Why is 0-60 so much faster with MT ?

[Lester]

Originally Posted by JimD

Tom,

...
It would be nice to know what other cars this AT is used in. If it is a bit weak for the N52, they could be trying to protect it from damage under hard acceleration by letting the torque converter slip to take up shock. That would make things hang together.

Jim

Part 24007594375 (Rmfd automatic transmission EH) was found on the following vehicles:


E82:
E82 125i Coupé, Europe

E88:
E88 125i Convertible, Europe
E90:
E90 323i Saloon, Europe
E90 325i Saloon, Europe
E90 328i Saloon, Europe

E90N:
E90N 323i Saloon, Europe
E90N 325i Saloon, Europe
E90N 328i Saloon, Europe


E91:
E91 323i Touring, Europe
E91 325i Touring, Europe
E91N:
E91N 323i Touring, Europe
E91N 325i Touring, Europe


E92:
E92 323i Coupé, Europe
E92 325i Coupé, Europe
E93:
E93 323i Convertible, Europe
E93 325i Convertible, Europe
E93 328i Convertible, Europe

[SJ]

Originally Posted by Yuzi

some magazines got 5.7sec stock

\

With AT or MT? I would believe that someone like C&D could get 5.7 with MT. Are you saying 128 AT? Can you give us the reference? That seems impossible (stock for sure, I mean). Maybe that was going down hill? ..

So, it seems we know the following:

- the AT on the 128 is a different unit than on the 135
- the unit on the 135 performs much better (very close to MT numbers)
- the unit on the 128 should be more than adequate (same unit on CTS),
but it provides disappointing performance.

I'm not much of a mechanical guy, but I still wonder, why the AT numbers are therefore so bad, relatively, in the 128 vs 135? Is it possible that because the 135 is turbo, BMW can so some fancy tuning in the ECU that jumps boost with an upshift that in some way compensates for what you see in the 128? Wouldn't that make the 135 seem lurchy?

Should it be possible to tune the 128 ECU so that AT delivers performance close to MT numbers? Of course, if so, I don't know BMW wouldn't have done that in the first place ...

[jeremyc74]

Originally Posted by SJ

\



So, it seems we know the following:

- the AT on the 128 is a different unit than on the 135
- the unit on the 135 performs much better (very close to MT numbers)
- the unit on the 128 should be more than adequate (same unit on CTS),
but it provides disappointing performance.

I'm not much of a mechanical guy, but I still wonder, why the AT numbers are therefore so bad, relatively, in the 128 vs 135? Is it possible that because the 135 is turbo, BMW can so some fancy tuning in the ECU that jumps boost with an upshift that in some way compensates for what you see in the 128? Wouldn't that make the 135 seem lurchy?

Should it be possible to tune the 128 ECU so that AT delivers performance close to MT numbers? Of course, if so, I don't know BMW wouldn't have done that in the first place ...

The reason the automatic is as fast as the manual in the 135i isn't because it's a better unit, it's because it allows the turbos to stay under boost during the shift. When you're shifting a manual transmission on a turbocharged car you're not only off the power the entire time the clutch is in, but the additional time it takes the turbos to spool back up. On the automatic the shift is made under power, and it makes it faster.

If you stuck the 135i transmission in the 128i, you'd have the same numbers, assuming the gear ratios were the same.

[RPM90]

Originally Posted by red-sauerkraut

I spent over 2 hours driving w/a 30 year field tech employee w/BMWNA, and he told me that the 135i AT was faster than the 135i Manual. He knew more about BMW's [and other marks] then anybody I have even had the grace to meet. I have no reason to doubt him.

That's one guys opinion.
However, I've yet to see an automatic 135i, stock, faster than a manual.
They are both as fast as each other, and the auto has a gearing advantage to help it out. The ZF auto is an excellent auto trans, very fast shifts, still it needs the gearing to help it out.

Also, even BMW, the people that make the car, rate the auto as .1 sec slower. Granted, that number is virtually pointless to claim the manual is faster. Most manual drivers probably can't shift as fast as the auto can, so I'm sure it leaves some with the impression that it's "faster".
The auto drivers simply need a good hookup and then let the auto take care of the rest, which also gives more consistent times.
That said, a manual driver who know's how to drive will be just as fast, and can better control the trans on twisty roads and tracks. As good and smooth as the auto is, it still has "lag" in it's shifts and isn't as smart as a good manual driver in knowing what gear is right for the turn.
Still, I'm amazed at how good auto transmissions have become. So much so that the argument I just made is becoming more of a moot point as technology gets better and better.
My favorite trans is still the true automated -manual trans. It's much quicker and more direct than a slushbox, and doesn't need the gearing advantage to be as fast.

[RPM90]

Originally Posted by jeremyc74

The reason the automatic is as fast as the manual in the 135i isn't because it's a better unit, it's because it allows the turbos to stay under boost during the shift. When you're shifting a manual transmission on a turbocharged car you're not only off the power the entire time the clutch is in, but the additional time it takes the turbos to spool back up. On the automatic the shift is made under power, and it makes it faster.

If you stuck the 135i transmission in the 128i, you'd have the same numbers, assuming the gear ratios were the same.

That is true, that auto turbo's have always had that advantage in being able to hold boost better during the shift. And, given how fast this auto shifts it's really taking advantage.

The 1st and 2nd gen Mits Eclipse auto was slower than it's manual counterpart, even with it's boost hold advantage. It was older tech auto so it wasn't as fast in it's shift as modern units.

The boost hold is helping, but I contend it's not the reason why the auto is as fast as the manual. It's the combination of boost hold and the quickness of the ZF trans that makes it so fast, along with the bigger factor, the shorter final drive and 1st gear. Give the auto the SAME gearing as the manual and I'll bet it's not as fast as the manual.
Also, manufacturers tend to gear their cars to get better 0-60 times, even though it may not be the best gearing for the engine.
In this comparison, I think BMW geared the auto this way on purpose, to keep the accel numbers to 60 as fast as they could, as most buyers are automatic buyers. BMW knows their market.

The 2 gears in particular, for the 0-60 run, are:
Manual
1st- 4.06
2nd- 2.40
Final- 3.08

Auto
1st- 4.17
2nd- 2.34
Final- 3.46

1st gear in the auto is shorter, thus greater torque multiplication for a launch. Add the shorter final drive, and the auto has a distinct advantage off the line compared to the manual.
2nd gear shows the manual getting back some gearing in comparison to the auto's taller 2nd, but the manual still has the disadvantage due to the shorter final drive of the auto, in both gears.
The only gear where the manual has an advantage is 6th,
oh, and reverse.

BMW smartly tuned the auto trans for excellent off the line accelleration, and then gave it taller higher gears to offset the shorter final drive, giving it decent MPG as well. Given the prodigious power the TT has along with it's very broad torque curve, and BMW has room to play with the gearing to get those great numbers.

The auto has the gearing advantage off the line, and the boost hold helps it carry through the 1/4 as it's gearing becomes taller in comparison to the manual.

Put that shorter drive in the manual, and the difference would be the manual being faster in 0-60 and 1/4 mile.
Give both cars the SAME gearing and I'll take the manual winning every time, regardless of it being able to hold boost between shifts.
In comparison of the 2 trannys, the auto was given an advantage to help it keep up with the manual.
Getting quick shifts is one thing, but you still have to overcome the disadvantage of the slushbox.

[Yuzi]

Originally Posted by SJ

\

With AT or MT? I would believe that someone like C&D could get 5.7 with MT. Are you saying 128 AT? Can you give us the reference? That seems impossible (stock for sure, I mean). Maybe that was going down hill? ..

So, it seems we know the following:

- the AT on the 128 is a different unit than on the 135
- the unit on the 135 performs much better (very close to MT numbers)
- the unit on the 128 should be more than adequate (same unit on CTS),
but it provides disappointing performance.

I'm not much of a mechanical guy, but I still wonder, why the AT numbers are therefore so bad, relatively, in the 128 vs 135? Is it possible that because the 135 is turbo, BMW can so some fancy tuning in the ECU that jumps boost with an upshift that in some way compensates for what you see in the 128? Wouldn't that make the 135 seem lurchy?

Should it be possible to tune the 128 ECU so that AT delivers performance close to MT numbers? Of course, if so, I don't know BMW wouldn't have done that in the first place ...

6MT (0-60mph 5.8s) (0-60 5.7s)

http://www.caranddriver.com/reviews/...t/specs_page_3

http://www.motortrend.com/roadtests/...est/specs.html

for me I constantly getting 6.2sec in 0-100km/h which is 0-62mph stock

I have driven both MT/AT 128i and the fact AT is much slower compare to the MT for some reasons. Hence, the decision of getting the 6MT.

[bbadillo]

dude, my AT 135i with JB is so fast, and when i get drunk, my gf can drive it haha

[Lopster]

Originally Posted by raceman

My local tuning shop does that and guys have many years experience of manipulating ECU software.
In theory, like some German tuners do it, ECU software can be easily loaded to original ECU block, but in reality they check all aspects and adapt SW to each particular car. Also, they give full warrantly and will re-load software in case of necessity later (if dealer 'updates' ECU to original data).
Point is that it's not big issue for software crackers to do it, but requires some equipment and experience.
There is really no need to 'suffer' from somehow underpowered 125i engine, when 100% same engine produces 272 HP with OEM software for X3/330i.

I haven't seen anything on the forum that claims to even come close to this level of power increase for a 125i simply by remap and no other mods. This is almost worth driving across Europe for if true. This guy should advertise.

[ORIGIN M.]

Originally Posted by bbadillo

dude, my AT 135i with JB is so fast, and when i get drunk, my gf can drive it haha

That has to be the best part, vs calling a Taxi!

[MattD]

Just to point out that the US 0-60 times could show discrepancy to Euro 0-62.5 (100 km/h) unless people have been very specific about what they're quoting and because of the dodgy "rollout" inclusion, same as on a drag strip, which we wouldn't tend to use in Europe. It's 0-xx mph, not 2-60 mph with the tyres keyed into the surface.

Having said that, 6.6 is still very slow as the above would only count for around 0.5s. Should be a second quicker without reducing your clutch to a smouldering wreck

[demosthenes]

Originally Posted by RPM90

The boost hold is helping, but I contend it's not the reason why the auto is as fast as the manual. It's the combination of boost hold and the quickness of the ZF trans that makes it so fast, along with the bigger factor, the shorter final drive and 1st gear. Give the auto the SAME gearing as the manual and I'll bet it's not as fast as the manual.
Also, manufacturers tend to gear their cars to get better 0-60 times, even though it may not be the best gearing for the engine.
In this comparison, I think BMW geared the auto this way on purpose, to keep the accel numbers to 60 as fast as they could, as most buyers are automatic buyers. BMW knows their market.

The 2 gears in particular, for the 0-60 run, are:
Manual
1st- 4.06
2nd- 2.40
Final- 3.08

Auto
1st- 4.17
2nd- 2.34
Final- 3.46

1st gear in the auto is shorter, thus greater torque multiplication for a launch. Add the shorter final drive, and the auto has a distinct advantage off the line compared to the manual.
2nd gear shows the manual getting back some gearing in comparison to the auto's taller 2nd, but the manual still has the disadvantage due to the shorter final drive of the auto, in both gears.
The only gear where the manual has an advantage is 6th,
oh, and reverse.

BMW smartly tuned the auto trans for excellent off the line acceleration, and then gave it taller higher gears to offset the shorter final drive, giving it decent MPG as well. Given the prodigious power the TT has along with it's very broad torque curve, and BMW has room to play with the gearing to get those great numbers.

The auto has the gearing advantage off the line, and the boost hold helps it carry through the 1/4 as it's gearing becomes taller in comparison to the manual.

Put that shorter drive in the manual, and the difference would be the manual being faster in 0-60 and 1/4 mile.
Give both cars the SAME gearing and I'll take the manual winning every time, regardless of it being able to hold boost between shifts.
In comparison of the 2 trannys, the auto was given an advantage to help it keep up with the manual.
Getting quick shifts is one thing, but you still have to overcome the disadvantage of the slushbox.

Great post!

[BSM 335I]

Ok seriously to all the noobs that claim there is a disadvantage to having the steptronic transmission in the 135i and that it lags can just go fly a kite. How many times do we the actual people who own the steptronic transmissions tell you that our extremely advanced piece of technology shifts through all 6 of it's gears in under .3 seconds. Though still carrying a torque coverter in sport mode it is locked 100% of the time and you are just as much in control with the vehicle as if you were in a manual driven car.

[JimD]

I'm not sure what the last post is about other than the guy is an automatic fan. It caused me to look at this again especially rpm90s post.

I think this is all gearing. If we multiply the transmission gears times the rear end gears for the 135i, we get (for the first three gears):

MT 12.5, 7.39, 4.86
AT 14.43, 8.1, 5.26

For the 128i, we get:

MT 13.95, 7.95, 5.36
AT 15.16, 8.81, 5.78

If we then compare the gearing of the two transmissions for the two vehicles, we find that the auto transmission of the 135i is geared 15.44%, 9.6%, and 8.2% quicker than the MT in gears 1-3 respectively. If we look at the same thing for the 128i, we get 8.7%, 10.8%, and 7.83% quicker. So the only big difference is in first gear where the 135i is much quicker geared with an automatic.

I don't know why the 128i auto gets to turn less revolutions to move the car than a 135i but it easy to see how that could lead to slower acceleration.

Those who think an auto is inherently quicker should also notice that their autos are given a gearing advantage - so that they can keep up.

Jim

[Evice]

why are you guys reviving very old topics ^^ just let it go, call it a personal choice and move on.

[JimD]

Evice,

In my case it is just curiosity. The GM automatic transmission in the 128i is used in sporty Cadillacs and it didn't seem right for the auto to be about the same in the 135i but significantly slower in the 128i. I do not know if the GM transmission won't take a low enough gear for first or whether BMW just decided 128i automatic transmission drivers were not that interested in their 0-60 time. But I am convinced that the dilemna has been solved - it is just a gearing issue. While the issue is old and rpm90s post is close to the answer, it took me a little more time with a calculator for the light bulb to go off.

Jim

[demosthenes]

Originally Posted by JimD

Evice,

In my case it is just curiosity. The GM automatic transmission in the 128i is used in sporty Cadillacs and it didn't seem right for the auto to be about the same in the 135i but significantly slower in the 128i. I do not know if the GM transmission won't take a low enough gear for first or whether BMW just decided 128i automatic transmission drivers were not that interested in their 0-60 time. But I am convinced that the dilemna has been solved - it is just a gearing issue. While the issue is old and rpm90s post is close to the answer, it took me a little more time with a calculator for the light bulb to go off.

Jim

Thanks for sharing. It's good that we understand why the 0-60 times are what they are, the role of gearing and what it says about AT vs MT.

Most people don't understand how torque, HP, weight and gearing affect performance. And we haven't talked about other factors like power loss in the drive train and traction.

[BSM 335I]

Originally Posted by Evice

call it a personal choice

+1 couldn't of said it any better. Personal Choice!

[demosthenes]

Because we want to understand what's going on. What's wrong with that? We aren't fighting over which tranny is better.

[Lucky1]

Old rule of thumb was that automatic transmissions = heavier and torque converters pulled additional power from the crank to slip the gears. I don't doubt the auto tranny in the 128i suffers this in addition to whatever gearing ratio differences there are. Plus don't forget you can dump the clutch at 4000rpm or whatever you want in 1st gear to get that instant power to the wheels...as far as I know the 128i tranny doesn't have that kind of launch control.

[BSM 335I]

Originally Posted by Lucky1

Old rule of thumb was that automatic transmissions = heavier and torque converters pulled additional power from the crank to slip the gears. I don't doubt the auto tranny in the 128i suffers this in addition to whatever gearing ratio differences there are. Plus don't forget you can dump the clutch at 4000rpm or whatever you want in 1st gear to get that instant power to the wheels...as far as I know the 128i tranny doesn't have that kind of launch control.

Do that and you'll see a cloud of smoke from the tires behind you lol. Now as for revving and dummping the clutch in 3rd gear while cruising around 70mph is a different story .

[JimD]

Actually you can't do more than chirp the tires if the DSC is engaged. I tried at an autocross. You can rev it up and dump the clutch, I did, but the DSC just adjusts the throttle position to something the tires can handle. You could probably start a little quicker with the DSC off by figuring out how high you could rev it for a quick start but I wanted the DSC on to keep me on the course (didn't want to ding my new bimmer). I picked up a trace of cone on the passengers side front wheel and lower body panels as it is. My son thinks he can buff it off.

Jim

[BSM 335I]

Originally Posted by JimD

Actually you can't do more than chirp the tires if the DSC is engaged. I tried at an autocross. You can rev it up and dump the clutch, I did, but the DSC just adjusts the throttle position to something the tires can handle. You could probably start a little quicker with the DSC off by figuring out how high you could rev it for a quick start but I wanted the DSC on to keep me on the course (didn't want to ding my new bimmer). I picked up a trace of cone on the passengers side front wheel and lower body panels as it is. My son thinks he can buff it off.

Jim

well then no you won't see tire smoke and it would be pointless to do that with dsc engaged. Dsc does for you what it does for me. It's meant to stop wheelspin period. So it's no different from you then it is me and I can spin my tires and produce smoke just as much as you can, maybe even a little more since I can change gears without letting off the gas . Again I don't hate manuals if anything I loved my 335i 6mt that I had prior to the 1.