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Discussion Starter · #1 ·
This is a very detailed page on Honda's VTEC technology. Enjoy!

What is VTEC?

Born some 100 years ago, the engine was, until VTEC (Variable Valve Timing and Lift Electronic Control), a clever balancing of compromises.

Improvement in one area was always achieved at the expense of another area. As "Driveability in everyday use" went up, "Outright performance" would go down, and vice versa.

Until VTEC, privileging ease of use affected outright performance. On the other hand, the pursuit of performance meant reduced drivability in everyday use.

VTEC was the first technology to make them equal.

Combining drivability in everyday situations with outright performance is what VTEC is all about.

VTEC: an entirely new approach to engine design
A 4-stroke engine goes through induction, compression, combustion and exhaust strokes to generate power. Before the advent of VTEC, the valves controlling the intake and exhaust strokes were operated according to fixed rules.

If the intake valves were made to open a relatively small amount to privilege drivability at low engine speeds as used in normal driving conditions, the engine would not be allowed to intake enough air at higher engine speeds, sacrificing outright performance. On the other hand, if the intake valves were made to open wide to privilege breathing at higher engine speeds, performance at low engine speeds would be compromised. This is a dilemma that has plagued engines for over a century.

The new approach was to regulate valve operation to optimize performance at all engine speeds: opening the valves a small amount at low engine speeds, opening the valves wider as engine speed increases. That’s the breakthrough we named VTEC.

Optimizing engine breathing: how VTEC works

An elegant, simple mechanism switching between high and low valve lift using two cam profiles and two rocker arms per cylinder.

The switch is made using hydraulic pressure to push/release the sliding pin, locking/unlocking the middle rocker arm and the other rocker arm.

At low engine speeds, the pin is retracted, disengaging the middle rocker arm. The valves are operated by the two outside, low-profile cams for a low valve lift.

At higher engine speeds, increased hydraulic pressure pushes the pin, engaging the middle rocker arm. The valves are operated by the middle, high profile cam for high valve lift.

VTEC: a deceptively simple mechanism that uses hydraulic pressure to switch between different cam profiles.

More about VTEC
Honda said:
100 years after the engine was born, VTEC technology finally reconciles drivability in everyday use and outright performance, creating the first uncompromising engine.

The 1989 Integra XSi/RSi were the first models powered by VTEC engines. They combined superior everyday drivability with a specific output of 100PS per liter of engine capacity, at the time an unheard of feat in a production engine.
1.6-Liter DOHC VTEC, Max. Power 160PS/7,600rpm (net)

The 2004 Legend is powered by a 3.5-Liter VTEC engine, the biggest engine in Honda’s line-up. It combines impeccable manners in everyday driving together with an outstanding maximum output of 300PS.

More Links
- VTEC at Wikipedia
- VTEC at Howstuffworks

Source: Honda

16 Posts
here is a few useful vid's i like to watch on utube, helps put things in to perspective !



7,629 Posts

Introduction to VTEC

The i-VTEC system found in the Honda K20Z3.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 (TDC or BDC). 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.

VTEC was initially designed to increase the power output of an engine to 100 ps/liter 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, or increased power output as well as improved fuel efficiency.

In practice, a fully variable valve timing engine is difficult to design and implement.

The opposite approach to variable timing is to produce a camshaft which is better suited to high RPM operation. This approach means that the vehicle will run very poorly at low RPM (where most automobiles spend much of their time) and much better at high RPM. VTEC is the result of an effort to marry high RPM performance with low RPM stability.

Additionally, Japan has a tax on engine displacement, requiring Japanese auto manufacturers to make higher-performing engines with lower displacement. In cars such as the Toyota Supra and Nissan 300ZX, this was accomplished with a turbocharger. In the case of the Mazda RX-7 and RX-8, a rotary engine was used. VTEC serves as yet another method to derive very high specific output from lower displacement motors.

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.

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.

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.

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 (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 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.

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.

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.

and a personally think the h22 is still the best engine for all round driveability , just my humble opinion thou :)

Premium Member
7,193 Posts
Just thought id add this that i found over google.

Vtec troubleshooting Credit goes to Gs-rDelsol on JDM Universe.

1: Oil level, it has got to be FULL. I'm talking at the upper mark on the dipstick.

2: Solenoid, Ok this is a 2 part fix.

A: Take a wire (any wire) disconnect the grey plug on the vtec solenoid and
touch the wire to the pos. battery terminal and the solenoid side of the grey
1 pin connector. there should be an audible click from the solenoid.

B: If A checks out, remove the solenoid and clean the filter screen. (self
3: Speed, the car must be going over 10 mph so the Speedo must be working. That
means the VSS has to be working. Vtec is temperamental isn't it?

4: More oil, check the oil pan. If its dented POUND IT OUT! This is why mine
wasn't working. The pan was dented in far enough to hit the oil pickup for the
pump to cause a low-pressure situation in the head, no pressure no VTEC plus
eventually no engine.

5: ECU Swap out to another ECU that you KNOW Vtec works on.

6: Car must be at I believe its 80 degrees or higher so let car get to a normal
operating temperature.

7: If none of the above work, you might want to pull the solenoid off the head, remove the solenoids filter and verify the piston moves freely.

3,393 Posts
there are lots of versions of vtec. The version you have it not for performance, its just part of the way the engine runs.

The type-r which uses the K20 engine has vtec designed for performance aswell as the B16 and B18 engines.

If you look on wikipedia there is a page describing all the different kinds of vtec, about 11 I think.

People need to stop thinking of it as a performance thing nowadays as afaik ALL honda engines use a vtec system. Its a variable valve system, nothing more.

7 Posts
ryan. said:
there are lots of versions of vtec. The version you have it not for performance, its just part of the way the engine runs.

The type-r which uses the K20 engine has vtec designed for performance aswell as the B16 and B18 engines.

If you look on wikipedia there is a page describing all the different kinds of vtec, about 11 I think.

People need to stop thinking of it as a performance thing nowadays as afaik ALL honda engines use a vtec system. Its a variable valve system, nothing more.

Thanks ryan!!! i ll have a look on wikipedia. cheers

231 Posts
okay so what about the d15z6 Vtec-e haha.
another way you could of said it was just:
oil pressure is built and then solinoid releases and locks the middle lobe with the two outer lobes, this gives a larger diamitor of lobe pressing onto the valves to allow them to stay open longer. longer valve duration more air/fuel can enter the cylinder.
so Eco v tec works the opposite the oil pressure is dropped in any gear at under 2k rpm. this releases one valve per cyinder, so ends up runing on 12valves. which give good cruzing speed but great mpg. 45 roughly.

1 Posts
Improvement in one area was always achieved at the expense of another area. As "Driveability in everyday use" went up, "Outright performance" would go down, and vice versa.:lol::lol:
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