SOHC vs DOHC

arlenok · Post by **arlenok** » Sat Feb 28, 2009 11:56 pm

After reading up on howstuffworks.com, I'm confused as to why DOHC 2.0's make more power than SOHC 2.0's. It said that the only advantage to DOHC is that it allows twice the valves to be in a chamber. But both DOHC and SOHC 2.0's have 16 valves. So whats the secret?

SOKADAO954 · Post by **SOKADAO954** » Sun Mar 01, 2009 12:39 am

its speaks for its self
DOHC= DUAL over head cam
SOHC= SINGLE over head cam

like im not being a a hole but it does speak for its self

Post by **occasional demons** » Sun Mar 01, 2009 12:44 am

They are mainly using that argument from the early 16 valve engines. Most 4 valve per cyl. engines had DOHC, and 2 valve per cyl. where SOHC, or push rod engines. So there was a huge difference in power. Now referring to the 1gn 2.0's and 4 valve engines in general, the DOHC set up has it's advantages in the overlap, and lobe seperation can be tuned more due to there being seperate cams for the intake and exhaust. The timing of each cam can be changed to better suit your needs. The SOHC is adjustable, but it move the whole powerband, because both intake and exhaust events are being shifted together. The DOHC lets the intake timing to be advanced and the exhaust be retarded, giving it an effect of being a longer duration cam. Just as one example. It isn't that simple/easy, but it gives an idea.
In the 2.0 the power difference isn't nearly as big. in stock form. the advantage of the DOHC, was made up with the larger exhaust ports, a mild cam change and PCM tuning, in the form of the Magnum engine. That could never have been done with an eight valve 2.0. But if they would have used the DOHC for the R/T's, they prolly could have done better. But it prolly wasn't "cost effective."

arlenok · Post by **arlenok** » Sun Mar 01, 2009 4:36 am

Ah, I never thought about tuning it separately.
But @ SOKADAO954 I wasn't asking what SOHC and DOHC mean... I have a pretty nice grasp on it.

SOKADAO954 · Post by **SOKADAO954** » Sun Mar 01, 2009 11:49 am

arlenok wrote:Ah, I never thought about tuning it separately.
But @ SOKADAO954 I wasn't asking what SOHC and DOHC mean... I have a pretty nice grasp on it.

i understand...

03blackrt · Post by **03blackrt** » Sun Mar 01, 2009 1:08 pm

The only real advantage the DOHC head has over the SOHC is that it was designed for the 2.4L, so it flows more in stock form. Kinda like how 360 heads can be put on a 318 SB Chrysler.

SOKADAO954 · Post by **SOKADAO954** » Sun Mar 01, 2009 2:05 pm

03blackrt wrote:The only real advantage the DOHC head has over the SOHC is that it was designed for the 2.4L, so it flows more in stock form. Kinda like how 360 heads can be put on a 318 SB Chrysler.

i agree much...

Donkeypuncher · Post by **Donkeypuncher** » Mon Mar 02, 2009 2:10 am

I know the dohc 420a performs much better above 5k than our sohc, but I'm not sure if that's tuning or the different head design. The 420a head was designed by lotus from what I've read, so it is definitely a quality piece. I do think that the sohc performs a little better from 3.5k to 4.5k, but both are pretty weak below 3k.

Then again, there are so many variables between the 2 you can't really compare them fairly. Different manifold designs, tuning, gearing, and wheel size make for a hard comparison.