an achievement, though doubts do linger about its refinement potential. Crank the engine and it starts with a ‘vibey’, raucous note, before settling down to a light clattering rhythm. The idling rpm is at about the 800-900 level with the air conditioner off and with the aircon power take off it is at about 1000-1100 rpm. There is only mild vibration on the steering and seat edge while idling.

Driving off after selecting the first gear in the 5-speed manual transmission gives you the first taste of this two-cylinder engine. The first impression one gets is that it clearly isn’t as refined as a 4-cylinder, but it still manages to surprise. Maybe, we expected it to be more hoarse and noisy, but the cabin is fairly well insulated and the noise levels are quite low. Maruti engineers say that the Celerio diesel’s need for higher structural and torsional rigidity, slightly heavier sub-frames and additional reinforcements have been added making it about 11 kgs heavier.

To improve the engine’s refinement, its compression ratio was also brought down to about 15.5 and a higher EGR (exhaust gas recirculation) rate was chosen to make sure that the efficiency of the engine (both mileage and emissions) is not affected. Two other parts in the engine had to be assisted by a unique management system – the small turbocharger and the custom developed fuel injection system. There is no common rail fuel injection system here because it is only a two-cylinder unit. So, the fuel control unit and the engine management compensates by making sure that the air and fuel mixture remains optimal.

Some of the other parts that this all-aluminium engine sports include low-friction piston rings, a balancer shaft and an aluminium oil pan, all of which go on to improve NVH (noise, vibration and harshness). The engine has been tuned to deliver as much power and torque proportionately, in terms of its linearity, as larger engines. A hydraulic clutch also makes the diesel Celerio more driveable.

On the road, you don’t feel the expected underperformance from an engine its size. There is enough torque available from about 1500-1600 rpm. Yes, there is turbolag and you do feel that you could do with more low-end torque, but the engine revs up quick, so you don’t find it lacking in punch completely in city traffic. The city tarmac is its natural turf. On the highway, the Celerio DDiS will certainly not satisfy your thirst for performance and will behave very much like its petrol sibling.

The Celerio DDiS 125 is a striking new development coming from the car market leader. Unfortunately, in our experience, it was not so much for its mind-blowing fuel efficiency claim of 27.62 kmpl (ARAI rated). Yes, our testing was mostly on crowded city roads, but our mule returned just 12 kmpl. That number could get much closer to the 20 kmpl mark if you cruised on the highway at constant speeds. As for its emissions performance, it is BS IV compliant and Maruti engineers claim it can be tuned to meet future norms too. What Maruti might have done with this new engine is set off a new race. Prices for the new Celerio DDiS start from ₹4.65 lakh and go up to ₹5.71 lakh ) ex-showroom, Delhi).