StephenK

This is not SL specific, but I figured the people in here would know the answer!

Curious about why different engines have a different number of valves and what the reason for it is:

V-6 24 Valve
v-8 24 Valve
V-12 36 Valve - Mine
V-8 32 Valve
V-12 48 Valve

vraa

3 per cylinder.
Four on the newer engines.

Mercedes is so slow on technology.

E55AMG99

How so? MB has always been an innovator and holds more patents than any other car maker. 3 valve technology was a cost cutting move from the 4 valve engines they had up until the mid to late 80's. Going back to 4 valve now that the public's desire to get more performance out of a car is greater than their aversion to cost increase.

tiggerfink

New Technology has made the 4-valve cheaper to build for Mercedes and give better gas milage. Just remember all the carmakers share technology. Who ever invented the technology first has the exclusive right to use it first or charge royalties.

Has anyone watch the windows go down and up when you open and close the door. Audi had that technology first. BWM will start using the nano paint in 2006 or 2007. BMW will also have the keyless enter system like on the SL where you touch the door handle to open in September of 2005.

E55AMG99

Most of what you are saying is true but it is still more expensive to build 4 valve DOHC heads than 3 valve SOHC heads because the same new technology that benefits the former, also benefits the latter. Fewer valves, springs, retainers, followers, seals, cams, etc. obvioulsy mean fewer $$$.

The performance and efficiency will be better on the 4 valve heads which is what the market wants.

tiggerfink

If Mercedes kept the 3-valve engine until now because it is cheaper, why would Mercedes have the following?

anti-locking brakes
more than two pistions per brake
SBC
air suspension
Sensors everywhere
Telaid
7-speed tansmission
knee air bags
etc

I just think the Mercedes engineers made decision on the 3-valve in the past and did not want to change, because they did not think of it first. For example, MY 2002 R170 SLK320 has the rail steering wheel system. The rack and pinion steering wheel system has been out for over 10 years. Mercedes has now made rack and pinion steering a standard in all its cars.

RadSteve

I can confirm the BMW keyless system on my 06 750Li works just the same as the Mercedes one, except you simply push the whole handle in to lock instead of fingering the tiny square button like on the mercedes.

E55AMG99

What rock do you live under?

First, MB did not invent multi (3 or 4) valve technology nor is it a recent development. You need to go back to the early 20th centuty when Ettore Bugatti was building cars. He was considered the first to put 3 and 4 valve DOHC cars into production. No car company sticks with a particular product or technology purely becasue of the shame of not thinking of something better first.

Second, MB was using 4 valve heads in the 70's and 80's on almost every engine from 4 to 12 cyls. They still use it on I4 today and the I6 until they stopped production a few years ago. They switched to 3 valve heads with SOHC to cut costs and to a lesser degree, emissions. The reason they are just now going back to 4 valves is that the market is demanding more performance that a 3 valve head cannot supply.

Your other examples are laughable. Those items are there becasue they either add to performance, efficiency, safety or cost reduction or that the public demand for them is high. If MB did not include most of them, the car would be called a KIA. Hell, it wouldn't even be able to compete with a KIA!

vraa

How much do you think they saved per engine by going to 3-V?

Cuz I mean, the Toyota Camry and Echo have 4-V/Cylinder.. ?

E55AMG99

Good question to which I don't have the answer but I can guess that it would be something like this....(typical 8 cyl)

2 camshafts
8 saddles
8 bearings
2 cam gears
2 cam chains
8 valves
8 valve springs
8 valve retainers
8 valve seals
8 cam followers

50% less cams to time
25% less valves to assemble
50% less cam assembly
50% less cam bore machining
25% less valve seat machining

Anything else? Maybe it adds up to several hundred dollars per engine. Multiply that by the number of engines produced annually and you've got some serious coin.

tiggerfink

Do not have to get testy about it. I never did say Mercedes invented the 3-valve engine. I said the engineers made a decision and did not want to change.

Mercedes did not invent the engine, but they design one for their cars. Are you trying to tell me that all 3-valve engines and 4-valve engines are exactly alike from different automakers? Maybe at the time it was cost, but Mercedes designed the new 4-valve engine to be cheaper than the old 3-valve engine. I also was told that Mercedes went to the 3-valve engine because of emissions. The owner of the Memphis dealership told me that technology has made the new engine cheaper to produce and have better emissions. If you think about; a lot of stuff today is cheaper and better, because we discovered a new process of creating it.

You may think my examples are laughable, but I was pointing out that Mercedes is one of the few automakers that have more car technology in their cars as compare to the others. I just do not see how cost can be an issue when Mercedes put extra technology in their cars that even their competitors do not have. I guess Mercedes found another way to cut cost by putting in outdated user interface technologies like the NAV, phone, and other stuff.

If the 3-valve cost so much less, why did the cheap slow Japanese carmakers use the 4-valve engine? Ford is the other carmakers thats still uses 3-valves in their autos.

vraa

Ah yes, but aren't you making a lot more on the return?

E55AMG99

Not testy at all. I'm grinning ear to ear every time I see posts like this.

You are not looking at the big picture. Yes, MB made a decision to go DOWN to 3 valve from 4 valves. Was it the right one? At the time, absolutely. It reduced costs and emissions. Other improvements in the engine made up for lost performance. Your assertion that they somehow made a mistake going to 3 valve and couldn't go back to 4 valve because of *pride* or something like it is what has me laughing. No auto manufacturer can research, design, develop, tool and impliment an engine on this scale and scrap it in a short period of time. Think of the supply chain too. Sometimes the costs run into the billions. Even if it was a total bomb, they would improve it and not scrap it altogether. Those costs have to be recouped over 100,000's of units.

There are new sets of design criteria for the new engines from MB. More performance and efficiency are in the top 5. Lower profile and lower costs are also there as well. The current 3 valve motor cannot produce the kind of power needed for the next gen motors in naturally aspirated form. However, it will still cost MORE to build a 4 valve motor than a 3 valve motor no matter who is building it. There are simply more parts and labor.

Building a car is easy. Running a profitable car is not. R&D costs big $$$. I'm sure the bean counters have a big say as to why every detail is what it is on every model of car. If it does not help sell the car and it is not cost effective to produce, it isn't going in the car. They also have cost projections that tell them how many units they need to sell of a particular type to be cost effective. Haven't you asked "Why can't they just add X to this car?" It's all about the $.

You are right about how MB can put so much technology in their cars that others can't. They skimp on certain items like the antiquated NAV system or the lack of full guages, etc. Their market research must have told them that these items were not as important as 27 airbags or else it wouldn't happen. They don't sit around the coffee pot and say, I think I'l add another airbag to the S class this year and take out the volt meter. They start with focus groups and marketing surveys and when the bean counters say make it cheaper, they look for items they can cut without sacrificing brand integrity, performance, efficiency, etc. like one valve per cylinder.

This is why I'm laughing.

Patrick1990

i thought Mercedes SL was the most high-tech car in the world. With ESP ABS ABC SBC BAS. etc. it have more technology than whole kirgistan. It isn't because they need money, because they have sold more cars han BMW every single month in 50 years (exept September 2003 because everyoe gotta have bangles new cars before he stopped his deign.) It might be because it run some few miles more per gallon with 3 valves

Patrick1990

Yeah okay..but i surrive with 2 valves and a whole cylinder that dosen't wanna run all the time so..yeah..."It weight to much, the engine sucks, the roof dosn't work, it has 200 issues that cost u self the breakfast, but u are driving in the best looking car ever so what is the problem!?" - Christian Frost (Said it about a Ferrari but i've changed the story a bit)

People who drive SL don't care about tirespin, and horsepower, they just wanna could drive to the store everyday in style with..something..weird, i can't remeber the last... - Jeremy Clarkson

tiggerfink

Lets try another approach. The new 4-valve modular engine is made in a different process than the old 3-valve engine. That could be the reason why the new engine is cheaper and faster to build as compare to the old 3-valve engines. If Mercedes built a new 3-valve modular engine with today’s technology, I can see why it would be cheaper to build the 3-valve as compare to the new 4-valve engine.

But cost was never a factor on why Mercedes decided to build the 3-valve engine. At that time the 3-valve engine did a better job on emissions. It was a decision that Mercedes made, and I do not know why. I do know that the other manufactures start using the new 4-valve engines in the mid 80s even though the 4-valve engines had a problem of not generating enough low-end torque. In the 90’s the carmakers discovered a cost-effective way of generating low-end torque on the 4-valve engines. The articles below show that cost was never a factor for Mercedes to build the 3-valve engines.


http://www.findarticles.com/p/articl...93270#continue

http://www.autozine.org/technical_sc...h_engine_2.htm

http://www.ukcar.com/features/tech/E...tivalve345.htm

sillydriver

I’ve also heard the three valve design had to do with emissions. One reason is the quicker hating of the catalyst mentioned above. I believe the other is that the 3 valve design allows for the placement of twin spark plugs to eliminate misfires, which produce unburned hydrocarbons. I think the 3 valve design with single overhead cams is not a bad one for an engine that doesn’t rev so high that DOHCs are needed. Multi-valves improve airflow on the intake side, drawing in a larger air-fuel charge for more power. The 3 valve engines have two intake valves for this purpose, just as the 4 valve engines do. Having only a single exhaust valve will not eliminate the multi-valve benefit since charging the cylinder only involves the intake valves.