[quote]Originally posted by tailslide:
ah, desperate liao muz scold ppl moron ah? relax relax. dun
let ppl know u buay steady liao
eh dunno what started personal assaults and name callings first
loh... u idiot here and retarded there then i use moron loh...
liddat also ish buay steady ah 
let me ask u this, at high engine speed how u advance the
timing huh? speed up the cam ah? make the cam move faster den ur
engine rpm ah? obviously another intellectually challenged
individual who cannot understand how cam phasing works.
"cam phasing is controling the timing at which the valves open and
shut WITH RESPECT TO the egine speed to ensure efficeint
breathing". if the "timing" of the valves is dependant on the
engine speed, then u are not controlling any timing at all. the
engine go fast, the cam has to go fast. the engine go slow, the cam
has to go slow. like dat call variable valve timing for wad?
as for ur link which never say turn the cam backwards, never say
means CANNOT turn the cam backwards ah? can bet somemore izit? wow.
i'll never understand the workings of a deranged mind. who dunno
how to cut and paste links? my 5 year old neighbour can do
i
wah then at high engine speeds turn the cam backwards ah?? u keep
insisting it turns backwards i also dunno how u come to have this
idea.. how... jam brake then pah reverse gear ah at 8000rpm ah like
u said... 
a SOHC engine has a single cam with both exhaust and intake
lobes built into the full length of the cam. when u advance it, the
WHOLE sequence of intake and exhaust valve timing would have been
advanced by turning the cam in the same direction of the engine.
obviously, when u retard it, the WHOLE sequence of intake and
exhaust valve timing is retarded by turning the cam in the opposite
direction of the engine. u have a situation whereby the number of
degrees advance (setting cams forward) or retard (setting the cams
in the reverse direction) of a single cam is dictating the the
timing of BOTH the exhaust and intake ports. thats the reason why
DOHC is superior to SOHC. each cam is independant of the other.
either cam be advanced or retarded without the exhaust cam
affecting the intake cam and vice versa. thats also how DOHC
engines equipped with variable valve timing are able run variable
amounts of overlap at different rpms via the number of degrees of
advance or retard programmed into the ecu.
ur inability to know how a SOHC cam advance or retard its timing
speaks loads of ur ability to reason. need further proof that u are
a complete engine idiot?
dun think u know what u talking about.. and so full of errors i dun
even know where to start correcting u... machiam pri skool essay
liddat.. tiring to mark sia...
so i have. and praytell from which one of my previous posts
did u derive that i do not know the diff between vvt-i and DUAL
vvt-i? eyes playing tricks on you or premature brain
rot?
this is what u spruot out of ur mouth: " i find ur
explanation of this the most interesting by far "dual vvt-i means
varying valves timing on the intake and exhaust". almost anyone can
tell me that vvti stands for variable valve timing. wads the point
of expanding the whole meaning of dual vvti?"
btw, i dun need to write a thesis for u 2 know how cam
phasing works. i never expected a retard to understand a
thesis.
why scared ah.. ball shrink.. scared write everything kenna
exposed..acherlli u know nuts.. juz like to shoot pple cos they
junior member nia...
well this is my explanation on cam phasing before u start saying i
know nothing...
cam phasing basically is to vary the valve timing by shifting the
phase angle of camshafts.... in high speed, the inlet camshaft will
be rotated in advanced by 30° so to enable earlier intake... at
lower engine speed it may be retarded to say 5° as the engine speed
doesnt require valves to open as early as when the engine is
running at higher loads...so cam phasing allows earlier or
later valves opening
so if in a SOHC .. if the phase angle of intake camlobes to exhust
cam lobes is fixed... simply by changing the speed of rotation of
the cams like u said.. how do we vary the phase angle of the intake
with respect to the exhaust throughout the entire engine speed???
and turn backwards some more.. *snigger*
1 feature of cam phasing systems is overlap... overlap is whereby
the intake valves and exhasut valves are opened simultaneously...
at high engine speed this is to ensure efficient breathing...
whereas at low engine speed it is a means of fuel efficeincy..Since
the exhaust valves do not close until the intake valves have been
open for a while... some of the exhaust gases are recirculated back
into the cylinder at the same time as the new fuel / air mix is
injected.... as part of the fuel / air mix is replaced by exhaust
gases.. and the exhaust gas may also contain uncombusted fuel/air
mix ... therefore less fuel is needed... the engine runs properly
at the leaner fuel / air mixture without failing to combust... and
combustion is more complete with the exhaust having less
uncombusted fuel/air mixture..
