VTEC（ブイテック、Variable valve Timing and lift Electronic Control system）は、本田技研工業が開発した4サイクルエンジン用の可変バルブタイミング・リフト機構および、その名称である。
目次
- 1 概要
- 2 歴史
- 3 VTECのバリエーション
- 4 VTEC採用状況
- 5 四輪車以外のVTEC
- 6 脚注
- 7 関連項目
- 8 外部リンク
概要[編集]
一般的に、4サイクルエンジンは燃焼ガス（ガソリンと空気の混合気）を吸気し、それを燃焼させることで動力を発生させ、燃焼済みのガスを排気するというサイクルを繰り返す仕組みになっている。吸気量および排気量は、ピストンの上下動に伴うバルブの開閉時間（バルブタイミング）・リフト量によって制御される。
エンジンの回転数が低いときは、バルブを少ない時間で少なく開け、回転数が高いときは、バルブを長い時間に大きく開けるなど、吸気効率の良いバルブタイミングとバルブリフト量を回転数にあわせて調整することが望ましい。VTECは、バルブの開閉タイミングとリフト量をエンジンの回転数に応じて変化させ、吸排気量の調整を行う技術「可変バルブ機構」のひとつである。
「可変バルブ機構#概要」も参照
初期のVTECは、カムシャフトにハイ／ロー2種類のカムを設け、そこに接するロッカーアームを一定の回転数に達した際に切り替え、バルブタイミング・リフト量を変化させる。VTEC以前にも、カムシャフトを油圧によりスライド（回転）させ、クランクシャフトに対する相対的な位相（角度）を変える方式は実用化されていたが、リフト量とバルブタイミングを同時に変化させる機構はVTECが初めてであった。これにより、低回転域と高回転域それぞれにおいて、バルブタイミングおよびリフト量が最適化され、低回転域のトルクと高回転域のパワーを両立させることが可能となった。B16A型エンジンに初めてこの機構が搭載され、自然吸気エンジンでありながら排気量1Lあたり100馬力超を実現した。NAエンジンユニットとしては非常に高回転型エンジンとして知られており、そのかん高いエンジンサウンドを好むファンも少なくない。
この機構の発案については、焼き鳥屋でねぎまを焼いている様子を見ていた技術者が、串に打たれた具材が回ったり回らなかったりする（ネギは回るのに肉は回らない、など）のを見て、発想したものである[1]。 また、VTEC-Eを開発する際にはスワールの研究ではトイレの小便器で用を足す角度まで参考にしていた[2]。
歴史[編集]
1989年4月19日、インテグラに搭載されたB16A型エンジン（1.6L 直4 DOHC）に初めて採用された。1991年9月10日発表の5代目シビックには、SOHCエンジンにも搭載された。この際には2種類のVTECが設定され、ひとつは吸気バルブをDOHC VTECと同様に低回転、高回転で切り替える「VTEC」と、もうひとつは2つある吸気バルブのうち片側をほぼ休止し、リーンバーン運転をするVTEC-Eである。1995年9月4日発表の6代目シビックでは、2つを統合した3ステージVTECが搭載された。
2000年、それまでの、ハイ／ローカムを回転数によって切り替える制御方法に加え、吸気側のクランクシャフトに対する位相を、回転数や負荷に応じて無段階で連続変化させるVTC（Variable Timing Control、連続可変バルブタイミングコントロール機構）も加わったi-VTECへと進化[3]。名称にはintelligentの頭文字のiが付与され、エンジンの知能化を示している。2003年には、i-VTECにホンダ初の直噴ガソリンエンジンとなるi-VTEC Iや、V型6気筒のうち片バンクの3気筒を休止させるVCM（Variable Cylinder Management 、可変シリンダー機構）を備えたものが開発されるなど、さまざまなバリエーションが存在する。
VTECのバリエーション[編集]
H22A型DOHC VTECエンジン。
赤いカバーのVTECエンジンは特に高出力化が成されている。
- DOHC VTEC
- 1989年4月19日に発売されたインテグラに初めて搭載された。吸気側、排気側ともに二段のカムシャフトを備えており、バルブタイミングとリフト量を変化させる。以後、i-VTECが登場するまでは、高回転・高出力型エンジンのみの設定であった。
- 基本的な仕組みは以下のとおりである。カムは高回転用・低回転用の2種類を同じシャフトに隣接して備える。バルブはカムの直押しではなく、同じく2種類のロッカーアームをそれぞれ間に挟んでいる。このうち、バルブに直接接しているロッカーアームは低回転用のみで、高回転用は低回転時において空振りするようになっている。高回転時はピンが油圧によってロッカーアームを貫き、低回転用と高回転用の動きを同調させる。この際、カムがロッカーアームを押し下げるにあたって、カム山は高回転用の方が大きいため、今度は低回転用カムがロッカーアームに届かず、空振りする。これにより、高回転用カムによる動作が高回転用ロッカーアーム、さらにはピンを介して低回転用ロッカーアームへ伝わることで、バルブの動作は高回転用カムに従う。この動作はエンジン油圧・エンジン温度・車両速度・エンジン回転速度とスロットル位置などを考慮し、ECUでコントロールされる。
- インテグラの他、シビック/CR-Xが、B16A型エンジンを搭載し日本とヨーロッパで販売された。北米には、1990年にアキュラ・NSXがC30A型エンジン（3.0L V6）を搭載し販売された。他の車両では、1992年のアキュラ・インテグラ（B17A型 1.7L 直4）、1993年のプレリュード（H22A型 2.2L 直4）やCR-X delSol（B16A型）などに採用されている。
- SOHC VTEC
- 1991年9月10日に発売された5代目シビックに初めて搭載された。吸気側のみのバルブタイミング・リフト量を変化させる。DOHC VTECに対して発表当時は単にVTECとのみ表記された。以後、ホンダ車の大衆エンジンに広く用いられる。カム切り替えに関する機構の面ではDOHC VTECと共通である。
- VTEC-E
- 上述のSOHC VTECと同時にシビックに初めて搭載された。2つあるSOHCエンジンの吸気バルブのうち、片方をほぼ休止させることによりリーンバーン運転を行う。
- 3ステージVTEC
- 1995年9月4日に発売された6代目シビックに初めて搭載された。SOHC VTECとVTEC-Eを統合したもので、低回転域では吸気バルブのうち片方をほぼ休止してリーンバーン運転を行い、中回転域では吸気バルブ2バルブ運転、高回転域では高速カムによる運転を行う。
- シビックのモデルチェンジにより一時ラインナップから消えたが、2005年9月20日に発表されたシビックハイブリッドでは3ステージi-VTECとして復活した。これはハイブリッドカー向けのIMAシステムとの連携最適化を見据えたもので、減速時に全気筒休止を行うように改良されたものである。
- i-VTEC
- 2000年10月26日のストリームの発表において、VTCを採用したK20A型エンジン（2.0L 直4）に初めて搭載された。
- 以後、同社のカム切り替え機構を備えたエンジンはi-VTECと称され、VTCに限らず何らかの新機軸を盛り込んだVTECのことを指す。そのため、名称は同じでも機構面ではいくつかのバリエーションが存在する。2002年10月10日にK24A型エンジン（2.4L 直4）がアコードとアコードワゴンに搭載された。2003年6月18日にはVCM仕様のJ30A型エンジン（3.0L V6）がインスパイアに搭載された。2007年10月18日にはVTEC-E仕様のL13A型ならびにSOHC VTEC仕様のL15A型が2代目フィットに搭載された。
- A-VTEC advanced-VTEC
- 2005年、3年以内に導入するとホンダからアナウンスされた。連続可変バルブリフトを実現するものであるが、現在まで搭載された車種は発売していない。
- VTEC TURBO
- エンジンのダウンサイジングを目指し、ターボチャージャーを組み合わせたもの。2013年11月に開発発表された[4]。2.0L、1.5L4気筒、1.0L3気筒の3種類がある（搭載車などは未定）。
VTEC採用状況[編集]
1989年のインテグラでの初採用以来、「ホンダ車のエンジン＝VTECエンジン」というイメージがユーザー間に植え付けられるほど、VTECエンジン採用車種は多くなった。国内においては2010年現在、同社によって生産されている軽自動車用以外のエンジンは、ほぼ何かしらのVTEC機構を備えている。
2000年にi-VTECが登場してからは、VTECエンジンはエンジンの世代交代と共にi-VTECへの移行が進み、2010年現在、i-VTECへ移行していないVTECエンジンは一部の大排気量エンジンと少数になった。
以前の1.5L以下のエンジンにおいては、VTEC機構採用・非採用のエンジン双方生産されており、こうした小排気量のエンジンには、より低燃費化が図れるi-DSIの採用が拡大していた。VTECエンジンとi-DSIエンジンの双方をラインナップに揃えている車種では、VTECエンジンではパワフルさを、i-DSIエンジンでは経済性をアピールすることで、棲み分けを図っていたが、2007年発売の2代目フィットから1.3Lのi-VTECエンジンが標準で搭載されるようになった。
四輪車以外のVTEC[編集]
二輪車[編集]
オートバイ用には、設定回転数以下で吸排気バルブのそれぞれ一つを休止し、4バルブから2バルブへと切り替えるREV機構（CBR400F、1983年12月発売）があり、その後HYPER VTEC（CB400SF、1999年2月発売）へと発展し、VFR800の一部モデルにも採用された。
- HYPER-VTEC
1999年2月に発売されたCB400SFに搭載された。基本動作はVTEC-Eと同じであるが、構造的には四輪エンジンとは全く異なる、二輪特有のREV機構の発展型である。ロッカーアームを持たない直押しタイプでのバルブ休止を世界で初めて実現した。直押しタイプはバルブの動的荷重が軽くなり、より高回転での追従性が高くなる。続く2002年にフルモデルチェンジしたVFR800（RC46-2）にも新規で搭載されている。
船外機[編集]
大型の船外機の製品の一部にVTEC機構が採用されている。これら製品は機関部が自動車用エンジンから発展してきたためVTEC機構の構造や特性も似ている。
脚注[編集]
- ^ Honda | Honda ism-log | Vol.2 ｢焼き鳥から生まれた革新」
- ^ ホンダの企業広告でも同様の内容で紹介された。
- ^ i-VTECは、VTCに限らず、従来のVTECに何らかの付加価値的要素を追加したものとされている。
- ^ クラストップレベルの出力性能と環境性能を両立した直噴ガソリンターボエンジン「VTEC TURBO」を新開発 本田技研工業プレリリース、2013年11月19日
関連項目[編集]
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ウィキメディア・コモンズには、ホンダのエンジンに関連するカテゴリがあります。 |
- 本田技研工業
- 可変バルブ機構
- バルブタイミング
- バルブオーバーラップ
- i-VTEC
- VTEC-E
外部リンク[編集]
Not to be confused with "Vtac" or "V-tac," abbreviations for ventricular tachycardia.
This article is about the valvetrain system. For E. coli strain, see Verotoxin-producing Escherichia coli.
VTEC (Variable Valve Timing and Lift Electronic Control) is a valvetrain system developed by Honda to improve the volumetric efficiency of a four-stroke internal combustion engine. The VTEC system uses two camshaft profiles and hydraulically selects between profiles. It was invented by Honda engineer Ikuo Kajitani,[1][2] and was the first system of its kind.[citation needed] It is distinctly different from standard VVT (variable valve timing)which advances the valve timing only and does not change the camshaft profile or valve lift in any way. Different types of variable valve timing and lift control systems have also been produced by other manufacturers VVTL-i from Toyota, VarioCam from Porsche, NeoVVL from Nissan, etc.
Contents
- 1 Context, and description
- 2 History
- 2.1 DOHC VTEC
- 2.2 SOHC VTEC
- 3 VTEC-E
- 4 3-Stage VTEC
- 5 i-VTEC
- 5.1 K-series
- 5.2 R-series
- 5.3 i-VTEC with Variable Cylinder Management (VCM)
- 5.4 i-VTEC i
- 6 AVTEC
- 7 VTEC in motorcycles
- 8 References
- 9 External links
Context, and description[edit]
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VTEC was initially designed to increase the power output of an engine to 100 HP/litre or more while maintaining practicality for use in mass production vehicles. Some later variations of the system were designed solely to provide improvements in fuel efficiency.
Japan levies a tax based on engine displacement, and Japanese auto manufacturers have correspondingly focused their research and development efforts toward improving the performance of smaller engine designs through means other than displacement increases. One method for increasing performance into a static displacement includes forced induction, as with models such as the Toyota Supra and Nissan 300ZX which used turbocharger applications and the Toyota MR2 which used a supercharger for some model years. Another approach is the rotary engine used in the Mazda RX-7 and RX-8. A third option is to change the cam timing profile, of which Honda VTEC was the first successful commercial design for altering the profile in real-time.
The VTEC system provides the engine with multiple cam lobe profiles optimized for both low and high RPM operations. In basic form, the single barring shaft-lock of a conventional engine is replaced with two profiles: one optimized for low-RPM stability and fuel efficiency, and the other designed to maximize high-RPM power output. The switching operation 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 valves open and close 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-down back from high to low RPM cams is set to occur at a lower engine speed than the switch-up (representing a hysteresis cycle) to avoid a situation in which the engine is asked to operate continuously at or around the switch-over point.
The older approach to timing adjustments is to produce a camshaft with a valve timing profile that is better suited to high-RPM operation. The improvements in high-RPM performance occur in trade for a power and efficiency loss at lower RPM ranges, which is where most street-driven automobiles operate a majority of the time. Correspondingly, VTEC attempts to combine high-RPM performance with low-RPM stability.
History[edit]
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VTEC, the original Honda variable valve control system, originated from REV (Revolution-modulated valve control) introduced on the CBR400 in 1983 known as HYPER 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 an angle measurement of when a valve is opened or closed with respect to the piston position (BTDC or ATDC). 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 working fluid (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 filling of the cylinder with 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.
DOHC VTEC[edit]
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Introduced as a DOHC system in Japan in the 1989 Honda Integra[1] XSi which used the 160 bhp (120 kW) B16A engine. The same year, Europe saw the arrival of VTEC in the Honda CRX 1.6i-VT, using a 150 bhp variant (B16A1). The United States market saw the first VTEC system with the introduction of the 1991 Acura NSX, which used a 3-litre DOHC VTEC V6 with 270 bhp (200 kW). DOHC VTEC engines soon appeared in other vehicles, such as the 1992 Acura Integra GS-R (B17A1 1.7-litre engine), and later in the 1993 Honda Prelude VTEC (H22A 2.2-litre engine with 195 hp) and Honda Del Sol VTEC (B16A3 1.6-litre engine). The Integra Type R (1995–2000) available in the Japanese market produces 197 bhp (147 kW; 200 PS) using a B18C5 1.8-litre engine, producing more horsepower per liter than most super-cars at the time. Honda has also continued to develop other varieties and today offers several varieties of VTEC, such as i-VTEC and i-VTEC Hybrid.
SOHC VTEC[edit]
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As popularity and marketing value of the VTEC system grew, Honda applied the system to SOHC (Single Over Head Cam) engines, which share a common camshaft for both intake and exhaust valves. The trade-off was that Honda's SOHC engines benefitted from the VTEC mechanism only 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 cannot be utilized by both the intake and the exhaust, limiting the VTEC feature to one side.
However, beginning with the J37A4 3.7L SOHC V6 engine introduced on all 2009 Acura TL SH-AWD models, SOHC VTEC was incorporated for use with intake and exhaust valves. The intake and exhaust rocker shafts contain primary and secondary intake and exhaust rocker arms, respectively. The primary rocker arm contains the VTEC switching piston, while the secondary rocker arm contains the return spring. The term "primary" does not refer to which rocker arm forces the valve down during low-RPM engine operation. Rather, it refers to the rocker arm which contains the VTEC switching piston and receives oil from the rocker shaft.
The primary exhaust rocker arm contacts a low-profile camshaft lobe during low-RPM engine operation. Once VTEC engagement occurs, the oil pressure flowing from the exhaust rocker shaft into the primary exhaust rocker arm forces the VTEC switching piston into the secondary exhaust rocker arm, thereby locking both exhaust rocker arms together. The high-profile camshaft lobe which normally contacts the secondary exhaust rocker arm alone during low-RPM engine operation is able to move both exhaust rocker arms together which are locked as a unit. The same occurs for the intake rocker shaft, except that the high-profile camshaft lobe operates the primary rocker arm.
The difficulty of incorporating VTEC for both the intake and exhaust valves in a SOHC engine has been removed on the J37A4 by a novel design of the intake rocker arm. Each exhaust valve on the J37A4 corresponds to one primary and one secondary exhaust rocker arm. Therefore, there are a total of twelve primary exhaust rocker arms and twelve secondary exhaust rocker arms. However, each secondary intake rocker arm is shaped similar to a "Y" which allows it to contact two intake valves at once. One primary intake rocker arm corresponds to each secondary intake rocker arm. As a result of this design, there are only six primary intake rocker arms and six secondary intake rocker arms.
VTEC-E[edit]
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The earliest VTEC-E implementation is a variation of SOHC VTEC which is used to increase combustion efficiency at low RPM while maintaining the mid range performance of non-vtec engines. VTEC-E is the first version of VTEC to employ the use of roller rocker arms and because of that, it forgoes the need for having 3 intake lobes for actuating the two valves—two identical lobes for non-VTEC operation and one lobe for VTEC operation. Instead, there are two different intake cam profiles per cylinder—a very mild cam lobe with little lift and a normal cam lobe with moderate lift. Because of this, at low RPM, when VTEC is not engaged, one of the two intake valves is allowed to open only a very small amount due to the mild cam lobe, forcing most of the intake charge through the other open intake valve with the normal cam lobe. This induces swirl of the intake charge which improves air/fuel atomization in the cylinder and allows for a leaner fuel mixture to be used. As the engine's speed and load increase, both valves are needed to supply a sufficient mixture. When engaging VTEC mode, a pre-defined threshold for MPH (must be moving), RPM and load must be met before the computer actuates a solenoid which directs pressurized oil into a sliding pin, just like with the original VTEC. This sliding pin connects the intake rocker arm followers together so that now, both intake valves are now following the "normal" camshaft lobe instead of just one of them. When in VTEC, since the "normal" cam lobe has the same timing and lift as the intake cam lobes of the SOHC non-VTEC engines, both engines have identical performance in the upper powerband assuming everything else is the same.
With the later VTEC-E implementations, the only difference it has with the earlier VTEC-E is that the second "normal" cam profile has been replaced with a "wild" cam profile which is identical to the original VTEC "wild" cam profile. This in essence supersedes VTEC and the earlier VTEC-E implementations since the fuel and low RPM torque benefits of the earlier VTEC-E are combined with the high performance of the original VTEC.
3-Stage VTEC[edit]
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Main article: 3-stage VTEC
3-Stage VTEC is a version that employs three different cam profiles to control intake valve timing and lift. Due to this version of VTEC being designed around a SOHC valve head, space was limited and so VTEC can only modify the opening and closing of the intake valves. The low-end fuel economy improvements of VTEC-E and the performance of conventional VTEC are combined in this application. From idle to 2500-3000 RPM, depending on load conditions, one intake valve fully opens while the other opens just slightly, enough to prevent pooling of fuel behind the valve, also called 12-valve mode. This 12 Valve mode results in swirl of the intake charge which increases combustion efficiency, resulting in improved low end torque and better fuel economy. At 3000-5400 RPM, depending on load, one of the VTEC solenoids engages, which causes the second valve to lock onto the first valve's camshaft lobe. Also called 4-valve mode, this method resembles a normal engine operating mode and improves the mid-range power curve. At 5500-7000 RPM, the second VTEC solenoid engages (both solenoids now engaged) so that both intake valves are using a middle, third camshaft lobe. The third lobe is tuned for high-performance and provides peak power at the top end of the RPM range.
i-VTEC[edit]
Honda i-VTEC (intelligent-VTEC)[3] has VTC continuously variable timing of camshaft phasing on the intake camshaft of DOHC VTEC engines. The technology first appeared on Honda's K-series four-cylinder engine family in 2001 (2002 in the U.S.). In the United States, the technology debuted on the 2002 Honda CR-V.
VTC controls of valve lift and valve 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. Phasing is implemented by a computer-controlled, oil-driven adjustable cam sprocket. Both engine load and RPM affect VTEC. The intake phase varies from fully retarded at idle to somewhat advanced at full throttle and low RPM. The effect is further optimization of torque output, especially at low and midrange RPM. There are two types of i-VTEC K series engines which are explained in the next paragraph.
K-series[edit]
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Main article: Honda K engine
The K-Series engines have two different types of i-VTEC systems implemented. The first is for the performance engines like in the RSX Type S or the Civic Si and the other is for economy engines 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. Performance i-VTEC is a combination of conventional DOHC VTEC with VTC.
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 engine are easily distinguishable by the factory rated power output: the performance engines make around 200 hp (150 kW) or more in stock form and the economy engines do not make much more than 160 hp (120 kW) from the factory.
R-series[edit]
i-VTEC with Variable Cylinder Management (VCM)[edit]
In 2003, Honda introduced an i-VTEC V6 (an update of the J-series) that includes Honda's cylinder deactivation technology which closes the valves on one bank of (3) cylinders during light load and low speed (below 80 km/h (50 mph)) operation. According to Honda, "VCM technology works on the principle that a vehicle only requires a fraction of its power output at cruising speeds. The system electronically deactivates cylinders to reduce fuel consumption. The engine is able to run on 3, 4, or all 6 cylinders based on the power requirement, essentially getting the best of both worlds. V6 power when accelerating or climbing, as well as the efficiency of a smaller engine when cruising." The technology was originally introduced to the US on the 2005 Honda Odyssey minivan, and can now be found on the Honda Accord Hybrid, the 2006 Honda Pilot, and the 2008 Honda Accord. Example: EPA estimates for the 2011 (271 hp SOHC 3.5L) V6 Accord are 24 mpg combined vs. 27 in the two 4-cylinder-equipped models.
i-VTEC VCM was also used in 1.3L 4-cylinder engines used in Honda Civic Hybrid.[4]
i-VTEC i[edit]
A version of i-VTEC with direct injection, first used in 2003 Honda Stream.[5]
AVTEC[edit]
The AVTEC (Advanced VTEC) engine was first announced in 2006.[6] It combines continuously variable valve lift and timing control with continuously variable phase control. Honda originally planned to produce vehicles with AVTEC engines within next 3 years.
Although it was speculated that it would first be used in 2008 Honda Accord, the vehicle instead utilizes the existing i-VTEC system.
A related US patent (6,968,819) was filed on 2005-01-05.[7][8]
VTEC in motorcycles[edit]
Apart from the Japanese market-only Honda CB400SF Super Four HYPER VTEC,[9] introduced in 1999, 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. Honda seemed to agree, as their VFR1200, a model announced in October 2009, came to replace the VFR800, which abandons the V-TEC concept in favor of a large capacity narrow-vee "unicam", i.e., SOHC, engine.
Honda incorporated the technology into the NC700 series, including the NC700D Integra, released in 2012, using a single camshaft to provide two timing routines for the intake valves.[10][11]
References[edit]
- ^ a b "The VTEC Engine". Honda Motor Co., Ltd. Retrieved 2011-03-11.
- ^ "The 'Father' of VTEC". Honda Motor Co., Ltd. Retrieved 2011-12-04.
- ^ "acura.com". acura.com. Retrieved 2010-12-04.
- ^ "Honda Civic Hybrid Technology". Autospeed.com. Retrieved 2010-12-04.
- ^ "Honda Worldwide". World.honda.com. Retrieved 2012-11-07.
- ^ Nunez, Alex (2006-09-25). "Honda reveals the Advanced VTEC engine". Autoblog.com. Retrieved 2010-12-04.
- ^ Tan, Paul. "Honda Files Advanced VTEC Patent". Paultan.org. Retrieved 2010-12-04.
- ^ "A-VTEC Details Break Cover at USPTO; TOV Analyzes". Vtec.net. Retrieved 2010-12-04.
- ^ "Honda Worldwide | Technology Close-up". World.honda.com. Retrieved 2010-12-04.
- ^ Hanlon, Mike. "Honda announces next generation motorcycle engines with outstanding fuel economy and useability". Retrieved 28 May 2012.
- ^ Beeler, Jensen. "700cc Honda Integra Motor for Mid-Sized Motorcycles". Asphalt & Rubber. Retrieved 28 May 2012.
- "Technology Close-up". Honda Motor Co., Ltd. 2004. Retrieved 2006-07-25.
- "Honda Worldwide Technology Closeup". Honda Motor Co., Ltd. 2004. Retrieved 2007-07-12.
- "Honda Worldwide IVTEC Video". Honda Motor Co., Ltd. 2009. Retrieved 2009-05-17.
External links[edit]
- Honda tech pages: VTEC, i-VTEC DOHC, S2000 2.0L DOHC VTEC, Type-R 2.0L DOHC i-VTEC, 2.0L DOHC i-VTEC I, V6 3.0L i-VTEC, V6 3.5L VTEC
- Honda Technology Picture Book, VTEC
- World Honda: New i-VTEC Technology
