PDA

View Full Version : Sport Automatic trans - rev match?


Kar Don
01-03-2011, 08:43 PM
I've searched endlessly on this and cannot find an answer. Does the $500 option for sport automatic do anything besides add paddles and a fancy leather boot for the shifter? I want rev-matching downshifting like on the E92 6 speed steptronic. Does the F10 have it?

JoeRoadster
01-03-2011, 09:00 PM
It improves throttle response time. I experienced it myself, and decided that for me it was a must have feature.
Note that I never tried the paddles, so cannot speak for them.

Search on SAT and you'll find some in depth discussions on this.

jzcrna
01-03-2011, 09:26 PM
It improves throttle response time. I experienced it myself, and decided that for me it was a must have feature.
Note that I never tried the paddles, so cannot speak for them.

Search on SAT and you'll find some in depth discussions on this.

I loved my sport auto transmission in my cars. Not to take away from the new F10s I am seeing, but I cannot help to notice everyone getting their vehicles without the sport auto transmission or even the sport package. For $500, this is a no-brainer to me (for Sport Auto transmission).

In regard to the shift paddles..I had them in my E90335i and they were fantastic in both ergonomics and functionality. My E60 paddles looked pretty, but I did not use them because of the crappy ergonomics compared to the ones in the E90.

Now, fast-forward to the F10. The 528i that I drove had newly designed shift paddles, which were an improvement on ergonomics and feel, but they did also change the functionality to where you upshift on the right side and downshift on the left side. The previous generation's paddles had the same functions on each side (press forward to downshift and pullback to upshift.) This may not be such a bad thing, but would take getting used to and will probably be a better design when one grows accustomed to it.

Lastly, the sport auto transmission took the 528i to the next level. I would never buy one without having the option to change the settings to sport or sport plus. I could not imagine driving the 528i in "Normal" mode all of the time. That would be a pure killjoy.

With the sport auto transmission the 528i is a fun car to drive IMO.

hmr
01-03-2011, 09:41 PM
I've searched endlessly on this and cannot find an answer. Does the $500 option for sport automatic do anything besides add paddles and a fancy leather boot for the shifter? I want rev-matching downshifting like on the E92 6 speed steptronic. Does the F10 have it?

Isn't "rev-matching" a concept that's applicable to manual transmissions only?

Needsdecaf
01-04-2011, 05:15 AM
Isn't "rev-matching" a concept that's applicable to manual transmissions only?

No.

Many of the newer auto transmissions do it.

quackbury
01-04-2011, 07:32 AM
Isn't "rev-matching" a concept that's applicable to manual transmissions only?

You need to test drive an M3 with the DCT. Pretty amazing.

hmr
01-04-2011, 07:38 AM
No.

Many of the newer auto transmissions do it.

Sorry, but that's impossible. Rev-matching is a concept for synchro gear manual transmissions only, not planetary gear slushboxes with a lock-up torque converter.

You need to test drive an M3 with the DCT. Pretty amazing.

True, the DCT in the M3 is nice. But, the DCT is not an auto slushbox. It's a dual clutch (automated) manual transmission.

raleedy
01-04-2011, 09:32 AM
sorry, but that's impossible. Rev-matching is a concept for synchro gear manual transmissions only, not planetary gear slushboxes with a lock-up torque converter.



True, the dct in the m3 is nice. But, the dct is not an auto slushbox. It's a dual clutch (automated) manual transmission.

+1

quackbury
01-04-2011, 09:43 AM
Sorry, but that's impossible. Rev-matching is a concept for synchro gear manual transmissions only, not planetary gear slushboxes with a lock-up torque converter.


Guess you better break that to the folks over at Nissan. The spec sheet for the 370Z says they have a "7-speed automatic transmission with manual shift mode, paddle shifters and Downshift Rev Matching":

http://www.nissanusa.com/zcoupe/specifications.html

It's really going to p*ss off the guys who bought Z cars to have Bimmer owners tell them their trannies don't rev match:

http://www.the370z.com/nissan-370z-general-discussions/8835-7-speed-automatic-transmission-synchrorev-match-vs-non-synchrorev-match.html

DXK
01-04-2011, 10:29 AM
I realize that some members (they know who they are) won't believe it, but shh

The new transmission is said to be both more fuel-efficient and cheaper to manufacture than the current six-speed unit, and its performance is also claimed to be comparable with the more advanced seven-speed dual-clutch unit launched last year in the M3.

Speaking with Automotive News, BMW development chief Klaus Draeger said the luxury carmaker plans to focus on automatic transmissions instead of dual-clutch units for its high-volume models.

The eight-speed automatic that we developed with ZF can compete with dual-clutch transmissions on shifting times, but its lighter and more efficient and has cost advantages, he revealed. The incompatibility with high engine-speed designs is a disadvantage, however.

Draeger went on to explain that dual-clutch transmissions are complex, expensive and heavy, especially for cars with longitudinally mounted engines and RWD.

ZFs new eight-speed auto, meanwhile, has been designed for both RWD and AWD cars and will appear in several BMW and Audi models later this year. The extra cogs have the added benefit of improved fuel economy because the gearbox can better match engine speeds with the right gear since theres more to choose from. To further enhance fuel-economy, the new ZF gearbox will also have an engine stop-start feature.

hmr
01-04-2011, 10:29 AM
Guess you better break that to the folks over at Nissan. The spec sheet for the 370Z says they have a "7-speed automatic transmission with manual shift mode, paddle shifters and Downshift Rev Matching":

http://www.nissanusa.com/zcoupe/specifications.html

It's really going to p*ss off the guys who bought Z cars to have Bimmer owners tell them their trannies don't rev match:

http://www.the370z.com/nissan-370z-general-discussions/8835-7-speed-automatic-transmission-synchrorev-match-vs-non-synchrorev-match.html

Sorry, Nissan may call it "Downshift Rev Matching" on their auto, but all it is is just regular downshifting. Probably a marketing idea to match their SynchroRev Match manual transmission feature, which was praised highly in the press.

http://www.youtube.com/watch?v=HCWkQFJ2lwQ&feature=related

Needsdecaf
01-04-2011, 10:30 AM
Sorry, but that's impossible. Rev-matching is a concept for synchro gear manual transmissions only, not planetary gear slushboxes with a lock-up torque

As was stated above, definitely not impossible.

DXK
01-04-2011, 10:35 AM
Also, for more info from the ZF itself, see this link

http://www.zf.com/corporate/en/products/innovations/8hp_automatic_transmissions/8hp_automatic_transmission.html

markl53
01-04-2011, 12:25 PM
As was stated above, definitely not impossible.

OK, but what is it rev matching to? The purpose of rev matching in a manual transmission is to prepare for a smooth transition during a downshift, getting the engine up to the speed that it will be at once the lower gear is engaged. On an automatic trans, I just don't understand what rev matching is all about. My 535i downshifts without a moment's hesitation, one of the most responsive downshifts in any car I've driven. If it "paused" to match engine speed it would do nothing other than delay the shift. :dunno: Also, let's not confuse rev matching with double clutching -- different techniques for different purposes.

Alecop77
01-04-2011, 01:57 PM
I'll say this Al - its fun jumping on 128 with them!

markl53
01-04-2011, 02:20 PM
Sorry, Nissan may call it "Downshift Rev Matching" on their auto, but all it is is just regular downshifting. Probably a marketing idea to match their SynchroRev Match manual transmission feature, which was praised highly in the press.


The video is kind of "OK, so?" to me. It sounds like they do the rev just for the "cool" sound of the engine -- looking at the tach, it jumps right up just like any auto downshift, at least to me.

Needsdecaf
01-04-2011, 04:16 PM
OK, but what is it rev matching to? The purpose of rev matching in a manual transmission is to prepare for a smooth transition during a downshift, getting the engine up to the speed that it will be at once the lower gear is engaged. On an automatic trans, I just don't understand what rev matching is all about. My 535i downshifts without a moment's hesitation, one of the most responsive downshifts in any car I've driven. If it "paused" to match engine speed it would do nothing other than delay the shift. :dunno: Also, let's not confuse rev matching with double clutching -- different techniques for different purposes.

What you are discussing above is downshifting during a request for more power. Where it matches revs is when you are downshifting on the overrrun, as in coming into a corner and slowing down. In other words, the same place you would do so with a manual trans not to upset the balance of the car.

Modern autos in some performance cars do this. I can recall reading about it in several reviews including, I think, a Jaguar (XK, I believe), Maserati Quattroporte (NOT the Duoselect, but the fuall auto) and a couple of others.

On my Volvo and Acura, if you pull the Geartronic for a downshift while slowing, you get that "I just popped in the clutch" sudden deceleration when the lower gear engages. I do not have enough seat time to understand if this happens on the F10 or not, but I am positive (100%) that I have read about it on other cars.

Here is one thing I found quickly by googling "Jaguar Rev Matching".

http://www.nadaguides.com/Cars/2010/Jaguar/XK/2dr-Conv/Expert-Reviews/6876

"The six-speed automatic transmission with paddle shifters is smooth and tight with rev-matching downshifting."

More known source:

http://www.caranddriver.com/reviews/car/07q1/2007_jaguar_xkr-road_test

" No manual transmission is offered, which will turn off some shoppers, but the six-speed automatic in the XK features rev-matching downshifts, paddle shifters on the steering wheel, and a sport setting that does an amazing job of channeling Tom Walkinshaw by perfectly downshifting into the right gear for upcoming corners."

quackbury
01-04-2011, 04:16 PM
Sounds like the question is: Are the RPM's rising because the ECU is blipping the throttle before engaging the lower gear? Or because the lower gear is revving the engine?

I think most Z owners would know the difference between the two. I can't imagine Nissan would officially market the trans as "Rev Matching" if the only thing matching the revs was the contact patch between tire and pavement.

OTOH this guy would have no problem exagerating the truth like that:

raleedy
01-04-2011, 04:20 PM
The video is kind of "OK, so?" to me. It sounds like they do the rev just for the "cool" sound of the engine -- looking at the tach, it jumps right up just like any auto downshift, at least to me.

In any automatic, "rev matching" may involve a throttle blip that sounds cool, but it's a useless, wasteful marketing gimmick.

Needsdecaf
01-04-2011, 04:24 PM
In any automatic, "rev matching" may involve a throttle blip that sounds cool, but it's a useless, wasteful marketing gimmick.


The purpose of rev matching downshifts in ANY car, regardless of transmission, is to avoid sudden changes in vehicle attitude during braking while entering a corner. Those sudden jerks can change the contact patches and upset the car, possibly causing a spin, etc.

Granted, this is only useful when driving in a spirited manner, but for any car with a sporting pretention, it is certainly not a marketing gimmick.

quackbury
01-04-2011, 04:29 PM
In any automatic, "rev matching" may involve a throttle blip that sounds cool, but it's a useless, wasteful marketing gimmick.

Having spent the better part of 5 years moonlighting as a driving instructor in the Mercedes ride and drive program, I respectfully disagree.

If you downshift a slushbox at speed in a car with high compression engine, you can chirp the tires. If you do that under heavy braking (entering Big Bend at Lime Rock, or diving onto the infield course at Daytona), you can break the rear end free. Been there, done that - riding in the right seat while some ham-fisted CA tries to gather up a sideways E420 - and it's no fun.

ABS doesn't work in those situations, and I doubt that DSC does much good either. But having a trans that would blip the throttle so that Sammy Salesman couldn't get us sideways - that would have been really, really sweet.

Doesn't take a racetracck either. Downshifting manually on black ice, or on a rain slicked road with semi-bald tires would have the same effect.

quackbury
01-04-2011, 04:41 PM
" No manual transmission is offered, which will turn off some shoppers, but the six-speed automatic in the XK features rev-matching downshifts, paddle shifters on the steering wheel, and a sport setting that does an amazing job of channeling Tom Walkinshaw by perfectly downshifting into the right gear for upcoming corners."

Wow. Tom Walkinshaw! Good to know somebody else out there is as old as I am!

(Please tell me you've read Sam Moses' "Fast Guys, Rich Guys and Idiots").

markl53
01-04-2011, 05:02 PM
What you are discussing above is downshifting during a request for more power. Where it matches revs is when you are downshifting on the overrrun, as in coming into a corner and slowing down. In other words, the same place you would do so with a manual trans not to upset the balance of the car.


So I think you might be saying that in our F10's if this is a capability, I would guess that rev matching would only occur when shifing manually, not through throttle input alone in auto mode for "more power". Next time I'm in manual mode I'll try a couple of "coasting" downshifts as opposed to "apply power" ones. Could be if it happens at all, might be the Sport trans which I don't have.

Needsdecaf
01-04-2011, 05:32 PM
So I think you might be saying that in our F10's if this is a capability, I would guess that rev matching would only occur when shifing manually, not through throttle input alone in auto mode for "more power". Next time I'm in manual mode I'll try a couple of "coasting" downshifts as opposed to "apply power" ones. Could be if it happens at all, might be the Sport trans which I don't have.

Correct.

Next time you're on a windy road, carry a lot of speed into the corner. As you are on the brakes, pop a couple of downshifts in manual mode.

I am sorry that I don't have enough seat time to really tell if it's happening or not.

Needsdecaf
01-04-2011, 05:32 PM
You need to test drive an M3 with the DCT. Pretty amazing.

Yes, it is like crack.

Kar Don
01-04-2011, 05:48 PM
Wow 24 posts and no answer to the question, this is what I was afraid of. Rev-matching is useful and like others said it allows for a smooth manually initiated downshift. So yes I guess I should have asked does the engine computer blip the throttle prior to allowing the transmission computer to engage the lower gear when the driver manually requests a lower gear via the paddles or shifter in the manual gate? Is that better?

Kar Don
01-04-2011, 05:53 PM
Watch this video.

At 28 seconds into it, they downshift from M3 to M2 on a 335i. You can see the throttle is blipped prior to engaging the gear. This is what I'm asking if they kept this for the F10 in the SAT or normal 8spd.
http://www.youtube.com/watch?v=enlIoO5vkbs

Kar Don
01-04-2011, 06:00 PM
Here is a quote about the 2007 BMW 335i from Car and Driver.

We also noted snappy rev-matching throttle blips when downshifting using the manumatic function (or paddles)

Here is the full article
http://www.caranddriver.com/reviews/car/07q3/2007_bmw_335i_coupe_automatic-short_take_road_test

quackbury
01-04-2011, 06:14 PM
Correct.

Next time you're on a windy road, carry a lot of speed into the corner. As you are on the brakes, pop a couple of downshifts in manual mode.



But just in cas the F10 doesn't rev match, do it where there's no oncoming traffic. :angel:

quackbury
01-04-2011, 06:16 PM
Yes, it is like crack.

I'll have to take your word for that - I'm too old for crack. But not too old for the M3. (Though my wife tells me otherwise) :D

quackbury
01-04-2011, 06:17 PM
Here is a quote about the 2007 BMW 335i from Car and Driver.

We also noted snappy rev-matching throttle blips when downshifting using the manumatic function (or paddles)

Here is the full article
http://www.caranddriver.com/reviews/car/07q3/2007_bmw_335i_coupe_automatic-short_take_road_test

Wait a minute. I thought the other guy said that it was impossible to rev match on an automatic? (He says, tongue-in-cheek......)

Seriously, nice find. I'd say that answers the question - at least for the E9X.

mlai
01-04-2011, 07:15 PM
My F10 550i with SAT definitely rev matches on sudden manual downshifts. I live on a hill with a long stretch of 30deg incline up and down to my estate. With my C55, I routinely downshift when going down hill so the engine can help with braking the car. With the F10, when I downshift when coasting down, it revs up before engaging the lower gear and passengers in the car doesn't even notice the shift down.

But unfortunately, that does mean that achieving engine braking is slightly more problematic......

Kar Don
01-04-2011, 08:26 PM
mlai, THANK YOU!!! This has been the first post to answer my question. Now the question is do I have to get SAT for this or does the normal 8spd do it? :) (My current order has SAT)

vortexx
01-04-2011, 08:54 PM
Wow 24 posts and no answer to the question, this is what I was afraid of. Rev-matching is useful and like others said it allows for a smooth manually initiated downshift. So yes I guess I should have asked does the engine computer blip the throttle prior to allowing the transmission computer to engage the lower gear when the driver manually requests a lower gear via the paddles or shifter in the manual gate? Is that better?

The straight answer to this question is YES. The CPU blips the throttle on a manually initiated downshift to match the engine revs with the anticipated lower gear. It works great, shifts fast, and it is a nicely implemented feature.

Needsdecaf
01-05-2011, 04:05 AM
I'll have to take your word for that - I'm too old for crack. But not too old for the M3. (Though my wife tells me otherwise) :D

LOL, never tried it, unlike the M3. But they say about crack, "first hit and you're hooked" and so it was for me and the M3. Good lord what a glorious noise banging down through the gears!

hmr
01-05-2011, 08:36 AM
Here is a quote about the 2007 BMW 335i from Car and Driver.

"We also noted snappy rev-matching throttle blips when downshifting using the manumatic function (or paddles)"

Here is the full article
http://www.caranddriver.com/reviews/car/07q3/2007_bmw_335i_coupe_automatic-short_take_road_test

Nicely embellished description but rev-matching and throttle blipping don't jive with my experience in the 335i, except to say that the downshifts are quick.

Say what you will, but rev-matching or throttle blipping (to briefly raise engine rpm) with a slushbox is simply not possible because the engine and transmission are never decoupled like with a manual transmission.

Rev-matching:

http://www.youtube.com/watch?v=27gW9ZS0rkI

Needsdecaf
01-05-2011, 10:19 AM
Say what you will, but rev-matching or throttle blipping (to briefly raise engine rpm) with a slushbox is simply not possible because the engine and transmission are never decoupled like with a manual transmission.

Really? Must be kind of difficult to stop without stalling then.

markl53
01-05-2011, 10:47 AM
Really? Must be kind of difficult to stop without stalling then.

Technically, they're still coupled at a stop. The torque converter slips due to the fluid coupling between the driveshaft and trans to avoid stalling. In any event, I tend to agree with "hmr". It would be too complex and time consuming, IMO, to decouple the engine and trans during an automatic shift. Watching that video, I didn't see a jump in the tach during the "blip" prior to the actual downshift -- maybe hard to notice.

Houseofpang
01-05-2011, 12:52 PM
Found this on another forum that is pretty interesting and good read, but it is for 2008 550

http://forums.5series.net/topic/42608-rudys-full-review-of-the-2008-550i-sport-automatic/

markl53
01-05-2011, 02:35 PM
Found this on another forum that is pretty interesting and good read, but it is for 2008 550


First, he stated he only drove his new car 220 miles before writing up his "review". Second, interesting how we take the word of a "lay person" to be gospel truth. The words he wrote represented his opinion, not really a technically proven conclusion, IMO.

Houseofpang
01-05-2011, 03:22 PM
Thats what i thought too, but after checking out his profile.. I saw that he had 2004/2008/2011 5 series under his belt and also a moderator at another 5 series forum and alot of experience with SMG, I gave him alot more credibility and posted that URL. But yea, for sure i won't recommend anyone to take the words without more research and hands on.


First, he stated he only drove his new car 220 miles before writing up his "review". Second, interesting how we take the word of a "lay person" to be gospel truth. The words he wrote represented his opinion, not really a technically proven conclusion, IMO.

quackbury
01-05-2011, 03:38 PM
First, he stated he only drove his new car 220 miles before writing up his "review". Second, interesting how we take the word of a "lay person" to be gospel truth. The words he wrote represented his opinion, not really a technically proven conclusion, IMO.

Calling Rudy a "lay person" is like claiming that Chris Botti is just a guy who plays the trumpet.

quackbury
01-05-2011, 03:40 PM
I know next to nothing about automatic transmissions. But if they are never decoupled, why does BMW make a big deal about the new "converter clutch" in the (ZF) 8 speed? If you never decouple, why do you need a clutch?

markl53
01-05-2011, 04:27 PM
I know next to nothing about automatic transmissions. But if they are never decoupled, why does BMW make a big deal about the new "converter clutch" in the (ZF) 8 speed? If you never decouple, why do you need a clutch?

Automatic transmissions are full of clutches and gears. This doesn't mean they decouple from the engine during shifts. It's an internal mechanism. That said, a typical converter clutch (related to the torque converter) is still basically a fluid coupled mechanism except during lock-up operation. The torque converter is what couples your transmission to the engine's rotational drive. At speed, these typically have a mechanical connection which is engaged to prevent the slipping inherent in all fluid coupled mechanisms, thus helping to improve gas mileage. At idle, the "clutch" mechanism allows the transmission to slip, rather than be connected to the engine which would cause a stall situation. I'm not sure about the mods made to the new transmission converter clutch, but I'm still of the opinion that the transmission is not disengaging from the engine other than when placed in neutral or park. If the transmission disengaged fully at a stop, your car would not creep forward when you let off the brake on level ground.

markl53
01-05-2011, 04:29 PM
Calling Rudy a "lay person" is like claiming that Chris Botti is just a guy who plays the trumpet.

Sorry, I don't know Rudy's credentials. But when I read he was surprised that the car crept forward when in gear, I started questioning his knowledge of basic transmission/engine coupling.

raleedy
01-05-2011, 04:38 PM
Technically, they're still coupled at a stop. The torque converter slips due to the fluid coupling between the driveshaft and trans to avoid stalling. In any event, I tend to agree with "hmr". It would be too complex and time consuming, IMO, to decouple the engine and trans during an automatic shift. Watching that video, I didn't see a jump in the tach during the "blip" prior to the actual downshift -- maybe hard to notice.

I believe it's done with a sound clip played through the audio system and a synchronized, computer-generated blip of the tach needle.

quackbury
01-05-2011, 04:39 PM
Automatic transmissions are full of clutches and gears. This doesn't mean they decouple from the engine during shifts. It's an internal mechanism. That said, a typical converter clutch (related to the torque converter) is still basically a fluid coupled mechanism except during lock-up operation. The torque converter is what couples your transmission to the engine's rotational drive. At speed, these typically have a mechanical connection which is engaged to prevent the slipping inherent in all fluid coupled mechanisms, thus helping to improve gas mileage. At idle, the "clutch" mechanism allows the transmission to slip, rather than be connected to the engine which would cause a stall situation. I'm not sure about the mods made to the new transmission converter clutch, but I'm still of the opinion that the transmission is not disengaging from the engine other than when placed in neutral or park. If the transmission disengaged fully at a stop, your car would not creep forward when you let off the brake on level ground.

My curiosity is piqued, so I checked ZF's website. While they do not mention anything about rev matching, they do note that they manufacture the transmission with 3 different couplings for different customers: a conventional torque converter, an electric motor for hybrid applications, and a multi pack wet clutch for performance cars. They specifically mention the MB E63; I don't know whether the F10 SAT also gets this or not. But with the disclaimer that I know almost nothing about automatic transmissions, I DO think it is possible / probable that in these applications the ZF HP8 transmission does, in fact, "disengage from the engine when other than in park or neutral".

markl53
01-05-2011, 04:50 PM
I believe it's done with a sound clip played through the audio system and a synchronized, computer-generated blip of the tach needle.

OK, your second reply to me. Now I can't tell if you're "dissing" me or what -- whatever :).

Needsdecaf
01-05-2011, 05:55 PM
My curiosity is piqued, so I checked ZF's website. While they do not mention anything about rev matching, they do note that they manufacture the transmission with 3 different couplings for different customers: a conventional torque converter, an electric motor for hybrid applications, and a multi pack wet clutch for performance cars. They specifically mention the MB E63; I don't know whether the F10 SAT also gets this or not. But with the disclaimer that I know almost nothing about automatic transmissions, I DO think it is possible / probable that in these applications the ZF HP8 transmission does, in fact, "disengage from the engine when other than in park or neutral".

The only cars to use the multi pack wet clutch in place of the torque converter are the Benzes. THe F10 uses a standard torque converter.

Kar Don
01-05-2011, 10:27 PM
Nicely embellished description but rev-matching and throttle blipping don't jive with my experience in the 335i, except to say that the downshifts are quick.

Say what you will, but rev-matching or throttle blipping (to briefly raise engine rpm) with a slushbox is simply not possible because the engine and transmission are never decoupled like with a manual transmission.

Rev-matching:

http://www.youtube.com/watch?v=27gW9ZS0rkI

Simply not possible? Tell all the engineers that at Lexus, BMW, Mercedes-Benz, Infiniti, etc... I'm willing to bet they know more about transmissions than you.

Guess what, an auto trans never decouples from the engine but there are 2 ways to achieve neutral, decouple the engine and trans (clutch in a manual trans, not possible on auto) or disengage all the gear sets (possible on both!). The engine can rev freely when no gear set is engaged (between shifts) and match the speed of the lower gear set the driver is manually selecting.

I'm still of the opinion that the transmission is not disengaging from the engine other than when placed in neutral or park.

Good thing it is an opinion, because fact is an automatic transmission can never disengage from the engine unless you go and unbolt the T/C from the flywheel. Neutral and Park just disengage the gear sets (de-activates the bands or clutch packs).

hmr
01-06-2011, 09:35 AM
Simply not possible? Tell all the engineers that at Lexus, BMW, Mercedes-Benz, Infiniti, etc... I'm willing to bet they know more about transmissions than you.

Guess what, an auto trans never decouples from the engine but there are 2 ways to achieve neutral, decouple the engine and trans (clutch in a manual trans, not possible on auto) or disengage all the gear sets (possible on both!). The engine can rev freely when no gear set is engaged (between shifts) and match the speed of the lower gear set the driver is manually selecting.



Good thing it is an opinion, because fact is an automatic transmission can never disengage from the engine unless you go and unbolt the T/C from the flywheel. Neutral and Park just disengage the gear sets (de-activates the bands or clutch packs).

Are you saying the automatics are going to neutral when shifting?

Kar Don
01-07-2011, 02:31 PM
Finally had time to go to the dealer an drive an F10 with SAT. I confirmed it does rev match when manually downshifting.

raleedy
01-07-2011, 03:45 PM
OK, your second reply to me. Now I can't tell if you're "dissing" me or what -- whatever :).

I don't know either.