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Inline 6 Cylinder
Question:
What is the advantages and/or disadvantages of an inline 6 cylinder versus a V6??? Thanks for clearing this up, Mike
Response:
> What is the advantages and/or disadvantages of an inline 6 cylinder > versus a V6???
The inline-6 is inherently smoother than a V6 – the vibration modes that cause shaking are not present in the I6 configuration. Disadvantages are that it isn’t quite as compact, and the fact that the relatively long crankshaft and camshaft(s) are required to be beefier than the short V6 ones. However, one (or two) fewer camshafts are required. It’s also a little harder to engineer the cooling system to cool the long block and heads. It’s also easier to turbo-charge an I6, since the exhaust is all on one side – shorter runs mean less turbo lag. FloydR
Response:
An in-line six has perfect primary balance and avoids add-ons like harmonic balancers and/or balance shafts to make the engine smoother. Mechanical simplicity is another advantage, since overhead cam(s) require just a single belt/chain drive for actuation (in the simplest cases). Intake and exhaust routing is also simplified, with a single manifold possible for each application. Finally, there can be benefits for the owner, since engine work is often less complicated, e.g. with only a single valve cover to remove. For the manufacturer, the in-line six is good & bad: Good = fewer parts in the engine build-up, more lateral room for accessory drives, cheaper to work on. Bad = more difficult to implement in driveline (almost always longitudinal orientation), requires longer hood/forward crash zone, not as much torque as a V-configuration. Mercedes, BMW, and Toyota have extensive in-line six experience, and continue to use this engine configuration effectively in quality high-end cars where smoothness is a benefit. Finally, I have an M42 four cylinder wich I love, but it’s still a buzzy 4 banger compared to BMW’s M50 motors! If the Lotto fulfills its promises, I’ll someday transplant a silky-smooth BMW 6 into my E36! Max
– Hide quoted text — Show quoted text -> What is the advantages and/or disadvantages of an inline 6 cylinder > versus a V6??? > Thanks for clearing this up, > Mike
Response:
I agree with you, except Mercedes has stopped using inline-6, most probably because of the crash tests results. — Best regards. G. Tarantino Bevaix (NE) Switzerland 1992 BMW 320i 198′000 km 1997 Audi A4 2.8 Q 150′000 km – Hide quoted text — Show quoted text -> An in-line six has perfect primary balance and avoids add-ons like harmonic > balancers and/or balance shafts to make the engine smoother. Mechanical > simplicity is another advantage, since overhead cam(s) require just a single > belt/chain drive for actuation (in the simplest cases). Intake and exhaust > routing is also simplified, with a single manifold possible for each > application. Finally, there can be benefits for the owner, since engine > work is often less complicated, e.g. with only a single valve cover to > remove. > For the manufacturer, the in-line six is good & bad: > Good = fewer parts in the engine build-up, more lateral room for accessory > drives, cheaper to work on. > Bad = more difficult to implement in driveline (almost always longitudinal > orientation), requires longer hood/forward crash zone, not as much torque as > a V-configuration. > Mercedes, BMW, and Toyota have extensive in-line six experience, and > continue to use this engine configuration effectively in quality high-end > cars where smoothness is a benefit. > Finally, I have an M42 four cylinder wich I love, but it’s still a buzzy 4 > banger compared to BMW’s M50 motors! If the Lotto fulfills its promises, > I’ll someday transplant a silky-smooth BMW 6 into my E36! > Max > What is the advantages and/or disadvantages of an inline 6 cylinder > versus a V6??? > Thanks for clearing this up, > Mike
Response:
>> What is the advantages and/or disadvantages of an inline 6 cylinder > versus a V6??? >The inline-6 is inherently smoother than a V6 – the vibration modes >that cause shaking are not present in the I6 configuration.
And that is what it is all about. You also have perfectly equal firing impulses 120 degrees, which means you can take the extra weight of the longer crank , and the harmonic balancer, and the flywhee, right back off. OH, and the sound of a straight six beats the General Motors flatulent cow sound of the V-6. Orphaned M-50
Response:
- Hide quoted text — Show quoted text ->> What is the advantages and/or disadvantages of an inline 6 cylinder >> versus a V6??? >The inline-6 is inherently smoother than a V6 – the vibration modes >that cause shaking are not present in the I6 configuration. > And that is what it is all about. You also have perfectly equal firing > impulses 120 degrees, which means you can take the extra weight of the > longer crank , and the harmonic balancer, and the flywhee, right back off. > OH, and the sound of a straight six beats the General Motors flatulent cow > sound of the V-6. > Orphaned M-50
GM though now has, I believe, a 3.5 liter I6 for use in it’s trucks and SUVs. Supposedly a fantastic engine with a number of possible upgrade applications thru their model lineup (though it may never fit into their car lineup). Nice to see an American company return to the I6….the 4.0 from Jeep is getting rather long in the tooth and I believe that was the last American I6 available.
Response:
No, nothing at all to do with crash tests or performance (I don’t think the BMW in-line 6 gives up torque because it is an in-line six) or any other part of the discussion. Mercedes stopped using in-line 6 engines because they are cheap b*st*rds. They didn’t even build a 60-degree V-6, nope. They wanted to re-use as many parts from the 90-degree V-8 (three-valve) engines. Thus the imperfect 90-degree V-6 seen since 1997 I believe. Cheap cheap cheap. But since sales have soared, who misses the inlines? >I agree with you, except Mercedes has stopped using inline-6, most probably >because of the crash tests results.
– Gary Talda
Response:
> > What is the advantages and/or disadvantages of an inline 6 cylinder > versus a V6??? > The inline-6 is inherently smoother than a V6 – the vibration modes > that cause shaking are not present in the I6 configuration.
In practice V6s are just as smooth. Especially the even firing ones. The real difference is that it’s easier and cheaper to make a smooth, even firing I6 because it can be done with a single plane crank. > Disadvantages are that it isn’t quite as compact, and the fact that > the relatively long crankshaft and camshaft(s) are required to be > beefier than the short V6 ones. However, one (or two) fewer > camshafts are required. It’s also a little harder to engineer the > cooling system to cool the long block and heads.
The cooling issue is a really big one. You can see it in tearing down an old BMW 6. The cylinders wear quite unevenly. With an I6, it’s also more difficult to design intake and exhaust manifolds that flow evenly to all cylinders, and this has a much bigger effect on smoothness than anything else. One head is way cheaper than two, in both parts cost and assembly. A single plane crank is way cheaper than one which requres multi stage forging. > It’s also easier to turbo-charge an I6, since the exhaust is all on > one side – shorter runs mean less turbo lag.
Not true. Making 6 even runs all on one side is difficult, and requires all the pipes to be longer. And if lag is an issue, a twin turbo arrangement with two smaller turbos is usually superior anyway. The bottom line is that V6s are superior in ways that more than make up for any differences in the inherent balance of rotating masses. You’re thinking in the 1950s. BMW continues to use the I6 mostly because of tradition. It doesn’t hurt that it’s cheaper to make. Matt O.
Response:
Matt, you are taking the short view of economics. Company wide it is decidedly more expensive to make inline 6’s because there is no modular application from the 8 cylinder engines. This is why Mercedes went the way of V6’s and why Jeep will soon deliver the V6 based upon the 4.7 V8 (possible relegating the 4.0 to the trash heap) and why Volkswagen engines are so interrelated. It is cheaper for any company to produce both 6’s and 8’s in the "V" configuration because of the shared architecture. It is also not true that, per unit cost, making equally refined I6 vs. V6…the I6 is less expensive. The cost of either engine (given equal displacement, electronics, refinement and power) is arguably the same. In the case of BMW it would be much cheaper to produce V6’s based upon the V8 architecture they already produce.
– Hide quoted text — Show quoted text -> > What is the advantages and/or disadvantages of an inline 6 cylinder > > versus a V6??? > The inline-6 is inherently smoother than a V6 – the vibration modes > that cause shaking are not present in the I6 configuration. > In practice V6s are just as smooth. Especially the even firing ones. The > real difference is that it’s easier and cheaper to make a smooth, even > firing I6 because it can be done with a single plane crank. > Disadvantages are that it isn’t quite as compact, and the fact that > the relatively long crankshaft and camshaft(s) are required to be > beefier than the short V6 ones. However, one (or two) fewer > camshafts are required. It’s also a little harder to engineer the > cooling system to cool the long block and heads. > The cooling issue is a really big one. You can see it in tearing down an > old BMW 6. The cylinders wear quite unevenly. With an I6, it’s also more > difficult to design intake and exhaust manifolds that flow evenly to all > cylinders, and this has a much bigger effect on smoothness than anything > else. > One head is way cheaper than two, in both parts cost and assembly. A > single plane crank is way cheaper than one which requres multi stage > forging. > It’s also easier to turbo-charge an I6, since the exhaust is all on > one side – shorter runs mean less turbo lag. > Not true. Making 6 even runs all on one side is difficult, and requires > all the pipes to be longer. And if lag is an issue, a twin turbo > arrangement with two smaller turbos is usually superior anyway. > The bottom line is that V6s are superior in ways that more than make up for > any differences in the inherent balance of rotating masses. You’re > thinking in the 1950s. > BMW continues to use the I6 mostly because of tradition. It doesn’t hurt > that it’s cheaper to make. > Matt O.
Response:
>Jeep is getting rather long in the tooth and I believe that was the last >American I6 available. > No, the Cummins Turbo diesel fitted to Dodge trucks since ‘89(?) is an inline > six.
Different animal…we were talking about petrol engines….course…you knew that
Response:
> The inline-6 is smoother in theory, but the newer Mercedes V-6 engines > are just as smooth in practice. I have driven both. The newer V-6 > engines have a much better overall driving character due to the broader > torque curve. I’ll never go back to the "no low end torque" inline-6.
This is funny, you make it sound like the 3.2 is a 6 liter torque monster. I have driven both cars (528 and E320) as well and do not find any particular difference in the low end, neither one carry enough displacement to alleviate the need for a couple thousand rpms before any real power kicks in. Essentially neither has much low end torque, though both deliver 80 to 85% of what torque they have at a couple thousand rpm. What I do find is that the BMW is more willing to rev into the powerband than the Merc. I suspect this is due to the inherent breathing deficiencies of the V configuration (as well as the counter rotating balance shaft) as compared to the I. The response from throttle input is almost always better in an I than a V (probably because of the need to spool up the speed of the counterbalance or rotating shafts in the V6). Mercedes tried to overcome this reality by going for the dual spark arrangement (necessitating one less valve per cylinder) for a more efficient use of intake charge hopefully resulting in optimal combustion….but the inputs still lag in the 3.2 V6. But in any case it is always about how the crank power is geared to the wheels…I doubt that very many people, by the seat of their pants, could tell if weak low end was the result of poor engine output or poor gearing :^) Both engines are great..indeed almost works of art, but don’t kid yourself…Mercedes went in the V direction because of the economies of modular design and construction as well as the physical advantages of applying the V6 configuration to some of their smaller cars. Still, there is no effective difference in low rpm torque output between these two engines, both are small displacement and have to fight for every low end lb-ft they can muster.
Response:
> > > What is the advantages and/or disadvantages of an inline 6 cylinder > > versus a V6??? > The inline-6 is inherently smoother than a V6 – the vibration modes > that cause shaking are not present in the I6 configuration. > In practice V6s are just as smooth. Especially the even firing ones. The > real difference is that it’s easier and cheaper to make a smooth, even > firing I6 because it can be done with a single plane crank.
Absolutely untrue. The M50 in my 525i is much much much smoother than the V6 in my NSX. Not even any comparison, really. FloydR
Response:
The inline-6 is smoother in theory, but the newer Mercedes V-6 engines are just as smooth in practice. I have driven both. The newer V-6 engines have a much better overall driving character due to the broader torque curve. I’ll never go back to the "no low end torque" inline-6. Del Johnson > What is the advantages and/or disadvantages of an inline 6 cylinder > versus a V6??? > Thanks for clearing this up, > Mike
Before you buy.
Response:
>Jeep is getting rather long in the tooth and I believe that was the last >American I6 available.
No, the Cummins Turbo diesel fitted to Dodge trucks since ‘89(?) is an inline six. Great engine… Health & Peace
Response:
- Hide quoted text — Show quoted text -> The inline-6 is smoother in theory, but the newer Mercedes V-6 engines > are just as smooth in practice. I have driven both. The newer V-6 > engines have a much better overall driving character due to the broader > torque curve. I’ll never go back to the "no low end torque" inline-6. > This is funny, you make it sound like the 3.2 is a 6 liter torque monster. > I have driven both cars (528 and E320) as well and do not find any > particular difference in the low end, neither one carry enough > displacement to alleviate the need for a couple thousand rpms before any > real power kicks in. Essentially neither has much low end torque, though > both deliver 80 to 85% of what torque they have at a couple thousand rpm. > What I do find is that the BMW is more willing to rev into the powerband > than the Merc. I suspect this is due to the inherent breathing > deficiencies of the V configuration (as well as the counter rotating > balance shaft) as compared to the I.
How do you figure? A V6 most likely has better breathing, because it’s so much easier to build a manifold for it that flows evenly among all cylinders. This alone will usually overshadow the inherent balance differences of the rotating masses. Evenness of power pulses matters a lot more. If one of these motors revs better than the other, it’s most likely due to different tuning, ie, valve timing, etc. I or V cionfiguration has nothing to do with it. > The response from throttle input is almost always better in an I than a V > (probably because of the need to spool up the speed of the counterbalance > or rotating shafts in the V6). Mercedes tried to overcome this reality by > going for the dual spark arrangement (necessitating one less valve per > cylinder) for a more efficient use of intake charge hopefully resulting in > optimal combustion….but the inputs still lag in the 3.2 V6.
Again, this is a load of garbage. It’s all in how the motor is tuned by a particular automaker, for its particular vehicle. also each automaker has its own idea of how its cars hsould feel. Mercedes have always had slower throttle response. You have to mash the pedal harder to get the car to jump. It goes along with their stately image. If they wanted the car to feel more nervous, they would simply adjust the throttle linkage, change the size of the throttle plate, etc. The motor has little to do with it. And that’s not even taking into account weight and gearing, which are also different. > But in any case it is always about how the crank power is geared to the > wheels…I doubt that very many people, by the seat of their pants, could > tell if weak low end was the result of poor engine output or poor gearing > :^) > Both engines are great..indeed almost works of art, but don’t kid > yourself…Mercedes went in the V direction because of the economies of > modular design and construction as well as the physical advantages of > applying the V6 configuration to some of their smaller cars. Still, there > is no effective difference in low rpm torque output between these two > engines, both are small displacement and have to fight for every low end > lb-ft they can muster.
There are disadvantages to offset every "advantage" of an I6. These days, it’s a moot argument. Matt O.
Response:
>The bottom line is that V6s are superior in ways that more than make up for >any differences in the inherent balance of rotating masses. You’re >thinking in the 1950s.
Superior only to the packaging/bean-counter/shareholder hostages in Corporate-think Car Companies run by Bottom-line Business School Brats. Intrinsic superiority indeed, does have to resist the new "modular-think" where they try to save money by sharing tooling. BMW does not waste the time to develop the M-50 for sops to tradition. The damn thing works better, period. Orphaned and when you discover that the smaller BMW chassis plans still decide on rear-wheel drive, it isn’t for tradition, it is because that is the best way to blast around a damn corner
Response:
then why would BMW continue to produce a I6? I think the inline sixes of BMW is better than most v6’s. the 2.5 in my 325is performs better than most v6’s that are similar, actually I think it performs the best of similar cars. How many v6 cars do you see that compare to the m3? NSX? and that cost quite a bit more. and the others are most likely to be turbo or super-charged. just what I think chris
Response:
> Matt, you are taking the short view of economics. Company wide it is > decidedly more expensive to make inline 6’s because there is no modular > application from the 8 cylinder engines. This is why Mercedes went the way > of V6’s and why Jeep will soon deliver the V6 based upon the 4.7 V8 > (possible relegating the 4.0 to the trash heap) and why Volkswagen engines > are so interrelated. It is cheaper for any company to produce both 6’s and > 8’s in the "V" configuration because of the shared architecture.
Maybe, but… (see below) > It is also not true that, per unit cost, making equally refined I6 vs. > V6…the I6 is less expensive. The cost of either engine (given equal > displacement, electronics, refinement and power) is arguably the same.
I disagree. There are more manufacturing operations involved in making a V6, particularly in the more expensive pieces, like the crank. > In the case of BMW it would be much cheaper to produce V6’s based upon the > V8 architecture they already produce.
But it wouldn’t matter. They sell so many more I6 cars that that the V8s are the afterthought, and those are at a price point where the cost of the motor doesn’t matter so much. They must, however, differentiate their product more strongly in the highly competitive midrange. Thus the I6. Plus, we’re forgetting the 4s. Where do they fit in this grand scenario? Matt O.
Response:
> Absolutely untrue. The M50 in my 525i is much much much smoother than > the V6 in my NSX. Not even any comparison, really.
And therefore, all I6s are smoother than all V6s. Matt O.
Response:
From what I understood, don’t you get MORE power from an inline 6 vs a V6 (all other things being equal) as well more torque? With the disadvantages being that it is more expensive to manufacturer, since the block is longer, and takes up more room in the engine bay? – Hide quoted text — Show quoted text -> No, nothing at all to do with crash tests or performance (I don’t > think the BMW in-line 6 gives up torque because it is an in-line six) > or any other part of the discussion. Mercedes stopped using in-line > 6 engines because they are cheap b*st*rds. They didn’t even build a > 60-degree V-6, nope. They wanted to re-use as many parts from the > 90-degree V-8 (three-valve) engines. Thus the imperfect 90-degree V-6 > seen since 1997 I believe. Cheap cheap cheap. > But since sales have soared, who misses the inlines? >I agree with you, except Mercedes has stopped using inline-6, most probably >because of the crash tests results. > — > Gary Talda
Response:
First of all torque has to do with the the bore/stroke ratio, a longer stroke gives more torque but limits rpm. One of the reasons i think that BMW has stuck with the I6 as well as other high proformance cars(such as the skyline) is balance. BMWs are weighted almost a perfect 50/50 front to rear weight. Longer spreads the weight out a little more and also needs a longer engine compartment which pushes the passenger compartment back putting more weight on the rear wheels. Balance is one the fundmental keys to making a great handling car
Response:
Adding this string up to get a consensus is as difficult (on a much lower scale) as finding a *clear* winner in the FL election.
Response:
> > Absolutely untrue. The M50 in my 525i is much much much smoother than > the V6 in my NSX. Not even any comparison, really. > And therefore, all I6s are smoother than all V6s.
Interesting. You’re being very selective about your editing. You clipped out the "modern V6’s are as good and smooth…" part. I counter your assertion with an example of a "modern" V6 that isn’t as smooth as the I6’s, and you counter with … sarcasm. Your assertion is not supported by science, or by fact. FloydR
Response:
I was comparing the Mercedes inline-6 to a Mercedes V-6, in which case the V-6 clearly has better low rpm response. If you need more then go for the V-8. Del Johnson – Hide quoted text — Show quoted text -> This is funny, you make it sound like the 3.2 is a 6 liter torque monster. I > have driven both cars (528 and E320) as well and do not find any particular > difference in the low end, neither one carry enough displacement to > alleviate the need for a couple thousand rpms before any real power kicks > in. Essentially neither has much low end torque, though both deliver 80 to > 85% of what torque they have at a couple thousand rpm. What I do find is > that the BMW is more willing to rev into the powerband than the Merc. I > suspect this is due to the inherent breathing deficiencies of the V > configuration (as well as the counter rotating balance shaft) as compared to > the I. > The response from throttle input is almost always better in an I than a V > (probably because of the need to spool up the speed of the counterbalance or > rotating shafts in the V6). Mercedes tried to overcome this reality by going > for the dual spark arrangement (necessitating one less valve per cylinder) > for a more efficient use of intake charge hopefully resulting in optimal > combustion….but the inputs still lag in the 3.2 V6. > But in any case it is always about how the crank power is geared to the > wheels…I doubt that very many people, by the seat of their pants, could > tell if weak low end was the result of poor engine output or poor gearing > :^) > Both engines are great..indeed almost works of art, but don’t kid > yourself…Mercedes went in the V direction because of the economies of > modular design and construction as well as the physical advantages of > applying the V6 configuration to some of their smaller cars. Still, there is > no effective difference in low rpm torque output between these two engines, > both are small displacement and have to fight for every low end lb-ft they > can muster.
Before you buy.
Response:
> I was comparing the Mercedes inline-6 to a Mercedes V-6, in which case > the V-6 clearly has better low rpm response. If you need more then go > for the V-8.
My apologies, being that this is a BMW ng I assumed you were talking about the BMW line of I6’s.