燃油效率要低得多。本田希望坚持自然吸气的直接响应和可预测的行为，但提供与强制感应电机相当的性能。
平衡
在高性能自然吸气电机中，气流是关键。流向气缸的气流通过凸轮轴上的凸角调节，凸轮轴通过凸轮轴凸角的蛋形轮廓协调排气门和进气门的打开。这些凸轮压在摇臂上，摇臂打开阀门。具有较长轮廓的凸轮更积极地压在摇杆上，打开它们的时间更长，并增加流向燃烧室的气流。
为了在红线前获得最佳性能，发动机需要尽可能大的气流。这就要求凸轮轴具有非常激进的凸轮轮廓——更多的空气、更多的燃料、更多的动力。不幸的是，这在电机转速范围的其他地方有很大的缺点。
发动机将大致怠速（在某些高性能汽车中可以听到断
断续续的声音）。它会对低端性能产生负面影响，因为当阀门在低活塞速度下打开时间过长时，气缸中无法产生足够的压力，这意味着燃烧循环减弱。如果阀门打开得太宽，气流会明显变慢，并且空气-燃料混合会受到阻碍。最重要的是，激进的凸轮使油耗非常高，因为电机需要大量燃油才能避免失速。
更小、更合理的凸轮可以解决所有这些问题，但它会损失高端动力，而这正是自然吸气发动机与涡轮增压汽车相比具有最大吸引力的地方。1989年，本田发布了一款旨在弥合差距的发动机。
解决方案
本田的解决方案在 1989 年的本田
Integra（日本）上首次亮相，非常巧妙且非常简单。凸轮轴有两组凸轮：一组是激进的，一组是随意的。在轻松驾驶期间的低转速下，只有不具侵略性的凸轮才能真正压在摇杆上。较大的凸轮与凸轮轴的其余部分一起旋转，但不会压在任何东西上。
在预编程（高！RPM
是一种电子电磁阀释放，允许油涌入连接所有摇臂的轴上雕刻的通道。油压啮合一个销，该销钉啮合另一个摇臂。该臂被锁定在激进凸轮下方的位置。激进的凸轮（及其相应的摇杆）现在决定了阀门保持打开的时间和深度。当转速下降时，电磁阀关闭，摇臂松开销，电机恢复到不太激进的轮廓。
其结果是一个具有出色城镇宜居性的发动机，但高端却很糟糕。在实践中，它最终给人留下了深刻的印象：1995 年推出的 Integra
Type R 由 200 升发动机产生 1.8 马力的功率。当时，自然吸气发动机每升超过 100
马力是最高端超级跑车的领域。当然，额外的好处是特有的
bwaaa-WAAAA VTEC 声音。
复利奖励
VTEC的美妙之处在于它在机械上非常简单，可以与其他发动机技术相结合，以更好地控制发动机的行为。本田利用这一点创建了i-VTEC，它将可变气门正时与VTEC配对，从而进一步优化气流。2006
年，本田开发了一种电机，该电机允许无级可变凸轮相位，同时还集成了
VTEC。该公司打算在2010年之前将其投入生产，但搁置了这一概念。
相反，在过去的十年中，随着排放法规和预期功率输出的不断加强，本田转向涡轮增压。在本田的涡轮增压VTEC发动机中，额外的凸轮仅在排气凸轮轴上，因为涡轮增压器由排气气流供给。在某些可能出现涡轮迟滞的条件下（例如部分油门或低转速加速），更具侵略性的凸轮会啮合，以帮助涡轮增压器更快地旋转。
不幸的是，仅排气的 VTEC 没有来自进气口的特有
的 bwwaaa-WAAAA
声音。尽管如此，本田还是很好地利用了它的优势，
思域Type
R因其油门响应和缺乏涡轮迟滞而获得了好评如潮。自然吸气式发动机是否会永远存在是任何人的猜测，但现在很明显，只要有本田发动机，就会有VTEC。
原文阅读
How VTEC Works: An Explainer
A closer look at one of the most iconic names in
engineering.
Jul 1, 2024 at 10:00am ET
By: Victoria
Scott
There are few sounds in the automotive orchestra as distinct as the
VTEC kick. Characterized by a sudden jump in tone (and volume)
coming from a high-revving, naturally aspirated Honda engine, the
VTEC
whomp has scored some of the greatest sports cars of
all time. And also the neighbor kid’s straight-piped Integra.
(Sorry—that was probably me).
It’s one of the longest-lived—and most oft-meme’d—pieces of
automotive technology. With naturally aspirated motors receiving a
stay of execution, it’s time to take a look at what, exactly, keeps
us so hooked on them. There’s no better place to start than
VTEC.
Honda And The Naturally Aspirated Motor
Honda has long sought ways to improve the technology found in
naturally aspirated engines. Its first runaway success in America
came with the introduction of Compound Vortex Controlled Combustion
(CVCC). Honda introduced CVCC with the Civic in 1974, at the height
of the OPEC fuel crisis. The system used a pre-chamber in the head,
allowing for more complete fuel burn. The pre-chamber’s auxiliary
valve sent a richer air-fuel mixture nearer to the spark plug,
while the standard inlet valve sent a leaner mixture throughout the
rest of the combustion chamber.
Honda’s CVCC was the first engine design to pass the new Clean Air
Act requirements for exhaust gas. It did so without a catalytic
converter—a huge step in an era when leaded gas (which clogged
catalytic converters) was still found at many pumps. This tech made
Honda’s small-displacement motors not just more efficient than its
larger American counterparts, but more practical.
VTEC stemmed from similar circumstances. In the mid-80s, forced
induction slowly became more commonplace, and car manufacturers
began to add turbochargers to their engines for better high-end
power. These systems had tradeoffs of their own, however.
Turbochargers naturally suffer from lag, as they require time to
build pressure, and they were (in the early days) much less
fuel-efficient. Honda wanted to stick with the direct response and
predictable behavior of natural aspiration, but offer comparable
performance to a forced-induction motor.
The Tradeoff
In a high-performance naturally aspirated motor, airflow is key.
Airflow to the cylinder is regulated via the lobes on the camshaft,
which coordinates the opening of both the exhaust and intake valves
via the egg-shaped profiles of the camshaft’s lobes. These lobes
press on the rocker arms, which open the valves. Lobes with longer
profiles press on the rockers more aggressively, opening them
longer, and increasing airflow to the combustion chamber.
For the best performance possible toward redline, the engine needs
the most airflow possible. This calls for a camshaft with a very
aggressive cam profile—more air, more fuel, creating more power.
Unfortunately, this has massive downsides elsewhere in the motor’s
rev range.
The engine will idle roughly (this is audible in some
high-performance cars as a
choppy sound). It negatively
affects low-end performance, as when the valves are open too long
at low piston speeds, adequate pressure cannot build in the
cylinder, meaning the combustion cycle weakens. If the valves are
open too wide, airflow is significantly slower, and air-fuel mixing
is hampered. On top of all of that, an aggressive cam makes fuel
consumption very high, as the motor needs large amounts of fuel to
avoid stalling.
A smaller, more reasonable cam solves all these problems, but it
does so at the loss of top-end power, which is where naturally
aspirated engines possess their greatest appeal vs. turbocharged
cars. In 1989, Honda released a motor meant to bridge the
gap.
The Solution
Honda’s solution, which debuted on the 1989 Honda Integra (in
Japan), was ingenious and remarkably simple. The camshaft has two
sets of lobes: one aggressive, one casual. At low RPMs during
relaxed driving, only the unaggressive lobes actually press against
the rockers. The larger lobe spins with the rest of the camshaft
but does not press against anything.
At a pre-programmed (high!) RPM, an electronic solenoid releases,
allowing oil to flood into a channel carved into the shaft
connecting all the rocker arms. The oil pressure engages a pin that
engages another rocker arm. This arm is locked into position
beneath the aggressive cam. The aggressive cam (and its
corresponding rocker) now dictate how long and deep the valves stay
open. When revs drop, the solenoid closes, the rocker unpins, and
the motor goes back to the less-aggressive profile.
The result is an engine with excellent around-town livability but a
wicked top end. In practice, it ended up being wildly impressive:
The Integra Type R launched in 1995 made 200 horsepower from a
1.8-liter engine. At the time, over 100 hp a liter from a naturally
aspirated motor was the realm of the highest-end supercars. The
added bonus, of course, is that characteristic
bwaaa-WAAAA
VTEC sound.
Compounding Reward
The beauty of VTEC is that it is so mechanically straightforward
that it can be combined with other engine technologies for more
control over an engine’s behavior. Honda has used this to create
i-VTEC, which pairs variable valve timing with VTEC, allowing for
further optimization of airflow. In 2006, Honda developed a motor
that allowed for infinitely variable cam phasing while also
incorporating VTEC. The company intended to put it into production
by 2010, but shelved the concept.
Instead, last decade, Honda moved towards turbocharging as
emissions regulations—and expected power outputs—continued to
toughen. In Honda’s turbo VTEC motors, the extra lobes are found
solely on the exhaust camshaft, as the turbo is fed by exhaust
airflow. The more aggressive lobe engages under certain conditions
where turbo lag is likely—such as partial throttle or low RPM
acceleration—to help the turbo spool more rapidly.
Unfortunately, exhaust-only VTEC doesn’t have the characteristic
bwwaaa–WAAAA sound—that comes from the intake. Still, Honda
has used it well to its advantage, with the
Civic Type R achieving rave reviews for its throttle response
and lack of turbo lag. Whether naturally aspirated motors are here
to stay for good is anyone’s guess, but it’s clear by now that as
long as there are Honda engines, there will be VTEC.
美国东部时间2024年7月1日上午10：00