Fully Automatic Transmission in City Buses: ‘Shifting to ‘D’ Mode’
How are fully-automatic transmission technology getting along in Indian city bus segment? We catch-up some insights from DTC’s experiences on low-floor city buses equipped with fully-automatic gearboxes.
Automated shifting is popular in cars, you like them? Well, I sure don’t. They are generally dull to drive and thirsty on fuel. I would rather like to row gears on my own, there lies the real fun of driving. But for a person who sits behind the wheels (rather large wheels!) for around eight hours every day, shifting ‘rock-like’ gears in bumper-to-bumper traffic can’t be fun. And the more he or she yank the bus while depressing clutch every time on gear shifts, commuters are going to be mad. No fun for them either! Automated transmission in a city bus is a solacement for both drivers and passengers. There are other benefits too.
Delhi Transport Corporation (DTC) is one of the first STUs in India to induct buses with fully automatic transmissions, gradually reaching to over 95 percent of its entire fleet by numbers. All of its 3,600-odd low-floor rear-engine Tata-Marcopolo and Ashok Leyland buses are equipped with fully-automatic transmission with retarder sourced from Allison Transmission, and some have clocked more than 700,000 kms without any transmission over-haul. Unlike many other STUs, DTC’s quick acceptance of these buses can be attributed to the technology’s operational advantages and the flexibility offered by the CNG fuel. Dr. R.S. Minhas of DTC explains that these buses with auto gears are driver-friendly, offering easier drive especially at nerve-racking city traffic and start-stop driving conditions, while the passengers are also comforted with less jerks and engine noise. Extended maintenance period is an added advantage. Oil filter replacement is warranted only at 120,000 kms, while the transmission oil needs replacement for every 240,000 kms only. Other than these, there is hardly any maintenance required for these fully automatic systems.
Shortfalls of these buses, from DTC’s point of view, are primarily higher procurement costs and lower fuel efficiency. “But with widespread usage, the operational benefits seems to overweigh the minuses. Commuters prefer these buses, consider it as a premium service, while we also observe a positive impact on drivers’ absenteeism. There are also less breakdowns owing to transmission-related issues”, he observed. At present, there are over 10,000 city buses running on Allison-equipped fully automatic transmission in over 30 cities in India. After the initial success of rear-engine automatic buses in cities like Delhi and Bengaluru, many STUs have even opted for front engine buses with automatic gearboxes, including that of cities like Mumbai, Ahmedabad, Surat, Pune, Naya-Raipur, Amritsar, and Chandigarh.
Also Read: DTC Buses: Rear-engined, Leap-forward
Attracting and retaining drivers is a solid reason for recommending automated transmission. Driver shortage isn’t going away, and automation sure flattens some of the bottlenecks that prevent youth from taking up this job. Now they have enough to worry about without stressing over shifting gears. Together with air-conditioning, the work ambience gets improved. It does help in safe driving, drivers can now spend more time focused on the road and their surroundings, with less distractions per se. Automatics facilitate speed management also, for instance, the slow acceleration in idling drive mode allows drivers to remove their foot from the pedal and easily manoeuvre at heavy traffic, parking, and other low-speed situations. They not only reduce the wear and tear of driver’s body and increase their productivity, but also takes care of some key driveline protection and overuse of components. As a corollary benefit, low noise-vibration-harshness (NVH) levels is a boon in city operations. Complemented with the low-floor layout and rear-engine configuration, these buses offer uncluttered dashboard and wider aisle up front, offering more space and facilitating easier flow inside the cabin. Complemented by air suspension and much-balanced center-of-gravity owing to the engine heaviness over the rear, these buses excel with enhanced stability especially at down slopes and curves.
Yet, compromised fuel efficiency is the single most pull away factor for the fully automatic transmissions. With improving technology and preciseness of electronics, they are making impressive levels of advancement in terms of powertrain management and fuel saving worldwide. There are systems that try to capitalise free momentum out of gravity on a down slope by dropping out the gear, with hardly any hint of risk that gears will mesh on re-engagement. They even jump into neutral at long stops automatically to save energy otherwise wasted chafing at the torque converter to get moving again. Such technologies help refine engine torque management by reading road grades and allowing ultra-low-rpm operation to save fuel. With broader market acceptance and improved demand, such exquisite technologies to improve fuel efficiency in fully automatic transmissions are likely to trickle down to affordable costs.
For instance, Allison’s sophisticated FuelSense packages in their fully-automatic gear systems increase fuel economy as per specific needs of the vehicle. FuelSense 1.0, launched in 2015 with Gen-5 TCM, features Dynamic Shift Scheduling, Neutral at Stop, and Acceleration Rate Management to get the maximum out of every unit of fuel. The company is expected to bring out much-improved FuelSense 2.0 by next year with better fuel efficiency figures.
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Fully Automatic Transmission in DTC’s low floor buses – Image Gallery
*An edited version of this article has been published in the 61st Anniversary edition (August 2017) of MotorIndia Magazine.