What i alwayz "kena"...My car is SOHC, alwayz kena tapau at first gear with kelisa. But now, goodbye kelisa.
So, the point is DOHC much pick up than SOHC ler
So, the point is DOHC much pick up than SOHC ler
you running a DOHC head now??Originally posted by najibkl@Feb 22 2005, 14:55
What i alwayz "kena"...My car is SOHC, alwayz kena tapau at first gear with kelisa. But now, goodbye kelisa.
So, the point is DOHC much pick up than SOHC ler
Agree too, look nice and more queit that before.Originally posted by ettk2003@Feb 23 2005, 10:46
hi
previously i was running a 4G92 sohc, with port & polish head and forged piston too...then i did the dohc conversion as well...and what i found is that for the pick-up its more or less the same but at high rpm i can feel slight increase in hpower...
might need a ecu that is for dohc to fully utilize the new head...i didnt do that so i cant tell u the result..
but the other things i found is that with dohc, the engine is much more quiet, and the sound from the exhaust is much nicer....also looks good with a dohc rather than sohc inside the engine bay :D
cheers
change valve spring..whats the effect on this?Originally posted by fstrader@Apr 17 2005, 12:57
ultimate satria, no need swap head lar bro.. change ur valve springs can edi...cos urs is carbie, same like mine.
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Originally posted by taqu@Feb 21 2005, 13:21
The more complete question is "4G92 12-valve SOHC convert to 4G92 16-valve DOHC, pros/cons?" :) Coz there're 4-cylinder engines having 16 valves but only use SOHC eg Waja engines or some Honda engines.
About pros & cons of 12-valves (3 valve per cylinder) vs 16-valves (4 valve per cylinder), I copy-paste this statement from Autozine :
Hmm it is correct to say that generally DOHC engines have abit weaker low-end compare to SOHC (coz DOHC results in larger intake area resulting in slower air flow) , but most DOHC engines have smaller-diameter & curved intake manifold to improve those low-end torque (I think this also applies to 4G92), so u won't notice that low-end loss, on the other hand this may effect hi-end power, but since DOHC have more potential for hi-revving than SOHC, this is OK.A typical 2-valve engine has just 1/3 combustion chamber head area covered by the valves, but a 4-valve head increases that to more than 50%, hence smoother and quicker breathing. 4-valve design also benefit a clean and effective combustion, because the spark plug can be placed in the middle.
4 valves are better to be driven by twin-cam, one for intake valves and one for exhaust valves. Honda and Mitsubishi models prefer to use sohc, driving the valves via rocker arms like the aforementioned Triumph. This could be a bit cheaper, but introduce more friction and hurt high speed power. Therefore the sportiest Honda and Mitsubishi still use dohc.
So, gor for it dude :)
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with 3 valves, the air will create a turbulent effect in the combustion chamber. and improves the combustion at the low-mid revs. why merc uses 3 valves? most of merc owners only revs two thirds of the entire rev range thus by using 3 valves gives better driveability(fuel economy). same also with honda D15 engine.Originally posted by yiheng85@Feb 23 2005, 13:47
read from a book..merc went back to using 3 valves because they wanna incrase fuel efficiency...:) the theory behind it i dunno :P
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