The dohc motor usually has bucket lifters that sit directly under the cams and on top of the valves. This eliminates all the rocker arms, rocker shafts and hardware, hence, a much lighter valve train. It also makes it easier to use multiple valves and locate them more easily.
A single overhead cam engine with 16 valves would only be cheaper to build if the tooling had been there for years and perhaps the company had a truck load of rocker arms they were trying to dump. Another consideration might be space, dohc is wider in the engine bay than sohc.
A SOHC 16 valve engine would have better torque on the low end where the DOHC valvetrain’s weight results in lower torque. But at high engine speeds, the 16 valve DOHC engine’s peak torque and horsepower would be greater. That’s the trade-off. With the amount of valves being equal, SOHC has better low-end torque because the valvetrain package is lighter while DOHC has better top-end power.
Other benefits of DOHC would be making it easier to implement variable valve timing technologies, and also you can tweak it better with adjustable cam pulleys. If you were to put high-profile cams in your DOHC engine, the cam lobe profile can also be more optimized than a SOHC engine because you can play around with the lobe shape easier with separate camshafts for the intake and exhaust valves.
SOHC is less aggressive on performance, marginally more economical, cheaper to produce, and probably longer engine life.
DOHC is more aggressive on performance, marginally less economical, more expensive to produce, and possibly shorter engine life
I would also say, engine life is more about how the engine is treated and properly maintained, so I'm just saying DOHC may last less long because it generates more power which generates more temperature which wears bearings faster because the boy racer likes to put his foot down, and the boy racer won't drive the SOHC, so when granny drives the SOHC she is gentle on the gas and so it lasts a longer time. But if granny drives a DOHC the same way it also lasts a long time.
With a double cam variable valve timing can be used to improve efficiency and employ valve overlap. Most engines today have 4 valves per cylinder. If they could do all of this with one cam they would as it is cheaper. In this case it is far better to have double cams and worth the extra cost.
Less moving parts means less complicated engine but if you have 2 cams, the potential for fine tuning and performance parts is greater.
as I know the only duty for cams is to open and close valves an certain times
and usually the engines with 16 valves use 2 cam shaft every cam control 8 valves (2 per cylinder)
I think it's kind of rare but there are some engines has only 1 cam that control 16 valves (SOHC 16v)
so is there any different in this sitution between DOHC 16v and SOHC 16v ?? about performance, FC, engine life...etc
