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Old 20th September 2005, 21:18   #1
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Exclamation Which engine is better? SOHC vs DOHC

Hello,

Just wanted to confirm which engine is better.
DOHC or SOHC.

Thanks
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Old 20th September 2005, 21:28   #2
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Any time DOHC is better than sohc
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Old 20th September 2005, 21:29   #3
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Can you tell me whats the difference between the engines.
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Old 20th September 2005, 21:54   #4
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Quote:
Can you tell me whats the difference between the engines.
here's the short version...

a SOHC or single overhead camshaft engine uses a single camshaft on the head to lift all the valves, whereas in a DOHC or double overhead camshaft head, two camshafts are used to lift the valves (a camshaft each for intake and exhaust valves) ; normally, SOHCs are used in both 16 valve or 8 valve configurations (for a four cylinder engine), but DOHCs are used in 16 valve configurations (or more) only. some exceptions are there, like the vRS, which has DOHC layout and 20 valves (5 valves per cylinder).

a DOHC layout is better than a SOHC layout in many ways- in DOHCs, the valve timing is more precise, and better valve lift is achieved. also, a DOHC setup eliminates the need for rocker arms, hence creating better timing, and valve contact is more direct too. but of course, these are all in stock form. a SOHC layout, when tuned, can be as efficient as a DOHC, but under proper tuning, DOHCs always achieve more power than SOHCs...
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Old 20th September 2005, 22:11   #5
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Thanks veyron for the brief info.
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Old 25th March 2006, 17:58   #6
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http://www.billzilla.org/2v4v.htm check it out, it covers push rod(2v single cam) SOHc and DOHC.
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Old 26th March 2006, 23:54   #7
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SOHC has an advantage of better low end torque than the same capacity DOHC.

Refer to this link: http://paultan.org/archives/2005/06/...c-valvetrains/

Last edited by Pankaj401 : 27th March 2006 at 00:05.
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Old 27th March 2006, 19:35   #8
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DOHC!! No doubts about it!!... Get two cams in there and roar into the sunset!!
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Old 29th March 2006, 16:33   #9
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Does anyone of them have any advantage over the other in terms of
a) Mileage
b) accleration

Thanks
-Sumit
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Old 5th April 2006, 17:12   #10
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Quote:
Originally Posted by sumitsingh
Does anyone of them have any advantage over the other in terms of
a) Mileage
b) accleration

Thanks
-Sumit
Experts? Please share your thoughts/comments on this?

In a real world scenario.. Given all things constant, would a car with DOHC be more fuel efficient than one with SOHC.

-Sumit
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Old 5th April 2006, 17:51   #11
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DOHC is the thing to have when given a choice!

But always see the performance of the particular engine you have on hands before choosing one!
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Old 17th August 2007, 10:34   #12
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Animated gif's explaining SOHC and DOHC engine's
OHV, OHC, SOHC and DOHC (twin cam) engine - Automotive illustrated glossary

Last edited by warchild : 17th August 2007 at 10:37.
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Old 1st March 2009, 18:13   #13
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Found a Good thread!

Now, ANHC engine is SOHC while Fiesta 1.6 is a DOHC. So, as per the logic given by members in the above posts Fiesta's engine should be better, but ANHC engine is believed to be futuristic ( due to H... factor)!

If DOHC is better, why didn't HONDA offer on this car (ANHC) ?

Couldn't find much about CIVIC engines on HONDA site ( IMO, 1.8L is SOHC & 2.0L is DOHC)
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Old 1st March 2009, 20:35   #14
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Default The shortest relative explanation I could think off.

Quote:
Originally Posted by abhibh View Post
Can you tell me whats the difference between the engines.
When you are resting or just lazing around or even going for a short walk you could close one of your nostrils with your finger and still not feel any discomfort but without doubt you would need both of your nostrils open if you are doing some exercise. Now GOD was so clever that he had the inlet and exhaust coming through the same exit pipe and the change over valve he made it closer to the exchange area; but occasionally we use the mouth too for exhaling which is similar to the 5 valve design where there are two inlet valves and 3 exhaust valves. Making a 5 valve design witha sohc design is near impossible and inefficient too.

In engines more the valves more are the possibles ways to extract power.
In engines the 2 valve design is well suited for city driving where instant throttle response is expected but on the highway power at higher rpm is expected and hence the 4 valve design is better sited.

The dohc design gives more precise control of these valves while the sohc is with more number of linkages. Its similar to the difference between a direct linked gear lever and one thats connected to the gear box through many linkages.
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Old 1st March 2009, 21:27   #15
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DOHCs offer 2 advantages over SOHCs, that of central spark plug placement and implementation of variable valve control on the exhaust side as well. Other than that, there's not much for the layman. In fact, due to the valvetrain package being heavier on DOHCs, their low-end torque might suffer, making the SOHC a better traffic/daily-drive bet.

Quote:
Originally Posted by drpullockaran View Post
5 valve design where there are two inlet valves and 3 exhaust valves. Making a 5 valve design witha sohc design is near impossible and inefficient too.
I don't know about God, but most 5 valve engines have 3 intake valves and 2 exhaust valves. All other things being equal, 5v also does not make a significant difference compared to 4v. In fact, Yamaha has gone back to 4v per cylinder for its flagship R1.

Quote:
Originally Posted by drpullockaran
In engines more the valves more are the possibles ways to extract power.
In engines the 2 valve design is well suited for city driving where instant throttle response is expected but on the highway power at higher rpm is expected and hence the 4 valve design is better sited.
I think there are arguments for it to be the other way round as well. 2v would mean the valves are larger, thus mass -- valves, springs etc -- would be higher. This means more power sapped at lower rpms. Addedly, charge intake speeds would be lower, because valve dia is bigger. This will also lead to lower torque and power in low-end scenarios. Which is why supercharged V8s in dragsters use 2v heads.
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