| [ car ] in KIDS 글 쓴 이(By): hongsang () 날 짜 (Date): 1995년02월09일(목) 05시55분13초 KST 제 목(Title): [Re]VTEC power! First of all, I would liike to ssay tahthaving more valves does not neccesarilly mean more power although that's the case in most applications. The reason is that more air can get into the cylinder more freely with more valves. So, you have more power. However, this does NOT guarantee higher efficiency. If more air means higher efficiency, why are turbocharging and supercharging not better in terms of eficiency. Turbocharging or cupercharging is used since it can provide more power given an engine displacemeent. Example, modern automobiles usually have 4-valves per cylinder which offers better performance over 2-valve-engines. In order to get more power out of the engine, DOHC is used, one cam for intake valves and the other for the exhaust valves. So, the DOHC is drived from Double-Overhead-Cam-Shaft. DOHC is usually used in multi-valev engines since there is no point to use it in 2-valve engines. Since two cam shafts are used, it's more noisy (although the "noise" mean "music" to some people's ears). Now, back to your new question; Accord EX produces 145hp with 2.2L displacement and intake VTEC while Integra GS-R makes 170hp with 1.8L entine and intake AND exhaust VTEC. In the case of Accord, the primary goal is refinement and smoothness w/o much vibration. But, since the Integra is supposed to be a little more sports-oriented, some noise is tolerated, or even promoted. In Accord, the VTEC's third valve is one the intake side ONLY. That is, more air can get into the chamber, but not so thru exhaust. In Integra, more flow is allowed all the way thru exhaust, thus producing more power. Bottom line, DOHC multi-valve engines produces more power over conventional 2-valve-SOHC engines. VTEC is patented technology of Honda, which combines more torque at low rpm and more power at higher rpm. Ferrari tried this in their new F355, but decided to go with 5-valves per cylinder design. I've said too much for the bottle line. Ok, hers's real bottom line, More valve + DOHC --->more power and, there's a difference between Accord's VTEC and Integra's VTEC. By the way, in auto industry, 0.4L difference of displacement can mean quite a big difference in performance. Well, I said too many things at the same time.If you've go more questions, I'll be glad to answer them as much as I can. I hope my answer is helpful... Acura NSX |