Is Vtec superior than Dual VVTi?

[Axela72]

As per above caption and advise why do you think so.

 

Cheers!

[Ithunk]

VTEC but lazy to explain

[Tleslie]

VTEC...

cos i am driving one

[Mach23]

Vtec cos VVTI works just on timing of the cam shafts while Vtec literally Lift the shaft higher for greater combustion which translate into pulling power past 4,600 rpm.

Edited July 26, 2009 by Mach23

[Ithunk]

SOHC VTEC

 

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 was that Honda's SOHC engines only benefitted 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.

 

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, thus 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 secondary intake rocker arm contacts a low-profile camshaft lobe during low-RPM engine operation. Once VTEC engagement occurs, the oil pressure flowing from the intake rocker shaft into the primary intake rocker arm forces the VTEC switching piston into the secondary exhaust rocker arm, thus locking both intake rocker arms together. The high-profile camshaft lobe which normally contacts the primary intake rocker alone during low-RPM engine operation is able to move both intake rocker arms together which are locked as a unit.

 

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.

[Ithunk]

VVTL-i

 

In 1998, Toyota began offering a new technology, VVTL-i, which can alter valve lift (and duration) as well as valve timing. In the case of the 16 valve 2ZZ-GE, the engine has 2 camshafts, one operating intake valves and one operating exhaust valves. Each camshaft has two lobes per cylinder, one low rpm lobe and one high rpm, high lift, long duration lobe. Each cylinder has two intake valves and two exhaust valves. Each set of two valves are controlled by one rocker arm, which is operated by the camshaft. Each rocker arm has a slipper follower mounted to the rocker arm with a spring, allowing the slipper follower to move up and down with the high lobe without affecting the rocker arm. When the engine is operating below 6000-7000 rpm (dependent on year, car, and ECU installed), the low lobe is operating the rocker arm and thus the valves. When the engine is operating above the lift engagement point, the ECU activates an oil pressure switch which pushes a sliding pin under the slipper follower on each rocker arm. This in effect, switches to the high lobe causing high lift and longer duration.

[Ithunk]

Vtec cos VVTI works just on timing of the cam shafts while Vtec literally Lift the shaft higher for greater combustion which translate into pulling power past 4,600 rpm.

 

LOL i think yr explanation is better

[Benarsenal]

Double post. Paiseh.

Edited July 26, 2009 by Benarsenal

[Benarsenal]

They're not really the same.

 

VTEC is more for power. VVT-i is more for durability and efficiency.

 

Although, VTEC is also very durable.

[Watwheels]

Dual VVTi is the same as DOHC i-VTEC.

 

Both have variable timing of opening & closing on the air intake valves and exhaust valves.

 

Like Jeremy Clarkson says it's playing with the "clever" valves.

Edited July 26, 2009 by Watwheels

[Axela72]

Isn't the words "DUAL" means double? Twice the performance of VVTi doesn't means double orginal performance? Does those who vote for VTEC is better means that VTEC is more than twice the performance of single VVTi?

 

If that is true, why people classified Honda and Toyota under the same level but not Honda is more than twice premium/performance than Toyota badge?

[Boyboy]

As per above caption and advise why do you think so.

 

Cheers!

 

nonsense poll again.

 

what u want? u want brute power from the smallest CC? then TC is the way, not vwhateverucallit

 

u want refined linear power? big cc is the best.

 

u want economy and the best low end? turbodiesel

 

u want high bhp sh!t low end small cc? then u got ur (wild cam) vtec.

 

choose your cake and eat it. but everyone wants different flavour of cake

[Vextan]

vtec is just a term used by honda to charge higher price.

[Axela72]

Dual VVTi is the same as DOHC i-VTEC.

 

Both have variable timing of opening & closing on the air intake valves and exhaust valves.

 

Like Jeremy Clarkson says it's playing with the "clever" valves.

 

 

OIC.

 

So does the mean VVTI is the same as SOHC i-VTEC? Is that is so, why most ppls mention VTEC is good but seldom ppls mention VVTI is good? In my understanding, VVTI is known as "common" only.

[Ithunk]

its 2 different technologies man

[Goincrazy]

i think vtec is mainly for more power at higher rpms while vvt-i is for better fuel economy??

[Detion]

Dual VVTI and I-vtec is similar technology.... using different name... the I-vtec used in cars like civic, city is not the old vtec where there the vtec will open.. The real vtec now only found in cars like type r.. VTEC is always mention because of marketing... Marketing always can psycho people to believe that certain things are better. Examples are like Iphone vs other smartsphones, Ipod vs other mp3 players.

[Watwheels]

The concept is the same cos both have variable timing only on the air intake valves. The application is slightly different and the difference is in their cam shaft design that control the valves.

 

Both have different target audience and different marketing strategies. T always go for fuel economy image. H go for sportiness image. To me it's all marketing, concept is still the same.