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Message: <blockquote data-quote="Veloc" data-source="post: 1063318858" data-attributes="member: 92511">TO ALL SIFUS PRO IN NA!!!!!VALVE TIMING!!!! VALVE TIMING!!!!Please help me... I think of this everyday I cannot solve!!! I cannot sleep and get bad headache.... I think all the time until stress the hell out of me... I take time in office to read everyday until I cannot work... I read so much until my eyes blurr.... PLEASE PLEASE PLEASE help to enlighten this NA noob... My brains are about to burst. There are a few things about NA that I find that I do not understand, or rather, there are contradicting facts...1. Advance timing will give more low-end torque (Intake valves only; on DOHC; all else same)Why? I know they said that if advance cam timing, it will enable the intake valves to shut earlier thus trapping more air & fuel building more pressure inside the cylinder. Fine. Acceptable. But what the heck? By doing this, if the intake valves shut earlier, the engine might not suck in enough air & fuel if the piston haven't reach the BDC. So doesn't this actually reduces the amount of air-fuel and pressure inside the cylinders?2. Retard timing will give more top-end power (Intake valves only; on DOHC; all else same)Why is this? People said that by retarding the cams, the valves will shut later thus allowing for more air-fuel to enter the engine. But making it shut later will also mean that the valves will open later! Then the air-fuel could not enter the cylinders yet when the piston start to move down! And also, doing this will miss the chance to make use of overlapping with the exhaust stroke (scavenging effect) which is suppose to help draw more air-fuel in.3. High duration & lift cams will improve top end power, reduce low-end torque and severe the fuel consumption.I understand about the top-end power and low-end torque compromise. But why does this affect the FC so badly? Suppose that we have a high duration and lift cam engine, at idle and low-revs, the high duration and lift will let the air-fuel escape back to the intake manifold because the valves cannot shut off when the pistons start moving up. Isn't this suppose to improve FC because we actually use less air-fuel? Doesn't this reduce the effective displacement of an engine? For example, a 2.0 L engine might have an effective displacement of only 1.8 L.This also cause the power/expansion stroke to have a longer movement downward compared to the compression stroke simulating an atkinson cycle engine which is more economical. Just like the camry 2.4 engine.Help help help help me please... I'd be really grateful if anyone can share your knowledge...</blockquote>

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