Kzang

I think the OP is asking why BMW has not made any inline 6 engines bigger than 3.0 liter ( aside from the M cars and V8's ).

Perhaps due to weight and mpg? Not sure why.

swajames

He was indeed, and I still think it's packaging - with the length of the 3.0 I6 powerplant as is, you'll struggle to increase the displacement too much as the enlarged unit simply won't fit in the engine bay on the E60 and on the smaller BMW models (the same engines are used the 1, 3 and Z4, and engine bay space is at an absolute premium in the E60 and these other models)

525iEnjoy

Be nice if they made a potent V6 like Nissans little 330hp one with a CVT trans hooked too it. Pin the the tach to number you desire and watch the speedo climb!

Diamond

Honestly guys a 3.2-3.4 Litre I6 would be no bigger than the current 3L-it would be no longer at all. I am no engineer and obviously I do not know features as ideal displacement per cylinder however I got this from readin one of the Euro boards where they discussed the 3 series with the N52 engine and a company tuner that was taking them and boring them out to 3.2 litres with about 300 hp-with no noticable change in anything engine size obviously since they are keeping the same n52 engine.

I am not saying people need tons of hp but obviously there is a need as they made the TT engine wtih 300hp. I am just saying instead of using turbos-which is cool IMO why not go NA with 300hp and a bit bigger displacement.

The m3 engines of the past at 3.2 L were putting out 333 hp and that was a high strung engine and to be honest is older technology. With their new technologies as of late I 3.2 l I6 engine with 300 hp seems really doable especially considering their current N53 I6 3l DI puts out 272. I think there is a large population who would choose a NA engine with 300hp over a TT engine. There is just no comparison to a NA engine nv.a TT engine for smooth linear power delivery-turbo lag is always going to be there despite it being quite little with BMW.

Anyway just a question-it seems like that would be more in tune with bmw to push the envelope of a I6 engine rather than throw TT on it-but I understand efficiency etc too

pukka

My T-Blazer had a 4.0L I6 and that thing was HUGE - no way could it fit in a BMW chassis.

A 3.0L can only be bored out so far before internal heat and cooling factors come into play. Especially since you are dealing with aluminum blocks.

swajames

If you bore out the cylinders without changing dimensions you're reducing clearance between cylinders and you're weakening the engine block. That might be acceptable to a tuner and their customers, but it wouldn't fly for a production vehicle due to the potentially increased likelihood of failure over millions of vehicles.

To put it into context, even the best tuner will spend a very limited budget on R&D when making changes like the re-bore you describe.

BMW, on the other hand, would spend tens if not hundreds of millions of dollars to expand displacement of the N52 from 3.0 to 3.2 or 3.3 liters, to mitigate or eliminate the associated engineering risks and challenges.

The OP speaks to one inherent limitation in the I6 which is that it is significantly larger (and more specifically longer) than than V6 of equal displacement.

While it is indeed possible to increase bore/stroke in the N52 I6, I believe that it would create and increase the risk of failure. That's essentially why an increased bore N52, which maintained BMW's required clearances and tolerances, is probably going to have to be physically larger. There's very little free engine bay space in the E90 and E60 as it is, hence the packaging challenges mentioned earlier in the thread.

Diamond

Well along those lines what is the point of continuing on with inline 6 engines? What is the benefit over a v6 design? I know it is smoother but I have driven some smooth v6 and especially if nissan gtr is getting 400 plus hp out of turbo v6 and nissan 370z are getting 330 plus out of a v6-seems like they are much more useable and by the way the 370z is a NA engine, no FI and it still ramps out that kind of power.

swajames

The I6 engine is naturally perfectly balanced - the front and rear cylinders mirror each other and the opposing pistons naturally counterbalance each other. The V6 engines require some pretty complex balancing shafts etc to maintain smoothness. It's perfectly possible to produce a wonderfully smooth V6, but that smoothness needs to be engineered in, whereas with the I6 it's a natural charcteristic of the design and it comes as standard.

skelevirus

cvt? that would be bizzare!!

BMWPower06

BMW follows the .5L/cylinder displacement as it feels its the smoothest and most efficient. Hence the 4.0L V8, 5.0L V10, and the 6.0L V12