OHV, OHC or SOHC & DOHC ENGINES

[airomerix]

Nice info. Thumbs up

[kamilali]

Its one of the most informative thread on PW,
cleared my most of the wrong concepts..
good going.

[sherwan_88]

This is a very strange question. You are essentially asking if a sewing machine can be converted into loom. Engine block and head are usually forged. They can not be modified the way you are describing it. You can change components, like bearings and pistons but you can not add or remove cams or vales. You will have to change the whole engine.

Some Japanese Family of engines use the same block for the whole family. For Example the Toyota C Engine. If there was a variant with DOHC setup, you can easily swap the head with DOHC one, but your statement still remains effective, because this is not possible for all engines, plus one would need vast knowledge of engines to actually do so. Not your normal chaps daily thing.

[whisky]

@atherr

DOHC engines do not have double the valves. With two cams, you get the added benefit of having intake valves on one cam and exhaust on the other. This in turn increases efficiency because each cam does it's own work unlike SOHC engines where a single cam has to cater for both the intake and exhaust valves.

[asad_scorpio21]

nice sharing of info

[ZEESHAN84]

Dear I have d15b3 what about it...is it dohc and howz its performance.
thanx in advance...!!!!

[levin]

Well.Dohc is better than Sohc
Dohc engine has twice as many intakes and exhaust valves as sohc motor.
This makes the engine run more cooler,smoothly,more quietly and efficiently.
But yes the dohc engines costs more for repairs.
where as sohc engines r cheaper...

i thought dohc is better but when i test drove bmw 750il

12 cylinder sohc engine, it had massive low end torque and good high end rpm power
vs
my prevoius car bmw 740il

8 cylinder dohc it has bit less than 750 but nice low end rpm torque and went stable on high end rpm.

so i concluded sohc engines do have better low end torque and dohc engines have better high end torque. ,

[ahsanzs]

Dear I have d15b3 what about it...is it dohc and howz its performance.

Wikipedia is your friend. Apparently all D15B variants had SOHC heads, so no hope. However all D15B are 16-valve so you are luckier than Margalla owners. The performance is still very nice.

@atherr

DOHC engines do not have double the valves.

In some engines (in some parts of the world) you have the option of either 8-valve SOHC I-4 or 16-valve DOHC I-4. You can also have an option b/w 16-valve SOHC I-4 or 16-valve DOHC I-4. In the first case at least, there is a situation where the DOHC variant has twice the valves than the SOHC variant.

I would like to point out that the Pushrod (OHV) type engines are now primarily produced by American automakers, namely GM and Chrysler.

Bentley/Rolls Royce also favour pushrods. They are very robust and no timing belt breaking issue yay!

DOHC engines are more expensive to produce than SOHC models.

Very simple reason. You have one additional shaft. Plus other additional stuff. I mean since actual material (read mass=kg) is more therefore cost is more. Also, to justify DOHC vs. SOHC the design engineers must work pretty hard to optimize so there is an actual benefit in terms of power gains as compared to SOHC. Therefore more man-hours put in design = greater cost of product.

This is not correct at all. DOHC engines are more efficient than SOHC designs.

Yeah right. DOHC can be optimized to be a fuel miser but its absurd spending more to save more. So it is optimized to provide more power instead.

so i concluded sohc engines do have better low end torque and dohc engines have better high end torque.

And this is nature's gift for us. Cheap cars have small engines and not meant to run fast so need all the grunt down there at the start. And fast cars are costly and seldom loaded with trailer/cargo and enthusiastic drivers tend to press more for high rpm and the expensive DOHC's goodness comes out there. There are seldom perfect matches in nature.

[atherrr]

@atherr

DOHC engines do not have double the valves. With two cams, you get the added benefit of having intake valves on one cam and exhaust on the other. This in turn increases efficiency because each cam does it's own work unlike SOHC engines where a single cam has to cater for both the intake and exhaust valves.

Bhai jaan dohc engines r multivalve but not all dohc engines..pehlay dohc was common in two valve per cylinder and now mostly dohc engines r multivalve....

even u can read the info provided above for u...
thnx

[whisky]

@ahsanzs
Yes, but that's a very rare case like the 5 cylinder Honda G engine which no one believes exists. It would be wrong to say that DOHC engines have twice the valves. But it is not impossible for them to have twice the valves depending on engine design and specification.

@atherr
Sorry, I don't understand what you're trying to say. I think I know what I'm saying.

[daniyalahmad]

@OP
thanks alot for the share
its the info I always wanted to know and you explained it in the most simplified way
thanks alot

[JuGnO]

nice review and nice thread ... where is the appreciate button

[malikg115]

gr8 efforts bro

[BilalYusrat]

DOHC Pros: High efficiency, possible to install multiple valves per cylinder and adopt variable timing.

I have Honda City 09, it has a SOHC engine and 4 valves per cylinder?!? And plus the "iVTEC" symbol suggests that it has variable value timing as well? How come?

[Zaeem89]

@shariqak
Nice information but for your correction new civic has SOHC.
And Liana, Corolla have DOHC
The main difference i noticed between dohc and sohc is that dohc engines love to be revved and they are very smooth but they have less torque in lower revves.
To sum up DOHCs have more topspeed but the SOHC will have more acceleration (if both are of same capacity).
1.3 Baleno had more acceleration than Liana but Liana had much more top speed.

[daniyalahmad]

^hmmm
I have also heard the same
but what could possibily the reason that SOHC,s are having greater acceleration than a DOHC engine?

[atherrr]

welll how is it possible when dohc engines produce more horses...

[daniyalahmad]

^Thats what I want to know aswell

[airomerix]

A simple fact, R18A being stock does 0-100 in 8.6 seconds where as IZZ-FE being a DOCH does in 10. So technology and brand matters. Similarly iam sure Audis 1.8 FSi would smoke R18A. After its "Audi's"

[Bilaltq]

welll how is it possible when dohc engines produce more horses...

Because the engine can breathe better. Instead of one camshaft controlling the valves, you have two. So you can dedicate one camshaft to the intake, and one to the exhaust valves. You can add more valves i.e. give it better induction, and with a DOHC design, you can tune the car more efficiently in order to manage power at specific RPM's.