1. S I Engines as Automotive Prime Movers & Clues for Improvements
P M V Subbarao
Professor
Mechanical Engineering Department
Future Direction for Better Performance !!!

2. The Type of Prime Mover for Light Vehicle Sales in Two Decades
Clues for Improvements:
Identification and use of alternate fuels.
Reduction of losses.
Down sizing of engine.
Lowering of emissions.
Implementation of New Geometric and Kinematic Models

3. Otto’s Engine Cycle vs Thermodynamic Model
Intake
Stroke
FUEL
Ignition
Power
Stroke
Combustion
Products
Exhaust
Stroke
Fuel/Air
Mixture
Compression
Stroke
Actual
Cycle TC
Qin
Qout BC
Const volume
heat rejection
Process
Air
Compression
Process
Expansion
Process
Otto
Cycle
Const volume
heat addition
Process

4. Air-Standard Otto cycle
Process 1 2 Isentropic compression
Process 2  3 Constant volume heat addition
Process 3  4 Isentropic expansion
Process 4  1 Constant volume heat rejection
Compression ratio:
Qin
Qout v2 TC v1 BC TC BC

5. Effect of Compression Ratio on Thermal Efficiency
Present SI engines
7 < r < 11
Ignition
Power
Stroke
k = 1.4
Spark ignition engine compression ratio limited by T3 (auto-ignition) and P3 (material strength), both ~rk
For r = 8 the efficiency is 56% which is twice the actual indicated value

6. Total Time Available ~ 10 msec
Actual SI Engine cycle
Total Time Available ~ 10 msec
Ignition

7. Audi launches next-gen A4 with new Millerized TFSI engine; g-tron model w/ Audi e-gas 29 June 2015
The new A4 is the launch vehicle for the new high-efficiency 2.0L Turbocharged Fule Stratified Injection based on Miller cycle.
The new models deliver CO2 emissions as low as 95 grams per kilometer.
TFSI engin delivering maximum power of between 140 kW .
Compared with the previous model, their fuel consumption has been reduced by up to 21%, while their power output has increased by up to 25%
The new A4 Sedan has the best drag coefficient in its class at 0.23.
Its weight has been reduced by up to 120 kilograms, depending on the engine.
The body of the new Audi models is one of the lightest in its class due to an intelligent material mix and lightweight construction.

8. Audi A4 2.0 TFSI ultra (140kW) Engine
Engine type 4-cylinder inline spark-ignition engine with gasoline direct injection, exhaust turbocharger and Audi valve lift system.
Miller cycle
Compression ratio : 11.7:1
Air-fuel Mixture preparation :
Sequential high-pressure direct and multipoint manifold injection
Adaptive idle-charge control, overrun fuel cut-off, adaptive lambda control;
Cylinder-selective adaptive knock control….

9. Millirization of Engine