inline 6 vs V6

Originally Posted by SteVTEC

Could you please provide a good solid technical explanation as to why this is? I've yet to see one that was convincing.

GM currently has a 3.0L DOHC 60* V6 with Dual-VVT cam-phasing and direct injection and 11.7:1 compression and regular fuel is making 270hp/223tq SAE certified.

Look up engine code LFW: http://www.gmpowertrain.com/VehicleE...nProducts.aspx

This is practically the same as the Euro-spec full-tilt direct-injected N53 3.0L making 272hp and 228 lb-ft torque on a higher grade of gas. The biggest limitation here is finding engines that are truly comparable.

There Inline-6 does have the advantages of lower overall friction due to only driving two cams vs four, and having a short localized timing chain run vs a V-6 where it's going all over the place, but these are very small differences. In the grand scheme of things, I think other things matter a lot more having nothing to do with engine configuration. Such as specific cam profile selected, variable timing setup and strategy, head, port, intake manifold and exhaust system design, etc. The goal isn't always to give the maximum possible power at at very high RPM (like Hondas) but rather a good overall balance of power and a good powerband with accessible torque at low to medium engine speeds.

I love the Inline-6 and would always love to have one for its sound and feel and character. It really is something special, but I'd hardly argue that one is superior to the other. The V-6 does have a lot of advantages. Much more flexible in terms of layout. Can be mounted either transversely or longitudinally, and it's far more flexible in displacement ranges. Modern V-6 engine designs like from GM and Toyota and Nissan can span 2.5 to 4.0L in displacement. The Inline-6 due to the very long nature cannot have very large bore spacings or else it won't fit into smaller cars, so it's very bore limited and ends up needing longer strokes. You can't simply "punch out" most Inline-6 engines to 3.5L or 4.0L like you can with many V-6 engines. This is why pretty much everybody else except BMW (and Volvo) produces V-6 engines instead. V-6's clearly win in the marketplace and few people care, but I do. Nothing can match the sound and feel and character and refinement of the I-6. I've had lots of V-6's but the N55 in my 335i is the best 6-cylinder engine I've ever owned. It's tough to sell refinement to people, though. I hope BMW never makes a V-6 because the I-6 really is something special.

The inline-6 is a PITA with regards to packaging (it takes up more space than a damn V8 or V10), but it is easier to work on from a mechanic's standpoint.

It is insanely smooth, but that is less of an issue to today's engine mounts and computer-aided design.

I love me an inline-6, but I think it will eventually go away...

- Mike

Originally Posted by Inline Sixer

Here's a Car&Driver article that sheds light on the subject, entitled: "The physics of the V angle"

http://www.caranddriver.com/features...re?redirect=no

Didn't see a date, but that article seems a bit old. GM no longer makes their 90-degree V-6 engines aka the "3800" line. Retired a few years ago, but it did run very smoothly and was quite refined, so whatever they did to it to make it run so well worked. That engine has lots of fans to this day, myself being one of them. Mercedes also dropped their 90-degree V-6 awhile ago too. The 3.5L DOHCs are all dedicated 60* designs. It's a big advantage being able to share architecture with 90* V8 engines, but with the markets moving towards lower displacements it makes less sense to base a hotter selling V-6 off of a V-8 design, that doesn't run as smoothly and requires balance shafts to run well at 90*. Hence moving to dedicated 60* block designs for V-6 engines.

Originally Posted by Emission

Never say 'never' when profits drive engineering and design.

"Porsche will never sell an SUV." (Heard back in 1999 when the first X5 was introduced.)

"BMW will never make the M3 with an automatic transmission." (Heard back when the E30 M3 arrived.)

It would be rather easy for BMW to slice a few cylinders off the 4.4-liter V8 and create a compact and lightweight turbocharged 3.3-liter V6... making about 350 horsepower...

- Mike

I know....

But a 90-degree bank angle = required balance shafts on a V-6, so hopefully they won't do it. BMW has had larger displacement Inline-6 engines before, up to 3.5L or larger I think. I'm guessing the newer I-6 block designs are smaller? I know some of those older engines were also iron blocks too. Better rigidity, and you can squeeze out just a little bit more bore size from those too vs the modern aluminium and magnesium-alloy blocks. I remember looking up the specs on some of those and being wowed at how little cylinder wall separation there was on those.

BMW has the money to spend on trick materials and R&D. Maybe they'll come up with some advanced new alloy that will allow them to squeeze a few hundred extra cc's out of the N5x design I-6 engines using a new material?

I like V-6 engines up to about 3.0L. All the newer ones to me don't sound quite as good and you start to feel a lot more of the vibrations as thrashiness as you get to the 3.5L sizes. Plenty fine for luxo-barges where you're probably not going to be going past 4000rpm all that much, but if you want an engine to scream I just love the I-6's. They're in a whole different league compared to V-6's IMHO.

Originally Posted by rtgirard

Gotcha. I knew the N52/54 were really tight, but i didn't know about the V8/10.

All of BMW's engines have the same cylinder spacing - they only have to order/build one set of machine tools to bore/hone the cylinders.

The older M30 block had different spacing.

Originally Posted by floydarogers

All of BMW's engines have the same cylinder spacing - they only have to order/build one set of machine tools to bore/hone the cylinders.

The older M30 block had different spacing.

+1.

This is the reason why automakers knock cylinders off engines... tooling costs.

The N20 is an N55 minus two cylinders. The M3's S65 V8 is a chopped version of the M5's S85 V10... and the list goes on and on.

Even the 6.0-liter V12 is two 3.0-liter inline-6s...

- Mike

Originally Posted by Emission

Even the 6.0-liter V12 is two 3.0-liter inline-6s...

A tidbit of BMW history: The older M70 ('88-> '94) had TWO OF EVERYTHING! It was constructed from two M20 engines, and had two distributors, etc. And you guys swear at the cost of maintaining just one engine!

Originally Posted by floydarogers

A tidbit of BMW history: The older M70 ('88-> '94) had TWO OF EVERYTHING! It was constructed from two M20 engines, and had two distributors, etc. And you guys swear at the cost of maintaining just one engine!

Yes, that is why the '88 BMW 750iL has a resale value lower than the '88 325i of that era... maintenance is a bitch.

- Mike

Originally Posted by SteVTEC

Didn't see a date, but that article seems a bit old. GM no longer makes their 90-degree V-6 engines aka the "3800" line. Retired a few years ago, but it did run very smoothly and was quite refined, so whatever they did to it to make it run so well worked. That engine has lots of fans to this day, myself being one of them.

This article was from last year. It offered a good scientific basis for the smoothness of an inline 6, a boxer flat 4 (180deg) and a V8 (90 deg). "Physics is always relevant" is the elegance of it.

Originally Posted by Inline Sixer

"Physics is always relevant" is the elegance of it.

Yup. Or, as many a young man learnt the hard way on a racetrack (or, if unlucky, on the street), it is always better to call Lord Newton just that instead of being intimate on a first-name basis with him.

Too bad they grow up, forget the lesson and buy an SUV. Which needs $50,000 in mods from manufacturer in order to create the appearance of defeating Lord Newton. But that is a fable for another night. Good night kids.

One of the real advantages a straight six has over a V6 is that there is room for more and wider main bearings, and larger diameter crank journals. When an engine is constantly pushed near the limit this is a real advantage toward keeping them together. As for smoothness, a V6 can be just as smooth but it's done with smoke and mirrors, balance shafts and silicone filled 'tuned' motor mounts.
BTW, some of the most rugged engines, not neccessarily the most fuel or emission efficient, in US history have been I6's. The Chrysler 225, the Jeep 4.0, and the Ford 170 and 200 and 262, and the GM 194, and 230 and the 3.8 Litre. Aha you say, the 3.8 was a V6! Not in the early Firebird it wasn't. It was a 3.8L DOHC I6. A few of the Fords and GMs had 7 main bearings!
I agree with Emission that BMW will have a V6 sooner rather than later. There are just too many design and cost advantages over the I6 for a company with their mass market aspirations to ignore forever. The company isn't run by engineers, it's run by accountants beholden to stockholders.

Originally Posted by DSXMachina

I agree with Emission that BMW will have a V6 sooner rather than later. There are just too many design and cost advantages over the I6 for a company with their mass market aspirations to ignore forever. The company isn't run by engineers, it's run by accountants beholden to stockholders.

Well, this is the truth only for those who can't learn from somebody else's mistakes. Namely, the whole **** Sapiens Sapiens genus.

Ferdinand Porsche allegedly said "I was looking for a car, but I couldn't find one that fits my needs. So I built it.". Let's spare comments on why Feruccio Lamborghini created his own car after a bout with Enzo Ferrarri (Not Safe For Work - if you speak Italian, that is ).

The point is, GM already tried "proven and trusted" method of "This is how much it needs to cost, make it work!" and we all know how THAT ended up. It seems to me that we also have a whole another casualty of ignoring engineers - Fisker Karma. Can you say "This is how it needs to look, make it work!" ?

EDIT: isn't it cool how Bimmerfest replaces H*mo to asterisks (H*mo Sapiens Sapiens). Wow, we are really proper f*cked as a society! Time to move to another continent.

Originally Posted by Mark K

It seems to me that we also have a whole another casualty of ignoring engineers - Fisker Karma. Can you say "This is how it needs to look, make it work!" ?

Can't ignore the marketers either. Cases in point: the Edsel, 1980s Apple.

Originally Posted by Mark K

The point is, GM already tried "proven and trusted" method of "This is how much it needs to cost, make it work!" and we all know how THAT ended up. It seems to me that we also have a whole another casualty of ignoring engineers - Fisker Karma. Can you say "This is how it needs to look, make it work!" ?

Originally Posted by Squidget

Can't ignore the marketers either. Cases in point: the Edsel, 1980s Apple.

Ah, but what about Steve Jobs who insisted on just that with the iPhone, iPod and iPad, and would not accept anything less?

Wow, this thread resurrected from the dead.
Good follow-on conversation though.

Originally Posted by galahad05

Wow, this thread resurrected from the dead.
Good follow-on conversation though.

Great posts by you regarding heat and efficiency. A very misunderstood subject. I suppose it's because we were trained to think hot engine, bad, cool engine, good!
A few years ago I read a powertrain engineer's comment that he wouldn't be happy until engines were all ceramic, ran at a thousand degrees, and were cooled like exhaust valves, using liquid sodium. He knew what he was talking about.

[quote=DSXMachina;6701794]One of the real advantages a straight six has over a V6 is that there is room for more and wider main bearings, and larger diameter crank journals. When an engine is constantly pushed near the limit this is a real advantage toward keeping them together. As for smoothness, a V6 can be just as smooth but it's done with smoke and mirrors, balance shafts and silicone filled 'tuned' motor mounts.
BTW, some of the most rugged engines, not neccessarily the most fuel or emission efficient, in US history have been I6's. The Chrysler 225, the Jeep 4.0, and the Ford 170 and 200 and 262, and the GM 194, and 230 and the 3.8 Litre. Aha you say, the 3.8 was a V6! Not in the early Firebird it wasn't. It was a 3.8L DOHC I6. A few of the Fords and GMs had 7 main bearings!
quote]

I believe the Firebird Sprint 3.8L inline 6 was an SOHC engine. It was also not the only American OHC 6. In 1962 Jeep introduced the Tornado SOHC 6. Jaguar had a 3.8 (later 4.2) DOHC 6 during that era that both American engines were frequently compared to. The Firebird Sprint was introduced at the start of the Ponycar/Musclecar era and was soon eclipsed by the large V8s that Pontiac was offering in the Firebird. As good as the engine was in those days 6 Cylinder was synonomous with low performance in the eyes of most American car buyers and performace oriented Firebird drivers were more interested in the 326 and 400 (and later 454) cubic inch V8s.

The Hudson Hornet was an Inline-6.

Have to love the smoothness of the I6

great thread here

Have you guys ever driven, been in, or just heard an NSX? There are V6's and then there are V6's...

And wait until F1 switches to turbocharged V6 engines in the near future...

Originally Posted by adc

Have you guys ever driven, been in, or just heard an NSX? There are V6's and then there are V6's...

I had one. It's not as smooth as the inline 6. It wasn't even very smooth for a V6, as it was 90 degrees rather than 60. However, the very low mass of the pistons (titanium rods!) made it really zingy.

They're fabulous cars, extremely well-built and reliable. But just as costly as an M3 to work on. The ABS controller went out on mine just before I traded it in: $2500 for the part alone.

Originally Posted by adc

Have you guys ever driven, been in, or just heard an NSX? There are V6's and then there are V6's...

And wait until F1 switches to turbocharged V6 engines in the near future...

I was just thinking of nice sounding V6s. I got a ride in a supercharged NSX, sounded sweet. VW's VR6 also sounds nice but I guess that's not really a V6.

Can't think of any others that stand out. I don't like sound of the Nissan V6.

the Datson 240 thru 280 had a I6, Triumph TR6 has an I6,( I have one) toyota supra had a I6, My TR6 redlines at 5000, and my 335 at 7000. which all has to do with the stroke of the piston, longer stroke, lower redline, also more torque in the low end.. the other thing about I6 vs V engines is the crankshshaft are shorter, and one rod per journal where as V6 or V8, you have 2 rods sharing the same single journal, so shorter cranks shaft save weight too

Hondo