Topics: Internal combustion engine, Variable valve timing, Engine technology Pages: 9 (5366 words) Published: October 31, 2014

The most important challenge facing car manufacturers today is to offer vehicles that deliver excellent fuel efficiency and superb performance while maintaining cleaner emissions and driving comfort. This seminar deals with   i-VTEC (intelligent-Variable valve Timing and lift Electronic Control) engine technology which is one of the advanced technology in the IC engine. i-VTEC is the new trend in Honda's latest large capacity four cylinder petrol engine families. An internal combustion is defined as an engine in which the chemical energy of the fuel is released inside the engine and used directly for mechanical work.  The internal combustion engine was first conceived and developed in the late 1800’s.  The man who is considered the inventor of the modern IC engine and the founder of the industry is Nikolaus Otto (1832-1891). Over a century has elapsed since the discovery of IC engines.  Excluding a few development of rotary combustion engine the IC engines has still retained its basic anatomy.  As our knowledge of engine processes has increased, these engines have continued to develop on a scientific basis.  The present day engines have advances to satisfy the strict environmental constraints and fuel economy standards in addition to meeting in competitiveness of the world market. With the availability of sophisticated computer and electronic, instrumentation have added new refinement to the engine design. What is VTEC?

VTEC (standing for Variable valve Timing and lift Electronic Control) does Honda Motor Co., Ltd. develop a system. The principle of the VTEC system is to optimize the amount of air-fuel charge entering, and the amount of exhaust gas leaving, the cylinders over the complete range of engine speed to provide good top-end output together with low and mid-range flexibility. VTEC system is a simple and fairly elegant method of endowing the engine with multiple camshaft profiles optimized for low and high RPM operations. Instead of only one cam lobe actuating each valve, there are two - one optimized for low RPM smoothness and one to maximize high RPM power output. Switching between the two cam lobes is controlled by the engine's management computer. As the engine speed is increased, more air/fuel mixture needs to be "inhaled" and "exhaled" by the engine. Thus to sustain high engine speeds, the intake and exhaust valves needs to open nice and wide. As engine RPM increases, a locking pin is pushed by oil pressure to bind the high RPM cam follower for operation VTEC uses two camshaft profiles; one will lower duration for good low speed torque, and one with longer duration and valve lift for good high speed torque. The computer switches camshafts at about half engine speed to combine the best features of each camshaft. Sounds simple! The resulting torque curve is M shaped - it has a torque peak for the low speed camshaft (at about 3500 rpm in my car) and a torque peak for the high speed camshaft (at about 7000 for my engine). The part of the torque curve in between the low and high speed camshaft peaks, has a torque dip because the low speed camshaft torque is dropping off and the high speed camshaft torque is picking up. When the camshafts switch, you are actually at the lowest point of engine torque from about 2000 - 8000 rpm! I avoid this engine speed and try to keep the engine at the low speed camshaft torque peak (for normal driving) or the high speed camshaft torque peak (for getting somewhere fast). What is i-VTEC?

i-VTEC is one of Honda's greatest invention. Though an undisputed expert in turbo-charging as evidenced by years of Formula-domination while Honda was active in the sport, Honda's engineers feels that turbo charging has disadvantages, primarily bad fuel economy that made it not totally suitable for street use. At the same time, the advantages of working with smaller engines meant that smaller capacity engines with as high power output as possible (i.e. very high...

References: http://auto.howstuffworks.com/i-vtec.2htm.
Kirpal singh, “Automobile Engineering, Vol. 2” ,Standards Publications, New Delhi, 2011.
Honda Tuning Magazine by Honda car India.
Prof. R. K. Rajput, “Automobile Engineering” text book.
VTEC Sport Magazine by Honda Motors, Japan on www.inlinefour.com/vtecspormag.html
Automotive Engines: Diagnosis, Repair, Rebuilding by Tim Gilles.
http://www.hotrod.com/techarticles/engine Honda i-vtec user manual for Honda civic 1.8 i-VTEC.
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