I know this probably came up before but I was wondering if someone could describe the real + and - of SOHC vs DOHC. I've heard that SOHC because they use rocker arms aren't as good as DOHC. I didn't understand at all.
Why would mercedes go to SOHC?

The SOHC valvetrain of the M103 generation engines and the SOHC valvetrain of the new twin-plug/3-vavle are totally different. The new engine has 3 valves per cyl. Two intake and one exhaust. They use the extra room to add a second spark plug. The twin-plug ignition gives a much cleaner burn than the older engine families. This means better "power-per-gallon" and less emissions. All the new engines have a trick intake that helps the torque characteristics immensely. I answered a similar question in regarding new vs old in another forum. The latest SOHC engines don't quite make the power of the previous DOHC engines but they do weigh less so there is a positive power-to-weight improvement. Give article http://www.peachparts.com/ubb/Forum5/HTML/000023.html a look and if you have any more questions please post or email me.

Hope this helps...Lee

The engine mechanics are easier to build on the SOHC engine But the fuel managment system is more complex. So a cheaper engine w/expensive computer.

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MERCEDES BENZ MASTER GUILD TECHNICIAN
ASE MASTER TECHNICIAN
27 YEARS M.B. TECH

Thank you very much for your input. I was wondering if you could go to http://www.insidetheweb.com/messageboard/mbs.cgi?acct=mb241872
and also explain in more detail. This is a current discussion over there.