[posttosh]

Ford has moved all production of the Volvo Short Six to its new facility in Brigend, Wales.

Originally designed by Volvo (prior to the Ford acquisition) for the then-new Volvo S80 in the late 1990s, the tough part of the design exercise was to make the block short enough to be mounted transversely, especially difficult in vehicles with Macpherson strut front suspensions(and their space-consuming strut towers) such as the Volvos have. A 2.9 liter engine until this year, it was updated (engine designation SI6) to 3.2 liters at the Brigend production. At the same time, the transmission was rearragged so that the engine+transmission combo is even shorter than it was on the Volvo S80.

The Jaguar S-Type, which currently has the Jaguar AJ30 V6 engine, a variant of the same 2967cc Duratec that appears in the Mazda6S, will get the Short Six next year. Ford, obviously, considers the SI6 to be an upgrade to the AJ30. Of course, the S-Type is a RWD configuration.

I, for one, would love to see an inline-6 in the Mazda6. Does anyone know if the engine bay of the current Mazda6 has space for the SI6, what with the need for the front-wheel drive components?

 

[smokeU6s]

Im guess no. S80 is a larger car and a larger engine bay. you would have no place to lay out the tranny. I6's usually are mounted longitudily for RWD anyway... ie BMW

 

[Awong124]

I don't see why an I6 would be better than a V6. It might be smoother, but you'd have a higher center of gravity, and it's much less space efficient.

 

[brightwhite]

Don't I6's usually have better long term reliability though? I'm thinking of the BMW i6 and the Jeep I6. I don't have personal experience with the Beemer version, but they have legendary reliability, and my family has easily run up over 300,000kms on several Jeep straight 6s.

Are they better for power too?

 

[Awong124]

I don't see why it would make more power. It might have better reliability since it's a simpler design, less parts, but I don't see how it would have better performance though.

 

[blackmagik_13]

Straight-6 engines are simply two 3-cylinder engines mated symmetrically together, thus piston 1 is always in the same position as piston 6, piston 2 the same as piston 5 .... in other words, the engine is balanced end-to-end and requires no balancer shaft, unlike 3-cylinder engines.

The vertical and transverse forces generated by individual cylinders, no matter first order or second order, are completely balanced by one another. The resultant vibration is nearly zero, thus inline-6 is virtually a perfect configuration.

Inline-6 engines are not the only configuration that can deliver near perfect refinement, but it is the most compact one among them. All boxer engines are perfectly balanced, but they are two wide and require duplicate of blocks, heads and valve gears. V12 engines also achieve perfect balance, but obviously out of the reach of most mass production cars. Automotive engineers knew that long ago, that's why you can see most of the best classic engines were inline-6, such as Rolls-Royce Silver Ghost, Bentley Speed Six, Mercedes SSK, many Bugattis, Jaguar XK-series and BMW's various models.


As space efficiency becomes more and more important, most car makers favor V6's. The most influential V6 was perhaps Alfa Romeo's 2.5-litre 60-degree V6 used in the GTV6. It established a reputation for V6 that it can be compact, powerful and smooth. An equivalent inline-6 would have never fit the small and sloping engine compartment of that car. Compare the shape of BMW with the Alfa and you’ll know the packaging advantage of V6s.

Straight-six engines are nearly impossible to be used in front-wheel drive cars as well. Even a car as wide as Volvo S80 has to introduce the world's shortest gearbox in order to make space for the 2.9-litre straight-six mounted transversely in the engine compartment.

Longitudinal mounted inline-6's don't have such problems, but it engages too much space in north-south direction, thus engage some space which would have contributed to cockpit room.

However, BMW is still loyal to inline-6 engines. Ultimately, inline-6 engine is more efficient yet smoother. V6 has more energy loss because it duplicates valve gears and camshafts (which increase frictional loss), while the use of 2 cylinder banks leads to more heat loss. In terms of production cost, although V6 has 3 fewer main bearings, it has more valve gears - which is getting more and more costly these days, with the introduction of twin-cam, hydraulic tappets / finger follower and variable valve timing. Inline-6's are going to be cheaper than equivalent V6's in the long run.

 

[StylinM6s]

good info there Blackmagik Productions. I've heard that I6 has a little better gas milage dont know the specs on that and also the V6 has a little more power.

 

[Awong124]

It's a trade off, like I said before an I6 would be smoother and has less parts, but it's too long to be mounted transversely for use in an FWD car and it has a higher center of gravity. I personally think a V6 is a better design overall than an I6.

 

[blackmagik_13]

Eh, everyone has their opinions, but you can't beat the facts.

That'd be a neat swap though, albeit... you'd have to convert / totally change the drivetrain to rwd but, it'd be a cool project for sure.

 

[Awong124]

To convert to RWD would be absolutely crazy! Is there even enough room under the car to run the driveshaft and mount the differential in the back? Even if I could do that I would stick with the V6 and try to mount it longitudinally, since it's shorter than an I6 I can mount it further back and improve weight distribution.

 

[blackmagik_13]

I dunno, extra room underneath the 6 doesn't exist. If you have an exhaust pipe bent wrong by 1cm, it'll bang against the subframe. You have to be very exact. With a new drivetrain... man. Like I said, it'd be a neat project, but difficult and time consuming if even possibly.

 

[smokeU6s]

It would be cheaper and less of a PITA to transplant the new Duratec 3.5L in.

 

[Awong124]

It would probably be easier just to throw the Mazda 6 shell on a BMW 3 series or something, lol.