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HONDA CIVIC VTEC
- MODIFED CARS HONDA CIVIC
- Me, Myself, and I
Vtec Vtec Vtec........ life begins at 8000rpm
3rd gear at 6500, life doesnt get much better!!!!
Civics Vtecs Are Da Best So Fuk Da Rest
Who Doesnt Recognise Any Other Engine VTEC Be Thy Name
Thy Kingdom Come
VTEC Will Kick In
On Earth As It Does In Japan
Giv Us This Day
Our Daily Dose Of VTEC
And Praise Our Mighty Roar
And Forgive Those Who Repent Against The VTEC
And Deliver Us From Any Other Car That
Doesnt Wear The H Symbol
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Introduction to VTEC
In the regular four-stroke automobile engine, the intake and exhaust valves are actuated by lobes on a camshaft. The shape of the lobes determines the timing, lift and duration of each valve. Timing refers to when a valve is opened or closed with respect to the combustion cycle. Lift refers to how much the valve is opened. Duration refers to how long the valve is kept open. Due to the behavior of the gases (air and fuel mixture) before and after combustion, which have physical limitations on their flow, as well as their interaction with the ignition spark, the optimal valve timing, lift and duration settings under low RPM engine operations are very different from those under high RPM. Optimal low RPM valve timing, lift and duration settings would result in insufficient fuel and air at high RPM, thus greatly limiting engine power output. Conversely, optimal high RPM valve timing, lift and duration settings would result in very rough low RPM operation and difficult idling. The ideal engine would have fully variable valve timing, lift and duration, in which the valves would always open at exactly the right point, lift high enough and stay open just the right amount of time for the engine speed in use.
In practice, a fully variable valve timing engine is difficult to design and implement. Attempts have been made, using solenoids to control valves instead of the typical springs-and-cams setup, however these designs have not made it into production automobiles as they are very complicated and costly.
The opposite approach to variable timing is to produce a camshaft which is better suited to high RPM operation. This approach means that the vehicle will run very poorly at low RPM (where most automobiles spend much of their time) and much better at high RPM. VTEC is the result of an effort to marry high RPM performance with low RPM stability.
Additionally, Japan has a tax on engine displacement, requiring Japanese auto manufacturers to make higher-performing engines with lower displacement. In cars such as the Toyota Supra and Nissan 300ZX, this was accomplished with a turbocharger. In the case of the Mazda RX-7 (turbo) and RX-8, a wankel rotary engine was used. VTEC serves as yet another method to derive very high specific output from lower displacement motors.
 DOHC VTEC
Honda's VTEC system is a simple method of endowing the engine with multiple camshaft profiles optimized for low and high RPM operations. Instead of one cam lobe actuating each valve, there are two - one optimized for low RPM stability & fuel efficiency, with the other designed to maximize high RPM power output. Switching between the two cam lobes is determined by engine oil pressure, engine temperature, vehicle speed, and engine speed. As engine RPM increases, a locking pin is pushed by oil pressure to bind the high RPM cam follower for operation. From this point on, the valve opens and closes according to the high-speed profile, which opens the valve further and for a longer time. The DOHC VTEC system has high and low RPM cam lobe profiles on both the intake and exhaust valve camshafts.
The VTEC system was originally introduced as a DOHC system in the 1989 Honda Integra sold in Japan, which used a 160 hp (119 kW) variant of the B16A engine. The US market saw the first VTEC system with the introduction of the 1991 Acura NSX, which used a DOHC VTEC V6. DOHC VTEC engines soon appeared in other vehicles, such as the 1992 Acura Integra GS-R.
My car is nice.
 SOHC VTEC
As popularity and marketing value of the VTEC system grew, Honda applied the system to SOHC engines, which shares a common camshaft for both intake and exhaust valves. The trade-off is that SOHC engines only benefit from the VTEC mechanism on the intake valves. This is because in the SOHC engine, the spark plugs need to be inserted at an angle to clear the camshaft, and in the SOHC engine, the spark plug tubes are situated between the two exhaust
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