With the recent launch of Tata Bolt in India which is powered by a 1.2T turbocharged petrol engine, the above question rose in my mind and I am curious to know why it was not feasible to do this development earlier? Thanks in advance for the answers.
As stated by Dr. Maciej Mikulski, the main limitation for turbocharger application as well as the compression ratio is the spontaneous ignition of premixed mixture in petrol engines that leads to commonly known as engine knock (detonation + pre-ignition). In modern petrol engines, this problem has partially solved by (1) using fuel injection, so fully premixed fuel with air is not available the whole time, (2) stratifying the mixture such that the main charge containing fuel will be around the spark plug, and (3) use fuels that have high octane number (higher anti-ignition).
The main limitations are the exhaust temperature, which will burn the blades of turbine of turbocharger, knocking combustion and acceleration response, as well as bad emission and fuel comsuption at low load.
Of course, temperature needs to be controled because of turbine blades, like maximum pressure inside cylinders is also limited by the thermomechanical resistance of material... There are multiple reasons to limit the pressure of intake gases but the more restrictive one is usually the knock...
look into the equivalence ratio angle of the problem ....very good reply from Maciej Mikulski. As far as i see T/C concepts on SI engines ---problems at low loads with insufficient kinetic potential of exhaust...so super chargers.
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