MUMBAI, India — What does it take to build the world’s cheapest car? For Tata Motors of India, which will introduce its ultra-cheap car on Thursday, the better question was, what could it take out? The company has kept its new vehicle under wraps, but interviews with suppliers and others involved in its construction reveal some of its cost-cutting engineering secrets - including a hollowed out steering-wheel shaft, a trunk with space for a briefcase and a rear-mounted engine not much more powerful than a high-end riding mower. The upside is a car expected to retail for as little as the equivalent of $2,500, or about the price of the optional DVD player on the Lexus LX 470 sport utility vehicle. The downside is a car that would most likely fail emission and safety standards on any Western road, and, perhaps, in India in a few years, when the country imposes tougher environmental standards. But Tata is not looking to ply California’s highways. Instead, the company wants to provide four-wheel transportation for the first time to people accustomed to getting around on two, including hundreds of millions of Indians and others in the developing world. […]