What does VTEC stand for?
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From: Bowling Green, KY, USA
Re: What does VTEC stand for? (Mike Type R)
http://www.h22a.com/h22aengine.html
VTEC
To properly understand why this engine is so amazing, you need to understand what VTEC is:
VTEC stands for (Variable Valve Timing and Lift Electronic Control). It does not refer to any one engine or even to a specific series of engines, rather, VTEC is an original engine technology. It offers variability that is extremely useful in developing small, lightweight, and compact engines that are more powerful, more responsive and more fuel-efficient than conventional engines.
One of the stories often told about the development of the VTEC mechanism, relates to how the idea to link the rocker arms together came to a Honda engineer. As he watched small spits of chicken meat and green onions (yakitori in Japanese), being turned over a cooking fire, he noticed that one particularly long piece of onion was catching on the hot coals below and was not rotating with the others. He realized that thrusting a second spit through all the ingredients would force them to move together.
Valves in high performance engines are set to open wide for a long duration (high lift), generating high power at a higher rpm. At a lower rpm, the combustion cycle is much slower, making the engine less responsive.
In "fuel efficient" cars the combustion environment maximizes fuel economy by using a "lean" fuel/air charge. But an engine on a lean diet, can generate only a limited amount of power, even if you floor the accelerator.
This is where VTEC comes in. Honda's VTEC technology offers genie-like performance by switching between two different combustion environments in the same engine. It's almost like having two completely different engines trading places under one hood.
A VTEC engine uses a four valve-per-cylinder configuration. In regular engines, two pairs of cam lobes and rocker arms operate the valves. VTEC modifies this configuration by adding an extra, high profile cam lobe. This extra cam lobe actuates an extra rocker arm. Which in turn rests on a dummy valve spring. At a low to mid range rpm this extra rocker arm simply moves up and down on its own without acting on a valve.
As you step on the accelerator the magic begins. At a predetermined mid-range engine speed, a hydraulically actuated pin slides through all three rocker arms locking them together. This gives control of the entire set of rocker arms to the extra cam lobe. This cam lobe opens the valves even higher and longer, letting more fuel and air flow into the combustion chamber: The engine now generates more power to move the car faster. Once the desired speed is attained and the engine slows back down, the locking pin disengages, allowing the low-profile cam lobes and their rocker arms to resume their function.
By toggling the valve settings like this, VTEC allows two different combustion environments in the same engine. In this case, one for higher torque at low to mid-range rpm, and another for ultra-high power at a higher rpm. The result is an extremely responsive performance through the entire rpm range. The timing of the switch over is handled by an Electronic Control Unit (ECU) that activates the hydraulic pin. This pin snaps into place quickly and smoothly, sending the engine into high-power performance instantly.
VTEC
To properly understand why this engine is so amazing, you need to understand what VTEC is:
VTEC stands for (Variable Valve Timing and Lift Electronic Control). It does not refer to any one engine or even to a specific series of engines, rather, VTEC is an original engine technology. It offers variability that is extremely useful in developing small, lightweight, and compact engines that are more powerful, more responsive and more fuel-efficient than conventional engines.
One of the stories often told about the development of the VTEC mechanism, relates to how the idea to link the rocker arms together came to a Honda engineer. As he watched small spits of chicken meat and green onions (yakitori in Japanese), being turned over a cooking fire, he noticed that one particularly long piece of onion was catching on the hot coals below and was not rotating with the others. He realized that thrusting a second spit through all the ingredients would force them to move together.
Valves in high performance engines are set to open wide for a long duration (high lift), generating high power at a higher rpm. At a lower rpm, the combustion cycle is much slower, making the engine less responsive.
In "fuel efficient" cars the combustion environment maximizes fuel economy by using a "lean" fuel/air charge. But an engine on a lean diet, can generate only a limited amount of power, even if you floor the accelerator.
This is where VTEC comes in. Honda's VTEC technology offers genie-like performance by switching between two different combustion environments in the same engine. It's almost like having two completely different engines trading places under one hood.
A VTEC engine uses a four valve-per-cylinder configuration. In regular engines, two pairs of cam lobes and rocker arms operate the valves. VTEC modifies this configuration by adding an extra, high profile cam lobe. This extra cam lobe actuates an extra rocker arm. Which in turn rests on a dummy valve spring. At a low to mid range rpm this extra rocker arm simply moves up and down on its own without acting on a valve.
As you step on the accelerator the magic begins. At a predetermined mid-range engine speed, a hydraulically actuated pin slides through all three rocker arms locking them together. This gives control of the entire set of rocker arms to the extra cam lobe. This cam lobe opens the valves even higher and longer, letting more fuel and air flow into the combustion chamber: The engine now generates more power to move the car faster. Once the desired speed is attained and the engine slows back down, the locking pin disengages, allowing the low-profile cam lobes and their rocker arms to resume their function.
By toggling the valve settings like this, VTEC allows two different combustion environments in the same engine. In this case, one for higher torque at low to mid-range rpm, and another for ultra-high power at a higher rpm. The result is an extremely responsive performance through the entire rpm range. The timing of the switch over is handled by an Electronic Control Unit (ECU) that activates the hydraulic pin. This pin snaps into place quickly and smoothly, sending the engine into high-power performance instantly.
He he he
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Trial User
Joined: Oct 2000
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From: Bay Area, CA, USA
Re: What does VTEC stand for? (MRVTEC)
I'm sure I'm smarter than you...I don't know what newbie is
Honda-Tech Member
Joined: Mar 2001
Posts: 4,408
Likes: 4
From: Somewhere in California
Re: What does VTEC stand for? (MRVTEC)
I'm sure I'm smarter than you...I don't know what newbie is
You *might* be smarter then us, but you sure do lack common sense.
Senior Member
Joined: Feb 2001
Posts: 11,517
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From: Boo, did I scare you, US
Re: What does VTEC stand for? (MRVTEC)
I'm sure I'm smarter than you...I don't know what newbie is
Also, a little known fact, Honda motorcycles have VTEC too, but they run off of a very different sype of system, it uses a second set of valves that stay closed when not in "VTEC" but they open when it "kicks in." In fact, if I'm not mistaken, the bikes had VTEC first!
Member
Joined: Aug 2001
Posts: 1,817
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From: Clemson, SC
Re: What does VTEC stand for? (JG Luder)
I'm sure I'm smarter than you...I don't know what newbie is
Sweet Jesus alive.... does it HURT to be this stupid?
Also, a little known fact, Honda motorcycles have VTEC too, but they run off of a very different sype of system, it uses a second set of valves that stay closed when not in "VTEC" but they open when it "kicks in." In fact, if I'm not mistaken, the bikes had VTEC first!
Sweet Jesus alive.... does it HURT to be this stupid?
Also, a little known fact, Honda motorcycles have VTEC too, but they run off of a very different sype of system, it uses a second set of valves that stay closed when not in "VTEC" but they open when it "kicks in." In fact, if I'm not mistaken, the bikes had VTEC first!
Honda-Tech Member
Joined: Mar 2001
Posts: 4,408
Likes: 4
From: Somewhere in California
Re: What does VTEC stand for? (JG Luder)
Also, a little known fact, Honda motorcycles have VTEC too, but they run off of a very different sype of system, it uses a second set of valves that stay closed when not in "VTEC" but they open when it "kicks in." In fact, if I'm not mistaken, the bikes had VTEC first!
Interesting **scratches chin** when did they first start putting VTEC in motorcycles? I heard the NSX back in 91 was the first car that Honda put VTEC in...
