Evil Genius: VTEC,OHV,SOHC,DOHC cont~

When advertisements of cars mention, engine with DOHC, i-VTEC, Mivec, VVT-i........ sumorang mcm, woooh..... baguih ar kete ni, dier ader vvti kot, honda takder, dier ader VTEC jer..... tp bro mitsubishi ader mivec lg power....... Confirm yg ckp mcm ni or pikey camni tak tau mender tu MIVEC ke VTEC ker VVTI tu...... Sebenanyer, sume tu lebey kurang samer jer.... cume dier ader ubah2 skit untuk pelbagai aplikasi then panggil ar name lain sbbkan dier dr company yg berbeze tapi pokoknya diorang ni menggunakan concept yg samer jer.....

an i-VTEC engine.....

History skit, VTEC ni di-developkan oleh seorang engineer Honda Ikuo Kajitani,he was the father of VTEC,since 1983 lg research tu dijalankan punyer la zaman tok aku lg, time2 agak2 nyer kite wat per....? ha3. Concept ni di lancarkan melalui engine NCE (new concept engine) yg difitted kan dlm kete Honda Integra in1989......

honda integra 2nd gen~

(da ar tu history dia) nk lg, g ar google sendiri~he2

so....aper tu i-VTEC? i tu confirm ar intelligent kan.....yg VTEC tu (Variable Valve Timing and Lift Electronic Control). Gunenyer mender ni, ialah untuk meningkatkan kecekapan volumatrik dalam pembakaran dlmm piston kete tuh..... kirenyer nk kasi efficient ar engine tu, camner...? camni, biler engine rev at low RPM, musti takya pki minyak byk kan.... and biler engine rev at HIGH RPM, baru ar valve akan dibukak dengan lebey besa untuk membenarkan minyak byk masuk, br ader power. So basically, dier bekalkan power lebey biler diperlukan saje.... untuk lebey paham tgk ar vid kat bawah ni.....

LOBE

then ader plak, VTEC DOHC, SOHC...... ader keter yg OHV....? wei, ni mender lg nih...? OHV, DOHC and SOHC in sume bout the camshaft..... camshaft ni ialah mende yg memusing kan LOBE, keje dier is to bukak tutup injap dlm piston tu......

Back to the OHV, SOHC and DOHC..... so why some car manufacturers pilih untuk wat engine dier SOHC or DOHC....? OHV (overhead valve) tu oldschool da.... he3....cos dier kene pakai rocker arm to move the valve which is simple and durable, tapi susah nk precisely control the valve timing at high rpm........ kete nk laju, mane nk kete2 plahan2 da.... lopek ar kan.....

SOHC stands for single overhead cam, the name SINGLE cos ader satu camshaft jer, so with only 1 camshaft jer will pusingkan lobe tu..... simpler than the DOHC more complex than the OHV, basically dier evolusi dr OHV ar tu, The advantage is that valves are operated almost directly by the camshaft, which makes it easy to achieve the perfect timing at high rpm..... tapi dengan SOHC, the camshaft akan ader kat atas piston tu, so sparkplug takle nk letak kat ats tgh2 piston tu, tempat tu plg optimal untuk buh sparkplug tu...... while DOHC nyer camsharft kat tepi2 skit (ko tengok ar gamb kat bwh tu) so sparkplug bley buh kat tgh......

DOHC plak (double overhead cam) dier ader 2 camshaft, so piston tu bley ader lebih byk valve dlm satu piston..... lg byk lg senang ar kte tu nk benapas.... cam tu la kirenyer.......cube ko ader 1 je lubang idong, gile susah kot nk napas....kan kan...? so with more valves, more horsepower,....but the disadvantage is that dengan 2 camshaft n bagai, more machanical parts... more mechanical parts means susah nk pasang = complicated = engineer pening2 = MAHAL ar, ala nk engine power kuar ar duit lebey skit...... but most of the cars today pakai DOHC engine.... cos you'l get more horsepower with small engine volume....other advantages is that the valve timing easy to control......

Below are animations of the OHC, SOHC and DOHC.......