Motor Trend on why the inline-6 might come back

[A_Harman]

Originally Posted By: d00df00d
Originally Posted By: Darwin1138
Didn't all those problems were solved by VW with the VR6??

In terms of NVH and compactness, the VR6 is a middleground between an inline-6 and a V6. It's not a substitute for either.

In terms of performance, it's certainly a good way to get 6 cylinders into a small package, but there are some problems. The fact that all of the cylinders are crammed together like that really limits how the ports and combustion chambers can be designed. It also makes the intake and exhaust tracts run past each other, which heats the intake charge. And of course cooling can be an issue when you have so much heat in so little space.


And yet, the W16 in the Bugatti Veyron is based on the same architecture as the VW VR6. As is the W12 that Bentley uses. All the problems you mention do exist to some degree, but engineers are paid to find solutions to such problems. Maybe that's why the Veyron costs $1M+.

 

[19jacobob93]

I know some of you were expecting me to pop up here!
I hope the I6 does make a mainstream return though, a big kick in the bucket to the rare I6 RWD layout is the demise of our Falcon in 2016 :'(

 

[19jacobob93]

Originally Posted By: Hokiefyd
Originally Posted By: d00df00d
No one (competent) will argue against the packaging advantages of a V6.


Right. Just like no one will argue against the mechanical benefits of an inline-6 (there are many, as the article and others in this thread have pointed out). But the packaging compromises are huge unless you're looking at a longitudinal layout; for that reason, I believe that RWD is really the only market where an inline-6 makes sense. So it stands to reason that the only manufacturer still building an inline-6 is BMW...a company that produces only longitudinal powertrains (except perhaps with that new iBMW thing, or whatever its called).

I continue believe that an automaker doesn't have a compelling reason to design an inline-6 today. I suppose I'm not the only one; nobody but BMW has one. They just wouldn't see a return on their investment to design an engine that can be used in only one or two vehicles. GM, for example, can spend more money on the chassis and interior and other bits of its new Colorado because it can engine-share that 3.6L with other vehicles. The money saved from designing a purpose-built inline-6 can be spent on other areas of the vehicle.

You'll never read an argument from me that V-6s are inherently better than I-6s. That said, I just don't see this happening (an I-6 resurgence).


There's a small company called Ford that you may have heard of that currently build a longitudinal I6 RWD sedan
I don't expect you to know that though as they aren't sold over there

But is that really all we're down to? BMW and Ford Australia? If so in 2 years it will only be BMW, and they're already on the trend of turning I6s into turbo 4s

 

[d00df00d]

Originally Posted By: A_Harman
And yet, the W16 in the Bugatti Veyron is based on the same architecture as the VW VR6. As is the W12 that Bentley uses. All the problems you mention do exist to some degree, but engineers are paid to find solutions to such problems. Maybe that's why the Veyron costs $1M+.

I think you and I could agree that those are the exceptions that prove the rule.

Everything in the Veyron is quite literally a cost-no-object proposition; I'm not sure if the same is true of the Bentley W12, but obviously it's close for all practical purposes.

Both engines are also colossally inefficient. I'm sure that needs no elaboration...

 

[05LGTLtd]

I like I6's and Slant 6's...

But give me a (turbo) flat six and I'm a happy guy!

 

[Bgallagher]

Originally Posted By: MolaKule
Originally Posted By: DoubleWasp
Love my inline 6.

The I-6 in the Chevy TrailBlazer was and still is a torquey 6 cylinder and has the tenacity of a fighter.


My mother in law has one and it is great for the vehicle. Great acceleration and very quiet. Lot of power

 

[ARCOgraphite]

Originally Posted By: Hokiefyd
I don't share the author's prediction that inline-6 engines will somehow stage a comeback. I certainly don't have anything against them, but there's no compelling reason to design one today. For all intents and purposes for most passenger vehicles, the 60-degree V-6 is a far better solution than a long-and-skinny inline. You can sit an I-5 sideways pretty well, and it is possible to cram an I-6 sideways, but you're going to have some unpleasant compromises as a result (like an unconventional transmission layout, hard-to-access serpentine belts and engine-driven accessories, etc. A V-6 just makes too much sense to NOT use if you want to have six cylinders.

The only market, really, for an inline-6 today (talking about road-going cars here) is a limited enthusiast RWD market and/or limited luxury RWD market. Most people cannot tell the difference between a good 60-degree V-6 and an inline-6, and a FWD layout pretty much precludes an I-6 architecture. To most people, a "good engine" is one that starts when they turn the key. That's the reality to which cars are designed and I don't see that changing in the future.
Agree. I loved the 60 deg 1-2-3-4-5-6 firing sixer in my favorite car - a early eighties S10 with a Varajet carb and big port heads. Inline sixes are just to unwieldy to package in your average pass cars these days. No I would like to see a return to ULCA over Mac struts - tha all important steering on many cars is abysmal!

 

[A_Harman]

Originally Posted By: d00df00d
Originally Posted By: A_Harman
And yet, the W16 in the Bugatti Veyron is based on the same architecture as the VW VR6. As is the W12 that Bentley uses. All the problems you mention do exist to some degree, but engineers are paid to find solutions to such problems. Maybe that's why the Veyron costs $1M+.

I think you and I could agree that those are the exceptions that prove the rule.

Everything in the Veyron is quite literally a cost-no-object proposition; I'm not sure if the same is true of the Bentley W12, but obviously it's close for all practical purposes.

Both engines are also colossally inefficient. I'm sure that needs no elaboration...


Like they say, "if you have to ask what it costs, you can't afford it." I was sorry to hear the VR6 was going out of production, because it was a good attempt to make an engine with almost all of the benefits of an I6 package in the same space as an I4. The Germans have a penchant for designing dense-packed machinery.

 

[Lolvoguy]

FWIW IIRC Volvo still uses the 3.2 I6 in their base S80

 

[badtlc]

what about a boxer vs an i-6? Does any of the natural balancing effects of the boxer engine give it a leg up on the I6?

 

[leeharvey418]

Originally Posted By: badtlc
what about a boxer vs an i-6? Does any of the natural balancing effects of the boxer engine give it a leg up on the I6?

A V6 would actually be intrinsically balanced with a 120 degree v-angle. There are other higher-order vibration modes that make this less appealing, but that would be the ideal from a pure firing order standpoint.

 

[Darwin1138]

Originally Posted By: d00df00d
Originally Posted By: A_Harman
And yet, the W16 in the Bugatti Veyron is based on the same architecture as the VW VR6. As is the W12 that Bentley uses. All the problems you mention do exist to some degree, but engineers are paid to find solutions to such problems. Maybe that's why the Veyron costs $1M+.

I think you and I could agree that those are the exceptions that prove the rule.

Everything in the Veyron is quite literally a cost-no-object proposition; I'm not sure if the same is true of the Bentley W12, but obviously it's close for all practical purposes.

Both engines are also colossally inefficient. I'm sure that needs no elaboration...

Why they are so inefficient, please elaborate....

Originally Posted By: A_Harman
Like they say, "if you have to ask what it costs, you can't afford it." I was sorry to hear the VR6 was going out of production, because it was a good attempt to make an engine with almost all of the benefits of an I6 package in the same space as an I4. The Germans have a penchant for designing dense-packed machinery.

When did this happen??? The Passat still uses the VR6.

I think 20 years of production are more than just "an attempt"

 

[babbittd]

A very interesting article, thanks for posting the link!

 

[TiredTrucker]

I would be chomping at the bit for an inline 6 in my Silverado. I would much rather have a 6.0L inline 6 than a V8. Better low end torque out of the 6, and easier to work on. Plenty of room under the hood on a 1500 Chevy to drop in an inline 6. I have always been an inline fan. Ever wonder why they gave up on V8's in heavy duty commercial trucks? And you would think with all the new aerodynamic changes that semi trucks are undergoing that they would bring them back to be able to shoe horn them in there. Nope. Not a chance. Inlines offer the best bang for the buck. More reliable and stellar low end torque.

I can understand maybe not in a lot of autos, but there is no reason to not offer strong inline 6's in pickups, vans, larger SUV's, etc.

 

[d00df00d]

Originally Posted By: Darwin1138
Why they are so inefficient, please elaborate....

Veyron: 7 mpg city, 15 mpg highway
Continental GT: 12 mpg city, 21 mpg highway

The Koenigsegg Agera isn't far off the Veyron in terms of horsepower, and it manages 16 mpg city/19 mpg highway.

To find a comparison to the Bentley, you have to look at the Mercedes CL65 AMG. That car has over 100 lb-ft more torque, 1 fewer valve per cylinder, and 3 fewer speeds in its transmission, and there isn't a single molecule in its construction that cares in the slightest about fuel economy (Mercedes sells enough fuel efficient cars to meet CAFE standards). It still matches the Continental GT's city mpg and only falls behind on the highway (18 mpg vs. 21 mpg).

 

[Mitch]

what is old is new and new is old.
the early 225/231 gm v6(odd fire) was basicly a v8 with 2 cylinder hacked off ,you could use a v8 dist cap even. Then they went to split rod journals in 1979 to become the even fire. Ford in late 70s borrowed the v4 from saab and added 2 cylinders to become the 2.8/171. Loved those engines, gear driven cam,no chain and it was a 60 degree motor.

Then of course there was the gm boxer 6 cylinder in naturally aspirated or turbo charged(180 degree).And another piece of laughter which I owned, triumph tr8. The tr7 used the reverse engineered 215 ci gm aluminum v8(early 60s) cut in half, yeah a /4. The tr8 made it right and used both halves. The tr7 engine was not what you would call smooth
Then there was international trucks contribution, the scout came with a /4,the same engine with both halves was the 304 v8

 

[d00df00d]

Originally Posted By: badtlc
what about a boxer vs an i-6? Does any of the natural balancing effects of the boxer engine give it a leg up on the I6?

Can't get better than perfect balance.

Where a boxer-6 or flat-6 beats an inline-6 is in length and height. Obviously this makes it much better for a vehicle's center of gravity and polar moment of inertia, and makes it easier to package lengthwise. The downside is that its width and low position and can make it harder to package width-wise and harder to service.

 

[SwampSurvivor]

The I6 won't ever come back

Wish it would.

 

[hattaresguy]

I6's especially Jag's also put out all kinds of power. In vintage racing other than the 911 they are the only cars that can pull with the big block American cars like the 427 Corvettes on the straights.

 

[jrustles]

Originally Posted By: OneEyeJack
A V6 has never been anything better than a packaging solution. A front wheel drive car is only so wide and the fore and aft space only so much if you want to focus on passenger space.


Yea you are not kidding about that