4-stroke cycles compressed to single crankshaft revolution (Atkinson cycle) Fully valve controlled gas exchange Diesel or Otto engine Turbo charger and supercharger (piston compressor) 2-cylinder Z engine provides equal power output to a 4-cylinder 4-stroke engine HCCI combustion Internal EGR Easily balanced mass forces Good torque characteristics Ignition controlled by multiple variables High downsizing degree Excellent transient behaviour Driving fun

What is Z engine? 4/2-stroke, 2-cylinder engine Revolutionary working principle combines the best aspects of 2- and 4-stroke engines Part of the compression cycle is made outside of the working cylinder, so all of the cycles of 4-stroke engine can be done in a single crankshaft revolution Compact size Light weight Small emissions Low manufacturing costs

Exhaust cycle Exhaust valves opens 60° BBCD and closes 120° ABCD  2 x 180° = 360° pulses for the turbo charger Exhaust gases hot enough for 3-way catalyst

Injection Fuel injected during 110° - 120° ABDC, when the exhaust valves are closing Long mixing time before the ignition, 60° – 70° Injection pressure 200 – 700 bar, duration 5° – 12° Hollow cone spray Small spray penetration Small droplets Fuel injected to hot exhaust gas  Partial fuel reforming High temperature and low pressure during injection  Rapid fuel evaporation Gas temperature an pressure during the start of the injection: 700 – 800 K, 1,5 – 2,5 bar Temperature drop of the gas in the cylinder during injection: 200 – 400 K Heat for fuel evaporation from exhaust gas

The temperature and pressure curves between 80° - 40° BTDC

Intake cycle (scavenging) Intake valves opens 60° BTDC and closes 45° BTDC Intake pressure 4 – 15 bar  Velocity of intake gas: 300 – 500 m/s Intern EGR 15 – 45%, acts as an intern heat exchanger Hot, active radicals in EGR can be used to assist ignition No overlapping of intake and exhaust valves  No losses of intake gas Fuel evaporation cools the mixture: more air to the cylinder Electric heater in the intake channel for start

The theorethical valve flow

Final Compression Mechanical compression ratio: 14 – 15:1 Primary compression is made in piston compressor, secondary in work cylinder: 3-5:1 Short compression time  Low amount of heat transfer Fuel evaporation before final compression and high intercooling rate  Low compression temperature, more air in to the cylinder Compression temperatures at TDC: 800 K at part load, 700 K at full load  The compression temperature descend when load increases Lower gas temperature  Lower compression pressure, higher bmep

Ignition delay curve of HCCI mixture

PV diagram of the Z engine

Combustion and work cycle SAHCCI (Spark Assisted Homogenous Charge Combustio Ignition) Controlled By: Temperature at TDC, lambda, injection amount and timing, intercooling rate, valve timing Pressure and temperature at TDC controlled by adjusting intake air pressure and temperature Low temperature at TDC: no self ignition Start of combustion: 5-15° ATDC Short combustion duration: high efficiency Lambda 1.7-1.9: low Tmax, low NOx Active radicals assist the ignition Active radicals lower CO and HC No knock, as ignition at the right side of NTC area

Together = - 1400 € lower production costs per engine! Manufacturing costs compared to 4-cylinder turbodiesel engine equipped with Common Rail + DeNOx-catalyst + particulate filter = 2800 € 2 working cylinders less = - 600 € Compressor needed = + 200 € Low injection pressure, 2 low cost nozzles = - 400 € No DeNOx catalyst = - 500 € No particulate filter = - 100 € Together = - 1400 € lower production costs per engine!