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Jun 01, 2023

Honda VTEC Engine History and Technology

Related Video Though it's been called many things, the VTEC acronym stands for Variable Valve Timing and Lift Electronic Control. VVTLEC doesn't quite roll off the lips, but the adjectives one tends

Related Video

Though it's been called many things, the VTEC acronym stands for Variable Valve Timing and Lift Electronic Control. VVTLEC doesn't quite roll off the lips, but the adjectives one tends to spew out after experiencing it for the first time do. They run the gamut but almost always include the "F-word." Ol' Soichiro-san would've been pleased. April 2019 marked the 30th anniversary of VTEC in the automotive world. The 1989.5 Integra XSi was the first production Honda that featured the technology. Shortly after, Civics and CRXs received the same B16A engine.

But all of this began much earlier—sometime during the early 1980s, in fact—and none of it had anything to do with automobile engines. The technology behind VTEC originated from Honda's motorcycle side. Honda's engineers knew that four-valve engines made great top-end power, but that two-valve ones were more competent down low, and even idled nicely. The quest soon became for a 500cc engine that would spin to 11,000 rpm yet idle patiently at a mere 1,000 rpm. The result was what Honda internally labeled as its "REV" mechanism, or "HYPER VTEC" to the rest of us. The technology allowed for only one intake and one exhaust valve per cylinder to operate below certain engine speeds but for two intake and two exhaust valves per cylinder to function above that threshold. It allowed for the best of both worlds.

Honda launched the NCE (New Concept Engine) project in 1984, which aimed to push the limits of top-end torque production without sacrificing low-end performance. Japanese-market '85 Civic and Integra engines were the result of this project. More important, though, it convinced engineers that a dual-camshaft profile—or a mechanism that could dynamically alter camshaft timing—must be a part of the company's next-generation engine. Engineer Ikuo Kajitani, who was a part of the NCE team, was particularly enthusiastic about making this happen. The ideal engine would have better fuel economy and a higher output across the entire powerband—specifically, about 90 hp per liter. But 90 hp soon began to seem too low; it was, after all, only 10 more than the engine they'd just produced. Based on the suggestion of then Honda R&D president Nobuhiko Kawamoto, a new goal of 100 hp per liter was set.

"It felt like a dream," Kajitani recalled. "Conventional engines in those days could only produce 70 or 80 hp per liter. But here we were, being asked to increase it all the way to 100 horses. It wasn't going to be easy. An engine becomes subject to a higher load as you increase its rpm," Kajitani said. "So, we had to keep in mind the quality-assurance target of 15 years, or 250,000 km, for a mass-production engine. We all wondered how on earth we were going to reach that number while ensuring the required quality of mass production." After all was said and done, Kajitani officially set the goal for the new VTEC Integra engine: 160 hp and an 8,000-rpm redline. A goal is one thing, but the technology had yet to be created. All of this led to daily arguments about whether or not such an engine was even possible. After three months, Kajitani put it all on the line, ordering his team to move forward. A technology proposal would soon be chosen and developed.

Of course, we know the results, but the time spent developing VTEC proves to be as fascinating as the final product. Take the camshaft gears, for example—engineers elected to build these out of a new high-strength sintered alloy for a thinner profile and a 10-percent lower moment of inertia. The intake valves were increased to 33mm, a then unheard-of size for such a small engine. The VTEC valve timing and lift specs were similar to race-only engines of that period. To prevent breakage, VTEC camshafts were made from a completely new high-carbon, high-chrome cast-steel alloy, which was given a combination of heat and surface treatments.

Even the exhaust valves were made of nickel-based, heat-resistant steel combined with molybdenum, titanium, and tungsten—not your average mid-'80s economy car technology. And all of this had to be durable. This is perhaps where Kajitani's team did its greatest work. Gearboxes, crankshafts, and many other Honda components have become legendary for the abuse they can handle. "That's why we so thoroughly carried out our malicious tests," Kajitani said. "We were very near the point of overdoing it." Building a VTEC pin-engagement system that could endure 400,000 cycles is arguably a masochistic endeavor. No one knew the impact that VTEC would have. It's likely that in Japan there were smiles, but the reality was that Honda was a much smaller player in its homeland, so even there, such an event fell short in terms of hype, and would have paled in comparison to things like the introduction of the new GT-R. Today is different; you're reading an article from a magazine devoted entirely to the brand. The rest, as they say, is history.

America's first exposure to VTEC came in the form of the '91 Acura NSX. However, because of the NSX's supercar personality—in terms of price and availability—the '92 Integra GS-R is often credited as being the U.S. 's first real taste of VTEC. Yes, the D16Z6 was released around the same time, but SOHC VTEC powerplants simply didn't excite anyone back then. By 1994, Honda had its pieces in place and was poised to put its competition in checkmate. The company released three powerhouses practically at once: the redesigned Integra GS-R's B18C, the Prelude Si VTEC's H22A, and the Del Sol Si's B16A. Combine that with the attention that the second-generation CRX and '88-current Civics had garnered for themselves and the company soon had the makings for a new super-drug. The sport compact juggernaut as we know it was just getting started, and Honda's timing couldn't have been better. It's possible that VTEC even turned the sport compact molehill into the mountain that it is now; today, there are whole companies that exist because of it. Sure, many would modify Hondas were VTEC to have never existed, but it'd be like swimming in the kiddie pool.

Hasport is one such business. Everyone knows that the GS-R's B18C is cool, but it's even cooler when swapped into a lighter, smaller '92 Civic hatchback. To be fair, the business of engine-swapping is an industry all its own. Just think: If it weren't for engine swaps, the GS-R wouldn't top the country's most-stolen-cars list year after year. When asked where he thought he might be now had VTEC never been invented, Brian Gillespie, Hasport's frontman, simply said, "I'd be a tennis pro! I'd recently started working for my brother at his Honda-only junkyard with the promise of my own racecar. I'd grown up racing motocross, and my brother's '90 CRX was really fast. But honestly, if I hadn't taken the bait, I'd still be teaching tennis and driving my Volkswagen GTI. That was the only real alternative to Honda and that is what I would be driving and modifying if it weren't for VTEC."

ECU-tuning company Hondata owes homage to VTEC arguably as much as companies like Hasport. The company was started by a couple of Kiwis who had a passion for racing and continue to today. Co-owner Doug MacMillan says, "We built our business around what the aftermarket tuning community was doing with Honda engines, especially forced induction. It's fairly safe to say that modifying Honda engines has been central to the sport compact car scene, and the VTEC system has allowed Honda to stand head-and-shoulders above the crowd. Had Honda not created VTEC, Honda would have been more like one of the crowd, with fewer people selecting their cars and engines for modification. We would still be doing what we are now, which is building great programmable engine management systems for Hondas and Acuras, but we would be doing fewer of them."

But what about racing? Although the need to implement VTEC into Honda's championship Formula 1 engines wasn't there, the technology played a major role in early import drag racing. When asked how VTEC helped shape sport compact drag racing, longtime drag racer Stephen Papadakis said, "The VTEC cars weren't as fast as the non-VTEC ones until 1997 or so. The scene was well on the way at that time." This is likely true; Mitsubishi's DSMs had been out for some time and tuners were getting decent numbers from non-VTEC Honda engines. "When the '94 Integra GS-R came out, that was when Japan finally gave the U.S. market a good engine. That car was fast! That was when VTEC changed from trendy to fast, in my experience," Papadakis says.

The late '90s was an explosive time for Honda enthusiasts. The GS-R was selling in large numbers and Honda finally got wise and released the B16A-equipped Civic Si. The VTEC experience was so strong for one old-school gearhead that he went so far as to purchase a brand new Si just for development purposes. Up until the release of the '99 Si, John Grudynski, owner of HyTech Exhaust, had only manufactured his custom-made headers for race cars, Formula Fords, Indy cars, and other spec classes. He was soon hooked on VTEC though. "It was 1998 and Dan Paramore took me for a ride in an ITR and I was blown away with the performance of it. I didn't even know what VTEC was or how it worked then, but it piqued my interest for sure. The rest is history," John says. Today, HyTech's Honda-specific headers work so well that they've been copied time and again, despite the company's best efforts to keep its designs exclusive. Though many recognize the value of a HyTech-style header, only a select few pay for the real thing. Despite the piracy, John says that without VTEC and Honda's popularity, he'd basically be out of work. "About one-third of my business is from [Hondas], the rest is the Formula car stuff and miscellaneous junk," he says.

It's difficult to quantify the impact that VTEC's had on the average enthusiast, but I can do so for myself—it had to do with a brand-new '94 Integra GS-R that I paid the full sticker-price for. It may sound strange today, but the purchase was a toss-up between the GS-R and a Ford Probe GT. As odd as it may sound, the Probe was a serious sport compact contender in 1993. It wasn't bad-looking and its V-6 made nearly as much power as the 170-hp Integra.

Today, there's little I remember about test-driving the Probe. The GS-R is a different story. It was visceral, so much so that I remember details about that day that I shouldn't, like the shirt I was wearing. It's like mental playback in IMAX. I wasn't going all that fast and I found myself in third gear, so I floored it. Not too impressed initially but then came the "boom," and the engine's tone changed completely. As I let off the gas and my sphincter unloaded a brick I contemplated just how much this blown-up VTEC engine was going to cost me. As I coasted down, I realized that the engine was still running, and that the tie-guy sitting next to me was laughing at me.

"That's the VTEC," he said. "Come on, go again, but don't lift off, it's supposed to do that." There was no use hiding the embarrassment; I just obeyed, this time using second gear since we'd slowed so much. Bam! It came again and then, seemingly a mere half-second later, once again. I almost lifted, but I kept getting the "go-go" hand signal from the passenger seat. Up through third and far beyond the speed limit, there was just no way I was going to buy anything else. Twice on the way back, I deliberately slowed down just to hear it kick in again … the sound, the pull, the way it would go to 8,000 rpm so easily. Despite the years of screwing around with cars, up to this moment, there had been nothing like it. Later on, at the dealership, as I was looking under the hood, drooling at the sight of the engine, I noticed that the air filter was exposed. I asked the salesman if it was supposed to be like that and he said, "No, we take the lid off so it makes more noise when VTEC turns on." My head clocks from the filter back to him, and there's his wide smile. No wonder they were getting full sticker-price for these cars, and I was stuck waiting for the next shipment.

Others have had similar experiences. Larry Widmer, owner of Endyn, says, "In 1992 I was driving my Civic Si and a kid in a '92 GS-R decided to test me. I won the impromptu street race … barely. The kid followed me to a nearby parking lot and we looked over each other's equipment. From the sound change his car made, I figured he had nitrous, but it turned out to be the VTEC event. He took me for a ride and I was amazed at how hard the relatively stock car pulled. I remember thinking, 'what a great thing Honda's come up with. '"

When it comes to competing technologies, they're out there, but nothing seems to touch VTEC. Today, nearly all automakers offer variable valve timing, or VTC as Honda now refers to it for its K-series engines. It wasn't until recently that other automakers implemented a true variable-lift system in its engines, though. Now the new 370Z, the Porsche 911, and BMW engines all have it, and there are others. Interestingly enough, those that have the VTEC-style moniker on them don't even have variable lift. The Evo's MIVEC engine only has variable camshaft timing—not lift—even though the original MIVEC iteration featured both, just like today's i-VTEC.

Honda's since aimed to take its technology one step further with continuously variable valve lift, the so-called Holy Grail of internal combustion engine control. An electronic or pneumatic valvetrain could accomplish this. The premise is that the valve could open any amount at any time. Patents have been filed and it even has a name: A-VTEC—another clever acronym that, this time, stands for Advanced VTEC. Unfortunately, budgets and a slowing demand have put A-VTEC in the tech freezer for the time being. BMW's similar Valvetronic system has gone into production, however, so maybe there is a future for A-VTEC.

It's somewhat amazing, all these years later, to muse about what exactly VTEC's done for Honda enthusiasts. Love it or hate it (you only hate it when a VTEC engine beats your non-VTEC engine), this is the stuff that will go into the engine hall of fame. Instead of another Fast and Furious, Hollywood should do a Mad Max spin-off that depicts the realities of a huge fuel crisis, where turbo Civics and Integras kick everyone else's asses. Or, as Papadakis puts it, "We raced with a 650-800-hp H22A VTEC engine for years with no porting and stock cams. That just shows the potential of what Honda developed and sold to the general public."

Editor's note: This story was originally published in the May 2009 issue of Honda Tuning and has been lightly edited. Lead image design by Markas Platt and additional photo work by Ryan Lugo.

The results are high-rpm power and low-rpm torque, but the system's simplicity is arguably its most amazing attribute. It's almost entirely mechanical, with the exception of the pressure sensor and VTEC-specific ECU. It's also durable, and the design specifications called for 400,000 engagements, but at an astonishingly low cost.

Stick out the three longest fingers on your hand and put them together. Unless you've got unusual hands, your middle finger will be the longest. In simple terms, this is what a single cylinder's camshaft lobes on a VTEC cylinder head look like. Pretend that those three fingers are a paintbrush and that you're painting your desk. Your middle finger hits the surface first. But what if the desk was soft? What if when you pushed on it, it gave way, much like a spring would? If it did, your first and third fingers would rub or "paint" the desk next. Imagine your middle finger as the largest cam lobe, and imagine a spring that's positioned directly underneath it. Honda calls this its LMA (Lost Motion Assembly).

In non-VTEC or primary-lobe operation, the two outer two lobes (your first and third fingers) open the valves. Such camshaft profiles provide for a nice idle, excellent emissions, and immediate torque. Moving up the powerband, there might be as much as a 20-percent loss in power compared to a camshaft that was designed to go past 6,000 rpm. The valves open via rocker arms, not unlike what you'd find on a pushrod V-8 like a Chevy small-block. There's a rocker for each valve, but there's also one in between each of them—a characteristic that's nothing at all like that small-block. Once VTEC is activated, the middle rocker arm is put into action. Do that same thing with your three fingers again, but this time keep in mind that the desk is rigid. Notice how only your middle finger touches the desk. The middle finger's added length represents the middle lobe's added lift. But it isn't just its lift; the VTEC lobe is different in every way from the outer two lobes, like its duration, hence the whole variable valve "timing" and "lift" part of the VTEC acronym.

A single pin is all that's responsible for allowing the middle camshaft lobe to control valve movement instead of the outer two. It's simply pushed from one of the outer rocker arms, via oil pressure, toward the middle rocker arm, engaging both about halfway through. This locks the two arms together. Meanwhile, another pin moves from the middle arm toward the opposing outside arm by the motion of the first pin, also about halfway through. All three rocker arms are now locked into place, essentially acting as one big rocker arm. Of course, only the large VTEC lobe will control the valves at this point, since it's the tallest of the three. Once oil pressure subsides, a spring pushes everything back into position and the smaller outer lobes once again take over.

It's simpler than it sounds, and the whole system only requires a few extra parts per cylinder. There's the extra rocker arm, its respective LMA, the pins, and the extra cam lobe. Multiply all of that by eight and you've got the makings for a typical DOHC VTEC configuration. All of this is activated by a 12-volt signal from the ECU to the VTEC solenoid, which pressurizes the oil channel inside the rocker arms for pin movement. Once the ECU stops sending the signal, and oil pressure drops, VTEC shuts off. The whole thing is triggered based on a specific engine speed, which varies by ECU and by vehicle.

The "i" in i-VTEC stands for "intelligent." The system features variable camshaft timing, but the "VTEC" part doesn't exactly stand for VTEC as we know it. Let's start with the variable valve timing part. Nearly everyone's seen aftermarket adjustable cam gears. Honda's i-VTEC system dynamically adjusts camshaft timing using an oil-driven system that positions the camshaft within a 50-degree timing range depending on the circumstances. It's a heck of a lot easier than loosening and tightening a bunch of cam gear bolts just to pick up a few horsepower. The technology is only featured on the intake camshaft, and is almost exclusive to the K-series. Alone, Honda refers to it as VTC (Variable Timing Control). The obvious benefit is improved emissions. At startup and while idling, the camshaft can be retarded, reducing valve overlap for cleaner combustion. It also works well for midrange power. Advancing the intake cam in the low- and midrange areas provides a noticeable bump in torque. To date, Honda has not used this technology on the exhaust side.

Honda's also been known to match i-VTEC on engines for use as a valve-idling mechanism rather than a timing- and lift-oriented one. This system operates a single intake valve per cylinder until the VTEC mechanism locks the two intake rocker arms together, causing both intake valves to open. It's not the three-lobe mechanism we're accustomed to by any means, but it's still referred to as VTEC. K-series engines like the Accord's are different. Here, i-VTEC allows for variable intake camshaft timing as well as the valve-idling mechanism. Most SOHC engines like the L-, R-, and J-Series engines simply take advantage of the valve-idling, where as few as 12 out of the 16 valves can operate at a time. The "intelligent" camshaft timing changes won't work with SOHC engines like these, since both the intake and the exhaust share the same camshaft gear.

A-VTEC is the pinnacle of camshaft timing. It'll allow for continuously variable camshaft timing and lift. Much like a pneumatic or an electronic valvetrain promises, the valves would be able to open at any time, for any amount of time, and at any lift. Of course, this all depends on whether or not the technology goes into production, as it hasn't made its way onto any Honda yet. At this point, it's little more than a patent application.

As you might have guessed, the "A" in A-VTEC stands for "advanced." In A-VTEC systems, the camshaft remains enclosed within a sleeve, with openings between 270 and 360 degrees of camshaft rotation. Also occupying that space is a semi-rocker arm that features a roller, spanning the same 270-360 degrees, which rides along the camshaft lobe. The system also features a "shoe" that's positioned on top of the roller for the conventional rocker arm (the one that actually activates the valves) to ride on. The previously mentioned sleeve also traps the semi-rocker arm. The semi-rocker arm features a curved profile—it's thick on one end, thin on the other. The sleeve rides along a gear positioned on its bottom side that controls the orientation of the semi-rocker arm.

From here, it's relatively easy to see how the variable lift part happens. As the gear that's attached to the camshaft sleeve rotates, the thicker portion of the semi-rocker arm transitions over the camshaft lobe, creating maximum lift. As it rotates the other way, and the rocker arm's thinner portion transitions over the camshaft lobe, lift decreases. It's all kind of like BMW's Valvetronic system, but far less complex and with less reciprocating mass. By adding i-VTEC's VTC system, camshaft timing becomes variable. With both systems in place, there's potential for both economy and efficiency to make significant leaps.