VTEC (Variable Valve Timing and Lift Electronic Control) is a technology introduced in 1983 for motorcycles of the company Honda variable valve timing in engines.
The purpose of the system
A variable valve lift is required in order to achieve both a higher overall level of torque at low speeds, as well as a higher maximum power output at high speeds with high rotating sport engines. This is intended to prevent one of the starting weakness and thus increase the suitability for daily use, allow to another from a predefined speed a sportier engine setup. The engine has two camshafts profiles for this reason, because the valves are not controlled directly but via oil pressure-controlled rocker. VTEC was invented by Honda's engine designer Kenichi Nagahiro.
Depending on the engine version ( Eco - engine concept or racing engine ) either another according differently shaped rocker arm is thus above a certain speed by oil pressure with a locking bolt in the oscillating rocker arm system is switched on, which increases the valve opening height and the opening time or another exhaust valve per cylinder, which is the power at higher rpm beneficial. Decreases the engine speed drops below this value, the exhaust valve, or the Zusatzkipphebel is switched off again using the back releasing the locking pin, and remains unused.
The VTEC system is a way to equip a motor with different camshaft profiles:
- An optimized fuel consumption and quiet running profile for low rotational speeds and
- A high- profile optimized for high speeds.
Switching between the profiles is influenced by the following factors:
- Load condition
- Motor temperature
- Water temperature
- Engine speed
- Vehicle speed
If the engine speed increases and all other factors give the green light for a change, opens a solenoid valve, an oil filled channel, the oil pressure actuates a locking pin which connects three separate cam follower or roller cam with each other. The largest (dominant ) cam now takes over the valve control at high speeds. The valve is now open earlier and longer. Moreover, the valve lift is increased by the " high " cam profile. The DOHC VTEC system has these different profiles on both the responsible for the intake valves and camshaft on the exhaust valves.
DOHC VTEC was introduced in the passenger car segment for the first time in only sold in Japan Honda Integra 1989. This had a 119 - kW version ( 160 hp ) of the B16A engine. The U.S. market saw the first VTEC system 1990 Acura NSX. This is used in its V6 DOHC engine. From now on, published DOHC VTEC engines in other models of Honda. The first German models with DOHC VTEC system in 1990 /91 Civic, CRX and NSX.
After the DOHC VTEC system had a lot of appeal found, VTEC was built in SOHC engines. The disadvantage of this transfer is that in a SOHC engine camshaft for intake and exhaust valves is responsible. VTEC the system can be applied only to the intake valves, since the space required for the spark plug to prevent a variable control of the exhaust valves. In SOHC engines, the spark plug must demonstrate at a certain angle in the combustion chamber to effectively ignite the mixture in the cylinder can. This prevents installation way that the exhaust can get a VTEC cam profile.
SOHC VTEC -E
The E stands for economy. VTEC -E uses a modified type of VTEC. VTEC E is not optimized, the performance at high speeds, but the increased efficiency at low speeds.
The camshaft in an engine with VTEC E has two cam profiles for the intake valves. One of these profiles enables the first (and later second ) inlet valve full opening. The other profile is used to open the second inlet valve at the initial time minimal. The valves are opened with roller.
At low speeds, the first intake valve is fully opened, while the second is minimally open. This creates a better air-fuel mixture is achieved, which allows a very lean mixture. If the engine speed is increased, the hitherto only minimally opened second inlet valve coupled to the first intake valve opening completely in order to ensure an adequate mixture. This coupling of the valves is affected by the control unit. It calculates the switch-over based on engine speed and load, vehicle speed and engine coolant temperature. When the engine is under full load, the valve is switched on at 2700 min - 1, in the partial load only at 3300 min -1.
- As SOHC and DOHC VTEC a small locking pin is used to connect to both valves.
- Cars with a VTEC -E engine have a characteristic green lamp with the inscription " ECONO " in the instrument cluster. When the engine is operating in an economic operation, the lamp is switched on.
- The Civic VEi with VTEC -E engine was in 1994 as one of the most fuel-efficient gasoline engines worldwide.
DOHC i -VTEC
The i stands for intelligent VTEC system. The valve opening times of the motor changes when starting and accelerating to provide an optimal, high-torque performance. In calm and no-load driving, the intake valves close later to keep fuel consumption as low as possible. The i- VTEC system expands the DOHC VTEC by a phase adjustment on the intake side. The phase can be adjusted up to 50 ° here, thus leading to a lower consumption, and to on the other hand for more torque and power.
Compared with the DOHC VTEC (or SOHC VTEC) programming is much more complicated. Where 4 maps are used for the DOHC VTEC (2 each for the ignition and the injection quantities ), it is the i -VTEC ( 4x6 2 maps, 2 each for ignition and injection volume, in addition for different phase positions (0-50 ° ) and the phase position as such for non -VTEC and VTEC)
Honda also introduced a 3-stage VTEC system in selected markets. It combines the operations of the SOHC VTEC and VTEC -E. At a low speed only an intake valve ( the VTEC -E), at intermediate speeds are open. At high speeds is on the cam profile for high-speed switching ( from VTEC). This low fuel consumption is guaranteed at low speeds, but also a high power output at high engine speeds.
Movement was used the 3-stage VTEC D15B engine in the EK3 (sixth generation Civic ), which was not offered in Germany. The engine reached at 7000 min - 1, a power of 130 hp.
Vehicles with VTEC engine
- Honda Accord
- Honda City
- Honda Civic
- Honda CR-V
- Honda CRX
- Honda CR -Z
- Honda FR-V
- Honda HR-V
- Honda Integra
- Honda NSX
- Honda Prelude
- Honda S2000
- Honda Stream
- Ariel Atom
- Honda Jazz from BJ. 11.2008
- Honda Insight
- Honda Ridgeline
- Honda Shuttle
- Honda VFR 800 FI
The technique of variable valve control has been adopted and implemented by other manufacturers.
Thus, for example,
And other manufacturers (Ford, Nissan, Porsche) comparable systems developed.
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