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This means providing extra fuel and air to the engine at higher speeds. The oil pressure sent through the system forces the pins to move, allowing the center cam to function. Activation of the high-performance lobe results in better lift and longer duration. When speed is reduced, the pins retract again to disengage the center rocker arm allowing the two low profile cams to work alone.
In addition to the benefits that arise from variable valve control and timing, the mechanics of the system allow the fuel to swirl in a manner that maximizes combustion.
Many automakers released some sort of variable valve control system in the years following the VTEC's release. Honda's technology is unique in that it works with both timing and lift on both the intake and exhaust.
Toyota's VVT-i, for example, results in different valve timing on the intake alone. In January , a year before the NCE program began, a research team was formed to study the mechanism as a means of enhancing fuel economy.
Even though by the end of Honda engines were already capable of a world-beating 50 miles per gallon mpg , there would be an effort to improve. A possibility was thus identified through the study of a new valve mechanism. Specifically, it was believed that the installation of a new set of cam followers and rocker arms for high-speed operation on the intake and exhaust sides would help, along with the switching of cam hills according to engine speed.
This was to be their solution to higher engine efficiency. As a core technology for Honda's proposed new line of engines, the mechanism then underwent a program of study and refinement under the careful supervision of Honda's research staff. Launched via the Integra, this innovative technology surprised the world with a new level of performance from a compact, fuel-efficient engine.
Since it had originally been created to improve fuel economy, the engineering staff's new assignment would be to combine outstanding mileage with impressive output across the entire powerband.
This proposal was approved as a D-development project, and was instituted in November The objective was to develop a new engine for the Integra. Kajitani, serving as LPL of the engine development project, was excited about the new opportunity.
Kajitani believed the specification for Honda's new engine - 90 horsepower per liter, or in all from a 1. After all, the DOHC engine already produced horsepower, but the new engine would only have ten more than that. He knew it just was not enough. It had always been thought that a normally aspirated engine could not be made to produce horsepower per liter. But Kajitani could see in Kawamoto the passionate vision of an engineer, and he felt inspired by such a straightforward proposal.
Of course, he knew it would mean horsepower from only 1. Kajitani knew that in order to embark upon a challenging path, they must set their goals high. It was decidedly easier to set the goal than to convey it to the development staff. When Kajitani sat down with his associates and gave them the news, he was immediately swept back by a barrage of questions. For example, the target 8, rpm was almost 20 percent higher than the maximum output of 6, rpm achieved by current 1.
Moreover, the inertial force upon various engine parts would increase by 40 percent. Naturally, the engine would be subject to considerably higher loads due to its increased interior heat.
Therefore, to reduce inertial mass under such high revolutions, the weight of each part would have to be reduced. At the same time, it was obvious that doing so would result in lower rigidity, causing problems in durability and reliability. No one knew how to achieve the goal or what approach they should take. A big debate was started within the team as to whether the goal was even reachable.
It was a natural reaction, of course. They were told to develop a dream engine like nothing they had ever seen before. To achieve it, they would have to enter a new realm of technology.
Discussions were held day after day for three straight months. Imagine that we are running an engine at just 10 or 15 RPM, to complete a cycle the piston will take seconds to do it. The camshaft would grind, when the piston begins moving downward in the intake stroke, the intake valve would open.
Right as the piston bottoms are out, the intake valve would close. Then the exhaust valve would open right as the piston bottoms out at the end of the combustion stroke, and would close as the piston completes the exhaust stroke. This is great as long as we can run the engine at a very low speed. The bad news is that when we increase the RPM, this configuration for the camshaft does not perform well.
If the engine is running at 4, RPM, the valves are opening and closing 2, times every minute.
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