Sohc Vs Dohc

[luckyd]

Hello everyone,

Thought of starting a new topic (assuming this hasn't been discussed before)to discuss the relative advantages of SOHC and DOHC engines.

AFAIK, SOHC engines have only one cam shaft common for both the inlet and exhaust valves. ie. in an inline engine there would be only one cam shaft whereas in V type or horizontally opposed (such as the Subaru Boxer)there would be only two (one for each cylinder bay)

On the other hand DOHC would have separate cam shafts for inlet and exhaust valves.

But, which type is better?

I' ve heard that SOHC engines have relatively lesser resiprocating mass and hence generates higher engine power and torque especially at lower RPM.

[Sumiya]

  On 9/28/2010 at 11:24 AM, luckyd said:

But, which type is better?

Hi Mate

in simply

Both are better on some fact that is like

SOHC : - simple and less costly and less power

DOHC : - Complex costly and more power

only think is that whether you would like

more power and more cost or

less power and less costs

http://paultan.org/2005/06/22/sohc-vs-dohc-valvetrains/

this explains a bit technical review about them , hope it might help

thanks

regards

sumith

Edited September 28, 2010 by Sumiya

[Ripper]

not a honda expert but i suppose SOHC motor only has to drive one camshaft so it's gotta have better lower end throttle response!

but it lacks power when compared to the DOHC cos SOHC will only have Vtec working on the intake while DOHC will have it working on both intake and exhaust.

better air intake and better gas expelling... more power and a smoother running motor!

I really don't think DOHC is complex given the era we live in most cars if not all nowadays are dohc

So i suppose the mild low end throttle response you get in a SOHC is not enough to outdo the gains of a DOHC...

If that was the case at least more performance oriented cars should have continued with SOHC.

Chances are...SOHC must be doing better gas mileage

[shanX]

DOHC

[charitha19]

DOHC all the way baby.. and the lower end thottel thing. u can eliminate that by putting in a calcualted exahuast piping and free flowing air filters.

long live DOHC....

[luckyd]

  On 9/28/2010 at 12:02 PM, Sumiya said:

Hi Mate

in simply

Both are better on some fact that is like

SOHC : - simple and less costly and less power

DOHC : - Complex costly and more power

only think is that whether you would like

more power and more cost or

less power and less costs

http://paultan.org/2005/06/22/sohc-vs-dohc-valvetrains/

this explains a bit technical review about them , hope it might help

thanks

regards

sumith

Thanks guys for all the responses.

I was of the mind that SOHC gives higher power and torque due to lesser reciprocating mass. Am I wrong on that?

And, also that DOHC is favourved since it is cleaner, smoother and more efficient since the valve operations are more precise.

[Elvis_Pil]

You're referring to the info on the Wiki page I guess.. SOHC or DOHC both have disadvantages and advantages- either less economy or more performance; you can't really generalize which is better, cause it boils down to the engine and its application and if variable valve timing is used and in the end the overall engine displacement and finally goals of the manufacturer

  On 9/29/2010 at 3:35 AM, luckyd said:

Thanks guys for all the responses.

I was of the mind that SOHC gives higher power and torque due to lesser reciprocating mass. Am I wrong on that?

And, also that DOHC is favourved since it is cleaner, smoother and more efficient since the valve operations are more precise.

Edited September 29, 2010 by Elvis_Pil

[MkX]

  Quote

not a honda expert but i suppose SOHC motor only has to drive one camshaft so it's gotta have better lower end throttle response!

but it lacks power when compared to the DOHC cos SOHC will only have Vtec working on the intake while DOHC will have it working on both intake and exhaust.

Why Honda and VTEC came in to this? If we leave Honda aside.. There are both SOHC and DOHC engines isn't it. Having VTEC or any other variable valve timing system again a different matter as some of the focused on economy and some power.. some times both together..

But in general if SOHC engine that equipped with valve timing system that focuses on high power out put in high RPMs will some times can equal as some DOHC engines.. isn't it?

Edited September 29, 2010 by MkX

[luckyd]

  On 9/29/2010 at 4:12 AM, MkX said:

Why Honda and VTEC came in to this? If we leave Honda aside.. There are both SOHC and DOHC engines isn't it. Having VTEC or any other variable valve timing system again a different matter as some of the focused on economy and some power.. some times both together..

But in general if SOHC engine that equipped with valve timing system that focuses on high power out put in high RPMs will some times can equal as some DOHC engines.. isn't it?

Your thoughts are a bit inline with mine.

More than whether it is SOHC or DOHC, it is the no. of valves per cylinder that determines a lot. Like the DOHCs, there are SOHCs which have 4 valves per cylinder. This coupled with lesser mass will result in higher torque at lower RPM for SOHCs compared to DOHCs.

But, afaik, the power output at higher speeds is more in DOHCs even when compared with 4 valve SOHCs.

[Sumiya]

Hi Guys

I guess the main purpose of the DOHC is to increase the valve per cylinder since sohc lack of space to have more valves per cylinder,most modern engines almost most of them are dohc or either vtec,

i think the old days car manufactures achieved power by increasing no of cylinders, now a days it is achieved through increasing valve per cylinder since the lack of space in engine bay instead of tunneling a big engine like v6 or v8 etc.

thanks

regards

sumith

[Lance]

In SOHC more low end torque, That means fast pickup, and in DOHC less low end torque, consequently low speed pickup but high end torque is there which would probably pull higher ks.(more power in cruising than SOHC). SOHC's are good for driving in traffic.

When it comes to evaluating we take DOHC performance calculations.

Edited October 1, 2010 by Lance

[BLu3HaZe]

  On 10/1/2010 at 5:46 AM, Lance said:

In SOHC more low end torque, That means fast pickup, and in DOHC less low end torque, consequently low speed pickup but high end torque is there which would probably pull higher ks.(more power in cruising than SOHC). SOHC's are good for driving in traffic.

When it comes to evaluating we take DOHC performance calculations.

Can you explain why that is so? Lower reciprocating mass as someone said? Or some other reason according to you?

[luckyd]

  On 10/1/2010 at 5:46 AM, Lance said:

In SOHC more low end torque, That means fast pickup, and in DOHC less low end torque, consequently low speed pickup but high end torque is there which would probably pull higher ks.(more power in cruising than SOHC). SOHC's are good for driving in traffic.

When it comes to evaluating we take DOHC performance calculations.

Yep, spot-on! I think with SOHCs you get the peak horsepower at a lower RPM compared to DOHCs, but, the peak RPM is relatively lower.

SOHCs are by no means out dated. If you take the CIVIC FD1 (1800CC), it has SOHC (correct me if I am wrong)

[BLu3HaZe]

  On 10/1/2010 at 6:35 AM, luckyd said:

Yep, spot-on! I think with SOHCs you get the peak horsepower at a lower RPM compared to DOHCs, but, the peak RPM is relatively lower.

SOHCs are by no means out dated. If you take the CIVIC FD1 (1800CC), it has SOHC (correct me if I am wrong)

Relatively lower but not always so, when you compare Toyota and Honda for example. And the Civic does have a SOHC engine while putting out more power than the DOHC 141 And it revs higher too in the Civic than 141, so it's not always the config itself as it seems but the manufacturer?

I feel that direct contact DOHC without rocker arms would be having best of both worlds though?

[heavyD]

This is a good read; http://paultan.org/2005/06/22/sohc-vs-dohc-valvetrains/