...further to the BMW mention, it is worth noting that the new and seriously kick-a$$ BMW M3 has a 333 HP naturally aspirated inline 6...I've been in one and to hear it revving up around 8K is something to behold - a killer engine!

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Chris
2007 E550 4Matic - 61,000 Km - Iridium Silver, black leather, Sport package, Premium 2 package
2007 GL450 4Matic - 62,000 Km - Obsidian Black Metallic, black leather, all options
1998 E430 - sold
1989 300E - 333,000 Km - sold
1977 280E - sold
1971 250 - retired

"And a frign hat. They gave me a hat at the annual benefits meeting. I said. how does this benefit me. I dont have anything from the company.. So they gave me a hat." - TheDon

What a bunch of hokey. I'm familiar with the perfect balance of an I6 vs. the imbalance of a 90-degree V6. That's the theory. In practice it's impossible to claim one of these engines is smoother than the other. Seat of the pants at idle, moderate acceleration, full throttle - there's no difference. Both are impressive in their control of NVH. I'll grant the sound of an m104 - or any inline six - is more soulful than the generic mooing of a V6.

In practice I like the m112 in my 210 car quite a bit better than the m104 in my 124 car. The m112 has wonderful midrange torque that pulls the car smartly along without working hard. In contrast, the m104 has to be revved hard to get anywhere. And the workings of its various manifold flaps (for Helmholtz tuning) and intake cam advance/retard mechanism are clearly perceived as slight hesitations and surges in acceleration. I find it quite annoying actually.

The three valve design of the m112 (and m113) engines was largely driven by emissions. The single exhaust valve retains more heat in the exhaust gasses and brings the catalyst online sooner. That's why these cars qualify for ULEV status - they are very clean running.

As for why BMW uses only inline sixes? I think there are two fairly obvious reasons. Primarily because it is their trademark, so to speak. A BMW isn't a BMW unless it has a straight six - the two are inseparable. A second reason is likely financial. BMW is not a particularly large automobile company. In fact, they are one of the smallest remaining independent manufacturers in the world. Developing a completely new engine line is a hugely expensive proposition - one that would strain their finances. So they soldier on with the inline six, turning what most companies would perceive as a liability into an asset. With BMW the engineering is solid, but it's the marketing that really impresses me.

- JimY

Duke,

Is it possible te elaborate on the 1st, 2nd, 4th order rocking couples? Sounds like a Grateful Dead concert. OK I mean Phish... Seriously, I would like to understand it.

Mike

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

Too bad the tourque rating is so low. Still a great engine but apparantly BMW did not thing so anymore since the next M3 gets a V-8!

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~Jamie
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2003 Pewter C230K SC C1, C4, C5, C7, heated seats, CD Changer, and 6 Speed. ContiExtremes on the C7's.

1986 190E 2.3 Black, Auto, Mods to come soon.....

Much of the perceived balance & smoothness is in the execution and packaging of any given cylinder layout. Many engines outside of MB will make do with a counterbalance on only one side of a given connecting rod. Some oldies even did without a main bearing in between cyinders. I was impressed with the MB sixes I've seen apart. Tapered counterweights on both sides of every connecting rod. Very stout main bearing saddles. The sides of the block (skirt) come well below the main bearing parting line, adding to the block's stiffness. Oil passages inside each connecting rod to lube the wrist pin & cool the inside of the piston. Steel inserts inside aluminum pistons to control thermal expansion, allowing much smaller piston to bore clearances. All of these details cost time & money to implement, but add significantly to the smoothness the driver feels. As each engine mount seems to have a diffeent part number even though many of them look alike, I'd bet money that they are tuned to each particular engine. This doesn't hurt either.

Much more to an engine than cylinder layout. That's just the beginning.

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Norm in NJ
Next oil change at 230,000miles

Nglitz has quite eloquently expanded on the point I was trying to make. The execution is much more important than the basic design choice. A well designed V6 is going to be a much nicer, more robust engine than a less well done I6. This despite the I6 being an inherently "superior" design. I use quotes because which engine layout is best depends completely upon how one defines the measurement criteria.

BTW, as to that amazing 333HP BMW six, they seem to be coming apart (in small pieces...) at pretty good clip. Try typing something like "bmw m3 engine failure" into google and see what you come up with. Here's a moderately interesting link: http://members.roadfly.com/jason/m3engines.htm

- JimY

My 1994 E320C 104 motor is consistently in the high 20s on the highway, with no more than 91 octane. It has been over 30 mpg on occasion but probably wind aided.

Jim Y wrote"A second reason is likely financial. BMW is not a particularly large automobile company. In fact, they are one of the smallest remaining independent manufacturers in the world. Developing a completely new engine line is a hugely expensive proposition - one that would strain their finances. So they soldier on with the inline six, turning what most companies would perceive as a liability into an asset."

Er..no BMW overtook mercedes in passenger car sales some time ago and are the worlds most profitable car company.They make inline 4's & 6's, v8, v12 and v10 in the current M5.How many configurations do Mercedes make ?

adam

There are a number of variables that could skew or affect mileage numbers -- aerodynamics of the car, weight, transmission gearing, rear-end, presence of a tailwind, etc. -- that a direct comparison is probably not valid.

My wife's 1995 E320T can obtain 26 MPG over long distances using cruise control.

Cheers,
Gerry

I thought Porsche was the most profitable car company in the world, but BMW certainly is up there.

MB had a tradition beginning back in the 1950s with the inline-6 engines, I'm thinking of the Gullwing era moving down into the Adenauers and fellow 300 models, evolving into the M130 engines and then to the M110 twincams. Then MB went back to a single cam with the M103 and back to two cams with the M104.

Each engine had its quirks and issues, but a well-maintained (and even a not-so-well maintained) MB inline-six is a real tank of an engine. It was sad to see this tradition go away. I have not owned an M112 (and will not) so I can't vouch for them; time will tell when many thousands of these engines have hundreds of thousands of miles on them. I'll bet they'll have their weak points as did the recent inline-sixes did.

Cheers,
Gerry

I have driven BOTH types of engines (L6 and V6) on several different models and can testify for sure that the L6 is smoother than the V6, not by much, but it is.

I always thought that Mercedes made a big mistake switching from an inline configuration to a V. It appears it was done to better polution figures.

Time, as history, always tells the truth. When M-B switched to the V configuration, it also switched to a 3-valve design instead of a 4, claiming numerous advantages.

Now, the new state-of-the art 350 is back to four valves per cylinder (instead of three). Maybe soon enough they will go back to an straigth six instead of a V-6.

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A. Rosich
CL 500, 1998
S 500 L, 1998
E 320 T, 1995 [Sadly sold ]

you have to remember that there is years of technology and knowhow in the V6s that isnt the the straight sixes. if the same advancements were employed im guessing the straight sixes would be far superior to the vees.
the iron block 103 motor came out in 1985 in the first 300Es. the v6 first debuted in 1996 in the european E320s. thats a nice ten year gap; development, advancements, research, materials etc all stood to gain/ benefit from that ten year period.
the 104 was hastily contrived riposte to BMWs engines which were producing more horsepower and better economy than the 103. a lot of the short block is the same. in fact i think i remember reading mercedes materials that said essentially the difference was in the chain/ guide/ mechanism. and maybe oil squirters too. i cant remember, in that much detail, back to 1992/3.

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'O=00=O'
bmw 2002.
long live the legend

your car has better aerodynamics, a fifth gear, a more fuel efficient engine (multivalve) and so on and so on.

but i can beat that in my 300E 2.6, on arco 87, driving at that speed. ive averaged 27mpg at a 90mph avg speed from phoenix to los angeles last december. (the 260Es have a lower (numerically higher) diff ratio than 300Es. so its fuel economy should be worse on that fact alone.)


and just last month i got all the way from half moon bay (just south of san francisco) to just north of bakersfield on less than 3/4 of a tank. doing a steady 70. at some point i decided i was going to get home too late and mashed it. i probably averaged 90 the rest of the way home.

i normally head straight to the gas station when i get home from a long trip so i can see how much my fuel consmption was, but in that case i was too tired, it was too late, and i hadnt bothered to try to maintain good economy in the last hour.

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'O=00=O'
bmw 2002.
long live the legend

Unless you have a good math and physics background it may be tough to understand, but a mathematical expression can be derived for the forces generated by a crank and rod assembly as a function of crank angle and rod angle. This equation is then expanded using the binomial theoem to an infinite series that has individual terms that are a unique function of crank angle and even multiples of crank angle - 2,4,6... These terms are sinosoidal and the coefficients indicate the frequency. The "2" coefficient indicates the frequency is twice engine speed, 4 is four times, etc.

Magnitude drops rapidly with frequency. Second order forces are on the order of about 25 percent of primary and fourth order are only about four percent. For this reason, only first and second order forces are considered significant.

The calculation is only approximate because an assumption is usually made that half the rod weight is reciprocating and half rotating, but in actual fact the amount of rod mass that is reciprocating and rotating varies throughout the cycle.

The forces for each crank and rod are vector added for the cylinder arrangement and then moments are computed to determine any residual shaking forces or rocking couples. These calculations have all been done and the basic derivation and resultants for most common engine configurations are listed in various references, one of which is Taylor's IC engine textbook, which is still available both new an used.

Engines generate a wide spectrum of vibrations, but torsional, valve gear, and combustion generated vibrations are usually low in magnitude compared to first and most second order reciprocating/rotating vibrations of the bottom end, and engine mounting schemes are usually used to isolate higher order reciprocating/rotating bottom end vibrations and the others I mentioned. Second order rocking couples from V6 configurations are usually handled quite well with good engineering of the engine mounting.

The toughest to control is the second order vertical shaking force generated by inline fours. The twin counter-rotating balance shaft scheme was invented and patented by an Englishman named Lanchester in 1914, but was seldom, if ever, used during his patent protection because with the relatively crude technology of the time, it was cheaper just to make an inline six rather than the drive and extra machining and bearings required for the balance shafts. Engine "packaging" and size weren't that important back then.

Somehow Mitsubishi managed to patent what was basically the same scheme in the seventes (I've never figured out how.) and Porsche bought a license for their 944 engine. After about 1993 when the patent expired the scheme found wider use in inline four's, especially those over 2 liters, but Mercedes never adopted it.

Duke

Adam -

Would you mind supplying some references to backup your assertions? I believe you are completely wrong.

Let's look at the relative size of Daimler-Chrysler vs. BMW group. We'll use 2003 year end figures for comparison.

Daimler-Chrysler had revenue of over 136Billion Euros in year 2003. At year end DC employed 362,063 people. Refer to http://www.daimlerchrysler.com/dccom/0,,0-5-7193-1-169896-1-0-0-0-0-0-36-7164-0-0-0-0-0-0-0,00.html for the aforementioned information.

In contrast, BMW group had revenues of over 41Billion Euros in year 2003. At year end BMW employed 104,342 people. See http://www.germancarfans.com/news.cfm/newsid/2040414.014/bmw/1.html

DC had higher operating income than BMW, but lower net income. Given the available information I cannot discern why.

BMW unit sales in 2003 were 928,151 vehicles. This is the figure for BMW branded vehicles. The Mini brand included 176,465 vehicles. I'm having difficulty finding the number of Mercedes branded cars delivered in 2003. Based on what I see on the web it's anything but obvious that BMW is delivering more cars. Overall DC is delivering many, many more vehicles than BMW simply because they are in so many more market segments.

Where's your proof?

- JimY