The last blog the topic was on the timing belt & the importance of the correlation of exact timing between the camshaft & crankshaft. In this blog, we explain what are the VVT or VTEC Stickers on your car.
The key to engine power is air flow/air density. The trick is to get as much air molecules compacted into the engine cylinder as possible when the piston goes down the cylinder on the induction stroke.
The pictures below shows a easy pathway for the air to travel (In this great cutaway example). The more air the greater force generated on the piston during power combustion, resulting in more torque at the crankshaft. The amount of air filling the cylinder is known as volumetric efficiency.
VVT or VTEC Stickers
The intake valve is the gate way for air entering the engine cylinder. This is the V part of the initials in VVT. The valve is controlled by the camshaft either directly on top or by a push rod & lever shown by the different example photos. The camshaft has two important roles:
- It lifts the valve off its seat to a specified distance (valve lift or valve curtain area)
- It keeps the valve open for a certain time (valve duration)
So all this thermodynamics is good but the problem is volumetric efficiency described above.
Most car engine revolutions (revs) about 7000rpm the speed of the piston is so fast that there is not enough time for enough air to fill with cylinder in milliseconds, so eventually the engine runs out of air at high rpm resulting in loss of power.
Then in the late Eighties Honda came up with Variable cam shaft profile. This is the other V in the initials. In the late eighties the Honda engines were so good with immortal drivers of Ayrton Senna , Nigel Mansel , Alain Prost, that they kicked butt out of the opposition.
The Variable part allows the camshaft to open the valve longer & even higher at different rev ranges also by being able to control exhaust valves emissions. Technically the intake valve can be opened longer at precise high engine speeds allowing more air to enter the cylinder. The volumetric efficiency as described before can go higher than a 100% normally aspirated, but add a good turbo like Honda did back in the 80`s, they were getting over 1000hp from a 1.5 litre engine with over 160% efficency!
There are many variants of control applied in The Variable Valve Timing (VVT). The most common is oil pressured phasers which are computer pulse width activated via a oil pressured activator. The Hondas use a pin locator and Holden use a special lifter to deactivate cylinders in their AFM vehicles.
VTEC Car Maintenance
If you have a car that has VVTOR VTEC, well then use good quality synthetic oil!
The trend of car manufacturers is to make smaller capacity engines which mean lower emissions but with excellent power output.
What are the VVT or VTEC Letters on your car?
Variable Valve Timing is now nearly in all makes & models.
Manny`s Mechanical Repairs helps you understand more about your vehicle.
We invest in the best equipment, we go to the best courses, we continually use the best parts, the best oil & use the best skill on your car.
I hope this has helped.
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