The BiFuel Petrol/CNG powertrain as an option for passenger vehicles has been around for almost two decades. It steps into the limelight every time petrol prices shoot up or occasionally when there is an increase in awareness about the environment.

Depending on the price of petrol, the answer to the eternal “kitna deti hai” question is enough of a trigger to push buyers into giving BiFuel-CNG variants a try.

After years of retrofitting CNG kits in the after market and their yo-yoing levels of reliability, factory-fitted CNG kits have become the choice amongst most buyers.

Improved safety, higher reliability levels and the prospect of the engine being tuned to handle the difference in combustion and performance have led to increased preference for factory-fitted BiFuel vehicles. Yet, the buyer has often had to contend with CNG versions being available only in the entry segment or has had to accept compromises in the equipment levels offered compared to their petrol engine counterparts.

Tata Motors is attempting to change that scenario and has launched the BiFuel versions of its Tiago hatch and Tigor small sedan. While the Tiago gets as many as five trim variants, the Tigor gets three, including dual tone paint jobs (optional) on the top trim XZ+ variant.

Design and features

Both the Tiago and the Tigor are good looking modern cars that have successfully taken on the fierce competition in the B and entry C segments. I observe that the design and overall equipment levels for the exterior of my test mule Tiago iCNG continues to be identical to its petrol counterpart.

The sharp nosed front with the humanity line running from one headlamp to the other like a smile, and the Tata trademark tri-arrow design on the bonnet grille give the Tiago an appealing small car profile.

It now also gets projector headlamps and LED DRLs. Both the models - Tiago and Tigor - get one new body paint colour each exclusive to the iCNG variants.

The one you see in these pictures is the Midnight Plum shade. The rest of the exterior design is a carry over from the petrol counterpart.

The cabin in my XZ+ test mule Tiago iCNG sported all the features that the facelifted petrol Tiago is loaded with.

The dark grey and beige colour theme for the interior brightens up the cabin, and the fabric seats with contrast stitching and contoured squabs feel good to sit in.

There is the auto aircon controls, 7-inch touchscreen infotainment display and set of buttons for fog lamps and door unlock controls. The one addition to this bunch is the CNG switch over button. Similarly, while the all-digital instrument cluster is similar in overall layout to the petrol version, in the Tiago iCNG, there is the addition of a CNG fuel gauge, in addition to the petrol gauge.

There is also the addition of a fuel-in-use indicator with an orange fuel-pump indicator lighting up every time I switch to CNG. The rest of the cabin, including the 3-spoke steering wheel, is similar in design and layout.

Heart of the matter

The iCNG versions of both the Tiago and the Tigor feature the 3-cylinder, 1.2-litre Revotron petrol engine with BiFuel injection. The 1,199cc generates 73.4PS of peak power and 95Nm of torque in CNG mode.

The output is lower in CNG mode; peak power is about 12.5PS lower and the torque generated is also 18Nm lower than petrol mode. But the calibration seems to have been done with an eye on retaining the experience offered by the regular petrol variant. In the iCNG variants, the engine is mated to the same 5-speed manual gearbox that we have already seen in the Tiago. There no option of an AMT gearbox.

The ECU, in the Tiago iCNG, operates on a completely different engine map compared to the petrol mode. But no discernible difference in on-road performance between the petrol and CNG injection cycles. It is not an exact match between the two fuels, and there is a small difference in acceleration times, but the overall experience was similar.

Also, roughly there is a difference of 100 kgs in kerb weight between the regular petrol Tiago and the BiFuel iCNG variant. To handle the 11-12 per cent differential in weight, there have been some tuning changes to the springs and damper character to ensure that the ride and handling balance is maintained.

The common ECU handles both the petrol and CNG modes. The knock-sensor and exhaust have also been tuned for consistent performance across all weather conditions.

Tiago iCNG’s ARAI certified mileage is 26.5kms per kg. The petrol only Tiago has a rated fuel efficiency of 20.1 kmpl.

The one problem in the Tiago iCNG variant will be quick and easy access to the spare wheel in the boot. All the space in the boot is taken up the CNG cylinder (60-litre liquid capacity or 10kgs). So, there is nearly no room for luggage. If the buyer plans to take it out of town for the weekend, a roof-mounted luggage carrier will be needed.

Accessing the spare wheel is possible only by folding down the rear seat and pulling out the smaller 155/80 tyre shod on 13-inch rims. But, it is simple and conventional in the Tigor iCNG, which has 210-litres of usable boot space, despite the presence of the CNG tank.

Bottom Line

The Tiago iCNG didn’t feel like a de-tuned, compromise version of the petrol original. With the performance and the ride quality sorted and matching the regular petrol version, it is also good to see that this didn’t feel stripped down and built-to-a-price.

Features like auto headlamps, rain-sensing wipers, rear parking camera, etc. should give the iCNG version the required appeal. The Tiago iCNG starts at a price of ₹6.1 lakhs (XE) and goes up to ₹7.65 lakh (XZ+ dual tone). Compared to the petrol only versions, these are priced at about ₹80,000 to ₹90,000 more.

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