Musikmann

Hi friends,

I have been wondering this for some time:

1) Are there 2 intake valves and 1 exhaust valve on the M-Bs or vice versa?

2) Why then do several of the high-output american engines have 2/2?

Parenthetically, I'm NOT second-guessing the german Daimler engineers, but this has always seemed a bit odd to me.

Thanks in advance,

Musikmann

lkchris

The new V6 and V8 are 4-valvers.

So are the diesels.

Musikmann

OK, sounds good, but why did the Daimler engineers decide that the (gasp!) american idea was better, and why?

Maybe I should have posted this in the Tech section, but it seems to me that a lot of you guys are quite technologically astute.

Sorry that I am so ignorant about the mechanical workings of internal combustion engines, but I am a mere medical type who LOVES his Daimler-Benz, as old and decrepid as it might be

Musikmann

Bigdot

if i remember, its two intake and one exghaust, but teh exghaust is the size of two put together. i think thats right. and its for fuel econ. and emmitions.
mark

Musikmann

Thanks Mark

Nice Benz collection you have too!

MercedesFTW

Well the old SL500 had aporx 300 hp, while the new Sl550 has 380 some. Despite the extra power the new engine still has the same feul econ due to the more efficient engine.

Kinda off topic...my friend says his Audi A4 has 5 valves per cylinder...? Anyone care to explain how this works? One camshaft? Two?

Musikmann

Thanks for the feedback MercedesFTW.

I have no idea about the 5 valves/cylinder, but I hope someone with an answer sees this because I am curious too.

I think I DO know that the A4 base model only has a 1.8 liter turbocharged 4-cylinder. At least one optional engine is a pretty expensive smallish 6.

M

Fifth Ring

Kudos on the curiousity. Firstly, the four-valve engine (2 intake 2 exhaust) is NOT by any stretch an "American" thing. In fact, the American car makers have been very slow to adopt this configuration which has been used in Europe and Japan for many years. The current Corvette is still a 2-valve engine.

To run a 4-valve engine, you generally need double overhead cams, and that's complex. You can run a 2 valve and 3 valve engine on single cams. So, the Benz 3 valve setup was as far as you could go with a single overhead cam.

Valves are all about breathing -- getting fuel/air into the cylinder fast, then getting the exhaust out. The more valve area, the better, and you can use bigger valves, but you are limited because there's only so big the valves' circular holes can be. But by using more smaller holes, you get more area. Imagine a big circle, 5" in diameter as your cylinder. If you put two big circles inside it, they are each 2.5" in diameter, and give an area of 9.8 inches. If you use three smaller circles (sorry can't do the math) you'll cover more area. Audi has used 5-valve engines (3 intake, 2 exhaust) for several years.

All that being said, the Corvette V8 is a very strong engine, using two valves (and I won't even get into the issue of pushrods versus overhead cams).

So, to summarize. 4 valve technology has become very standard and common, with a few going up to 5 valve, and a few lagging with 3 or even 2 valves.

lkchris

Hah!

4-valve technology dates to the 1920s and I believe Peugeot.

The Mercedes M104 I6 that preceded the 1996 V6 was 4-valve.

The 500E engine was 4-valve.

American manufaturers were probably the LAST to adopt 4-valve technology.

American manufacturers mostly build 3rd-world cars and 4-valve technology is too expensive for this market. Designs from the 1950s remain prevalent.

e1000

um. ok. I don't pretend to know a ton about engine internals but I believe the D-Series engine in my 1996 Honda Civic EX was an SOHC 4-valve engine and I KNOW that the J-Series engines Honda currently produces are all SOHC 4-valve.

http://en.wikipedia.org/wiki/Honda_J_engine

1985mb

Mercedes' parent DaimlerChrysler (a.k.a. "DCX") is a public company, i.e. DCX is a listed stock on the stock exchange.

Consequently, the management are always under pressure to deliver the profitability and profit growth that is expected by institutional investors, wall street analysts, etc. This is true for most, if not all, public companies.

Many decisions, possibly (or not) including the 3 valves vs. 4 decision, are dictated as much by the bottom line as they are by engineering or automotive benefit. In an ideal world, automakers would input 100% of their technology and know-how into their production cars. But, in a commercial world, they know that sometimes 90% or even 80% will yield the best results on the bottom line.

Remember, any given compromise in a car is not just about saving X dollars per car (tens of dollars here or maybe hundreds there). There may be equivalent or greater savings by saving Y hundred million or billion dollars on the Research & Development costs.

Developing cars is a huge expense (which is why you see car companies merging or getting bought out), and manufacturers think about these things every day on every model. If they can save $200 million dollars on NOT fully developing something that perhaps only 5% of owners will notice, you can bet that they will probably keep the money in the bank.

It's not just about coming up with the idea -- taking that idea from the proverbial drawing board to the production line and showroom takes a lot of investment dollars.



PS: I may be wrong, but weren't there some MB models which actually regressed from 4-valve to 3-valve in the late 1990's?

lkchris

Guess you missed where I posted

The Mercedes M104 I6 that preceded the 1996 V6 was 4-valve.

"Regressed" is a word used only by those that believe "more is better." It's a simplistic belief.

Musikmann

I appreciate everyone's thoughtful, and informed, feedback.

This is what I like about these boards - nearly EVERYONE knows a helluva lot more than I do, so it's ALWAYS a learning experience to read the various posts and answers to my questions.

Musikmann

patrick_y

I think it's 2 exhaust valves and one intake valve.

1985mb

You try to judge or generalize people based on a single word choice? Now that's simplistic, to say the least!

Yes, you're right I missed your earlier post and you're probably right that the "M104 I6 that preceded the 1996 V6 was 4-valve." However, you're missing the bigger picture.

As an MB enthusiast, it hurts me to see that MB management made a lot of mistakes and cut some corners leading up to, during and after the Chrysler acquisition (leaving aside the wholly separate debate around the Chrysler "mistake"). Too many decisions were made for financial purposes, and for short-term financial gain at that. If you think I'm wildly off the mark, ask Jurgen Schremp, DaimlerChrysler's disgraced former CEO. I wouldn't criticize a car manufacturer for making financial decisions, as long as they have the long-term health of the company and brand in mind.

Took a while for MB to further develop the 1996 3.2L SOHC 18-valve V6 (221hp/232lb-ft) to the new-for-2006 model year 3.5L DOHC 24-valve V6 (268hp/258 lb-ft), don't you think? The decision to delay or spread out the development of that engine was, in most part, a financially-driven decision (IMHO).

10 years in a highly competitive market with essentially the same unchanged engine? In a simplistic view, that's not a lot of progress.

Holson

For whatever it's worth, I think that the 4 Valve/Cyl 4.2L M119 V8 (275hp/295lb ft TQ) in my E420 sounds much sweeter than the 3 Valve/Cyl 5.4L M113 V8 (342hp/376lb ft TQ in my CLK55. However, there's no denying that the M113 seems to have much more TQ down low.

Staying with the discussion, the 3.5L V-8 in the Ferrari F355 has 5 valves/cyl. (3 Intake, 2 exhaust)

alpinweiss

The Audi 1.8T has now been superseded by a new 2.0T engine (also known as 2.0 FSI). Interestingly, the new 2.0 has 4 valves per cylinder, instead of the 5 valves per cylinder in the old 1.8T.

The 1.8T engine had double overhead cams; one cam operating 3 valves per cylinder (intake), and the other cam operating 2 valves per cylinder (exhaust). A timing belt connected the crankshaft to the exhaust camshaft. The two camshafts were connected by a chain within the cylinder head. The 1.8T had turbocharging and indirect injection (intake port). Power ratings 150 hp to over 240 hp.

The 2.0 FSI engine is available in Audi A3, A4, and A6 in the USA. Volkswagen uses the same engine in the new Passat, new GTI, and a few high performance Jettas (GLI, etc.). It has double overhead cams (2 valves per cam), turbocharging, and direct injection. Power ratings 200 hp and up.

MercedesFTW

Thanks for the info alpinweiss!

The SLR only has 3 valves per cylinder. Wonder what they can do with 4 more?

AndrewAZ

Here is an article about the V6 engine used in the ML 320 C320 E320 and so on.

Three-Valve Technology Reduces Emissions by 40 Percent

The new Mercedes-Benz V6 engine features innovative three-valve-per-cylinder technology which can reduce exhaust emissions dramatically over 40 percent particularly during the critical warmup stage, before the catalytic converter usually begins to operate. Catalysts must heat up to work effectively, and this takes nearly two minutes with most modern engines. Increasingly strict emissions limits mean this converter light-off time must be reduced to about one minute, and the new Mercedes-Benz V6 meets this tough criteria. There's about 30 percent less surface area at the exhaust port, relative to a comparable four-valve engine, which dramatically reduces exhaust heat losses between the engine and the catalytic converter. This translates to higher exhaust temperature (about 70 degrees Centigrade or 125 degrees Fahrenheit) and converter "light-off" about 12 seconds earlier.

In the new V6, combustion heat in each of the large, single exhaust valves is dissipated through a sodium-filled valve stem, while exhaust heat is retained and insulated by double-wall piping in the exhaust manifold. The seamless double-wall manifold is made by using high-pressure liquid-forming technology, for greater durability and lighter weight.

There is no tradeoff in horsepower and torque with the new three-valve technology compared to a four-valve design. In any efficient, well-designed engine, exhaust valve size needs to be somewhat smaller than the intake valve area, simply because the "leftovers" of combustion (especially in a modern, clean-burning engine) take up less space than the incoming fuel-air mixture.

Forgot to give Three-Valve Technology Reduces Emissions by 40 Percent

The new Mercedes-Benz V6 engine features innovative three-valve-per-cylinder technology which can reduce exhaust emissions dramatically over 40 percent particularly during the critical warmup stage, before the catalytic converter usually begins to operate. Catalysts must heat up to work effectively, and this takes nearly two minutes with most modern engines. Increasingly strict emissions limits mean this converter light-off time must be reduced to about one minute, and the new Mercedes-Benz V6 meets this tough criteria. There's about 30 percent less surface area at the exhaust port, relative to a comparable four-valve engine, which dramatically reduces exhaust heat losses between the engine and the catalytic converter. This translates to higher exhaust temperature (about 70 degrees Centigrade or 125 degrees Fahrenheit) and converter "light-off" about 12 seconds earlier.

In the new V6, combustion heat in each of the large, single exhaust valves is dissipated through a sodium-filled valve stem, while exhaust heat is retained and insulated by double-wall piping in the exhaust manifold. The seamless double-wall manifold is made by using high-pressure liquid-forming technology, for greater durability and lighter weight.

There is no tradeoff in horsepower and torque with the new three-valve technology compared to a four-valve design. In any efficient, well-designed engine, exhaust valve size needs to be somewhat smaller than the intake valve area, simply because the "leftovers" of combustion (especially in a modern, clean-burning engine) take up less space than the incoming fuel-air mixture.

Forgot to give wolfgang credit for this http://www.whnet.com/4x4/new_V6.html

1985mb

Good article ... thanks for posting

Musikmann

Thank you for what is, in my opinion, a very intelligent analysis of what we as car owners are facing in our quest of automotive design excellence.

Do you happen to know what was the situation (private vs public) of Daimler before their acquisition/merger with Chrysler?

Musikmann

Musikmann

Andrew,

I'd like to thank you as well for this article - very informative.

Musikmann

1985mb

I believe Daimler had been public before their acquisition/merger with Chrysler. However, I don't think that acquisition was well-received by the stock market. As stocks started to decline post-2000, DCX's stock price and its market value took a significant hit. Not only was the whole market going south, but DCX was undertaking a large and risky merger, and investors were understandably very very skeptical.

In such an environment, management's thoughts focus even more than usual on the bottom line. If you can boost profits, the stock price might recover. You can boost profits by increasing sales and/or cutting costs.

DCX had to do both, but in some instances they took a short-sighted view of things. Does anyone want to argue the few extra sales of the C230 Coupe really helped the long-term brand or financial future of MB?

Cutting costs in an automotive company is very tricky and quite a fine line to walk. MB and DCX did not exactly do the best job of that in the late 1990's and early 2000's.

BMW made its own strategic and financial blunders in that era (namely, Rover). However, with the Quandt family owning a significant chunk of the voting shares in BMW, the management had slightly more breathing room to take a long-term view of things. DCX felt the pressure to "make the numbers" and show earnings-per-share growth quarter in, quarter out, year in, year out.

On a side note, a somewhat parallel set of circumstances is in play at GM and Ford. GM, like DCX, has more of a normal ownership structure ("common stock"holders are the owners of the company), while Ford has the Ford family which owns a disproportionate amount of special "voting" stock. Hence, the Ford family exerts a lot more control/influence over the company than at most public companies.

This wouldn't have been such a problem if the Ford family hadn't insisted on putting their scion (Bill Ford) at the helm. While Rick Wagoner at GM has no birthright to the company and is accountable to all shareholders equally, Bill Ford is nicely secure in his job and is accountable to two different sets of shareholders (his family, and everyone else). All else being equal (which they aren't), bet on the company with a professionally hired CEO to come out ahead of one which has family connections at the top (Bill Ford came up through the FoMoCo management ranks "without ever really being tested," say some sources).

AndrewAZ

All car makers are cost cutting Mercedes a few years back decided it ended up costing them more in the long run by cost cutting so they have since reversed it. Just look at the quality of the ML's after 2002 and they ever improved, now look at the quality on the new W164 ML its a big improvement.

I dont get why everyone bashes the C class I think its a great car and most dont realize that it accounts for over 50% of cars sold by Mercedes.

But it is going to take Mercedes some time to recover from the cost cutting from 1998-2002.

Musikmann

Hello again,

WOW, you seem to know the NYSE pretty well (specifically the automotive industry). I see that you are in NY, NY - if I were a betting man, I'd say you have an office somewhere near Wall Street, and are an investment analyst for one of the major brokerage houses. If you're not an analyst or a broker, I advise you to look in that direction

On a serious note, I really appreciate your learned input as to what began as my stupid question about cylinder valves.

Lastly, I sold some stock for a long-term gain in order to buy DCX because (hehe, I guess I really AM a betting man) I thought that they will outshine Ford and GM over the long term. Truthfully, maybe I should have bought Toyota, but those shares cost about $100 each at that time.

Regards,

Musikmann