Toyota used to make inline 6 engines. Heck they probably made the inline 6 with the most notoriety, the 2JZ foe the Supra and other vehicles. It also used an inline 6 in the Land Cruiser. But they moved away from inline 6 to V6 or other V configurations.
BMW on the other hand, embraced the inline 6, and has kept an evolution of its engine going for the past few decades.
What’s the business case for the divergence from inline 6 by Toyota and the embrace by BMW? What makes their business choices best for their respective models across Toyota/Lexus, and BMW?
If I remember correctly, the V6 is the most efficient engine arrangement for its power/ volume ratio. It's really compact. Inline-6s are perfectly balanced by their nature and well suited for longer nosed, longitudinal drivetrains (Front engine, RWD configurations) most BMWs are set up that way, especially the older ones. V6s have balance issues (an uneven number of pistons are always going up and down, among other things) so they have heavy counterweights. The compact size lets them power front wheel drive vehicles efficiently. For an idea on how small the V6 is compared to a V8, look under the hood of a 2017 Mustang V6 and Mustang GT. You can see the ground underneath the car in the V6. The V8 is crammed in there.
Here's a little extra tid-bit. The Italian supercars use V12 engines because that arrangement is also perfectly balanced like the straight-six; the V12 engine is essentially a pair of straight-6s that share a crankshaft. V8s are like a pair of 4-bangers sharing their crank, and V6s are like a pair of straight-3s sharing a crank.
Packaging, the V6 is much shorter and more compact. It is difficult to install an inline six in a transverse front-drive configuration. (Though it has been done in a few vehicles.)
The V6 engines are smoother, may be this is why Toyota switched to these.
I always though that inline 6 was smoother since it is perfectly balanced?
My bad,
you're right. Inline 6 are more balanced.
but a V6 is smoother than any 4 cyl