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andreo
26th October, 2010, 04:38 PM
Hello and sorry if i post wrong.


I need some documentation about ,,Variable valve timing''.
I found something on the forum but not much, can someone help me?I understand that are there are 3 types
- i need something about: advantage,disadvantaje,and operation

Thanks in adanice :)

andreo
26th October, 2010, 06:41 PM
Something about ------> VVT

-expect other...............

teuton
2nd November, 2010, 10:14 PM
Here you'll find "something basic about".
Variable Valve Timing (VVT) (http://www.autotropolis.com/wiki/index.php?title=Variable_valve_timing)

andreo
6th December, 2010, 11:04 AM
The name for Variable Valve Timing



Variable Valve Timing, often abbreviated to VVT, is a type of piston engine technology that deliberately delivers inconsistent timing of the intake and/or exhaust valves. The benefit of this is improved gas mileage and flexibility for an engine to deliver peak performance over a variety of driving conditions. For example, traditional piston engines often are required to sacrifice low-end torque for high-end power (or vice versa). A VVT engine more easily accommodates both of these preferred performance conditions.
Variable Valve Timing - How it Works

As with traditional piston engines, VVT engines use cams on a camshaft to drive the flow of air into the intake and exhaust valves. The timing of this valve lift directly affects how much air is taken in during each engine cycle. At times when the engine requires more air flow (for example high speeds or acceleration), a traditional piston engine often does not allow enough air to flow during each cycle, resulting in lower output performance. Conversely, a traditional piston engine that has been designed to feature longer exhaust and intake cycles will result in reduced fuel efficiency at slower speeds.
There are several proprietary VVT engine technologies that work slightly differently to prolong exhaust and intake cycles at high speeds and reduce cycles at slow speeds. The three major solutions to varying the valve timing of an engine are as follows:

The actual timing of the intake or exhaust valves are slowed or sped up as needed
Two sets of cam lobes are utilized and switched between as needed
Timing and lift is continuously altered for maximum efficiency (called continuous variable valve timing)
History of Variable Valve Timing (VTT)

Variable valve timing was originally used in the 19th century to power steam engines. Fiat (http://www.digital-kaos.co.uk/wiki/index.php?title=Fiat) patented the first variable valve timing system for automotive use in the late 1960s. GM (http://www.digital-kaos.co.uk/wiki/index.php?title=GM) also patented an early system in 1975, but scrapped it due to lift problems. It was not until 1980 that a vehicle with VVT technology was made available for the North American market. This was achieved with the debut of the 1980 Alfa Romeo Spider (http://www.digital-kaos.co.uk/wiki/index.php?title=Alfa_Romeo_Spider&action=edit). Throughout the 1980s and 1990s, many automakers followed suit by introducing VVT engines of their own. Notable landmarks include the Nissan (http://www.digital-kaos.co.uk/wiki/index.php?title=Nissan) NVCS (Nissan Valve-Timing Control System) in 1986 and the Honda VTEC system in 1989.
Due to increased pressure from the EPA (http://www.digital-kaos.co.uk/wiki/index.php?title=EPA) and other government agencies, improved fuel efficiency is becoming a major concern for automakers. Today, many of them are turning to VVT technology to accommodate stricter rules and regulations regarding vehicle emissions and efficiency.
Proprietary Terms for VVT

While some automakers simply use "variable valve timing" or "VVT" to denote an engine with such technology, many manufacturers use proprietary technology and therefore affix a proprietary term to distinguish their engines from the competition. Following is a list of terms used by each automaker to denote an engine with VVT technology:

Alfa Romeo (http://www.digital-kaos.co.uk/wiki/index.php?title=Alfa_Romeo) - Twinspark technology
Audi (http://www.digital-kaos.co.uk/wiki/index.php?title=Audi) - VVT
BMW (http://www.digital-kaos.co.uk/wiki/index.php?title=BMW) - Valvetronic, VANOS and Double VANOS
Ford (http://www.digital-kaos.co.uk/wiki/index.php?title=Ford) - Variable Cam Timing
GM (http://www.digital-kaos.co.uk/wiki/index.php?title=GM) - Double Continuous Variable Cam Phasing (DCVCP), Alloytec and Variable Valve Timing (VVT)
Honda (http://www.digital-kaos.co.uk/wiki/index.php?title=Honda) - VTEC, iVTEC and VTEC-E
Hyundai (http://www.digital-kaos.co.uk/wiki/index.php?title=Hyundai) - MPI CVVT
Lexus (http://www.digital-kaos.co.uk/wiki/index.php?title=Lexus) - VVT-iE
Mazda (http://www.digital-kaos.co.uk/wiki/index.php?title=Mazda) - S-VT
Mitsubishi (http://www.digital-kaos.co.uk/wiki/index.php?title=Mitsubishi) - MIVEC
Nissan (http://www.digital-kaos.co.uk/wiki/index.php?title=Nissan) - N-VCT, VVL , CVTC and VVEL
Porsche (http://www.digital-kaos.co.uk/wiki/index.php?title=Porsche) - VarioCam and VarioCam Plus
Subaru (http://www.digital-kaos.co.uk/wiki/index.php?title=Subaru) - AVCS and AVLS ? Toyota (http://www.digital-kaos.co.uk/wiki/index.php?title=Toyota) - VVT, VVT-i and VVTL-i
Volkswagen (http://www.digital-kaos.co.uk/wiki/index.php?title=Volkswagen) - VVT
Volvo (http://www.digital-kaos.co.uk/wiki/index.php?title=Volvo) - CVVT


:wavey:

airbag dude
7th December, 2010, 05:28 PM
In the USA only turbo subaru vehicles include varible valve timing and then only on some models. Here in the states you can get the subarus in three engine variations : 1.plain old engine 2.5L no vvt one cam shaft per side. 2. base turbo around 240hp or 220hp has vvt but only on the intake side has two cam shafts per side. 3. upgraded turbo as on the STI has full vvt both intake and exhaust puts out 305hp also has 2 cam shafts per side. And if you were wondering if it was possible to upgrade your engine to have vvt i would say its not practical as it would cost too much.

Most cars that have vvt dont have full vvt such as the 04-09 prius which only has vvt on the intake side.

losspokos
8th March, 2011, 10:04 PM
Hello
I found several information about multiair:

MultiAir - The ultimate Air Management Strategy (http://www.fptmultiair.com/flash_multiair_eng/home.htm)
http://www.mechadyne-int.com/vva-reference/papers/ETI-lift-off-article-on-vva-2010.pdf

http://www.pattakon.com/pattakonHydro.htm

maby somebody heve more information ,diagrams,methods of stering

I apologize for my english.