8th Generation Honda Civic Forum - View Single Post

JVanBus · 10-27-2006, 06:02 PM

There seems to be some Confusion about the Definition of VTEC and it's Purpose.

This is because the K20 i-VTEC engine was built for performace, while the R18 i-VTEC was built for Fuel Economy.

This thread is intended to give a Basic Definition of Honda's VTEC System.

For Additional Info, Follow the Link at the Bottom of the Page.

VTEC Defined

VTEC is an Acronym used to describe the Valve Train used in a Honda Engine.

i-VTEC stands for Intelligent Variable Valve Timing and Lift Electronic Control, which now includes Variable Timing Control.

It's a system developed by Honda to improve the Combustion Efficiency of its internal combustion engines throughout the RPM range.

A more Detailed Description of the K20 & R18 Engines

K20Z3: 2.0L 16-Valve DOHC i-VTEC

This particular engine is set up more for performance than fuel efficiency.

It uses an aluminum cylinder head and a dual overhead cam, four-valve-per-cylinder valvetrain incorporating the i-VTEC system.

High performance camshafts are used that allow for aggressive intake and exhaust valve openings to boost the rate that air moves into and exhaust moves out of the cylinder.

At high engine speeds, valve lift phase on the intake side is increased by five degrees and on the exhaust side by 10 degrees.

At Low RPMs, the valves follow low lift, short duration camshaft profiles to help boost low-end torque.

At High RPMs (above 5,800 rpm) the intake and exhaust valves are operated by high-lift, long-duration cam profiles, for maximum high rpm horsepower.

Variable Timing Control

As engine RPM builds, a VTC actuator advances or retards the intake cam throughout the 50 degree range, optimizing engine output and reducing emissions.

During typical operation, the intake camshaft timing is almost fully retarded at idle to help provide more stable idling.

As rpm increases, the intake camshaft is advanced, opening the intake valve sooner and providing additional valve overlap.
Roller Rockers reduce friction in the valve train.

The Camshaft is capable of advancing between 25 and 50 degrees during operation. This means the Timing in which the valves open and close are automatically retarded at idle and advanced at full throttle.

The Camshaft Lobes and Timing are implemented via an oil driven adjustable cam gear controled by your ECU/EMS.

To generate additional power throughout the rev range, the intake camshaft is continuously varying the amount of advance or retard, instantly adjusting to provide additional power as required by the driver.

R18A1: 1.8 L 16-Valve SOHC i-VTEC

Instead of optimizing performance at high RPMs, this engine is used to increase efficiency at low RPMs.

OK, So let's Check Out the Graph Below:

Bottom Line: During Low RPMs the i-VTEC system switches the Valve Timing Duration, which Optimizes Fuel Efficiency.

Top Line: During High RPMs the i-VTEC system provides High Output Valve Timing for Maximum Power.

At low RPMs, one of the two intake valves is only allowed to open a very small amount, increasing the fuel/air atomization in the cylinder and thus allowing a leaner mixture to be used.

As the engine's speed increases, both valves are needed to supply sufficient fuel/air mixture.

A sliding pin, which is pressured by oil, as in the regular VTEC, is used to connect both valves together and allows the full opening of the second valve, thus allowing a larger air/fuel mixture into the combustion chamber and ultimately generating more power.

For Additional Info, Visit HondaNews.com

http://www.hondanews.com/CatID2013?m...41013&mime=asc

Hope This Helps!

10-27-2006, 06:02 PM	#27 (permalink)
JVanBus Member Join Date: Oct 2006 Location: S.F. Bay Area Posts: 32 Josh	VTEC Confusion There seems to be some Confusion about the Definition of VTEC and it's Purpose. This is because the K20 i-VTEC engine was built for performace, while the R18 i-VTEC was built for Fuel Economy. This thread is intended to give a Basic Definition of Honda's VTEC System. For Additional Info, Follow the Link at the Bottom of the Page. VTEC Defined VTEC is an Acronym used to describe the Valve Train used in a Honda Engine. i-VTEC stands for Intelligent Variable Valve Timing and Lift Electronic Control, which now includes Variable Timing Control. It's a system developed by Honda to improve the Combustion Efficiency of its internal combustion engines throughout the RPM range. A more Detailed Description of the K20 & R18 Engines K20Z3: 2.0L 16-Valve DOHC i-VTEC This particular engine is set up more for performance than fuel efficiency. It uses an aluminum cylinder head and a dual overhead cam, four-valve-per-cylinder valvetrain incorporating the i-VTEC system. High performance camshafts are used that allow for aggressive intake and exhaust valve openings to boost the rate that air moves into and exhaust moves out of the cylinder. At high engine speeds, valve lift phase on the intake side is increased by five degrees and on the exhaust side by 10 degrees. At Low RPMs, the valves follow low lift, short duration camshaft profiles to help boost low-end torque. At High RPMs (above 5,800 rpm) the intake and exhaust valves are operated by high-lift, long-duration cam profiles, for maximum high rpm horsepower. Variable Timing Control As engine RPM builds, a VTC actuator advances or retards the intake cam throughout the 50 degree range, optimizing engine output and reducing emissions. During typical operation, the intake camshaft timing is almost fully retarded at idle to help provide more stable idling. As rpm increases, the intake camshaft is advanced, opening the intake valve sooner and providing additional valve overlap. Roller Rockers reduce friction in the valve train. The Camshaft is capable of advancing between 25 and 50 degrees during operation. This means the Timing in which the valves open and close are automatically retarded at idle and advanced at full throttle. The Camshaft Lobes and Timing are implemented via an oil driven adjustable cam gear controled by your ECU/EMS. To generate additional power throughout the rev range, the intake camshaft is continuously varying the amount of advance or retard, instantly adjusting to provide additional power as required by the driver. R18A1: 1.8 L 16-Valve SOHC i-VTEC Instead of optimizing performance at high RPMs, this engine is used to increase efficiency at low RPMs. OK, So let's Check Out the Graph Below: Bottom Line: During Low RPMs the i-VTEC system switches the Valve Timing Duration, which Optimizes Fuel Efficiency. Top Line: During High RPMs the i-VTEC system provides High Output Valve Timing for Maximum Power. At low RPMs, one of the two intake valves is only allowed to open a very small amount, increasing the fuel/air atomization in the cylinder and thus allowing a leaner mixture to be used. As the engine's speed increases, both valves are needed to supply sufficient fuel/air mixture. A sliding pin, which is pressured by oil, as in the regular VTEC, is used to connect both valves together and allows the full opening of the second valve, thus allowing a larger air/fuel mixture into the combustion chamber and ultimately generating more power. For Additional Info, Visit HondaNews.com http://www.hondanews.com/CatID2013?m...41013&mime=asc Hope This Helps! Last edited by JVanBus; 10-30-2006 at 01:53 AM.