DOHC VTEC

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 engine is asked to operate continuously at or around the switch-over point.

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 (200 kW). DOHC VTEC engines soon appeared in other vehicles, such as the 1992 Acura Integra GS-R (B17A 1.7 liter engine). And later in the 1993 Honda Prelude VTEC (H22 2.2 liter engine with 195hp) 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.

Vtec

VTEC (Variable Valve Timing and Lift Electronic Control) is a valvetrain system developed by Honda to improve the volumetric efficiency of a four-stroke internal combustion engine. This system uses two camshaft profiles and electronically selects between the profiles. It was invented by Honda R&D engineer Ikuo Kajitani. It can be said that VTEC, the original Honda variable valve control system, originated from REV (Revolution-modulated valve control) introduced on the CBR400 in 1983 known as HYPER VTEC. VTEC was the first system of its kind, though other variable valve timing and lift control systems have been produced by other manufacturers (MIVEC from Mitsubishi, VVTL-i from Toyota, VarioCam Plus from Porsche, VANOS from BMW, VVL from Nissan, etc).

Vtec have the same idea with DVVT and VVT-i. It acts like a normal fossil combustion engine in low RPM, however when the user revs until certain limit (usuall 5000rpm). The valve timer would activate (this is what people usually calls Vtec change) and produce a noisy sound.

It sounds a little bit like a 2-stroke motorcycle engine revs high. You feel like the torque suddenly increases and you have more power to accelerate.

What actually happens is that the valve intake open longer than normal. Allowing more air to come into the combustion chamber. The more air in the chamber, the more efficient the fuel burns.

COMPARING DVVT & VVT-I

Normal engines is good in the low RPM. However, when the RPM reaches higher level, the amount of power produced per fuel is lesser. This is because the air from outside the engine couldn't get into the combustion space in a short period of time. That's what Yamaha sees, and they developed YPVS, VVT-i and DVVT.

DVVT and VVT-i valve works like a normal engine while in low RPM. However, as the RPM increases, the valve timer shifts the time of opening of the valve a little bit earlier. The higher the RPM goes, the earlier the valve opens.

By doing this, air would hav enough time to go into the ignition room, thus making the fuel burning in high RPM more efficient than conventional internal combustion engine.

DVVT

The main change between Perodua Viva and it's predecessors (Perodua Kelisa and Perodua Kancil) would be their engines. Then it came the term of DVVT, and Perodua claiming their 1.3l DVVT saves fuel and provide power as same as normal 1.5l engines.

Let us get back to the basics, DVVT or it's full name Daihatsu Valve Variable Timing is based (copycat) on Daihatsu mother company Toyota engine, which is VVT-i (Variable Valve Timing - intelligence). We believe that DVVT is just VVT-i's engine brand name for Daihatsu cars.

DVVT and VVT-i is based by Yamaha's YPVS (Yamaha Power Valve System). Yamaha was bought over by Toyota for it's YPVS because Toyota afraid of losing to Mitsubishi's MIVEC and Honda's Vtec. Yamaha has been provinding Toyota and Daihatsu engines since.

DVVT and VVT-i engines are always put together to be compared with V-tec (Variable Valve Timing and Lift Electronic Control System), i-DSI (intelligent Dual and Sequential Ignition) that is developed by Honda earlier.

All of the Vs (DVVT, VVT-i, i-DSI, Vtec, CVCC, MIVEC, CVVT...) was meant to increase fuel efficiency which is to use less fuel and produce more power from the engine. The objective is the same, the only difference would be their methods.

Corporate info

As compared to Proton, Perodua has been quite successful in its business ventures. Its cars are very popular among Malaysians, such as the recently introduced Perodua Myvi, which sold 80,327 units in 2006, outselling its rivals best selling car, the Proton Wira, which only sold 28,886 units in Malaysia. In 2006 and 2007, Perodua became the best selling car company in Malaysia.

Perodua is set to become the largest compact carmaker in South-East Asia. It currently has capacity to make 200,000 cars annually. By July 2007, it is expanding to 240,000 per year. In October 2005, it had produced a cumulative total of 1 million cars.^[1]