S2/S3 Drivelogic settings upset the balance of the car

[Hobbination]

Originally Posted by Hoopumpers

Ha well, if you like Nickelback, then your opinion no longer counts

Not a chance haha

[Boss330]

Originally Posted by JoeFromPA

So let me make one technical point for you:

You can't actually have both instantaneous shifts and perfectly smooth shifts.

Smoothness comes from a clutch slipping the difference in spin rates of the wheels * gearing vs. flywheel/engine. And to achieve smoothness, you need some level of clutch slipping....which is a delay in gear change.

DCTs, especially 7 speed DCTs, minimize this through of course precision but also close gearing. Nonetheless, it's still a reality.

However, when you actually want an instantaneous gear change, there is nothing to be done about the fact the engine is spinning 500 RPMs higher than the wheel speed warrants. And so, when the computers tell the clutch to engage instantaneously, you are going to get driveline shock.

That shock is actually a sign of a faster shift.

DCT is a wonderful transmission technology in that it allows essentially uninterrupted power flow because there is no time-lag as the gear selection changes....but that doesn't alter the fact that the engine and wheel speed are meshed up smoothly (or not) by a delay induced from clutch slipping (or not).

My point behind ALL of this is to say: You can't say "I want instantaneous perfectly smooth shifts". It's contradictory. If the M5 was perfectly smooth, then it's because a clutch was slipping more than your M3 is in S3 - and thus the actual gear change is not complete instantaneously.

Just something to think about. Sounds like you should be in S2 + MDM for chassis control reasons.

One other feature that is important to shift strategies is the amount of ignition timing being pulled.

Many cars, like the Audi RS, A45 AMG and M cars, often have a crack/fart/burp noise when changing to a higher gear at full throttle. This noise isn't from clutch slippage obviously

It's actually the ignition timing being pulled (or even shut off) for a brief period of time. This is done to drop engine torque and create a smoother transition to the next higher gear.

Since ignition timing is pulled (or even shut off completely) unburnt fuel escapes to the exhaust manifold, where it ignites and makes the cracking noise

You can even buy aftermarket WOT boxes that replicate this torque drop and creates a smoother shift, where you can keep the accelerator pedal to the floor during a WOT shift on a MT car.

http://www.npcompleteperformance.com/wotbox

[Wregie]

Originally Posted by Hoopumpers

Solstice go drive a 991 GT3 with PDK-S. Then you'll know what I'm asking for.

I like the DCT but am just a little disappointed with how it's been tuned for the F8x

There doesn't seem to be an elegant way to modulate the shift ferocity with the throttle. Sure, you can drop throttle to 20%, then shift, but you're losing the value of uninterrupted dual clutch power delivery.

I am with you and know exactly what you mean. When people ask me how it compares to my Porsche I tell them that the M4 is more brutal and cruder.

[Hedoniste]

Originally Posted by Hoopumpers

... I find the DCT is unnecessarily sharp on upshift. It completely upsets the balance of the car, for no reason, other than to make you "feel" fast with a shove in the back. In S3 the rear tires just light up on upshift at only half throttle. It feels very synthetic to me.

S2 is better, but still has a balance upsetting shove.

S1 upshifts are slightly delayed but much smoother (which is good). Sadly S1 downshifts are sllllllow.

I'd prefer to have a setting with S1 upshifts and S3 downshifts.

Throttle response is also unnecessarily sharp in sport plus in the M4. It's as if they've engineered the car to "feel" fast...but unsettling the car is certainly not fast in reality.

I totally agree with you

[thebishman]

Originally Posted by Hoopumpers

I had a F10 M5 prior to the F82 M4. The DCT in the M5 was damn good. I drive with traction control off (unless in the wet), and with the M5, sport plus throttle, S3 shifts, I had no issues at all. Pretty close to perfect.

Fast forward to the M4. I find the DCT is unnecessarily sharp on upshift. It completely upsets the balance of the car, for no reason, other than to make you "feel" fast with a shove in the back. In S3 the rear tires just light up on upshift at only half throttle. It feels very synthetic to me.

S2 is better, but still has a balance upsetting shove.

S1 upshifts are slightly delayed but much smoother (which is good). Sadly S1 downshifts are sllllllow.

I'd prefer to have a setting with S1 upshifts and S3 downshifts.

Throttle response is also unnecessarily sharp in sport plus in the M4. It's as if they've engineered the car to "feel" fast...but unsettling the car is certainly not fast in reality.

I'll put $10 that the first response to this thread is "you should have bought a manual"

I also came out of a F10 M5 and do find the DCT in the F82 M4 a little 'wanting' in respect to 'smoothness' of shifts compared to its bigger/older brother, especially in the more sport oriented settings. I find myself driving in Sport mode for engine/S2 when just trolling around. Works for me.
Bish

[MaynardZed]

Originally Posted by Hobbination

Not a chance haha

[JoeFromPA]

Originally Posted by Hoopumpers

Thanks Joe. Appreciate the thoughtful response. Of course nothing is truly instantaneous... but <100ms is virtually, and can be accomplished without shock.

Again, I can only speak from personal experience in a fairly wide range of double clutch sports cars, and the M4 has a jolt which isn't to my liking. Apparently I'm the only one...so maybe I just need more time with the car. Or perhaps the tranny will smooth out a bit once broken in (doubtful).

BMW traction control cuts power very abruptly, so is not my preference for spirited driving. Traction control in a Mclaren, for example, is truly amazing and prevents wheel slip in a manner which is non-invasive and seemingly almost magical. How that car puts power to only the rear wheels is astounding. BUT, how an M car can spin its wheels and remain balanced is also a thing of beauty.

Anywho...I'll spend more time coming to terms with my feisty DCT

BMW traction control can be quite intrusive.

This morning I went WOT in 2nd gear at around 30mph on a flat, straight surface with full DSC on.

My tail wiggled about 1" to each side even with DSC fully on. Was surprised at how much movement it allowed.

Pretty sure I scared a few other cars nearby....wasn't even intentional, was just the first time i went WOT in 2nd gear when the ambient temp was 51 degrees.

[JeffM-Houston]

Honestly, I was expecting more support from owners on this. It really stands out to me as a driver.

I don' think many people actually have a problem with it. I run mine in S2 for daily driving, and kept it in S2 for autocross last weekend, it seems about perfect to me.

I agree that S3 is just too much in both throttle and shifting, but the good news is that it is there for people that like it.

Great to know that like most forum sites, we have a bunch of fanboys, where their cars are perfect.

That's me, my last BMW was a 1985 535iS (which I drove until the mid-90's). And I do indeed think this is the best I have driven. After 1400 miles and one autocross I honestly don't have anything I would change, it's as close I have ever come to a perfect compromise.

[shortseller]

Originally Posted by JoeFromPA

BMW traction control can be quite intrusive.

This morning I went WOT in 2nd gear at around 30mph on a flat, straight surface with full DSC on.

My tail wiggled about 1" to each side even with DSC fully on. Was surprised at how much movement it allowed.

Pretty sure I scared a few other cars nearby....wasn't even intentional, was just the first time i went WOT in 2nd gear when the ambient temp was 51 degrees.

Bet it felt pretty good, didn't it? Yeah, you know it did!

[JoeFromPA]

Originally Posted by shortseller

Bet it felt pretty good, didn't it? Yeah, you know it did!

Sorry, I just re-read my post.

It said my tail wiggled 1" to each side. It was meant to read 1' to either side, with full DSC on.

In other words: I know BMW's DSC was intrusive, but I was blown away by how much the rear end moved laterally (in both directions) before DSC reined it back in this morning. And that was when I was accelerating in a straight line, already rolling, and went WOT in sport mode.

Point being:

1. Maybe that intrusiveness is, here, in part because this car will wag it's tail for the slightest provocation or if a squirrel crosses the road.

2. My rear tires have written a letter to my attorney asking for a cease and desist, and I'm being gentle on them

[shortseller]

^ WOW!

[tooch]

I don't have a problem with it. It's a much lighter/smaller car than an M5 so I would assume it'll be at least a little more jerky. I love the transmission myself.

[peter_s]

I was at my first trackday yesterday with my M4 with the DCT.

Setting was S2 and I didn't feel any jerks. Even shifted in a corner with 50% throttle just to test it and it didn't get unsettled at all. I'm very impressed with the M-DCT

[heckyeahbro69]

Maybe a company will come out with some aftermarket software, or bmw will release an update in the future. They are always updating their software anyway, so maybe it's just a matter of time

[Maddict3]

The funny thing is that the M5 and M4 share the exact same transmission.

[Butty45]

Coming out of an F10 M5, I automatically use shift speed 3 in the M4, but I find it is too aggressive for the M4. When I shift from 2nd to 3rd in WOT the car gets unsettled and the traction cuts in. Even in good weather but particularly worse in the damp weather we have now. Not sure why as the M 5 never did this and it's the same gearbox as far as I know. It's the only thing that annoys me about this car. Anyone else find this and sticks with shift speed 2??

[antych]

Turn off traction control, problem solved. On more serious note, most people stick with S2 exactly because of what you described.

[Naz24]

Originally Posted by Hoopumpers

Thanks Joe. Appreciate the thoughtful response. Of course nothing is truly instantaneous... but <100ms is virtually, and can be accomplished without shock.

Again, I can only speak from personal experience in a fairly wide range of double clutch sports cars, and the M4 has a jolt which isn't to my liking. Apparently I'm the only one...so maybe I just need more time with the car. Or perhaps the tranny will smooth out a bit once broken in (doubtful).

BMW traction control cuts power very abruptly, so is not my preference for spirited driving. Traction control in a Mclaren, for example, is truly amazing and prevents wheel slip in a manner which is non-invasive and seemingly almost magical. How that car puts power to only the rear wheels is astounding. BUT, how an M car can spin its wheels and remain balanced is also a thing of beauty.

Anywho...I'll spend more time coming to terms with my feisty DCT

Have you tried getting the car coded for Euro MDM? This actually makes a world of the difference in power cut. i find it to be a nice in between for DSC ON and DSC OFF. In my opinion, the US spec MDM is way too inhibiting

[verruckt]

I think OP's problem is that the M4 is much lighter than the M5 - weight appears to be the problem here IMO.

Combined with a CF driveshaft and you're going to have a car that you feel much more in.

The M4 is just much more "direct".

[PhoenixBimmer]

Is there any way to set up S2 as basic setting when I start the car? Thanks,

[DS_BMW]

Originally Posted by BimmerDallas

Is there any way to set up S2 as basic setting when I start the car? Thanks,

Use your M1 or M2 modes and program it how you want, press that button after start up.

[CanAutM3]

Originally Posted by BimmerDallas

Is there any way to set up S2 as basic setting when I start the car? Thanks,

The DCT defaults to D1 on start-up but also default S mode in S2, so as soon as manually change a gear via the paddles or the lever (or if you flick the lever to the right) thr DCT will go into S2.