M110....why? - PeachParts Mercedes-Benz Forum

#1 12-20-2002, 09:48 AM

Why does the M110 have DOHC? It's not like it has 24v or variable valve timing; or anything that would require (or be made easier) with DOHC.

Mark DiSilvestro · #2 12-20-2002, 01:54 PM

The M110 engine has a crossflow head with (I think) hemi combustion chambers. This can be done with a single cam, like BMW, but many manufacturers chose the twin cam route in the '60s and '70s - eg. Fiat, Alfa Romeo, Aston Martin and Jaguar. It was supposed to be more efficient with lower emissions.

Happy Motoring, Mark

leathermang · #3 12-22-2002, 08:39 AM

Typically this arrangement would be designed to reduce both the number of pieces and the weight and flex/slop in the valve train...very hardy when done properly...in addition to the very nice crossflow/head configuration without introducing extreme offset bending forces in the valve opening mechanism....

240 Ed · #4 12-23-2002, 06:56 AM

Welcome to the forum Squareback!

It was done to increase the power and emissions. Simple!

leathermang · #5 12-23-2002, 09:01 AM

Sorry, that is TOO Simple....

The placement of the cams has nothing to do with power and emissions...
Power and emissions are determined by the cam lobe design (includes duration and lift), which includes valve overlap ( amount of time both the intake and exhaust valve in one cylinder are open at the same time ) , and valve timing....

240 Ed · #6 12-23-2002, 01:57 PM

Greg,

The placement of the cams were to permit a cross-flow design, which DOES increase stuff.
Apparently, the addition of another cam overcomes the complication of using rockers, etc. as in the Alfa V6...?

leathermang · #7 12-23-2002, 02:08 PM

The legendary Hemi Chrysler engines had crossflow but got it from a single normal placement cam... just using rocker arm/pushrod etc machinations...
Gravely tractor engines have great crossflow just like the lengendary Offenhouser Indy engines but place the cams under the valve and have flathead engines... the power still is in the cam profile... not the engine type with regards to cam placement...

240 Ed · #8 12-24-2002, 12:35 AM

...oh yeah?

neileg · #9 12-24-2002, 04:21 AM

Every era has its must-have engine development. Sometimes the idea is adopted more from fashion than engineering neccessity. During the sixties, the must have was DOHC. In the UK, Lotus took Uncle Henry's humble four cylinder and turned it into a ball of fire with a DOHC head. You could by a twin-cam cylinder head for a mini.

Bear in mind, however, that materials technology was under developed at this time. What is possible now with rocker arms and push rods, was just too complex for the steels and irons available in the sixties. The mass of the drive train and the acceleration needed for shorter duration cams was too much for all this valve gear. A cam placed directly over the valves eliminated a whole lot of mass. Thus, for an efficient cross flow head with sort duration valve timing, direct acting cams (requiring DOHC design) were the engineers solution.

Remember that MB always had relatively high output engines that lasted a long time. This was achieved by using the best design techniques, as well as care full engineering and assembly.

The quality of materials, precision mass production using CNC equipment, oils, electronic controls, all play their part in changing engine designs.

leathermang · #10 12-24-2002, 08:44 AM

Neil, actually your about a decade late in that description...
The early fifties at the Brickyard,,, Indy...had the offenhouser..... and the winner at Lemans about 1952 ( I think ) was an XK 120 Jag 6 cyl double overhead cams....
The Chrysler Hemi I was referring to was started about 1954 and was at 392 inches by 1957....
However, you could make a double overhead cam, crossflow hemi head engine with very modest output if you do not make the cam lobe design of sufficient overlap... ( meaning that the exhaust and intake valves are open at the same time to do as complete a job of getting the burned mixture out before closing the system to start the compression for the next stroke )...and duration...and lift....
Lotus's engine would not have been a ball of fire if they had kept Uncle Henry's same cam lobe specs...

need2speed · #11 12-24-2002, 01:22 PM

Quote:

Originally posted by squareback
Why does the M110 have DOHC? It's not like it has 24v or variable valve timing; or anything that would require (or be made easier) with DOHC.

Just curious...has the question been answered re the M110? Inquiring minds wanna know!

leathermang · #12 12-24-2002, 01:51 PM

I thought I answered it in my first post....

need2speed · #13 12-24-2002, 06:21 PM

Quote:

Originally posted by leathermang
Typically this arrangement would be designed to reduce both the number of pieces and the weight and flex/slop in the valve train...very hardy when done properly...in addition to the very nice crossflow/head configuration without introducing extreme offset bending forces in the valve opening mechanism....

I'm sorry, I though you were speaking generally. Was that the rational of the Mercedes engineers? I searched high and low for some official references but couldn't find any...I'd appreciate if you could share your sources.

leathermang · #14 12-24-2002, 06:37 PM

LOL, I am 53 and have been car crazy since the age of 14.....
It is a very good design,, which allows the stuff which others have mentioned also.... it is very simple, and it is important to keep the moving mass to a minimum when you want maximize efficiency, power, longevity, strength, etc... Engineers have known this a long time before they started using it on production vehicles .... so you may not be able to find some book or quote where someone says... " we engineers woke up this morning and decided to use a double head cam design because.... "...

My 1957 Jaguar xk140 had this design , with a 12 quart oil pan....

#15 12-24-2002, 10:51 PM

Wow, this turned into quite a discussion, lol.

I think my question has been answered. It's just something that I've been wondering about for the past 3 years (when I bought one).

Thanks