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|17th December 2005, 18:06||#1|
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Honda's VTEC Technology: Past, Present and Future
VTEC. Four letters that practically started a revolution. To Honda's engineers, it means Variable Valve Timing and Lift Electronic Control. But for some of us it sparks thoughts of many other things: space age-sounding technology, the unmistakable sound of a VTEC motor revving up, the innovation that yielded naturally aspirated engines 100 hp/liter before any other manufacturer--the very technology that arguably could have launched the sport compact scene in the early-'90s. But there's quite a bit more to it than that. VTEC innovations are evolving and constantly leaving their mark in the automotive world.
So how did it all begin? Variable valve timing, a technology adapted by many different automobile manufacturers, was a spin-off of another Honda project back in the early-'80s. At the time Honda's main goal was to create motors with decent power and excellent fuel economy. With the technology of the time, Honda engineers had already hit 50 mpg with the company's ultralow emissions CVCC technology, but Honda wanted more. By January 1983 a group of engineers were studying varying valve timing to improve mileage, but in October 1983 that team was split, with one group moving on to study more efficient fuel delivery systems and the other working on valvetrain technology.
THE B16 A started it all.The team responsible for fuel efficiency launched its NCE (New Concept Engine) project in March 1984. It was completed in 1985 with the release of fuel-efficient, low-emissions engines that had torque at low and high rpm and noticeable increases in horsepower-per-liter, 81 to be exact. These DOHC four-valve-per-cylinder engines found their way into the 1985 Integra and Civic and paved the way to even higher aspirations.
The NCE taskforce was reassigned to the D-development project in November 1986. Under the guidance of Ikuo Kajitani, the team's goal was to create a 100-hp/liter engine for the 1989 Integra.
At the same time, the valvetrain team was evaluating the Revolution-modulated Valve-control (REV) technology used in the 1983 Honda motorcycle, the CBR 400F. This technology allowed the four-valve head to operate with just two valves per cylinder for fuel economy at low rpm. A sensor detected engine speed and hydraulically controlled the locker arms, which at higher rpm would lock together with a pin, activating all four valves.
The team refined this technology over the next few years, eventually creating VTEC, which not only has variable valve timing, but also variable lift. Instead of turning off two valves during low rpm driving, as was the case with REV, the DOHC VTEC system employs all four valves at all times. The camshaft design had three lobes per cylinder, two low cam lobes and one high cam lobe. The two low cam lobes were tuned for drivability and economy. The high cam lobe actuated a cam follower that was disconnected from the two cam followers that actuated the valves while at low rpm. When the motor reached higher engine speeds, a VTEC solenoid sent hydraulic pressure to locking pins that connect all three cam followers. At this point, only the radical third cam lobe actuated the valves for timing and lift. The increased timing and lift increased airflow in and out of the cylinders at high speed, increasing power output.
This technology debuted in April 1989 in the Japanese-spec Integra as the B16A, a 1.6-liter DOHC engine boasting 160 hp. It was followed by the Civic SiR with the same engine in the fall of the same year. As is typical, the U.S. market heard about this, but didn't have the privilege of seeing any of this technology until 1991, when Honda decided to incorporate VTEC into its V6-powered NSX super car.
The NSX was an awesome Japanese exotic and as such was way beyond the reach of the average enthusiast. In 1992 we gained access to VTEC technology in the 1.7-liter, 170-hp Integra GS-R engine. The Integra was well received, sending a message up the ladder to Honda Corporate that the company had really hit the mark.
VTEC began popping up all over the Honda line, as the engineers incorporated it into both fuel-efficient and high-power applications. In 1992, the Civic EX was equipped with a SOHC 1.6-liter engine that had both excellent mileage and 125 hp. This powerplant only applied VTEC on the intake valves.
The Integra GS-R got a bigger motor in 1994, the B18C. This DOHC VTEC screamer had a two-stage intake and 8000-rpm red line that went all the way to 180 hp. When the limited-production, 195-hp Integra Type R hit our shores in 1997, Honda had exceeded the 100-hp/liter goal originally set in 1986. The venerable B16A motor survived virtually unchanged for 11 years, serving in the Civic Del Sol from 1994 to 1997 and the Civic Si from 1999 to 2000.The '90s marked the golden era for Honda's first VTEC motors. Import drag racing exploded in part because of this technology. Few import labels could compete with Honda's little four-banger, despite VTEC's front-wheel-drive configuration. All the top dogs in the scene--Stephan Papadakis, Ed Bergenholtz, Lisa Kubo, Christian Rado, Viet Lam, Charles Madrid, Myles Bautista, Kenny Tran, Jeremy Lookofsky and Dave Shih, to name a few--used Honda's VTEC motor to reach the podium and, for some, the record book. Some have even taken their love of the sport to a professional level, while others have moved on to the business side. Whatever the case, these trailblazers helped lay the industry's foundation with Honda's VTEC motor in tow.Spurred by the burgeoning scene, there was a progressive increase in the number of VTEC-equipped engines. In 1991, about 5 percent of all Honda engines had VTEC technology. That number increased to 25 percent in 1995, 65 percent in 1999, and 80 percent in 2001.
Remember, the valvetrain engineers were focused on economy and made VTEC variants for nearly every model. From high-performance machines, like the NSX, to the economy- and ecology-conscious hybrid Accord and Civic, VTEC is proudly badged on the valve cover. Even the Odyssey minivan and the Pilot SUV can brag about having the spirit of VTEC.In 2001 Honda released its next iteration of VTEC, i-VTEC, in its new K-equipped Civic Si. The "i" stands for intelligent, and incorporates VTC (Variable Timing Control), which is variable cam phasing on the intake cam. It takes VTEC to another level by optimizing the cam timing in addition to the valve timing and lift. The cam timing is computer controlled and optimizes the engine's performance at different rpm under different load conditions. This not only improves economy but also increases power. Imagine having timing gears that self-adjust and optimize throughout the rpm band.
Honda's i-VTEC continues to maintain an industry presence. On the drag racing front, Skunk2 has K-powered all-motor cars ripping the quarter mile in 9.85 seconds, while Papadakis is still taking his AEM RWD Pro Civic into record-setting territory. In the relatively new sport of drifting, Alex Pfeiffer and Papadakis are both campaigning Honda S2000s. VTEC continues to contribute to motorsports around the world, from drag racing and drifting to time attack and autocross.
On July 5, 2005 Honda announced the latest i-VTEC motor will debut in the new 2006 Civic. This 1.8-liter i-VTEC powerplant is the face of things to come. With economy and performance as its priorities, it appears to be the jack-of-all-trades. This motor promises to have the acceleration of a 2.0-liter but get the mileage of a 1.5-liter. Honda states that the i-VTEC system will switch to a highly efficient valve timing mode for acceleration and torque, then switch to an economy mode when cruising, delaying intake valve closure to promote enhanced fuel economy. When cruising, the throttle plate will be only partially opened. Therefore, only a limited amount of air is allowed to pass and creates "intake resistance" which translates into pumping loss. The delayed intake valve closure helps to reduce pumping loss by up to 16 percent, according to Honda. In addition, friction-reducing measures were taken throughout the engine to further increase overall efficiency.
So what's in the future for this pedigree of power and efficiency? Honda is working toward incorporating i-VTEC technology into most of its lineup. In addition, an advanced VTEC engine is slated to be released, sporting continuously variable-valve lift control and phasing of valve switchover timing. In conjunction with a variable-length intake manifold, the advanced VTEC engine anticipates having a 13-percent increase in combustion efficiency over current i-VTEC powerplants. We can hardly wait.
NOTE : PLEASE PROVIDE THE LINK, TO THE ORIGINAL ARTICLE
Last edited by Shan2nu : 17th December 2005 at 18:16.
|17th December 2005, 18:16||#2|
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Nice one. It really explains what Vtec is all about. Contrary to popular belief, Vtec isn't about power, it's about FE along with the already existing power.
|17th December 2005, 19:39||#4|
Senior - BHPian
Join Date: Feb 2004
Location: Hubli - Karnata
Thanked: 87 Times
Redlining a Vtec engine all day long wont help improve your FE. It has to be driven correctly to xtract the most out of it.
So, you not only get great performance but also, good FE. You just need to use your accelerator to switch between the 2 modes.
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