68 replies to this topic

[pa]

This may be a stupid question, but I'd like to know the answer, so no flames, please.

Why has BMW stuck with the straight 6 for so long now? I'm aware that they've shoehorned an M5 8 into some (race prepared) M3s this year - is that a sign of thing to come? Will the marvelous BMW 6 be history in a few years? Does it offer a particular advantage over the flat 6 or V6 configuration, in terms of power, weight, CG? What?

TIA...

[Bex37]

How do the following figures sound:
- 3.2 litre, straight six
- normally aspirated
- 8,000 rpm redline
- 252 kW (343 BHP) at 7,900 rpm
- 365 Nm at 4,900 rpm
- 8.4 L/100km highway cycle (32 miles/gall)

Show me another production engine that can do all of the above AND lope around in top gear at 1,000 rpm smoothly and quietly with progessive, smooth power increase all the way to red line.

If you had an engine like the above, why would you change?

[Nikolas Garth]

My limited understanding of the question at hand, is that inline six's are much smoother than a V6, not sure how they compare to V8's.

[BRG]

BMW have a very well developed and effective family of engines in the straight 6. They have very successfully made something of a virtue out of sticking to "traditional" elements like RWD and 6 cyl. engine and, given their marketing success, this has been a good decision. In the longer run, perhaps they will have to come up with an all new engine for packaging or fuel economy reasons, which might be a V6, but there is no sign of it happening yet awhile. If it ain't broke....

[sanat]

Just my 2 pennies:
As Nikolas mentioned, straight six is one of the most balanced engine configurations. If your engine does not vibrate, you can (other things being equal) achieve higher RPM, hence higher power output.
Another reason might be that it is just a tradition, and they do not want to deviate from it. What brand comes to your mind, if teh engine is front-mounted straight-six and the car is rear-wheel drive? Certainly BMW...

[jpf]

I-6s are an inherently balanced engine - primary and secondary shake are balanced by the collective movement of the pistons and rods, so the engine is very smooth. Also, with only a single bank of cylinders, cooling is simplified, and especially, the valve train is simplified -- with variable valve timing this is especially important because you only need half as many VVT assemblies compared to a V-6. The only real advantage of a V-6 is packaging. Sure you could go V-8 but that's more complex and wouldn't really make sense to scale down to the lower displacements either.

[jpf]

Incidentally, about that last bit -- are the sixes used in the 325 and 330 basically the same engine, bored or stroked to different displacements? Cause that's what I was assuming...

[BRG]

Originally posted by jpf
are the sixes used in the 325 and 330 basically the same engine, bored or stroked to different displacements?

I think that BMW originally had the 2.8 to 3.5 litre straight six, as used in the 635CSi coupes in the 70s. Then they built a smaller straight 6 of 2.3 to 2.5 litre to use in the 3 series. I believe that they have now dropeed the earlier, bigger engine, and that the current straight 6s are all variants of this later engine.

But I MAY be talking out of my a**e....

[Blade]

V-6 are inherently not stable and require software to ensure the engine operates smoothly.
Also, i'm not sure but V-6 are larger than I-6 so it wasted more space... that means V-6 would affect the handling of the car more so its not surprising cars place their v-6 engine in transverse configuration (ie. Acura 3.2 TL type-S etc) which severely affects the cornering ability of the car.

[tedmna]

Originally posted by BRG
I think that BMW originally had the 2.8 to 3.5 litre straight six, as used in the 635CSi coupes in the 70s. Then they built a smaller straight 6 of 2.3 to 2.5 litre to use in the 3 series. I believe that they have now dropeed the earlier, bigger engine, and that the current straight 6s are all variants of this later engine.

But I MAY be talking out of my a**e....

The current I-6 is not a direct variant of either of the older I-6's you mentioned.

[Arneal]

The main disadvantage of an inline 6 is the packaging. Because the cylinders are all in one long row it is not possible to mount them transversly between the front wheeels. This forces you into a longitudinal arrangement that takes up a lot of space. An inline 6 is twice as long as a V6 and 50% longer than a V8. Because the engine takes up so much real estate the cabin and trunk have to be made smaller. This is why BMWs have so much less legroom room and trunk room versus simliar V6 cars.

BMW is probably right to stick with the I6 as they have sold a lot of them over the years, but most other makers prefer the V6 because most consumers can't tell the difference between the smoothness of an I6 versus a V6, but they can easily spot the extra cabin and trunk space.

[desmo]

From an engineering standpoint for an engine in the 2.5-3.5l range, an in-line 6 is probably the ideal architechture. Jpf laid out it's primary advantages. If logic were the primary dictate, we'd likely all be driving in-line 6s. I even had an old M-B with a 2.2l in-line six which was a far better engine than the later 2.2l 4.

[RiverRunner]

Call me a dinosaur,but I've got to say I've had far more luck with I6's than any other engine around.
We had a 6.35csi for awhile and it was *the* Vegas cruiser,ran like a **** in serious heat and it was no problem at all to average 85mph through the deserts and over the mountains there and back from LA.It's only drawback was it's penchant for consuming mass quantities of fuel and the small tank it had required lotsa fuel stops.We currently passed on the V-8 and got the I6 version of the X5 and other than it's touchy throttle I like it a lot.
The other I6 I swear by is the Jeep 4.0L,it's been around forever in different specs,but the last one I had was a direct port injected one than I sold at 180K miles on the odometer and the only pricey thing it ever required was new injectors at a 100 bux a pop and I only had a cracked casing on one but replaced them all.Put it in 4WD and it would pull stumps out and not break a sweat,this one oddly enough was very easy on fuel even though it was larger than the BMW's.
I passed on a V-6 Jeep a few years back and stuck with the 4.0L I6 for my current Jeep and it's at 52K and still running like a champ.Great engine for towing too,which I do a lot of,loads of torque.

[Wolf]

Originally posted by Arneal
Because the cylinders are all in one long row it is not possible to mount them transversly between the front wheeels.

Tell that to ppl in Volvo, ignorant of this fact they did it.

[tedmna]

Arneal, there are packaging issues and then there are packaging issues. V-6's can complicate packaging: fitting intake tract, runners and plenum into the V, routing an additional exhaust, and, if mounted transversely for FWD, fitting in a transaxle and halfshafts.

BMW has traditionally tilted their I-6's, giving themselves room for intake runners and plenum, and typically a short intake tract.

The real packaging problem BMW faces comes from fitting in the longitudinal transmission, driveshaft, rear diff and axles. Actually, they do a pretty good job. I can remember the last Audi 80, which even with FWD had only a miniscule trunk.

In the US, we're used to big V-6's turning over relatively slowly, with gobs of torque, in relatively big cars. Turn those engines over at 7500 rpm's and I think you would notice the vibration.

I've had both BMW's with the I-6 and Audi's with the current V-6, and I can tell you there was a hell of alot more space in the BMW engine compartment vs. the Audi.

Also--I know it's nitpicking--a straight six is not twice as long as an equivalent V-6 due to the offset of the cylinder banks in a V-6 to allow for bigend clearance on the crank. Ditto for your V-8 comparison. Admittedly the difference doesn't change the validity of your assertion that I-6's are longer than equivalent displacement V-6's

[MN]

Maybe silky smooth BMW il6 image is too strong in public and BMW don't want any risks by replacing it with a V6.
Inline6 configuration advantage(smoothness) is long gone.
Today's engine technology allows car makers to build V6 as smooth as il6.

Thare a few V6 advantages....
1) shorter than il6, it can create more crashable zone for safety.
2) crank shufts can be shoter and stronger for the twist force.

If you read Japanese, go to Car Graphic site. They are talking about why Nissan threw away Skyline's il6 engine and replaced it with a V6. And also why Benz are started having V6 engines instead of il6.
http://www.webcg.net.../000011060.html

[AS110]

A straight 6 is two badly balanced 3cyl motors back to back that cancel each other out,and always need a harmonic balancer on the crank to help absorb crank flex.

Give me a sraight 6 any day....KISS!!!

[Arneal]

Originally posted by Wolf


Tell that to ppl in Volvo, ignorant of this fact they did it.

Twin turbos no less! Some ppl just can't follow the rules.

[JForce]

BWM did in fact toy with the idea of chucking the M5's V8 in the new M3. The bean counters wanted to do it to save money, but the engineers threw a wobbly. Apparently it would have thrown the handling off something chronic, as the V8's too heavy.

[H. Eckener]

Blade,

What does software do for the V6's vibration issues? Software may help prevent misfire or reduce the likely hood of improper combustion, but misfire in a V6 is probably just as bad as misfire in a I6. Old fashion carbs and points should work just fine in a V6. The basic engine geometry is the most important factor along with vibration dampening equiment.

[texfan]

GM still uses a 4.2 INLINE six in their new GMC Envoys and Chevy Trailblazers. I have driven the Envoy for two weeks,with its I-6 and even compared to my Honda Accord(I-4,Honda is the master of balance shafts and smoothness in small engines),there is no contest. NO VIBRATION WHAT SO EVER!

Specs on GM's Inline six:
270 HP @ 6000 rpm
Torque 275 @ 3600 rpm
I-6 DOHC,4-valves per cylinder
Alum. block/heads
4.2L

By the way,I hear you can place a coin on its edge on a I-6 and rev the engine and it will stay.

[jpf]

tedma- Agreed, V-6s pose their own packaging problems, as you say mostly involving plumbing and routing the powertrain. But later when you say

I've had both BMW's with the I-6 and Audi's with the current V-6, and I can tell you there was a hell of alot more space in the BMW engine compartment vs. the Audi.

That just seems to support the fact that V-6s have superior packaging -- the extra space in the BMW is wasted space! At least as far as the packaging people go. Shuffle things around and you could put someone's feet there...

Speaking of which, I think the issue of V-6s shorter lengths freeing up more crash crumple-zone space is important; that was one of the main things referenced when I heard some dirty, dirty rumors that BWM were going to switch to V engines. I guess it's not unheard of; Mercedes introduced their 3-valve heads to meet emission requirements. Maybe BMW is starting to think that in order to provide the accomodations they want under more and more stringent regulations they have to move to Vs. Let's hope not...

[RiverRunner]

As far as engine crush zones go,I doubt that there is much at all gained in the engine intrusion of the passenger cell between a v-6 and a i6.Even a Ford Taurus has a skidpan of sorts to guide the engine under the passenger area in a head on crash.Such systems utilize the engine itself as an crush/G load absorption device.

[marion5drsn]

BMW Inline six’s. The V-6 packaging is almost as long as a V-8. This due to the fact that to get a V-6 to operate in a smooth fashion it must have 3 extra crank arms to put the conrod pins in an angular position to prevent Secondary Shake, that is 60 degrees apart. One only has to look at the Turbo F1 Honda to find a real boneshaker due to the three-pin layout. Somewhere in F1 Atlas you might find an answer to me when I asked this question about the Honda. Remember V-6’s only have 4 main bearings! There’s a lot of overhang in the crank arms. I don’t believe BMW people with a lot of experience with BMW inline six’s would be very happy with this arrangement. This especially with the revolutions they would be expecting with a short stroke V-6. My V-6 Toyota is OK with the rpm’s it turns but would BMW people be happy with this? Not for how much more they cost!
Going with V-8s is not the problem that a lot of people think it would be, as so many millions of them have been built that BMW wouldn’t have the problems so many would anticipate. An example of this is the Turbo supercharging of six’s to achieve V-8 power. It is likely as cheap to go to A V-8 as to supercharge whether it be mechanically driven positive displacement or Turbo centrifugal. Remember Toyota had an Inline six also and I believe dropped it about 1994.Many of these I-sixes had fairly long strokes. This to keep the overall length down to a reasonable size.
Just what is BMWs production figure? This may have a lot to do with just how long and when they intend to go to a different engine configuration. How many sixes compared to fours? Has the tooling paid for itself?
Sketches reveal that a V-6 has it all over an I-6 and a V8 using similar BxS ratios and conrod ratios. The I-6 is 1.67 larger, a V-8 1.21 times the angle of the V-8 being the culprit and the length of the I-6 being its downfall. That 60-degree of the V-6 is very obviously the big factor in the decision by Honda on V-6s. Has Honda ever made a V-8? M.L. Anderson

[MN]

Originally posted by marion5drsn .... Has Honda ever made a V-8? M.L. Anderson

Not for street cars but CART engines are V8 aren't they ?

[RJL]

Originally posted by Arneal
The main disadvantage of an inline 6 is the packaging. Because the cylinders are all in one long row it is not possible to mount them transversly between the front wheeels. This forces you into a longitudinal arrangement that takes up a lot of space.

In addition to the Volvo example sited above I seem to recall that Ford (?) showed an inline six mounted left to right (ahead of the front wheels) and attached to a central (front to rear) transmission. It never made production, however. This goes back some 20 years or so, anyone else remember it?

Also worth noting are the across the frame inline six motorcycles from Honda & Kawasaki in the late 70's/ early 80's. The Honda CBX, in particular, has gained quite a loyal following.

[AS110]

I think that Ford was a straight 8,but as with you it's only a vague memory.
Benelli made a 6 as well.

Does packaging mean leaving no room left under the bonnet? Someone has to build,maintain and ullimatly repair these things.Good packaging means these thing are going to cost more.

[marion5drsn]

MN , you are right, altho I did have high production cars on my mind.

AS110. Ford has never made a straight eight that I know of. However Buick, Oldsmoble, Pontiac Chrysler, Duesenberg, Lasalle and many others did. My Dads old 1937 Buick had a very long hood which it needed to take that long 320 cubic inch engine. Many people in those days had the idea that a long hood meant a powerful car. Quite forgetting that the later V-8 La Salles were faster and more dependable. Not to mention the 1932 Ford V-8. M.L. Anderson

[jetsetjim]

If you do the basic calculations for the Primary and Secondary Rotational and Reciprocating forces on an engine configuration, you will find that an I6 is one of the configurations that requires the least amount of counterbalance on the crank. Applying these calculations to other configurations, and you find that a boxer 6 and V12 are also very well naturally balanced engines. It is simply a case of resolving the forces.

However this theory only works if the firing order is correct. Change the firing order and you can totally change the balance within an engine.

V6's don't need software to run smoothly, they just need a large amount of counterbalances on the crank to compensate for the forces in the engine. V engine balance also depends on crank orientation. This is particularly apparant in V8 engines when you compare the forces in a conventional bi-plane crank (Rover V8) and in-line Crank (most modern Racing engines).

If you want to go into the In-Depth theory behind engine balancing, then you need to read the book Internal Combustion Engine Fundamentals by John Haywood. Alternatively for a simpler explanation, read Advanced Engine Technology by Heinz Heisler.

I've had to sit through Power Train Engineering lectures on the subject, and have physically worked out the forces involved in a variety of engine configurations.

Incidentally, if anyone is interested.... one of the worst engine configurations for balancing is actually a V10!

[da Silva]

quote
In addition to the Volvo example sited above I seem to recall that Ford (?) showed an inline six mounted left to right (ahead of the front wheels) and attached to a central (front to rear) transmission. It never made production, however. This goes back some 20 years or so, anyone else remember it?

I think it was an British car, Austin? or something. I do remember that Volvo wasn´t the first to mount an inline 6 transverse into a production car.

About the discussion about BMW´s Il6 it´s an huge deal tradition to have an such engine in the car. And certantly an personal choise by Paul Rorshe.
One of the trademarks with BMW is to have an 100% smooth engine and in order to achive that you have either to have an Il6 or an V12. BMW could build the V8 for the latest M5 with good concious because they have an history to fall back on with V8 engines.
The V12 was the first german V12 after WW2 in an production car 1986.
I don´t think they will start with V6 because they want to, it would make the production if the
bodyconstructor demand that due to packaging.
I think they´ll stick to Il6´s fore the lesser versions and have V8´s for the top models like
M3 and M5, maybe even V10 for M5´s.

[desmo]

jetsetjim: "Incidentally, if anyone is interested.... one of the worst engine configurations for balancing is actually a V10!"

I am very interested! I am wondering what you base this on and what assumptions about crank geometry and FOs for a V10 you have to make to calculate the forces. My bible on engine balance issues (Charles Fayette Taylor's book) doesn't address the V10 configuration. I think I understand the crank geometry that has been arrived at for F1 V10s and have narrowed the possible FOs down, but information on V10s is very hard to come by.

[MN]

Originally posted by Arneal The main disadvantage of an inline 6 is the packaging. .....

Some engine room photos from the Car Graphic site.

http://www.webcg.net...ages/132/02.jpg BMW 525i 2.5liter IL6
http://www.webcg.net...ages/064/03.jpg BMW M3 3.2liter IL6
http://www.webcg.net.../R000012353.jpg Toyota 2.5liter IL6 Turbo

http://www.webcg.net.../R000017832.jpg Audi A4 3.0liter V6
http://www.webcg.net.../R000013135.jpg Jaguar Xtype 2.5liter V6
http://www.webcg.net...ages/046/02.jpg Benz E240 2.6liter V6
http://www.webcg.net.../R000017803.jpg Nissan Skyline 2.5liter V6 and Benz C240 2.6liter V6

[AS110]

marion5drsn,as RJL mentiond,it never went into production,just a design concept only.But it sure looked impressive with all those cyls across the engine bay.
The BMC tranverse 6 was the Tasman and Kimberly.Words fail me,there has never been a car as bad as these things.I remember seeing one of these where the driver hooked reverse instead of 5th,reverse idler was ripped out of the bottom of the box,and then smacked out the front of the engine by a passing con rod.A quick and timely death.I haven't seen one for years.

[Bex37]

Originally posted by sanat
Just my 2 pennies:
As Nikolas mentioned, straight six is one of the most balanced engine configurations. If your engine does not vibrate, you can (other things being equal) achieve higher RPM, hence higher power output.
Another reason might be that it is just a tradition, and they do not want to deviate from it. What brand comes to your mind, if teh engine is front-mounted straight-six and the car is rear-wheel drive? Certainly BMW...

Ford Falcon

[da Silva]

Jaguar with XK engine

XK 120
XK 140
XK 150

Mark 1 & II
Mark V, VII Mark IX, mark X
C-type, D-type, E-Type,
S-type, 420, 420G
XJ6 S1 S2 S3, X300, XJS

And even pre -48 before the XK120 came.
No other company was more known for using an straight 6 than Jaguar.
And still today for not having an 4 cylinder or Diesel engine in their programe.
But the Diesel will come.

[Garagiste]

You beat me to it Da Silva
But you forgot the XJ40 Afraid you're probably right about the Diesel

[marion5drsn]

JetSetJim, I can’t find that the V-10 is so much more difficult to balance than a V-8. Assuming that you are talking about a V-10 at either 72 or 144-degree bank angle and also with 10 counterweights to counteract the fore to aft Moment. I can’t see any problem. Now it you are talking about a 10-cylinder engine at 180 degrees (opposed) or 108 degrees (V-10) I can see the problem! These are the two worst angles to use if you want to stay away from the Secondary Shake. Just what orders are you talking about? Just what block and crank angles are you speaking of?
The firing order that the Viper uses are about as “Perfect” as one can get. This firing alternately each side results in a very smooth path of power impulses to the crank and also results in smooth exhaust pulses. The firing order of #1-10-9-4-3-6-5-8-7-2 we can notice that the even numbers are on the right side and odd on the left is similar to the Chevrolet with two more cylinders added on the back. One can notice this especially when making a linear diagram of the exhaust pulses. When I did this a few months back I was impressed by the way the pulses overlapped each other and reinforced the sonic effect of the slugs of gas. This was done using Iskenderians 330-degree cam timing.
Please elaborate on your statement. Yours M.L. Anderson

[Kaiser]

Originally posted by Wolf


Tell that to ppl in Volvo, ignorant of this fact they did it.

I think Volvo's FWD I6 mounted normally

[Ursus]

Originally posted by Kaiser


I think Volvo's FWD I6 mounted normally

Yes, in the normal way for a FWD car - transversly.

[freq019]

Originally posted by jpf
Incidentally, about that last bit -- are the sixes used in the 325 and 330 basically the same engine, bored or stroked to different displacements? Cause that's what I was assuming...

the 325 engine and the 330 engine are different blocks. I remember reading the in the Roundel that bmw was hesistant to bring back the 325 because people would assume that was the old block when that block has become the 330

[jpf]

Marion-

You say the Viper order is "#1-10-9-4-3-6-5-8-7-2" -- when I diagrammed that out, it looked like it had an extra big skip; it seems that the order #1-4-3-6-5-8-7-10-9-2", shown on the right in the image, would be simpler. That is, in the Viper order, there are three sets of adjacent firings that are not opposite cylinders or in sequential rows: 9-4, 7-2, and 1-10. But with the second order, there is only one such firing pair: 9-2. My knee-jerk assumption is that the second firing order would move the crank stress smoothly down the crank, then reset, rather than jumping all over the place.

Please note that this question is asked completely based on the look of the arrow diagram as shown, and not on any rigorous investigation of the underlying concepts!

[rdrcr]

Originally posted by Bex37
How do the following figures sound:
- 3.2 litre, straight six
- normally aspirated
- 8,000 rpm redline
- 252 kW (343 BHP) at 7,900 rpm
- 365 Nm at 4,900 rpm
- 8.4 L/100km highway cycle (32 miles/gall)

Show me another production engine that can do all of the above AND lope around in top gear at 1,000 rpm smoothly and quietly with progessive, smooth power increase all the way to red line.

If you had an engine like the above, why would you change?

In addition to the fine traits that this engine is known for, there are also the cost factors relating to the tooling for a totally new engine.


The straight six that BMW has produced for years has been fine tuned and developed for use in various vehicles with sales success. They get great results with a design that has, for the most part, been bought and paid for at least a decade ago. The Chevrolet Suburban is another example of a chassis that was used for 20 years, basically unchanged until recently. It's to the benefit of the manufacturer if the consumer truly likes the products performance, thus negating the constant change that is common among most American models.

[Zoe]

Originally posted by da Silva
quote
In addition to the Volvo example sited above I seem to recall that Ford (?) showed an inline six mounted left to right (ahead of the front wheels) and attached to a central (front to rear) transmission. It never made production, however. This goes back some 20 years or so, anyone else remember it?

I think it was an British car, Austin? or something. I do remember that Volvo wasn´t the first to mount an inline 6 transverse into a production car.

Austin Princess with the 2200cc engine. I had the dubious honour to buy one in 2000, only to have a crank bearing break after 120 miles. It also had the joint oil circulation for engine and gearbox since the engine was mounted on top of the gearbox! To inspect the crank bearings, you had to remove the engine from the car.

Zoe

[Garagiste]

Austin Princess with the 2200cc engine. I had the dubious honour to buy one in 2000

Oh lordy, empathy time Zoe - I used to run the Princess' replacement the Ambassador. What a terrible car! Still I was skint at the time and it cost £100 with a years MOT.
Used more bloody petrol than my current 4 litre Jag mind you

Edit - Jag was a bargain, but did cost more than 4 lire!

[marion5drsn]

JPF. You have the right idea but unfortunately the Chrysler crank is not constructed in that fashion. The throws are, drivers view in rotation from the front. #1 & 2, 0 degrees on the vertical C/L, # 5 & 6 are 72 degrees, # 9 & 10 are 144 degrees, # 7 & 8 are 216 degrees, and # 3 & 4 are 288 degrees. This is turning the crank in the usual counterclockwise direction, drivers view.

After making a paper crank and a 72-degree Vee I find it is not possible to make a crank in that configuration. This even if they made a completely new crank layout. This is one of the faults in making sketches. I found out the hard way that one needs a diagram as you made plus the paper crank layout plus the Vee to rotate the paper crank about, plus the ability to not get confused (My Problem). I’ve made 10 cyl. all the way from 180 deg. to 72 deg. using the Chrysler crank and found a lot of respect for the people who did this first. Its no wonder that Chrysler Hemi 1951 used the same bore and stroke that Cadillac used in 1949 plus the same firing order. It surely saved Chrysler Corp. a lot of time and money. Yours M.L. Anderson

[Chui]

I think it's been said already [maybe not], but Inline 6s are inherently balanced like V-12s and Horizontally Opposed 6s.

Disadvantages when compared to 60 degree V-6:

Lower crankshaft speeds [due to length] thus lower peak power capabilty;
Lower Powerplant Bending [both bending and torsion];
Lower Powertrain Bending;
Packaging for FWD applications;
OFFSET FRONTAL CRASH CONCERNS;


Advantages of Inline 6 to V6s:

Packaging easily allows for Equal Length Intake and Exhaust Manifolds designs;
Typically better Sound Quality due to above;
Less vibration transmitted to engine mounts;
Lower cost due to one cylinder head and half the number of camshafts;
60 degree V6 can be costly to produce with a six plane crankshaft and is also difficult to package;
90 degree V6s require 2nd Order Balance shafts;
Ease of maintenance due to packaging space.


Given a choice of engine configurations for a mid-sized sedan or coupe I'd opt for an Inline 6.

[Melbourne Park]

Originally posted by da Silva
Jaguar with XK engine

XK 120
XK 140
XK 150

Mark 1 & II
Mark V, VII Mark IX, mark X
C-type, D-type, E-Type,
S-type, 420, 420G
XJ6 S1 S2 S3, X300, XJS

And even pre -48 before the XK120 came.
No other company was more known for using an straight 6 than Jaguar.
And still today for not having an 4 cylinder or Diesel engine in their programe.
But the Diesel will come.

And don't forget, the XK engine was taken from a BMW pre war design. The BMW engine was a 4 cylinder, and Jaguar added two extra cylinders ... BMWs pre war six went to Bristol, who made a car just like the pre war BMW 320. Then Bristol made their own car, still with the pre war BMW six ... Funny how later BMW came and took the thunder from Jaguar with their straight six engines. Although one shouldn't forget, that most BMW cars are 4 cylinder 3 series, and they are poor in power ... in fact, most of the world's engines are 4 cylinders, so maybe they are actually the best compromise. Honda, the world's largest engine maker, still thinks 4 cylinders are the best way to go, although marketing may force them to change their minds and start introducing V6 sixes ...

Oh and Toyota do make straight sixes as well as the V variety.

What gets me about V6s is how Mercedes and others, like the previously mentioned GM 3.8 V6, can make 90 degree V6s. Those to me are the results of cost accountants , not engineers.

[Kaha]

I'd say that the advantages of a IL6 over a V6 is purely in marketing.

I can't think of any purpous build race car engine since the mid '50s that has been IL6.

[Earthling]

What none of you guys have mentioned so far, is the better weight distribution, lower C of G, and smaller Polar Moment of Inertia obtainable with a V6 when compared with an I6 (in a RWD car that is)... And I have no doubt that BMW's much vaunted equal weight distribution can be improved upon with a V6 by having the engine's center of mass lower and more set back towards the middle of the car. And I see little if no reason why designing for equal length intake and exhaust manifolds would be more difficult with a V6 when compared to an I6...

[Melbourne Park]

Originally posted by Kaha
I'd say that the advantages of a IL6 over a V6 is purely in marketing.

I can't think of any purpous build race car engine since the mid '50s that has been IL6.

For sure with racing.

On the road, its interesting to compare Toyota, who make both variants. Camry, Lexus ES300, 4Runner and their trucks have 60 degree V6 engines of 3 and more litres. The Lexus GS300 and IS 200/300 and several Toyotas in Japan have a straight six engines. The straight sixes have more low down torque and better laucnh feel. Although I have a Toyota SUV with a 3.4 V6 (closer to a 3.3 litre) and it has great low down torque and great launch feel. But it doesn't rev like the others, although it doesn't have variable valves. 60 degree V6 are reputed to lack low down torque, but of course are wonderfully compact and smooth. 90 degree V6s aren't smooth, but seem to have better low down torque. The seem to behave more like an INL6, but they are rough.