Straight 6 vs. V6
 

As far as gas (non diesel) engines go, I am a little confused about which cars have the srtaight 6 and which have the V6. I am thinking maybe they changed over in the early 90's? I have always like straight 6's in general. Does anyone have any opinion on the Mercedes engines? I think I would really like a C or E class car with a straight six and a stick and sport suspension. Does such a thing exist in the used car market? I am thinking maybe a 93 E320/300E or maybe 2001? Please help!!

Thanks,

Mike

Straight 6's were used until 1997 in all cars except the W140 S classes, which continued to use the straight 6 until the end of the model run in 1999.

Thus, with the exception of the above mentioned S class, all MB's have been using the V6 starting in 1998.

The 300E was available with a 5 speed stick, but is was only for two years early in the model run, I think '87 and '89. Very few were imported into the U.S.

Larry Bible has one.

The stick shift 300E's were sold only in 1986 and 1988.

Both the straight and the V's are great engines. The straight sixes do sometimes have head gasket problems, but they are very smooth, tractable and long lived engines.

The V6's are even better engines. They are an absolute masterpiece of an engine. I have seen one torn apart so I've seen firsthand the construction and features of thise engine. A few years ago I was surfing around looking for information on the V6 engine and found a site where they had chosen the top 10 engines in the world. The Daimler Chrysler V6 was number one on their list.

Beyond having outstanding construction features and being picked by someone as their top choice, these engines have proven to be unbelievably reliable as observed by the MB techs at the dealerships that I've talked to.

Have a great day,

Wow,,, that surprises me Larry, as I am an old die hard straight six proponent. I should have known.

Unless you consider the harmonic balancer part of the engine or exceed the FSS oil change interval with dyno oil.

Aside from the faulty harmonic balancer design, I have to agree with Larry's comments. My 98 E320 V6 has been very reliable, the only problem I had is minor oil leaks from the valve cover gasket and oil filler neck.

The V6s seem to be noisier, not as smooth. The techs at the dealerships have not seen that many high miles cars yet. I think the jury is still out on the question of longevity.

Part of what has always attracted me to Mercedes is that they stuck with the Inline-6 design long after many other manufacturers gave it up. The sound of an Inline-6 accelerating, and the lack of vibration associated with it, sends chills down my spine.
I hope they bring them back at a time when I am affluent enough to purchase a new Mercedes.
~D.J.~

"straight six, stick, sport suspension" - sadly you're describing a BMW, not a Mercedes.

Sadly, the move from inline-6 to V-6 was a Schrempp-driven move rather than an engineering-driven move. The move to the V-6 was driven mainly by economics -- it is a direct descendent of the V-8 design and can be produced on the same line. This significantly reduces manufacturing costs over the inline-6 engines, which required a separate production line.

There are demonstrated advantages (in general) to inline-six designs over v-6 designs, in terms of smoothness. The knowledge that MB made inline-six engines for many decades I guess was given up with the demise of the M104 in the mid-late 1990s. MB inline-six designs have been proven over many years, despite some warts (such as the head-gasket issues, which were an auxiliary part design (materials) flaw as opposed to an engine design flaw).

Notice that today's V-6 designs don't offer significant (discernable) power or efficiency improvements over the M104 designs. Also note that V-6 engines with balancers tend to steal horsepower from the engine.

It is also telling that BMW still continues to manufacture inline-six designs for its cars.

My two cents.

Cheers,
Gerry

The V6 is not as smooth running as the inlines????? You MUST be kidding, or you have never driven both of them.

My M103 engined 300E is indeed smooth running, but my M112 engined C240 was so smooth it was like driving a car with an electric motor!!!!

There are other advantages to a V design other than being built with parts interchangable with the V8. The V design allows for a lower hood and shorter engine compartment, allowing for a little better aerodynamic capability.

If you think that the 104 or 103 engine designs are superior to the 112, you have not looked into the innards of all these engines. All of them are great engines, but the 112 is an engineering masterpiece with such features as; roller rockers, three valves/cylinder, cold cracked connecting rods, alloy liners, short skirt piston design, low tension piston rings, cross bolted mains..................................

These engines have been out almost 8 years now and there are enough high mileage examples being seen to know that they don't have any achilles heels like the head gasket or timing cover sealing problems of the 103/104 engines.

The harmonic balancer problem was the rubber used in the harmonic balancer and could have/would have been a problem regardless of what engine they were bolted to.

The sludge problem was caused by the factory recommending the FSS intervals with dino oil. A huge blunder on MB's part, but again, regardless of what engine you did this with, the result would have been the same.

I like the 103 and 104 engines also, but if you think that they are better engines than the 112, then you are either not aware of, or not facing the facts.

I wonder if there were people with such resistance to change when the auto industry went from flathead to OHV?

Have a great day,

Currently owning both engines (97 E320 and 01 SLK 320), I'd have to say that the M104 idles a lot smoother than the M112. During idle, the M104 even sounds better than the M112. The M112 has always "ticked" during idle that I have heard in pretty much all the M112 cars, so I know it's nothing wrong with mine. Once you get going, both engines are smooth as silk. The M112 does have a much flatter torque curve.

This is not saying any one engine is better than the other, just some facts I've noticed owning both.

I can't say for longevity for either, since both my cars are considered low mileage for a Mercedes (SLK has 24k miles on it now and the E class has 99,000). The M104 in my E class has not missed a beat and I've had no head gasket or transmission issues whatsoever.

The ninety degree V6 configuration has both first and second order rocking couples. The first order couple is balanced by a counter-rotating balance shaft, but the second order couple remains. A 60 degree V6 lacks the first order couple, but still has a second order couple.

The inline six configuration is inherently balanced. There are no shaking forces or rocking couples below fourth order, so if the crankshaft is sufficiently robust to prevent torsional vibration problems, an inline six is inherently smoother than any V6 configuration.

Since both the V6 block and head are aluminum, it is less likely to have longer head gasket life than the iron block/aluminum head inline six. Also, the V6 has cast in high silicon alloy aluminum liners, which have a lower wear rate than cast iron as long as they don't score.

Duke

Alloy liners?
 

Larry - are you sure 'bout those alloy cylinder liners? I thought these were an aluminum/silicon alloy, with the aluminum etched away leaving a silicon surface (like the Chevy Vega 2300 motor of yesteryear).

My two m112 engines run great, but they are both still low mileage. The lack of a cylinder liner scares me the most with this engine.

thanks for your observations,
Dan

My point exactly, stated more eloquently and in more detail.

Given that the current V-6 is said to run rings around the inline-6 designs in every conceivable manner, I haven't seen any response or info as to an increase in overall efficiency or power generation of the V-6.

I think the benefits of 3-valve vs. 4-valve technology can and should be debated as well.

The bottom line, is that the V-6 engines were conceived, designed and produced to meet reduced cost targets. It's a decision that is in keeping with other MB quality, design and engineering decisions over the past 10-15 years.

Why does BMW refuse to go the V-6 route and maintain its inline-6 designs?

Cheers,
Gerry

Another point to consider: gas mileage.

2002 E320 4-matic 25K mi just did 29.0 mpg for an 80 mile round trip on highway, avg. speed 69 mph, windows closed, sunroof tilted open, a/c on, very light winds, no passengers, easy driving style, Sunoco 93. Looking thru the gas mileage thread, I don't think you'll get that with an IL6.

I find it hard to imagine a smoother running engine than this V6, but since I've never driven the IL6 I'll just have to take the word of those who have.

Inline 6
 

...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!

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

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!

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.

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.

Re-BMW engines
 

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.

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.

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.

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

BMW/Mercedes
 

Jim,

It was an article in the British weekly magazine "Autocar" about 3 months ago about Mercedes declining performance (sales down 1% vs BMW sales up 4.5% in 2003) including customer satisfaction and fleet reliability statistics.
From the links you provide BMW in fact employ more people in the car division than Mercedes 104342 vs 104151 !
Mercedes sold 1.2 m units vs 1.1 BMW's in 03 (I think it's fair to include Mini if you include A class as both are at the same price point) however BMW made 25% more profit overall.The "Autocar" article may of been using 04 sales figures,however the trend is clear and the new 1 series BMW will increase volume further.From the figures the two companies do seem evenly matched when all is said and done.
My main point,this being a tech forum, is I think BMW make more engine types than Mercedes.
If you get a chance drive a BMW 330 TD and a double vanos petrol and it's clear how much the inline 6 has moved on in recent times.The Merc V6 is also a fine engine as I've found in my own C280.

adam

Adam -

Thank you for the reply. I think we are basically in violent agreement here, but see the facts somewhat differently. So it appears that Mercedes branded vehicles outsold BMW brand vehicles by ~10% in 2003. Does this include only passenger cars? I'm curious because Daimler also sells heavy trucks, commercial vehicles, vans, etc. - they are in many markets in which BMW does not participate.

My main point is that overall DC is a much larger entity than BMW group, and as a result likely has financial resources not available to BMW. Don't forget that DC owns outright the Chrysler brand globally, and that adds 2.6M additional sales to the corporate portfolio. Also 500K commercial vehicles. And I don't think we are including Smart here, but that's small potatoes.

I'm aware the Mercedes car group is going through a rough patch while BMW is on a tear. BMW is certainly more profitable per unit than Mercedes. This certainly neutralizes some of the size advantage of MB.

I've read that on a per unit basis the most profitable automaker in the world is Porsche. Not having looked up the figures I strongly suspect Toyota is far and away the most profitable automaker in the world. I believe their margins are double those achieved by BMW and they sell several times more vehicles annually.

We have limited ability to sample either BMW or MB wares in the U.S. BMW does not import any diesels whatsoever. None at all. Virtually all BMWs currently sold here are powered by the 2.5 or 3.0 liter variants of their current inline six. We do of course get a number of the 4.4 liter V8 engines in the 5 and 7 series car. And of course a trickle of the V12 cars, but these are very rare.

Mercedes actually sells a broader variety of engines in the U.S. We receive cars with supercharged inline 4 cylinder engines, the M112 V6 in two different displacements, the M113 V8 in three different displacements, plus a few V12 powered sedans and coupes. AMG cars have supercharged variants of the v^ and V8 engines. MB sells a single diesel in the U.S - the E-class sedan is available with the 3.2 liter CDI engine. See how deprived we are?

- JimY