[Bandini3]

jk3355 started a couple of threads debating the merits (e.g. power, speed vs. 550i) of the 535i and the merits of the manual transmission. (See: Calling All 2011 535i Owners; Time to Pull the Trigger).

The comment regarding 1st and 2nd gears on the manual (posed below) warrants an explanation
===================================
jk3355: "I heard from my sales guy that 1st and 2nd are not strong enough in his opinion. Something to do with how close the auto on the 8 speed is spaced, it's not that way on the 6 speed.

needsdecaf: Yes, if you could clarify the point about "1st and 2nd are not strong enough in his opinion". On which transmission?
===================================
I think that question can be answered in words and numerically:

The 8-speed automatic offers certain advantages over the 6-speed manual because it offers (A) lower (or 'shorter') overall gearing in the first three gears, to achieve rapid acceleration, and (B) higher (or 'taller') overall gearing in its top two gears (7 & 8). The expected result: the AT version should be able to accelerate at least as quickly as the manual version, while achieving lower fuel consumption on the highway (better by 12-15% on the 535i, according to BMW's EPA estimates).

The numbers (derived from BMWNA brochure) appear in the pdf file. They show (i) transmission gear ratio and (ii) overall gearing, taking into account the final drive ratio. I also calculate 'Relative Gearing', which shows the overall gear multiplication of the automatic divided by the overall gearing of the manual for each gear.

The automatic has HIGHER multiplication than the manual (i.e. allowing a higher number of crankshaft revolutions per revolution of the drive wheels) in Gears 1 through 6. For any given level of engine torque, the lower effective gearing (i.e. higher numerically) allows a greater multiplication of this force at the driving wheels. In addition, the close spacing between ratios of the AT should, in theory, allow the engine to be kept at its 'sweet spot' on the torque curve. Both factors should, at least in theory, promote more rapid acceleration (other factors, including driver skill, will influence the real-world result).

The manual tops out in 6th gear with an overall ratio of 2.75. The automatic has the advantage of (a) 7th and 8th being overdrive gears (i.e. gear ratio <1.00) plus (b) a lower (numerically) final drive ratio. The overall gearing in 8th gear is just 2.06 -- just 75% of the overall ratio of the manual in 6th.

As a result, the AT version can cruise on the highway with low engine RPM, achieving improved fuel efficiency. (Of course, low torque multiplication in 8th means acceleration will be weak, but that can be remedied quickly by dropping down a couple of gears. Paddle shift with sports AT, Bam!).

I am sure anyone who has read this far is now sound asleep. That may limit the number of critical replies to this post, which will cite torque curves and defend the supremacy of their instantaneous manual shifts, which rival an F1 car.

[LuvMyE92]

Two thoughts:

When comparing the ratios of the transmissions, are you considering the rear end ratio to develop the final actual ratio (as you did only for the top gear)?

Second... if you have to use the flappy-paddles to downshift the car for proper performance, that's not truly automatic operation now is it?

[Bandini3]

LuvmyE92:

Point 1: If you read the post, you would see that it takes into account final drive ratio. That was an essential element in the post's reference to "overall gearing". The pdf file shows this measure for every gear on the AT and MT, for the convenience of discerning readers.

Point 2: I don't think there is a real point to your comment. The ZF automatic will, as most readers understand, downshift quickly with the application of throttle. The reference to paddle shift was intended simply to illustrate that the excellent fuel economy of the sports AT version did not result in any compromise in performance -- the sports AT will downshift in a flash. I am not sure anyone cares that this may not fit your definition of "truly automatic operation". I suspect most forum members are interested in discussing the attributes of F10 models and configurations in terms of actual performance and driving pleasure. (Selecting a manual transmission is a personal decision, obviously. My post simply presented a factual response to a question posed on this forum.)

[LuvMyE92]

Originally Posted by Bandini3

Point 1: If you read the post, you would see that it takes into account final drive ratio.

Ah, my bad, I read the post, not the attachment.

[JK479]

Originally Posted by Bandini3

jk3355 started a couple of threads debating the merits (e.g. power, speed vs. 550i) of the 535i and the merits of the manual transmission. (See: Calling All 2011 535i Owners; Time to Pull the Trigger).

The comment regarding 1st and 2nd gears on the manual (posed below) warrants an explanation
===================================
jk3355: "I heard from my sales guy that 1st and 2nd are not strong enough in his opinion. Something to do with how close the auto on the 8 speed is spaced, it's not that way on the 6 speed.

needsdecaf: Yes, if you could clarify the point about "1st and 2nd are not strong enough in his opinion". On which transmission?
===================================
I think that question can be answered in words and numerically:

The 8-speed automatic offers certain advantages over the 6-speed manual because it offers (A) lower (or 'shorter') overall gearing in the first three gears, to achieve rapid acceleration, and (B) higher (or 'taller') overall gearing in its top two gears (7 & 8). The expected result: the AT version should be able to accelerate at least as quickly as the manual version, while achieving lower fuel consumption on the highway (better by 12-15% on the 535i, according to BMW's EPA estimates).

The numbers (derived from BMWNA brochure) appear in the pdf file. They show (i) transmission gear ratio and (ii) overall gearing, taking into account the final drive ratio. I also calculate 'Relative Gearing', which shows the overall gear multiplication of the automatic divided by the overall gearing of the manual for each gear.

The automatic has HIGHER multiplication than the manual (i.e. allowing a higher number of crankshaft revolutions per revolution of the drive wheels) in Gears 1 through 6. For any given level of engine torque, the lower effective gearing (i.e. higher numerically) allows a greater multiplication of this force at the driving wheels. In addition, the close spacing between ratios of the AT should, in theory, allow the engine to be kept at its 'sweet spot' on the torque curve. Both factors should, at least in theory, promote more rapid acceleration (other factors, including driver skill, will influence the real-world result).

The manual tops out in 6th gear with an overall ratio of 2.75. The automatic has the advantage of (a) 7th and 8th being overdrive gears (i.e. gear ratio <1.00) plus (b) a lower (numerically) final drive ratio. The overall gearing in 8th gear is just 2.06 -- just 75% of the overall ratio of the manual in 6th.

As a result, the AT version can cruise on the highway with low engine RPM, achieving improved fuel efficiency. (Of course, low torque multiplication in 8th means acceleration will be weak, but that can be remedied quickly by dropping down a couple of gears. Paddle shift with sports AT, Bam!).

I am sure anyone who has read this far is now sound asleep. That may limit the number of critical replies to this post, which will cite torque curves and defend the supremacy of their instantaneous manual shifts, which rival an F1 car.

I love this tread. Than you so much for making this public!

[JK479]

Originally Posted by Bandini3

LuvmyE92:

Point 1: If you read the post, you would see that it takes into account final drive ratio. That was an essential element in the post's reference to "overall gearing". The pdf file shows this measure for every gear on the AT and MT, for the convenience of discerning readers.

Point 2: I don't think there is a real point to your comment. The ZF automatic will, as most readers understand, downshift quickly with the application of throttle. The reference to paddle shift was intended simply to illustrate that the excellent fuel economy of the sports AT version did not result in any compromise in performance -- the sports AT will downshift in a flash. I am not sure anyone cares that this may not fit your definition of "truly automatic operation". I suspect most forum members are interested in discussing the attributes of F10 models and configurations in terms of actual performance and driving pleasure. (Selecting a manual transmission is a personal decision, obviously. My post simply presented a factual response to a question posed on this forum.)

I can now finally compare the manual transmission gear ratios and rpm to the automatic.