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Introduction to VTEC
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; the other designed to maximize high-RPM power output. Switching between the two cam lobes is controlled by the ECU which takes account of engine oil pressure, engine temperature, vehicle speed, engine speed and throttle position. Using these inputs, the ECU is programmed to switch from the low lift to the high lift cam lobes when the conditions mean that engine output will be improved. At the switch point a solenoid is actuated which allows oil pressure from a spool valve to operate a locking pin which binds the high RPM cam follower to the low rpm ones. From this point on, the poppet valve opens and closes according to the high-lift profile, which opens the valve further and for a longer time. The switch-over point is variable, between a minimum and maximum point, and is determined by engine load; the switch back from high to low rpm cams is set to occur at a lower engine speed than the up-switch, to avoid surging if the engine is asked to operate continuously at or around the switch-over point. The DOHC (Dual Over Head Cam) VTEC system has high and low lift 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 and Civic CRX SiR models sold in Japan and Europe, which used a 160 bhp (119 kW) variant of the B16A engine. The US market saw the first VTEC system with the introduction of the 1990 Acura NSX, which used a DOHC VTEC V6 with 270 hp. DOHC VTEC engines soon appeared in other vehicles, such as the 1992 Acura Integra GS-R (B17 1.7 liter engine). And later in the 1993 Honda Prelude VTEC (H22 2.2 liter engine) and Honda Del Sol VTEC (B16 1.6 liter engine).
Honda has also continued to develop other varieties and today offers several varieties of VTEC: iVTEC, iVTEC Hybrid and VTEC in the NSX and some Japanese domestic market cars.
SOHC VTEC
As popularity and marketing value of the VTEC system grew, Honda applied the system to SOHC (Single Over Head Cam) 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 VTEC requires a third center rocker arm and cam lobe (for each intake and exhaust side), and in the SOHC engine, the spark plugs are situated between the two exhaust rocker arms, leaving no room for the VTEC rocker arm. Additionally, the center lobe on the camshaft can only be utilized by either the intake or the exhaust, limiting the VTEC feature to one side.
SOHC VTEC-E
Honda's next version of VTEC, VTEC-E, was used in a slightly different way; instead of optimising performance at high RPM, it was used to increase efficiency at low RPM. At low RPM, 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 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.
DOHC VTEC-DI
Honda also had a demonstration engine back in end 1999 where a 1.4 liter DOHC Honda engine was equipped with a VTEC-DI system. This was Honda’s first demonstration of direct injection to the public. The engine was installed in a Honda Logo (the predecessor to the Honda Fit/Jazz) and made power and torque outputs of 107 hp at 6200 rpm and 133 Nm at 5000 rpm.
3-Stage VTEC
Honda also introduced a 3-stage VTEC system in select markets, which combines the features of both SOHC VTEC and SOHC VTEC-E.
At low engine speeds, one intake valve is opened off an economy lift cam lobe, and the second valve is just cracked open a little to help promote better swirl in the combustion chamber. Used in conjunction with a 5-wire, wideband O2 sensor, great fuel ecomomy can be realized.
At medium engine speeds, both intake valves open off the economy cam lobe with equal lift allowing the engine to produce more power, but at the expense of economy.
At high engine speeds, both intake valves are actuated by a high lift cam lobe and produce much higher performance than at the medium speed range, but at an even greater expense of economy.
The 3-stage VTEC system was only offered in the Asian markets and not in the US market at all.
i-VTEC
i-VTEC (intelligent-VTEC) introduced continuously variable camshaft phasing on the intake cam of DOHC VTEC engines. The technology first appeared on Honda's K-series four cylinder engine family in 2001 (2002 in the U.S.). Valve lift and duration are still limited to distinct low- and high-RPM profiles, but the intake camshaft is now capable of advancing between 25 and 50 degrees (depending upon engine configuration) during operation. Phase changes are implemented by a computer controlled, oil driven adjustable cam gear. Phasing is determined by a combination of engine load and rpm, ranging from fully retarded at idle to maximum advance at full throttle and low rpm. The effect is further optimization of torque output, especially at low and midrange RPM.
The K-Series motors have two different types of i-VTEC systems implemented. The first is for the performance motors like in the RSX Type S or the TSX and the other is for economy motors found in the CR-V or Accord. The performance i-VTEC system is basically the same as the DOHC VTEC system of the B16A's, both intake and exhaust have 3 cam lobes per cylinder. However the valvetrain has the added benefit of roller rockers and continuously variable intake cam timing. The economy i-VTEC is more like the SOHC VTEC-E in that the intake cam has only two lobes, one very small and one larger, as well as no VTEC on the exhaust cam. The two types of motor are easily distinguishable by the factory rated power output: the performance motors make around 200 hp or more in stock form and the economy motors do not make much more than 160 hp from the factory.
In 2004, Honda introduced an i-VTEC V6 (an update of the J-series), but in this case, i-VTEC had nothing to do with cam phasing. Instead, i-VTEC referred to Honda's cylinder deactivation technology which closes the valves on one bank of (3) cylinders during light load and low speed (below 80 mph) operation. The technology was originally introduced to the US on the Honda Odyssey minivan, and can now be found on the Honda Accord Hybrid and the 2006 Honda Pilot.
An additional version of i-VTEC was introduced on the 2006 Honda Civic's R-series four cylinder SOHC engines. This implementation uses the so-called "economy cams" on one of the two intake valves of each cylinder. The "economy cams" are designed to delay the closure of the intake valve they act upon, and are activated at low rpms and under light loads. When the "economy cams" are activated, one of the two intake valves in each cylinder closes well after the piston has started moving upwards in the compression stroke. That way, a part of the mixture that has entered the combustion chamber is forced out again, into the intake manifold. That way, the engine "emulates" a lower displacement than its actual one (its operation is also similar to an Atkinson cycle engine, with uneven compression and combustion strokes), which reduces fuel consumption and increases its efficiency. During the operation with the "economy cams", the (by-wire) throttle butterfly is kept fully open, in order to reduce pumping losses. According to Honda, this measure alone can reduce pumping losses by 16%. In higher rpms and under heavier loads, the engine switches back into its "normal cams", and it operates like a regular 4 stroke Otto cycle engine. This implementation of i-VTEC was initially introduced in the R18A1 engine found under the bonnet of the 8th generation Civic, with a displacement of 1.8 L and an output of 140PS. Recently, another variant was released, the 2.0 L R20A2 with an output of 150PS, which powers the EUDM version of the all-new CRV
With the continued introduction of vastly different i-VTEC systems, one may assume that the term is now a catch-all for creative valve control technologies from Honda.
i-VTEC I
Honda’s i-VTEC I Engine is a variant of the K-series DOHC engine family featuring gasoline direct injection. It made its debut in the previous generation 2004 Honda Stream 7-seater MPV in Japan, but the current Stream does not use this engine anymore, instead using a 2.0 liter version of the R-series i-VTEC SOHC engine.
The engine featured the ability to use ultra-lean air-fuel mixtures of about 65:1, much leaner compared to the usual direct injection engine 40:1 ratio, and extremely lean compared to the stoichiometric air-fuel mixture of 14.7:1. As a result of this ultra-lean mixture fuel consumption dropped to 15km per liter. Power ratings remain the same at about 155 horsepower. [4]
Advanced VTEC
A September 25, 2006 press release announced the launch of the Advanced VTEC engine by Honda. The new engine combines continuously variable valve lift and timing control with the continuously variable phase control of VTC (Variable Timing Control). This new system permits optimum control over intake valve lift and phase in response to driving conditions, achieving improved charging efficiency for a significant increase in torque at all engine speeds. Under low to medium load levels, the valves are set for low lift and early closure to reduce pumping losses and improve fuel economy. In comparison to the 2.4L i-VTEC these advancements claim to increase fuel efficiency by 13%. Honda also claims that new engine also meets exhaust emission standards compliant with U.S. EPA - LEV2-ULEV regulations and Japanese Ministry of Land, Infrastructure and Transport requirements for Low-Emission Vehicles, with emission levels 75% lower than those required by the 2005 standards. Advanced VTEC engines should go into production for 2009 models.
VTEC in motorcycles
Apart from the Japanese market-only Honda CBR400F Super Four HYPER VTEC,introduced in 1983, the first worldwide implementation of VTEC technology in a motorcycle occurred with the introduction of Honda's VFR800 sportbike in 2002. Similar to the SOHC VTEC-E style, one intake valve remains closed until a threshold of 7000 rpm is reached, then the second valve is opened by an oil-pressure actuated pin. The dwell of the valves remains unchanged, as in the automobile VTEC-E, and little extra power is produced but with a smoothing-out of the torque curve. Critics maintain that VTEC adds little to the VFR experience while increasing the engine's complexity. Drivability is a concern for some who are wary of the fact that the VTEC may activate in the middle of an aggressive corner, potentially upsetting the stability and throttle response of the motorcycle.
GOOGLE 翻译
介绍vtec
dohc vtec
本田的vtec系统是一个简单的方法，赋予引擎与多个凸轮轴概况优化低和高转速的行动。不是一个凸轮驱动，每个叶瓣，有两个：一是优化低转速稳定及燃油效率;其他设计用来最大限度地高转速的输出功率。开关两国之间的凸轮叶是由欧洲货币单位考虑到发动机机油压力，发动机温度，车速，发动机转速和节气门的位置。使用这些投入， ECU的是程序切换从低电梯向高扬程凸轮叶的条件时表示发动机输出功率将得到改善。在开关点是螺线管驱动，使机油压力从滑阀操作锁定的PIN有约束力的高转速凸轮从动件，以低转速。从这个角度上，锥阀开启和关闭根据该高扬程的个人资料，打开阀门，并进一步为更长的时间。开关超过一点是变量，之间的最低和最高点，并决心通过发动机负荷;切换回由高向低转速凸轮是设定为发生在一个较低的发动机转速比起来开关，以避免风起云涌，如果发动机是要求经营，不断在或靠近开关超过一点。该dohc （双以上的头部CAM ）的vtec系统具有较高的低升降机凸轮叶剖面上都进气口和排气气门凸轮轴。
该vtec系统原本是作为dohc系统在1989年本田积分和公民crx主席先生模型出售在日本和欧洲，用了160匹马力（ 119千瓦）的变种，该b16a引擎。美国市场上看到第一vtec系统与引进的1990阿库拉nsx ，其中用了一个dohc vtec V6引擎与270马力。 dohc vtec引擎很快出现在其他车辆，如1992年的阿库拉积分一般事务住宅（ b17一点七升引擎） 。后来在1993年本田的前奏vtec （ H22荷2.2升引擎）和本田删除溶胶vtec （ B16黑色素瘤一点六升引擎） 。
本田公司也继续发展其他品种和今天提供了几个品种的vtec ： ivtec ， ivtec杂交和vtec ，在nsx和一些日本国内市场的汽车。
sohc vtec
由于人气和营销价值的vtec系统的增长，本田公司的应用系统sohc （单超过头部CAM ）的引擎，其中股票一个共同的凸轮轴均进气口和排气阀门。贸易小康是sohc发动机，不仅有利于从vtec机制，对进水口阀门。这是因为vtec需要第三方中心，摇臂和凸轮叶（为每个进气口和排气侧） ，并在sohc发动机，火花塞位于两国之间的排气摇臂，不留空间，让vtec摇臂。此外，该中心对叶凸轮轴，只能利用，无论是进水口或排气，限制vtec功能一方。
sohc vtec e
本田的下一个版本的vtec ， vtec E型，用在一个略有不同的方式;不是优化表现在高转速，它是用于提高效率，在低转速。在低转速，其中两个进水口阀是只允许打开一个很小的数额，增加燃油/空气雾化，在汽缸，从而让一个精简的混合使用。作为发动机的速度增加，无论是阀门需要提供足够的混合物。滑动引脚，这是由石油的压力，如在定期vtec ，是用来连接两个阀门一起，并允许全面开放的第二个阀门。
dohc vtec e
本田公司也产生了示范引擎早在1999年底，凡一点四升dohc本田发动机是配备了vtec娣制度。这是本田的首次展示了直喷式向市民公布。发动机安装在本田公司的标志（前身本田适合/爵士乐）和取得的权力和扭矩输出107马力， 6200 rpm的133牛顿米于5000 rpm的。
三阶段vtec
本田公司还推出了三阶段的vtec系统在选择市场，相结合的特点，既sohc vtec和sohc vtec娥。
在低速，一进气阀开启小康的经济体系，解除凸轮叶，第二阀只是破获开放一点，以帮助促进更好的涡流在燃烧室。使用联同一个五线，宽带氧传感器，伟大的燃料ecomomy可以实现的。
在中等速度的引擎，无论是进水口阀门开启小康经济凸轮叶与平等的电梯，让发动机产生更多的权力，但在牺牲经济。
在高引擎速度，无论是进水口阀门驱动由高扬程凸轮叶和生产高得多的性能比在中等速度范围，但在一个更大的牺牲经济。
第3阶段的vtec系统只提供在亚洲市场，而不是在美国市场上所有。
i-vtec
i-vtec （智能vtec ）介绍了连续可变凸轮轴逐步对进水口凸轮dohc vtec引擎。该技术首次出现在本田的K系列4缸发动机的家庭在2001年（ 2002年在美国） 。气门和持续时间仍然有限，以鲜明的低收入和高转速设定档，但摄入量凸轮轴是现在能够与时俱进，介乎二十五至五十度（取决于发动机的配置）在运作。相位的变化，实施由计算机控制，石油驱动的可调式凸轮齿轮。逐步取决于相结合的发动机负荷和转速，范围从完全迟钝，在闲置的最高预先在充分油门和低转速。效果是进一步优化扭矩输出，特别是在低转速和中端。
的K系列电动机有两种不同类型的i-vtec系统的实施。首先是为履行汽车一样，在rsx S型或在TSX和其他经济是汽车中发现的CR - V或协议。表现i-vtec制度基本上是一样dohc vtec系统的b16a的，无论是进气口和排气凸轮有3叶，每缸。不过，配气有一个好处，轧辊摇滚乐队和连续可变进气凸轮的时间。经济的I - vtec是更象sohc vtec - E的摄入量，该凸轮只有两个叶，一个非常小的和一个较大的，以及没有vtec对排气凸轮。两种类型的电动机很容易分辨的，由工厂额定功率输出：汽车的性能，使周围200马力或以上的股票的形式和经济的汽车不作远不止160惠普从工厂。
在2004年，本田公司推出的I - vtec V6发动机（一更新的J系列） ，但在这种情况下，i- vtec无关，与凸轮分期。相反，我- vtec提到本田的汽缸失活技术，关闭阀门就一银行（ 3 ）气瓶在轻负荷和低速（低于80英里）的运作。该技术最初是介绍美国在本田奥德赛面包车，和现在可以发现，对本田Accord混合动力和本田2006年的试点。
额外版本的I - vtec介绍了2006年本田Civic的R系列4缸sohc发动机。本实施使用了所谓的“经济凸轮”对其中的两个进水口阀门，各缸。 “经济凸轮”的目的是拖延关闭的进气阀后，他们的行为，并激活在低从RPMS下，轻负载。当“经济凸轮”被激活，其中两个进水口阀门，在每个气缸关闭后，活塞已经开始移动向上，在压缩行程。这样，一部分混合物已进入燃烧室是被迫再次进入进气歧管。这样一来，发动机“模仿”较低的位移超过其实际1 （其运作也类似一阿特金森循环发动机，与不平衡的压缩和燃烧杆） ，从而降低了燃料消耗和增加其效率。在行动中与“经济凸轮” ， （线）油门蝴蝶是不断全面开放，以减少抽水的损失。据本田，这项措施仅可以减少抽水损失了16 ％ 。在较高的从RPMS下，加重负荷，发动机开关回到纳入其“正常凸轮” ，它的运作就像一个经常四冲程奥托循环发动机。这个实施的I - vtec最初介绍，在r18a1引擎发现，根据帽的第八一代的公民，与排水量为1.8 L和1的输出140ps 。最近，另一种变体被释放，二点○升r20a2与输出150ps ，其中的权力eudm版本的所有新crv
与继续引进截然不同的I - vtec系统，一可以假定的任期现在是一个包罗一切的创意阀控制技术，从本田。
i-vtec i
本田公司的I - vtec i引擎，是一个变种的K系列dohc引擎族特色汽油缸内直喷。它首次在其前一代2004年本田流七人座的MPV的在日本，但目前的流不使用这个引擎了，而不是使用二点零升版本的R系列的I - vtec sohc发动机。
该引擎的精选能力，使用超精益空气-燃料混合物约65:1 ，远精简相比，通常的直喷式发动机40:1的比例，也是极精益相比，化学计量的空气燃料混合14.7:1 。由于这个超稀混合燃料的消耗量下降至15公里每公升。额定功率维持不变，约155马力。 [ 4 ]
先进的vtec
1 2006年9月25日新闻稿，宣布推出先进的vtec引擎的本田。新的引擎结合起来，不断可变气门升降机及定时控制与连续可变相位控制，职训局（可变正时控制） 。这一新的许可证制度，优化控制进气阀升降机及相在回应驾驶条件下，实现改善充电效率的一个显着增加，扭矩在所有引擎的速度。根据轻微至中等负荷水平，阀门定低升降机及早期封闭，以减少抽水的损失和改善燃油经济性。在比较向二点四升一vtec这些进步，要求增加燃油效率由13 ％ 。本田公司还声称，新的引擎也符合废气排放标准符合美国环保局-l ev2- u lev规章和日本外务省的土地，基础设施和运输的要求，低排放车辆，其废气排放量的7 5％ ，低于所规定的2 005年的标准。先进的vtec引擎应到生产，到2009年的型号。
vtec在电单车
除了从日本的市场，只有本田cbr400f超级4超线程vtec ，介绍了在1983年，首次在全世界实施vtec技术在摩托车发生与引进本田的vfr800 sportbike在2002年。类似该sohc vtec娥作风，一进气门仍然关闭，直到某一阈值7000 RPM的是达成共识，那么第二个阀打开一油压力驱动的PIN 。该谈论的阀门维持不变，作为在汽车vtec娥，和一点额外的权力是产生，但与平滑出的扭矩曲线。批评者认为， vtec增加了小到vfr经验，同时增加发动机的复杂性。驾驶是一个关注的一些谁是存有戒心的事实，即vtec可能激活在中咄咄逼人的角落，可能破坏稳定和油门的反应摩托车。
[ 本帖最后由 天空的感觉 于 2008-6-7 04:06 编辑 ] |
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Honda 
发表于 2008-6-7 03:56:35
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