DCT vs Conventional Automatic

[1speedbike]

I posted something similar in another thread recently but..



ZF tranny shifts around or under 200 ms (on downshifts, upshifts are faster) consistently

fastest manual shifter got 260 ms inconsistently

average manual shift time is 500 ms

first generation smg transmission shifts at 220 ms

dct shift times VARY from 30 ms to 200 ms http://www.m3post.com/forums/showthread.php?t=165773

[Aries932]

Originally Posted by 1speedbike

I posted something similar in another thread recently but..

ZF tranny shifts around or under 200 ms (on downshifts, upshifts are faster) consistently

fastest manual shifter got 260 ms inconsistently

average manual shift time is 500 ms

first generation smg transmission shifts at 220 ms

dct shift times VARY from 30 ms to 200 ms http://www.m3post.com/forums/showthread.php?t=165773

The DCT shift times only vary in 2 different ways.

1) Sports mode or non Sports mode (sports mode increases shift times)

2) Depending where your foot is on the throttle or if it is even on the throttle...I have noticed under full throttle shift times are exactly the same, but if i am backing off the throttle or my foot is off the throttle shift up time is a bit slower

I am pretty sure these are the only 2 reasons for the varying shift times.

Also keep in mind that the M3 DCT is a lot different from the 135i DCT...so the shift times are not necessarily going to be the same.

[BrokenVert]

Originally Posted by RPM90

Even after being owned by your lack of facts, you still have the nerve to write, "...ok you do realize....."?

I know brokenvert is quite aware of what you think you are schooling him on.

Lol thank you. I was going to go off on a rant about turbo vs NA torque curves and how a turbo effectively adds displacement.

Also an MB 6.2 L AMG engine (they are falsely badger as 6.3 for tradition. Makes it's power in an entirely different way that the GM pushrod 6.3L.

Again not really comparable. Europeans employ highly advanced technologies inorder to maximize the efficiency of their engines including exotic materials, tighter tolerances, forged materials, and a different bore and stroke. The LS1 (I believe that's what's in the GTO but I'm bad with what LS is in what) is a 15 or 20 year old design and it shows in the specs that you quoted.

You simply can't compare the two. Just like you can't compare an auto 128 and a auto/DCT 135 in a power shootout.

Damn. I ended up ranting. Ohh well might as well finish it.

A turbo car and an NA car are also incomparable in terms of the torque curve and the power curve. A turbo works by cramming more air into each cylinder. It effectively adds to the displacement of the engine by allowing said engine to burn a similar mixture of gases to a higher displacement engine.

If you don't believe me look at an autox car class roster. If you have a turbo 6 pot you are put in the same class as the V8 cars, if you have a turbo 4 banger you are placed in the NA 6 pot class.

Also, turbo cars naturally have more torque than a similarly sized NA car because of the larger explosion. Turbos also have variable boost, this is why our torque curves are flat at ~ 300lbft from 1300-5400.

Actually nevermind, this rant isnt worth it. We might aswell throw a rotary into this bench comparo.

Howablout a 1.3L RX-8 vs an auto 128 vs a DCT 135?

[KingOfJericho]

Originally Posted by Aries932

Umm actually not true...brake torquing starting in 2nd gear with the auto transmission is faster than DCT 0-60 due to not having to shift before you hit 60

The 335i below is only running a JB4 tune, intake, and meth.

What's up with the fuel gauge??

[BrokenVert]

Originally Posted by KingOfJericho

What's up with the fuel gauge??

It's coding. The fuel gauge is a boost gauge and the turn signals are shift lights

[KingOfJericho]

I was thinking that when I saw it but had no idea that was an option. Do they also light up on the outside?

[BrokenVert]

Originally Posted by KingOfJericho

I was thinking that when I saw it but had no idea that was an option. Do they also light up on the outside?

It's not an option. You need a coder to program it for you. Maybe that guy in the Bronx will do it

[KingOfJericho]

Originally Posted by BrokenVert

It's not an option. You need a coder to program it for you. Maybe that guy in the Bronx will do it

I saw him last weekend and we did a bunch of tweeks. By "option" I meant coding option. I wasn't thinking it was factory or anything...

[BrokenVert]

Originally Posted by KingOfJericho

I saw him last weekend and we did a bunch of tweeks. By "option" I meant coding option. I wasn't thinking it was factory or anything...

Doh sorry. I've been distracted today. Sorry about that, but yeah I need to see that guy.

[KingOfJericho]

Yeah you should definitely go. I love all the new changes he made! It's worth it just for shutting off the stupid legal disclaimer on the Nav.

[Amalfitano]

[QUOTE=Aries932;9353764]
2) Less power transfer loss. Automatics are usually around 20%-22% power loss, while DCT and manuals usually stick around 15%.

This still has not been proven to be incorrect. I am pretty sure that this is true.

A very difficult proposition, BUT, why would the premier n54 tuners consistently use the steptronic to demonstrate their products that are entirely based on getting power to the wheels if the drivetrain gives up 5% over the manual? 5% when you're going for 425 wtq is a HUGE gap. Why wouldn't they be testing on M/T's to have graphs with more supposed powertrain efficiency?

By the way, has anyone tested the limits of the torque the 135 DCT can handle? And a reminder, which i believe both "pissing" sides have pointed out, the M-DCT in the M3 is NOT the DCT in the 1 series. WHat torque the M-DCT can handle doesn't cut it. This obviously doesn't matter to those that will keep the car stock, but...

If you're going to bash drag racers about modding their cars, then defend how well the DCT downshifts through turns... are you really tracking your 1 series in stock form? And if you're not tracking your car, no offense but please don't tell me you know how well the cars behaves in turns and downshifts and yadayadayada. This was more a rant against all of internetdom, not specifically this thread. I HATE going on tirerack and hearing how great a tire behaves "at the limit", then have the person describe being on the streets. Streets do not equal at the limit. And if you're truly at the limit on the streets, please don't drive ANYWHERE near me.

[Aries932]

Originally Posted by BrokenVert

Lol thank you. I was going to go off on a rant about turbo vs NA torque curves and how a turbo effectively adds displacement.

Also an MB 6.2 L AMG engine (they are falsely badger as 6.3 for tradition. Makes it's power in an entirely different way that the GM pushrod 6.3L.

Again not really comparable. Europeans employ highly advanced technologies inorder to maximize the efficiency of their engines including exotic materials, tighter tolerances, forged materials, and a different bore and stroke. The LS1 (I believe that's what's in the GTO but I'm bad with what LS is in what) is a 15 or 20 year old design and it shows in the specs that you quoted.

You simply can't compare the two. Just like you can't compare an auto 128 and a auto/DCT 135 in a power shootout.

Damn. I ended up ranting. Ohh well might as well finish it.

A turbo car and an NA car are also incomparable in terms of the torque curve and the power curve. A turbo works by cramming more air into each cylinder. It effectively adds to the displacement of the engine by allowing said engine to burn a similar mixture of gases to a higher displacement engine.

If you don't believe me look at an autox car class roster. If you have a turbo 6 pot you are put in the same class as the V8 cars, if you have a turbo 4 banger you are placed in the NA 6 pot class.

Also, turbo cars naturally have more torque than a similarly sized NA car because of the larger explosion. Turbos also have variable boost, this is why our torque curves are flat at ~ 300lbft from 1300-5400.

Actually nevermind, this rant isnt worth it. We might aswell throw a rotary into this bench comparo.

Howablout a 1.3L RX-8 vs an auto 128 vs a DCT 135?

I am pretty lost at why you felt the need to go on a rant and try to explain to me how a turbo'ed car adds displacement when I already told you I realized how displacement works. I also already know how a turbo works. It was a mistake on my part as I have not checked the statistics of the 128i since the last time I owned a 128i it was a 97' sedan, which actually had a 2.8L engine.

Regardless all of your rant has absolutely NOTHING to do with the arguement at hand. The person I responded to was saying that the DCT was a great transmission because he spanked a 128i.

All I did was reply to him and basically tell him that arguement was not valid in that he won not because of the transmission, but because the car was 70hp behind the 135i. Then you come in and go off about how big a deal my mistake was about .2 displacement and how it matters due to the increased torque, and then argued that torque matters more for a drag race. The only reason I brought in the two different displacements of the AMG engine and the pontiac engine was to point out that really you should pay much more attention to the power and torque of a car rather than the displacement when comparing the two cars. It will give you a good idea of where they stand, however the actual power curve matters quite a bit I do agree with you there (again not needed to be discussed considering both engines are designed by BMW).

So I then explained to you that the 128i has only 200tq compared to the 135i 300tq and the displacement value really did not matter (refuting your drag race comment). Fact of the matter is that the car is completely below the 135i in terms of engine performance and that is why it lost. Not because of the transmission.

You then decided to further go off topic to attempt to "teach" me something. I already knew all of that information so you really did nothing, but go further off topic. In this case your arguement completely does not matter to the discussion at hand. I would ask you again to stay on topic...but I am sure you will find another smart ass way to reply to try to "teach" me something by throwing in more technical car facts that really have nothing to do with the discussion at hand.

[NewYearsBoy]

Originally Posted by Aries932

umm yes...no automatic blips the revs when it downshift...are you serious?

Do you even know how an automatic works...it uses a torque converter.

I will try to make a video of this when i get my exhaust so you can see exactly what I am talking about.

The reason why I didnt get DCt was because of the no TT... But I have been in a DCT M3 and it is FAST.. But my Auto Step 1 the shifts are just a little slower and it does blip when I downshift.

[GeeRam]

Originally Posted by BSM 335I

+1. GM vs ZF

Must be having a blonde day today.....but....

What's the GM refer to?

[BrokenVert]

Originally Posted by GeeRam

Must be having a blonde day today.....but....

What's the GM refer to?

GM = General Motors the worlds largest automaker

But yeah the auto transmission in the 128 is the same one that's in the CTS 3.6

Also I went on that rant to show how useless and pointless this thread is. Might aswell add some truthful information to it before it gets closed

[GeeRam]

Originally Posted by BrokenVert

GM = General Motors the worlds largest automaker

I was hoping that's not what it was refering to.

After a bit of a Google I never realised that BMW made so much use of GM slushboxes

And it's made in France......

[Prof T]

And it's made in France...... [/QUOTE]

France,

[elzorro4]

How about the new 8 spd automatic on the 235i vs the DCT on the 135i? I guess the DCT will be slightly faster but the auto on the 235i wont have that darn lag of the DCT on start and stops.

[Iron Man]

Originally Posted by Prof T

And it's made in France......

France,

To be fair, at least it is in Strasbourg , which has a lot of German culture (and at one time belonged to Germany). Though I believe GM sold the plant to ZF a few years back.

[Dylanize]

Originally Posted by KingOfJericho

I saw him last weekend and we did a bunch of tweeks. By "option" I meant coding option. I wasn't thinking it was factory or anything...

It's built into the JB4, you decide what you want.

[gabeyts]

My parents have a 128 and 328 auto and I wasn't aware that they arent ZF autos, but I dislike the torque converters because of the creep when you get off the brakes

[Tenspeed]

Originally Posted by Aries932

Just checked up what you said and you are somewhat correct. According to BMW the DCT gets less gas milage than the manual, but it is still better than the 335i automatic.

135i
Manual transmission – City/Highway 20/28 mpg

Automatic transmission – City/Highway (135i: 7-speed Double Clutch Transmission(DCT)) 18/25 mpg

335i
City/Highway17/26 (17/26) mpg

One difference between the automatic and the DCT is that the Automatic has an overdrive and the older 7 speed DCT (like in my '11 135i convertible) is 1:1 in 7th. If I understand correctly, the later DCT's went to 8 speeds and an overdriven 8th gear.

I actually got 30.5 MPG running 75-80 on the interstate on a 160 mile trip right after I got my car last summer (which was much better than the 25 mpg given on the sticker). I have also gotten 27.5 mpg on a trip up to the NC mountains and back (even playing some in the mountains). So, if you can cruise, it actually does well.

Driving around town is a different story. The acceleration is too fun and I am only getting about 19-20 when playing in town.

Driving this car is the most fun I have had in years!