I was in a friend's Boxster, and relearned that it was a flat 6.

I have a very general idea about the pros and cons of each are, but would anyone mind elaborating?

A Boxster is a rockin' car! A flat 6 engine is also called a boxer engine because of the way the pistons resemble the way a boxer jabs.

A F6 is supposed to wear less than an I6 or V6 because of its configuration. It also has a naturally lower center of gravity. I don't know of any other pros or cons.

Kuan

it is my opinion that
 

the flat (or "boxer") engine arrangement probably leads itself to be the "smoothest" running arrangement.
Jim

"Boxer"
 

As I understand it, the term Boxer came from the pistons' appearing to be 'boxing' each other...what do you think Kuan?

Of these arrangements, a straight six is the smoothest. However, it's the least easy to package (which is why they're often canted over to one side) and potentially has the highest center of gravity.

A flat six works better than the other configurations for Porsche for a couple of reasons:
1.) Low Center of Gravity
2.) Air cooled

A V-6 is a great configuration for packaging, but is only smooth when including some sort of active balancer to get rid of huge 2nd order vibrations (whatever the heck they are-engineers please chime in here); virtually all modern V-6s incorporate a crank-driven balance shaft of some sort

As to Kuan's contention that a flat 6 would wear less than the others, I'd not heard that nor do I really understand why that would be the case. Anyone care to elaborate?

The longevity of the engine really depends on the who made the car. I used to have a VW parts hauler which had the engine rebuilt at least 2.724 times! ;) The supposed ideal angle is (2*360)/number of cylinders. So for a V6 it would be 120 degrees. I don't know why the boxer would be so smooth but it is. Maybe it's one of those bumblebee things where we know that it should not be able to fly but does!

I too have heard the pistons boxing each other explanation for why it's called the boxer. I've always had a hard time visualizing this. Somehow my VW experiences have tarnished this image! The other advantage to the flat 6 is that you could drop it out of the body with nothing but a floorjack and two jackstands. This is a 20 minute job if you've practiced it a few times :)

Another advantage (on a VW, never tried it on a Porsche) is you could if forced to, install one just one new barrel and piston if you needed to. I guess it's possible in principle on a Porsche aircooled engine, but chances are slim that one would have an extra cylinder barrel and piston in the car!

Kuan

Ok, "boxer" comes from the H4 (horizontally opposed 4 cylinder) design. With two pistons on either side, it looks like the left right punches from a boxer from each end. A boxer is supposed to be the smoothest running due to the natural balance of 180 degree matched motion. This requires the least additional balance load on the crank shaft as well.

there are 3 engine configurations that are inherently perfectly balanced:
* inline-6
* flat-6
* 60-degree V12

the typical American 90-degree V8 can be brought into perfect balance via the use of counterbalance weights.

A Ferrari V8 however is different. Although it is also a 90-degree V8, it has a flat crankshaft (i.e. the throws are all on one plane). Although not perfectly balanced, it has an even firing order (i.e. the engine pulses are regularly spaced), which gives it better high-rpm breathing and that distinctive shriek that cannot be mistaken for the typical American V8.

V6 engines are not perfectly balanced. I believe the 60-degree V6 is easier to balance than the 90-degree one. (benz went for the 90-degree config to leverage the same assembly line components of its V8 engines).

I view the term "boxer" differently: if you were to mimic with your forearms, the way the connecting rods of the opposing cylinders move, you look like a boxer using you arms as a shield.

A flat-6 has the lowest center of gravity and perfect balance. But its exhaust plumbing is very convoluted considering the small spaces available. And since it sits down low, it is more difficult to service.

An inline-6 has perfect balance but is the longest, which makes it more difficult to package. A long crankshaft is also inherently less stiff than a shorter one (like those on H6 and V6 configs), other things being equal. But intake and exhaust plumbing are simplified because they are on opposite sides of the engine. This makes turbocharging simpler than with a V6 or H6. You can also place heat-sensitive components on the cold (intake) side of the engine.

A V-6 does not have perfect balance but is very compact, and can be mounted transversely or longitudinally (the extreme example is the VW VR6). If mounted transversely, exhaust plumbing is a challenge. The space in between the banks simplifies the intake plumbing, and makes it a natural for superchargers, especially for a 90-degree V6, which has a bigger space in that Vee.

They also make different sounds, because of the differences in exhaust pulse patterns.

An inline-6 has a simpler valvetrain, because there is only one head.

Finally, an inline-6 looks the sexiest from the engine bay, what with that long *thing* in there, and with those exhaust headers in plain view ... it's a guy thing ... ;-)

re V vs inline etc
 

Also in reply to the above examples the v6 layout I am told has more torque than an inline 6 but the inline 6 is inherintly more smooth running and is generally more balanced as was mentioned before.
The v6 therefore all things being equal should be a better motor for pulling and hard work (Tradesmens reqirements) thats why there is a lot of jap pick ups around.
we see this a lot down in Australia.
regards
BB
w123 wagon

Yes, I think that an inline 6 sounds more refined. I drove the CLK 320 today and it sounds more gruntled, like meatier, or more of a low tone. The C280 and the CLK320 seem to be about the same speed, acceleration-wise. But the inline definitly seems smoother and more refined.
My mom's Porsche has a flat six. I never really thought about it though. How are they able to get more power out of a 3.6 liter flat? That engine is just loud!

All to do with airflow
 

Im not a mechanic but im just interested (Im a Chef by trade)the difference is the rate of airflow dynamics and sequence of revolutions I think. with the v and flat motors the makers are able to get much more airflow and direct ramming(Turbo & Supercharging)without splitting the airflow which creates horsepower, but you sacrifice smoothness(Inline) the motor is actually a large air pump the more air that is fed through the motor the more power is created.
Thats why the japs run small motors in WRX"s and EVO"s but produce high HP And KW The Subaru is only 2litre but has phenominal power for small car (It has boxster layout like the Porsche also) but is turbo charged .
The newer benzes are comming out with V6 motors with supercharging and they are reasonably economical and have great torque so im told.
Maybe there is some tech out there able to verify these pionts im not totaly certain if this is correct (Im only a Chef not a mechanic as i said, just interested)

among other things, the V6 differs from the inline-6 in terms of the timing of the exhaust pulses. The inline-6 has evenly-spaced cylinder firing: a cylinder fires every 120 degrees of crank rotation (it's a 4-stroke, so you need 2 revs for a complete cycle). This gives it a very uniform torque profile at the crank, measured against crank revolution.

in a V6 however, the cylinders do not fire evenly with respect to crank rotation. Pairs of cylinders will fire closely together, which gives it that rougher exhaust note. Since a pair of cylinders will overlap more on their power stroke, the maximum torque reading on the torque profile could be higher than that of an inline-6.

However, the flywheel dampens out these torque fluctuations, so we do not notice them at normal rpms. On cars without traction control however, you might notice the difference between the 2 engine configs when you do a tire-spinning start: because the V config has a more ragged torque profile (and higher torque peaks), i believe it will produce a more irregular tire spin than the inline-6. It will be noticable because at low rpms, the flywheel cannot smoothen out the torque fluctuations enough.

I've seen a slo-mo video of a Porsche 968 (with the biggest inline-4, it produces a ragged torque profile) on a tire-screeching standing start, and you could see the rear tires spinning and stopping repeatedly, each spin corresponding to one of those big cylinders firing.

an American V8 produces a "burbling" sound at idle because it has 4 pairs of exhaust pulses, each cylinder firing closely with its pair. The Ferrari V8 produces a different sound, because of its even firing order.

the best example of the effect of a V config on engine sound is a Harley-Davidson. Not my cup of tea though. For me, the best sound is a small-bore Ferrari V12 at full scream ...

also, the exhaust plumbing also affects engine output. You want to optimize "scavenging", and you would want to consider the firing order in designing the way the pipes merge.

Something else to note about a "flat" configuration as opposed to the other types:

The engine "case" as opposed to a "block" supports the opposing dynamics of the pistons, contrary to an engine block, which requires huge "mains" to keep the whole setup from pushing itself out the bottom.

By the way, Subaru also uses the flat configuration on their 4-cylinder vehicles...

I found this to be an interesting topic, given that all of my vehicles each have a different engine configuration...

These flat fours are favorites of Home-Built
aircraft.
They are light and the VW is air cooled.
Good prop torque at low rpm. No need for gear
reduction.
I had a converted 1600 cc one with magneto and steel crank and used it to power a VolkPlane VP-1.

Others
 

What about the BMW (motorcycle) boxer, and the old Corvair flat air cooled six?

One thing about the V6 is the crank has to have split journals. I remember the first one didn't split them and had a "loap", the cylinder firing was paired and uneven, that didn't last long.

i know someone who owns a BMW bike with a boxer engine. Because the axis of the crankshaft is along the length of the bike, when he revs the engine at a stoplight, he feels a twisting motion along that axis. Quite wierd, according to him.

when the Viper first came out, it had separate sidepipes. They were said to sound like a UPS truck. A very fast one. When they rerouted the exhaust to the back, it sounded more sporting.

VW/Audi have some interesting engines:

- the straight-8 engines of the old racing Audis. Must have had really massive main bearings.

- the VW flat-4

- the Audi inline-5

- the VW VR6 engine

- the VW VR5 engine - this is the VR6 less one cylinder. As if the VR6 wasn't odd enough!

- and to defy all convention, they have those W-engines. Just add a few more, and it will be a radial engine (like those in old warplanes).

Speaking of radial engines, I heard that you could put a bullet through one of those barrels and the thing would still keep going. Could someone confirm or deny this?

Kuan

Whats a VW VR6 engine?

kuan,
i've seen a documentary of the P-47 Thunderbolt, and a testimony of a pilot who took a couple of rounds in the engine, and was able to make it home.

jim,
a VR6 engine is VW's narrow-angle V6 engine fitted into some Golf, (previous-generation) Passat and Corrado models. Because the V angle is very small, the engine has only one head for the 2 banks. This makes it compact enough to fit transversely into these small cars.

because of the single head servicing the 2 banks, you can imagine the design of the intake and exhaust plumbing passages cast into the head.

So if you had a choice?
 

Ok so this topic is pretty interesting lets say that Mercedese was reading these columns and trying to get into the heads of its clients,
what would be the layout that you as a customer would wish for if you had a say in the style of motor of future benzes and why that type? EG smoothness or travel comfort(Straight) Or V format for torque and low down grunt maybe a supercharger for top end performance and cruising (Towing and heavy loads / lots of people etc)

Boxster for staight out sporting about(Maybe throw in a turbo or two)You could get away with smaller motor but still have the power, it would save on fuel if nothing else.

Just a thought, what say the others?

Mercedes V8
 

I was fascinated when I heard this. I had always wondered why Ferrari manage to sound so different to the American V8. Makes me wonder, which type of V8 is the SL 500 V8? the American style or like the Ferrari?

James

BB,

I would take an inline (8 cylinder?) with a turbo. I would LOVE that!
Is the reason they never made inline 8s (mass, i mean, or did they), was because of the lack of proper space to place the engine?

My dad had a 49 Buick Roadmaster (2 door fastback style), and if my memory serves me right, it was a huge overhead straight 8. I was still teething on my Allstste scooter at the time and didn't have time for anything else.
Ernie

Chrysler, Packard, Pontiac, Buick all had straight engines in the 30s 40s and early 50s. I think the Duesenberg had a straight 8 Lycoming aircraft engine. Mercedes had straight 8 engines but possibly not in production models.
P E H

James,
i believe the Benz V8 engines use the traditional, American-style V8 arrangement ... refinement is more important than raucious sounds for the intended audience ...

BB,
i hope Benz brings back the inline-6. I hope they will improve on the M104 (engine gaskets, wiring harness, etc.). But if the existing V-sixes continue to live up to their initial reputation of reliability and build quality, then i would just not look under the hood ... a supercharger in between the banks will also help make me forget the inline-6 ... ;-)

the Lexus IS300 had to have the inline-6 to be a worthy competitor to the BMW 3-series. Volvo has a turbo inline-6 mounted transversely (the only one in the world mounted this way). Even GM has a new 4.2li inline-6 which outperforms many V8s.

until then, i hope there will be many many more kms in my 2.6 M103 ...

[Edited by bobbyv on 06-06-2001 at 12:05 AM]

Not only did we used to have inline 8's, but some folks built V-16s. When a friend of mine saw one he asked the owner how he would diagnose a miss. A moment later he realized that he probably simply wouldn't care.

Aren't there W9's out there?

-CTH

David,
They did build straight eights and Mercedes were the finest exponents of the art. Many pre-war GP cars were fitted with straight eights and Mercedes had the best of all. Alfa Romeo used a straight eight, as did Auto Union (now absorbed by Audi). I take it your mother has a 993?

The finest engine must surely be the V-12, and probably the finest V-12 is the Jaguar V-12 in 6.0 litre form. Normally aspirated: forced induction always seems to detract from engineering purity, hence the supremacy of BMW's M3 or M5 motors or, indeed, the V-12 they fitted to the McLaren F-1 (now that might pip the Jag).

As for interesting engines, how about the latest VW W-8 and Audi W-12? Bentley will apparently get a W-16 from the VW fold. Bugatti (also VW) will apparently utilise a 1001 bhp W engine, either 16, 18 or 24 cylinders, depending who you believe. This W configuration is in fact a double U format: two narrow angle V engines joined at the crank. A servicing nightmare!

Mercedes has, of course, threatened a 1000 bhp V-24 for the Maybach but this has apparently been shelved in favour of a less satisfactory twin turbo V-12.

jjrodger,

now what would they call that engine - a VW double-U ?

a marketing nightmare!

;-)

I had a 92 Jag XJS convertible with the 6.0L V-12 (traded it in for the 500SL). The engine was smooth and seemed to be able to accelerate to stratospheric top speeds, but you didn't have to worry about neck injuries when you tromped on the pedal...I guess Jaguar meant for the car to be a touring vehicle, and not a weekend drag strip contender...

G-Benz: you will remember that your Jag was fitted with a 3-speed GM slush box (strange, given that even then, Jag was owned by the General's arcg-rival, uncle Henry). The old 6.0 litre V-12 (or the 5.3 for that matter) had so much torque that a gearbox should have been an optional extra.

Sure, for all out punch it wasn't competing (7.3 secs to 60 if memory serves) but for smoothness and refinement, the Jag, despite its 20 year old technology (now 30 yr old) was better than anything that went before or since). I remember Georg Kacher, German auto journalist, prefering the Jag soft top over the 600SL simply because it was the more refined, and hence luxe, sports tourer.

All that said, I passed a copule of XJ-Ss in driving rain and otherwise foul conditions on the M62 today (the UK's highest motorway at 1,112 feet(!!!)) and I was glad I wasn't driving one myself. G-Benz, you will have seen under the bonnet, and that engine truly was "the plumber's nightmare". But the car had charm in abundance.

Boxing Anyone?
 

The Honda Goldwing has used the flat 4 for some 20 years, and I have owned 3 of them. I will never forget when they showed a silver dollar on the engine case with it running.
The low centre of gravity makes it ideal for motorcycles, and in my opinion, this makes it the perfect engine for a bike.My Goldwing 1000c.c. was actually easier to handle than my honda 750 which hade an inline 4 sideways in the frame. Most people cant feel the difference, but if you had a flat engine in your car, I think it would definetly handle better around corners.

Yes, when sitting still and revving the throttle, the bike will lean to the right side!!!!

Airplanes have used the flat 4 for 30-40 years in applications around the world, Continental, Lycoming, etc... Small compact, excellent balance, etc..

The in-line 6 has perfect primary balance.

Inline evoled to V for benz?
 

Ok so this thread is getting plenty of interest here, then can someone shed some light that benz should be seen as a luxo car maker per se. Then why are the leaving the inline format and getting into the V format in current models?
When BMW is still being toted as the best inline six in the world (The M3 Specifically ) for power and probably smoothness.
Is there any reason for this?
Is benz developing new technology to set the trends in the future both in packaging and design, maybe they may bring in a flat six? Wonder how that would go?
Any Ideas out there in the land of stars and stripes?
From down under sighning off!!!
BB W123 wagon & 190e

Ours is not to question why...
 

But in a nutshell, the M112 V6 engine is the M113 V8 with two fewer cylinders. Because they're "cast from the same block" they can share parts and act like the bobsy twins when they show up at cocktail parties together. It's a question of economics for Mercedes. The new V's aren't slouches either. They provide a little more torque and have consistently rated among the best engines in the world. The M112 has ranked among the ten best engines on Ward's list for the past three years.

Kuan

ditto with Kuan.

the priorities for Benz are economics and packaging. For reduced manufacturing costs, they have adopted a "modular" engine design, sharing manufacturing facilities with their V8s. And V-sixes make more efficient use of the engine bay space than an inline-6.

Benz and BMW have different design philosophies. A purist like me would be attracted to the BMW's inline-6, manual transmissions, and legendary steering and handling. Benz however, tends to see its customers differently, delivering a total package consistent with its traditional values of safety, reliability and longevity. This is for customers who are more interested in the total package than the technical and engineering details.

BMW goes for more power at higher rpm, typically with a smaller engine. Benz goes for low-end torque. BMW has a chassis that wants to dance. Traditional Benzes respond with measured responses to your inputs, not unlike a butler.

these two companies know their niches and play their cards. The interesting thing is that the latest BMWs have become more Benz-like (i.e., softer), and the new C-class for example, has become more BMW-like, in terms of handling. And Benz has (almost begrudgingly) reintroduced its manual transmission.

my ideal car would probably be the C36 with a 6-speed manual. Best of both worlds.

Specific question
 

Which is lighter?

I'd say the inline-6...overhead cam of course...single block and head and a minimum of valvetrain weight.