DOHC and SOHC
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hi, Can anyone pls tell me the diff between DOHC and SOHC. which is better.thanks
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DOHC = Double over head cam = high compression also = not very suitable for after market turbo charging (correct if wrong)
SOHC = Single Over head cam = low compression = suitable for TC-in (correct if wrong again)
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really meh high and low compression
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DOHC=damn on and hiong charger
SOHC=super on and hiong charger -
ehh.. SOHC and DOHC has got nothing to do wif compression ratio leh..Originally posted by johncooper:DOHC = Double over head cam = high compression also = not very suitable for after market turbo charging (correct if wrong)
SOHC = Single Over head cam = low compression = suitable for TC-in (correct if wrong again)
DOHC and SOHC basically refers to single or double OVERHEAD cam shafts. In the past, cam shafts were not located "OVERHEAD" (as in over the cylinders).
In a single cam shaft config, cam lobs for intake and exhaust valves are all located on the same single shaft. DOHC has their intake and exhaust cam lobs located on different shafts (which is why DOUBLE cam shafts, one intake the other exhaust).
Some V engines has Quad shafts.. this is effectively 2 sets of DOHC each mounted on different engine heads.
And which is better? I suppose the more the better lah.. but I have this feeling DOHC is more for "marketing" purpose, coz in a normal everyday car (not referring to high performance cars), I see no reason why we would need DOHC.
In fact, modern day manufacturing process can be so advance you can even have several different sets of cam lobs on a single shaft (such as Honda SOHC v-tech engines).
Well, maybe Heng can advice. -
As siaokao mentioned, the OHC design is pretty much standard practice these days, as opposed to the older OHV (overhead valve) engines in which the camshaft drives a set of pushrods which in turn operate the valves.
The advantage of the OHC over the OHV is that, because of the longer train of components driving the valves, flexion of the metal causes OHV engines to have less precise operation of the valves at higher revs.
As an extension of that, I would expect that the DOHC may have a slight advantage over the SOHC because with each camshaft being simpler, it may twist less when the torsion increases at high revs. Perhaps Heng could confirm if my suspicions are correct.
As for compression, the only inherently weaker design was the L-head, which was completely phased out in the 1950's by the OHV design. -
i think the primary advantage of DOHC over SOHC is "tuneability".
with 2 cams, u can select diff profiles, advance, retard, alter phasing with respect to each cam to achieve optimal performance over a wider rpm range. with technologies such as variable timing/ lift, the potential for tuning such parameters become virtually infinite.
something mechanically impossible with a single cam set up. -
True, true - didn't consider that one before my third coffee this morning.Originally posted by tailslide:i think the primary advantage of DOHC over SOHC is "tuneability".
with 2 cams, u can select diff profiles, advance, retard, alter phasing with respect to each cam to achieve optimal performance over a wider rpm range. with technologies such as variable timing/ lift, the potential for tuning such parameters become virtually infinite.
something mechanically impossible with a single cam set up. -
DOHC provide better emission,saves fuel,decrease valve lag as smaller valve are use...cannot think of other liao...later then put hahahaha
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2 heads are usually better than 1.
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so id DOHC is good then i dun understand y AMG tuned engines are only runnin on a single cam....
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Because if they are going to change thier tuning design halfway, they have to up another line just so to produce dohc, and they did thier own study and realise its not as profitable as their current.
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opps. by the time heng saw this, a lot of experts already explain le.Originally posted by siaokao:Well, maybe Heng can advice.
finally! can take a break -
copied from TCC on MCF?Originally posted by t3r:DOHC=damn on and hiong charger
SOHC=super on and hiong charger -
Oi, slacker! Get to work!Originally posted by HENG@:opps. by the time heng saw this, a lot of experts already explain le.
finally! can take a break -
thanks guys. now i understand better. really thanks alot
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tt's wat too much zhng my car do to u...Originally posted by huoye:copied from TCC on MCF? -
quick quick, have the 4th cup and u'll think of something newOriginally posted by Gedanken:True, true - didn't consider that one before my third coffee this morning. -
pls explain why DOHC engines have smaller valves.......Originally posted by tofushop193:DOHC provide better emission,saves fuel,decrease valve lag as smaller valve are use...cannot think of other liao...later then put hahahaha -
oei! take turns hor!Originally posted by HENG@:opps. by the time heng saw this, a lot of experts already explain le.
finally! can take a break -
i dono how to explain leh...not really smaller valve la...Originally posted by tailslide:pls explain why DOHC engines have smaller valves....... -
dun wan i like to slack, the rest of u can help me explain. damn long time waiting for this day to arrive!
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u have been slacking since god knows when....Originally posted by HENG@:dun wan i like to slack, the rest of u can help me explain. damn long time waiting for this day to arrive!