VARIABLE VALVE TIMING Guided by: Anoop Kumar G Lecturer Dept. of Mechanical Engg Presented by: Prashant S S7MB-112

CONTENTS CONTENTS Contents 5. Working Introduction 1.Introduction 6. Benefits 7. Future 8. Conclusion Introduction Need for VVT Development of VVT Types of VVT 1.Introduction 2.Need for VVT

Introduction Conventional engines no relation between valve timing and engine speed problems creep in at high rpm’s if valve is set for high rpm problems occur at low rpm’s VVT engines variable valve timing engines they can vary: 1)lift of valve 2)timing of valves 3)phase shift of valve timing 4)valve overlap

Need for VVT at high speeds more air for more power and combustion at low speeds prevention of leakage of charge and fuel efficiency get good mileage clean emission

Development of VVT HONDA - debut in 1991 in Honda NSX TOYOTA – follower eg. Corolla Nissan, Porsche, BMW, Ferrari followed but not all were same with each having their own improvisations

Types of VVT Honda VTEC – Variable valve Timing and Electronic lift Control Toyota VVT-i – Variable Valve Timing with Intelligence Nissan VVL - Variable Valve Lift Porsche Vario Cam Ferrari Valve Timing Advance

HONDA VTEC

3 cam lobes for 2 intake or exhaust valves one high rpm cam - high profile two low rpm cams – low profile correspondingly three rocker arms center one is free to move at high rpm’s sensors send signals to ECU ECU opens oil control valve

oil pressure couples all three rocker arms together valves move according to third cam profile timing is increased

this was DOHC VTEC Honda later developed SOHC VTEC only intake valves had VTEC then i-VTEC this system induced swirl ECU monitors : engine speed , cam position , manifold pressure this advances or retards the cam reduces exhaust emissions

Toyota’s VVT-i VVT- I completely different technique exhaust cam driven by crankshaft intake cam driven by exhaust cam via drive gears a cylinder behind drive gears of intake cams controls cam timing can change cam timing by 60 degrees controlling overlap from 0 to severe overlap at medium load to ideal for maximum power

Nissan VVL consists of two cam lobes with different profiles both cams operate 2 intake or exhaust valves needle bearing roller mechanism oil pressure pushes needle below the spring loaded slipper and follows high profile cam

BMW’s solenoid valve

BMW’s mechanical

Ferrari’s system 3-D profile one end least aggressive cam other end most aggressive shaft moves by hydraulic pressure

Benefits smooth idle valve overlap retarded to zero so pure mixture thus stable combustion low fuel consumption torque improvement low to mid-range torque is increased by increasing valve overlap exhaust sucks charge and due to early closing charge does not escape quicker response to sudden power requirements

EGR effect EGR valve used in conventional engine not required here exhaust mixes with charge and dilutes it so low combustion temp. and low NOx production also unburnt gases in exhaust will get completely burnt

better fuel economy approx. 20% increase due to fact that smaller VTEC engine produces equal power to that of non-VTEC larger engine Improved emission control No Nox production due to EGR effect due to low fuel consumption low CO2 emission

Future Electronically operated valve mechanism Infinitely variable valve timing

conclusion VVT is going to be affordable to the common man in a few years Very useful technology in this age of diminishing fuel resources Lots of R&D to be spent by companies

Thank you !