All VTECs are not created equal

[TJ213]

All VTECs are not created equal
An explanation of the various types of VTEC

I recommend watching this video, if you are anything like this guy you NEED to read this article.
YouTube - VTEC Cobra

What is VTEC?
VTEC stands for Variable Valve Timing and Electronic Lift Control, it allows Honda to specify different values when a valve is opened, and how much it is opened depending on a variety of factors.

The biggest factor is RPM, in engines with static lift and duration would be restricted to a setup that would let in enough air and fuel at a low RPM would not allow enough air and fuel in at a higher RPM, greatly limiting the engine’s potential performance.


However, if the timing and duration were setup so that enough air and fuel was let in so that the engine would produce a lot of power in the higher revs, the engine would not run smoothly at low RPMs, and would not idle well.

VTEC - the original formula

The original VTEC first appeared on the 1989 Integra in Japan. Using a B16A engine it produced 160hp, reaching the “magical” 100 hp per liter mark. In the United States this new technology was first seen in the 1991 NSX, and soon became more available as it became integrated into cars such as the 1992 Integra GS-R.

VTEC gave the engine two camshaft profiles, one for efficient smooth reliable low RPM operation, and one for power at high RPM operation. The profiles were switched based on oil pressure and engine speed. Oil pressure increases as RPMs increase, the engine uses this increased oil pressure to push a locking pin, which activates the high RPM cam profile.

DOHC

In double overhead cam engines the cam profiles change on both the intake and exhaust valve camshafts


SOHC

In single overhead cam engines the cam profiles change only on the intake valves


I thought that was it, I mean, VTEC is there for that high RPM performance kick, right? WRONG

This is what makes VTEC such a complicated system to understand as a buyer. Not all VTEC systems use the performance cam profile that is coveted by Honda enthusiasts.

VTEC-E

Available on SOHC engines, such as the 3-cylinder engine on the insight, VTEC-E was a version of VTEC that was designed purely for fuel economy. When running at lower RPMs one (of two) intake valves is only opened slightly, making the mixture leaner (lower gas to air ratio) saving fuel. As engine speed increases the valve is opened normally, the system is activated the same way VTEC is activated.

3-Stage VTEC

The VTEC D15B combined the technologies of VTEC and VTEC-E in one engine. It uses a single intake valve at low RPMs, saving fuel. At medium engine speeds the engine uses both intake valves, but is still on the low RPM cam profile. When the engine reaches up into the high RPM range it switches to the high RPM cam profile. This combines the improved performance of VTEC and the fuel economy advantages of VTEC-E

i-VTEC - The next generation of VTEC

Intelligent VTEC, although i-VTEC still uses distinct low and high rpm profiles for valve lift and duration, the intake camshaft can now variably advance 25 to 50 degrees during operation, this advancement is known as phase changing. A computer controls these phase changes through an adjustable oil driven cam gear. The computer makes these changes depending on engine load and RPM. The advantage of this technology is it helps to optimize torque output, mostly at low to midrange engine speeds.

i-VTEC for power

Used in the k series engines in the RSX-S, 8th generation Civic Si, and TSX, the performance version of i-VTEC uses high and low cam profiles like that in the older performance oriented VTEC, with the addition of the variable camshaft phasing. This gives these engines a relatively high amount of horsepower in the higher RPM range, and a smooth torque curve throughout the entire rev range.

i-VTEC for fuel economy

The other form of i-VTEC is used in the CR-V, Accord, 7th generation Civic Si Hatch, and Base RSX is made for fuel economy. This form of VTEC is similar to VTEC-R in that it has no VTEC on the exhaust cam, and controls the intake valves like VTEC-E does, providing a leaner mixture at lower engine speeds improving fuel economy.

i-VTEC with a different i

Okay, the “i” does still stand for intelligent, but in the J series engine in the 2004 Odyssey the i-VTEC is not talking about cam phasing, it is talking about VCM, Variable Cylinder Management. This technology effectively shuts down 3 cylinders by closing the valves on those 3 cylinders. This is done when the engine is not under load (cruising on level ground) at speeds less than 80 mph. VCM has also been used in the Accord Hybrid, and 2006 Pilot.

i-VTEC in the R18

The R18 engine used in the 2006 Civic gets another form of i-VTEC. This 4 cylinder SOHC engine uses economy cams. These cams cause one of the intake valves to delay closing until the piston has started moving up. This pushes some of the mixture already in the engine back into the intake manifold, making the engine run as if it was a smaller displacement engine. These economy cams are only used under light load, low RPM conditions.

i-VTEC Turbocharged

According to the Acura website the RDX uses “the latest version of i-VTEC” which has the ability to adjust timing and lift of the intake valves, achieving high RPM horsepower and low RPM torque.

advancedVTEC – The Future of VTEC

A new version of VTEC has been announced called Advanced VTEC, this new version of VTEC combines continuously variable valve lift and timing control with continuously variable phase control of variable timing control. This gives the engine complete control of intake valve lift and phase in all driving conditions at all engine speeds. Honda claims a 13% increase in fuel economy and a increase of torque across all engine speeds.

[mandipvtec]

Can a V6 Accord be a SOHC?

[mandipvtec]

Does anybody know where I can find a turbo for a V6 Accord?

[TJ213]

the v6 accord is SOHC

[EyesofFreedom]

how can you have a single cam on a v motor=2 heads?

one cam per head right?

[TJ213]

sohc - one cam per head
dohc - two cams per head

it is independent of the number of heads

[EyesofFreedom]

i know that...it is just the way he asked it.

sometimes it is fun to mess with people

[da-dale]

I have a sohc v6 accord and it is a j30a engine with 200hp. A turbo is allways nice and so is naturally asperated engines but there is a supercharger that comptech makes for the accord that will make it sweet.

[madriano]

Yes a v6 can be a V-tech

[chuckles]

are you for real with that vtec powerd mustang video ?if so why would you want too?