The K20A used in the new Honda STREAM is the first of the new generation i-VTEC engines. Eventhough the engine does not produce a humongous amount of power in absolute terms, the importance of the engine is that it tells us of the new technologies that Honda is working on, and directly indicates the technologies that will be used on the new generationi-VTEC super high-performance engines that is to come.
In the STREAM page on the official Honda of Japan's web-site, one sub-page was specifically dedicated to the implementation of the new i-VTEC mechanism on its K20A. There is a wealth of information contained on that sub-page so as usual, TOVA's japanese articles specialist Kaz Mori did a translation of that to english. After looking at thetranslation, I decided that the article was much too fragmented to be published just by itself. I decided that the most effective way to present the translation is to incorporate it into a K20A article of my own, written in such a way so that the whole will present a coherent and technically informative article that you are reading here.
As I have mentioned at the beginning, do not judge the K20Aby its mere 154ps power rating. What is important is not its specific power output but the sheer amount of technologies that Honda has put into it. It is truly a new generation VTEC engine - the DOHC iVTEC. As can be expected, a lot of wonderful current technologies have been carried over to the K20A, frequently enhanced in a way that makes the K20A overall a wonder-engine in its own way.
TheOriginal Honda of Japan's K20A articleFuel Economy, Ample Torque, Clean Emissions
- The i-VTEC provides it all depending on engine load - The DOHC i-VTEC utilizes smart valve control technologyThe i-VTEC system utilizes Honda's proprietary VTEC sytem and adds VTC (Variable Timing Control), which allows for dynamic/continuous intake valve timing and overlap control.The demanding aspects of fueleconomy, ample torque, and clean emissions can all be controlled and provided at a higher level with VTEC (intake valve timing and lift control) and VTC (valve overlap control) combined. | | | |
VTC (Variable Timing Control mechanism) The VTC actuator, installed on the intake camshaft, is controlled by oil pressure, to allow for dynamic and continuous valve timing to fit the load of theengine. | | |
| | | |
Additionally, the intake manifold length can be adjusted. Combined with the DOHC i-VTEC, in order to obtain both ample low/mid-end torque and high-end output, a rotary valve is used inside the dual-passage intake manifold.During low/mid rpm,, the rotary valve is closed, while it opens during high rpm's. By varying the intake path length according to engine rpm, ampletorque is gained at all rpm levels. Additionally, the rotary valve design is superior over past butterfly valve (flap) in that it reduces intake resistance. | | |
| | | |
An Imagery of the i-VTEC Implementation |
EGR Effect: By swirling back some of the exhaust air back into the combustion chamber, combustion temperature is lowered, and NOx output is reduced. |iVTEC = VTEC + VTC
Hopefully readers would have read my article on the new iVTEC and the basic operating principle that VTC or Variable Timing Control is based on. As Honda clearly stated in this K20A article, iVTEC is VTEC with VTC added. K20A uses a combination of VTEC-E and power-VTEC that switches between 12-valve economy mode and a 16-valve mode with a separate wild intake cam. VTC complementsthis VTEC variation. For the K20A engine however, outright power is not the sole objective of iVTEC, the other important parameters of fuel economy and emissions has been given equally important footing, a direction that Honda has always promoted in the past. This impossible balance of power and economy has previously only been realizeable in Honda's D15B 3-stage VTEC first used on the previous...