Why is 0-60 so much faster with MT ?

[ESC OFF]

I drive a manual 135i, I did 0-60 in .7 seconds on ice yesterday!

[Tom K.]

Originally Posted by BSM 335I

Do that and you'll see a cloud of smoke from the tires behind you lol.

Assuming traction control is disengaged, are you talking about the 128i that this thread refers to or your 335i? There is the slight difference of 100 ft. lbs of torque between the two!

Tom

[Fireflyer239]

"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."

Bing Bang Boom, there's your answer folks. So, while the slushiness of the slushbox is slowing the car down by the usual amount, the time spent "on-boost" compared to the manual is making up for it, and nearly equalizing things. I used to sell Jeep/Eagle products, and their Talon was available in turbo and NA. While the NA car was quite enjoyable with stick, it was a dog off the line with the auto. (The Tsi AWD cars were awesome to drive!) I have not driven an auto 128, but I don't believe BMW had 0-60 times as priority when considering demographics for that package.

[ORIGIN M.]

The manual is consistently not the faster of the two.

[BMW-driver]

lol. Than there is something wrong with your car (tracktion or less enige power). I could easely get a 5,3/5,4 sec from 0-62 and with the Schnitzer tune, I hit the 4,6 sec.

Originally Posted by ru55

It's rubbish....my stock 135i will never do 0 - 62mph in 5.3seconds!!

(And before anyone says, its not my driving...I am a qualified race driver and advanved police driver)

Best 0-60 time i've had in my 135i is 6.6 sec

[JimD]

FireFlyer,

The explanation about the turbos staying on boost is often given but I suspect at best only part of the answer. I think the bigger factor is the auto in the 135i is geared such that the engine is spinning over 15% more rpm (in first gear and a lesser amount faster in the next several gears) at a given speed than it would with a manual. Gearing the engine this way gets more torque to the pavement quicker and helps acceleration. The difference between auto and manual in the 128i is only half as much and the 128i is about .6 seconds slower to 60 with the auto.

For most of my shifts I would guess the auto is faster and would better keep a turbo engine (not what I have) on boost better. But it is possible to shift a manual pretty fast which would minimize that factor. In any event, I am confident that the gearing is also a contributor. I know of no simple way to prove it but my guess is that if you geared a manual the same as an automatic, on a 135i, it would accelerate noticably faster if shifted quickly. At least it would until you missed a gear.

Jim

[BSM 335I]

Originally Posted by Fireflyer239

"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."

Bing Bang Boom, there's your answer folks. So, while the slushiness of the slushbox is slowing the car down by the usual amount, the time spent "on-boost" compared to the manual is making up for it, and nearly equalizing things. I used to sell Jeep/Eagle products, and their Talon was available in turbo and NA. While the NA car was quite enjoyable with stick, it was a dog off the line with the auto. (The Tsi AWD cars were awesome to drive!) I have not driven an auto 128, but I don't believe BMW had 0-60 times as priority when considering demographics for that package.

lol your funny. There is no slowness, lag, play, or whatever you wanna call it in the new ZF transmissions that are in the 135i and not the 128i just to be clear were talking about the same car here. The converters are locked up %100 of the time when in sport or manual mode. Also you can't compare the TSI with it's AWD platform to the 135i's rear wheel or even the technology between the two transmissions. I too had a 1st GEN GSC a while back and of course it was a manual because the automatics back then sucked for the most part in any vehicle. As always though technology advances and so did the new ZF step found in our cars.

Again, I don't hate manual and would consider that my first choice still in a vehicle. Though since my last 7 cars including an E90 335i were all manual I decided to take a steptronic equipped 135i for a test drive and immediately fell in love. Placed my order and it was done. Now this isn't to say that my next car will have a Steptronic or DCT transmission but to state that these new ZF trannies are no joke and I guarantee that if BMW was like Mercedes and made the 135i/335i only with the stepronic transmission you all would still be driving it. See but you can't say the same for the manual transmissions as if BMW were to make all their 135is/335i's in manual then they would lose more sales than if they were to go the other route with the Steptronic. Although I wouldn't mind one bit if they did just offer the manual lol.

Just remember each owner has their own preference and that any of these transmissions whether it be the step or manual in our cars perform incredibly well.

[bmw13]

Originally Posted by BSM 335I

lol your funny. There is no slowness, lag, play, or whatever you wanna call it in the new ZF transmissions that are in the 135i and not the 128i just to be clear were talking about the same car here. The converters are locked up %100 of the time when in sport or manual mode. Also you can't compare the TSI with it's AWD platform to the 135i's rear wheel or even the technology between the two transmissions. I too had a 1st GEN GSC a while back and of course it was a manual because the automatics back then sucked for the most part in any vehicle. As always though technology advances and so did the new ZF step found in our cars.

Again, I don't hate manual and would consider that my first choice still in a vehicle. Though since my last 7 cars including an E90 335i were all manual I decided to take a steptronic equipped 135i for a test drive and immediately fell in love. Placed my order and it was done. Now this isn't to say that my next car will have a Steptronic or DCT transmission but to state that these new ZF trannies are no joke and I guarantee that if BMW was like Mercedes and made the 135i/335i only with the stepronic transmission you all would still be driving it. See but you can't say the same for the manual transmissions as if BMW were to make all their 135is/335i's in manual then they would lose more sales than if they were to go the other route with the Steptronic. Although I wouldn't mind one bit if they did just offer the manual lol.

Just remember each owner has their own preference and that any of these transmissions whether it be the step or manual in our cars perform incredibly well.

and the forum peace prize goes to...; all kidding aside, solid argument

[Fireflyer239]

Please understand I did not say an auto is a bad choice. I own 2 vehicles with autos and 1 with manual (my 128). When I used the term "slushiness of the slushbox" I was only throwing out the commonly used automotive slang term for an auto trans, and referring to the fact that they are usually a few ticks behind an identical car with manual. New-Tech autos/DSG's etc are obviously very efficient at transmitting power. I did not mean to imply that choosing an automatic means that someone might be happy with the characteristics of a slipping Powerglide, or made an inferior choice in any way. Also, I wasn't comparing a Talon AWD to anything, just saying they were lots of fun.

Hadn't thought of this before but in addition to any gearing differences, maybe it's a big factor: the torque curve of a turbo motor is fat right at the bottom, right? The engine sees this rpm range only ONCE during an accelleration run - at the start in first gear. I'm thinking this is where the difference can be seen. The N/A engine with auto trans has to struggle through the first few thousand RPM until it can finally start working, but the turbo can torque-blast through this low-RPM band much more easily, giving away little to the clutch dump of a stick car. Recalling those non-turbo Talons with auto, that's where the doggy portion of accelleration was, right off the line.

[JimD]

In my younger days I dreamed of the muscle cars. I never had the money to own one but I had the money to buy the magazines and dream. One of the things you did to your car to get a lower time in the quarter mile was to change the rear end gears to a higher ratio so that the engine was spinning more rpm, in this case in every gear. Lower ratio rear ends, sometimes less than 3 to 1, are for mpg in highway cruising. High ratio rear ends, usually between 3 and 4 to 1 and closer to 4 is the high end, are for quick acceleration. BMW changes the rear end ratio but also changes the transmission ratios to make the automatic equipped cars similar in quickness to the manuals. The fact that they do this proves that the manual is inherently faster (not to start and argument, and I am not saying it is better) but there still remains a bit of a question why the 128 was not geared the same 15-16% faster that the 135 is in first gear so that the acceleration would be more similar. My best guess is the GM transmission was not available with this gearing. And if BMW solved the first gear "problem" for the automatic equipped 128s by changing the rear end gears, it would create a different problem in 6th gear on the highway - mileage would suffer.

Jim

[Tom K.]

Re JimD's post, 6th actually is higher in the Auto to compensate for the lower (higher numerically) FD with an overall ratio of 2.50 vs. 2.75 for the stick.

The gearing differences for the 128i Auto & MT are:

1st: + 8% for the Auto
2nd:+10% for the Auto
3rd: + 7% for the Auto
4nd:+ 8% for the Auto
5th: - 2% for the Auto
6th:-10% for the Auto

Plus the torque converter gearing advantage, especially in the lower gears.

So the Auto gets a lot of ratio help in the lower gears for acceleration and in 6th for fuel economy. 5th (direct drive in the MT) is about equal - and overall, the MT is a closer ratio box than the Auto.

Tom

[demosthenes]

Originally Posted by Tom K.

The gearing differences for the 128i Auto & MT are:

1st: + 8% for the Auto
2nd:+10% for the Auto
3rd: + 7% for the Auto
4nd:+ 8% for the Auto
5th: - 2% for the Auto
6th:-10% for the Auto

Plus the torque converter gearing advantage, especially in the lower gears.

So the Auto gets a lot of ratio help in the lower gears for acceleration and in 6th for fuel economy. 5th (direct drive in the MT) is about equal - and overall, the MT is a closer ratio box than the Auto.

Tom

Your numbers include the 15% difference in the axle ratio (3.23 MT vs 3.73 AT), right?

[Tom K.]

Originally Posted by demosthenes

Your numbers include the 15% difference in the axle ratio (3.23 MT vs 3.73 AT), right?

Naturally. They represent the overall ratios, but don't include the TC stall ratio.

Tom

[demosthenes]

Originally Posted by Tom K.

Naturally. They represent the overall ratios, but don't include the TC stall ratio.

Tom

What's the TC stall ratio?

[Tom K.]

Originally Posted by demosthenes

What's the TC stall ratio?

As I understand it, it's the additional torque multiplication provided by the torque converter at the speed the drive wheels are engaged.

Maybe this will help.

http://en.wikipedia.org/wiki/Torque_converter


Tom

[demosthenes]

Thanks Tom.