m-benzw203

Qust. i have a C320 01' and i see that it has a SOCH in it but now i see the new models have a DOCH so my qust. is what is the difference and those this make more hp. how do they both differ and is it worth it

Thx

white_w203

first of all to clear things up its

Single Over Head Cam SOHC

Double Over Head Cam DOHC

robohopar

its just the way the engines are designed...DOHC means the engine would have 2 cams per head, one cam for the exhaust & one for the intake...& doesnt necessarily mean that DOHC is better then SOH...hope that helps

AMGizZLe

Correct me if i'm wrong, DOHC won't tap out easily at higher speed than SOHC. I noticed that from a DOHC integra and a single cam Civic. Yeah they are rice.

Capt Nemo o2

The switched to DOHC because the new engines are 4 valves per cylinder. It is very difficult to reliably put 4 valves on one cam shaft. It doesnt mean one is by default better, but 4 valves allows much better breathing, and can more effectively get rid of exhuast, and bring in fresh air, which can allow it to make more power, but it all depends on the tune.

And yes, having 4 valves instead of 2 or 3 will allow the engine to make more power at higer engine speeds because it can get rid of exhuast fumes out of the cylinder better, allowing you to have more fresh air to use in the combustion process. That is the whole idea behind "Vtech" and the likes. The have variable cam timing to change when the valves open and close because at higer RPMs opening at the same point as at lower RPMs is not efficient in expelling exhuast and replacing it with fresh air/fuel.

carsandkites

MB used SOHC because there were fewer parts (hopefully meaning longer service life), but HP drives sales so they had to change to DOHC.

BabyBenz6spd

DOHC is design to make more HP
SOHC is design to make more Torque

DOHC engine usually has higher Redline compared to SOHC
DOHC engine cost more to make than SOHC

The only high revving SOHC engine that I know is probably the 3.2L VTEC engine in the Acura TL. Pretty amazing engine if you ask me.

Performance car usually have DOHC setup, while SOHC is cheaper to maintain and probably more reliable due to less moving components.

Outland

Its cost. DOHC is for most applications the better solution. SOHC, and OHV(cam is in the block) are much cheaper designs. Less machining, fewer components, less cost.

As for more torque from SOHC...not really. Torque is a function of stroke and displacement x number of cylinders. Big displacement, long stroke and 8 cylinders always means gobs of torque...regardless of how many cams an engine has. Where OHV and SOHC comes into the torque realm has to do with air flow. Steady flow, high velocity air intake from a two valve design tends to emphasize torque...but a lot of that is by design...because two valves flow poorly at high rpm- where you make all your HP...so the engineers try to enhance the torque if the engine can't spin high...and usually it can't spin because of the design favoring torque.

The most satisfying engines for daily driving all have lots of torque...torque is what gives you that grunt, that hard pull in gear accelleration.

m-benzw203

thx for the replys that has been helpful now my question is how big of a differnce is it if u have the same engine but the only difference is the Doch and Soch

Capt Nemo o2

For that... Drive the last gen Mustang GT and Mustang Mach1... The standard GT was SOHC where as the Mach1 was DOHC (Similar to the Cobra, but without the blower)...

Engine Specifications
4.6L 260 hp V8 - 4.6L 305 hp V8
Horsepower - 260 @ 5250 RPM - 305 @ 5800 RPM
Torque (lb-ft) - 302 @ 4000 RPM - 320 @ 4200 RPM
Valves/Valve Config - 16/SOHC - 32/DOHC
Displacement (cc) - 4605 - 4605
Bore X Stroke (in.) - 3.55 X 3.54 - 3.55 X 3.54
Compression Ratio - 9.4:1 - 10.1:1
Fuel Type/System - Gas/SEFI -- Gas/SEFI
Turbocharger - No - No
Supercharger - No - No

Its a decent real world comparo, since all is the same but the compression ratio, but thats not that huge of a difference... Its just to give you an idea...

TA-9FF

When were OHV engine's popular??? I've never even heard of OHV's...

mctwin2kman

Uhm the Viper has an OHV engine in it. Any engine that is not SOHC or DOHC is OHV. Like old V-6's and even some still used today. As well as V-8's. Think Chrysler, GM and Ford Trucks.

e1000

OHV = pushrod

Outland

OHV shaped the car world for decades. Just about every muscle car has been an OHV, or pushrod- if you prefer, engine. Plenty of European cars have used them in the past as well. Nowdays, its mostly GM and Ford still pushing pushrods...and Daimler Chrysler! Its V10, and both of the Hemi's are OHV. There's nothing inherently wrong with pushrod engines. They cost less, use fewer components, have good reliability, and are considerably lighter and more compact than OHC designs. And with designs like the Corvette's V8 making serious HP- you can't argue the results.

BTW, OHC, and DOHC designs are nothing new. They date all the way back to the 1920's, perhaps even earlier. Complexity and Cost kept them a niche technology until the late 70's and early 80's.

patrick_y

Having both a SOHC car and a DOHC car in the garage, it's difficult to say which one is better.

I will say that I think that SOHC cars on average get better fuel economy. I could be wrong.

DOHC cars are definitely higher revving and more inclined to rev than SOHC cars.

Many people are wondering why their expensive cars have SOHC and think it's a compromise to DOHC, personally I can't really tell the difference.

We should have a poll, which do you prefer?
SOHC?
DOHC?
Either?

BabyBenz6spd

I prefer DOHC over both just because is more "advance" and all the race car uses this setup (JGTC, DTM, Formula One, etc..), allows higher ravving.

P.S. I'll take Rotary engine over all of the above~

m-benzw203

i was looking at the MB web site and most of the AMG models have SOCH even the SLR i think

tifosiv122

Can a mod please fix the title of this thread.

Erik

e1000

I believe F1 uses pneumatic valves due to the 18,000 to now 20,000 rpm they achieve.

fasteddie

DOHC allows better control of the the Variable valve timing. Variable valve timing does not work as well on a SOHC, since you change the intake and exhaust togeather, when what you really want to do is advance the intake timing, and retard the exhaust timing....or something like that.

Ed.

bwco

Wow, there's lots of misinformation in this thread ! Beware !

Outland

Yep. MB is el-cheapo. MB's outgoing family of V8 and V6 motors are all spawned from the same architecture. The three valve SOHC design was a compromise...to save money, yet get some improvement in breathing.

fasteddie

I agree;

Thus is why BMW engines had it over Merc Engines. Using their Double Vanos, BMW could keep the low end torque & efficiency, while still reving to get the HP.

Now that Merc has a decent platform, the score should be much more equal.


Note from 2002 the 230 was a dohc, with independant Variable Valve timing on intake & exhaust. I think Merc saw they had to play catch-up back in 2000, and the 1.8 was the development mule for the head.

fasteddie

You posess some knowledge you would like to share????.......or you just like to comment about other's?

Outland

The M111 engine which powered the SLK, and 2002 C230 had double overhead cams and four valves per cylinder from the get go...the variable valve timing, which, IIRC is intake side only, came in 2001.

The M271 had it on exhaust and intake. I don't really see the M271 as anything but a long overdue replacment for the M111. I prefer the M111(m271 didn't deliver on the performance), but standards for things like fuel economy, NVH, and emmisions always are marching forward.