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

2. 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

3. 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

4. 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

5. 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

6. 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

7. HONDA VTEC

8. 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

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

11. 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

12. 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

15. 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

17. BMW’s solenoid valve

18. BMW’s mechanical

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

20. 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

21. 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

22. 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

23. Future
Electronically operated valve mechanism
Infinitely variable valve timing

24. 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

25. Thank you !