An Old DCT Lag Rant

[alee0729]

The shift times are just navel gazing. DCT's advantage is about consistency. Long after the manual driver is tired and shifting slower at every turn, the DCT driver will still be banging out quick shifts.

[jeff4598]

Yes- Middle suspension mode (forget what it's called) gets MUCH firmer than full sport suspension mode- I switch to sport mode for relief and the engine/exhaust sound is much louder and always at the SAME time- comes and goes now and then- cannot reproduce for dealer- was more frequent- along with surge issue- before updates but still comes and goes now.



You car has intermittent stiffness adjustments made to the EDC system without you changing anything? I've never heard of anything even remotely similar to that.[/QUOTE]

[CSBM5]

Originally Posted by alee0729

The shift times are just navel gazing. DCT's advantage is about consistency. Long after the manual driver is tired and shifting slower at every turn, the DCT driver will still be banging out quick shifts.

It's also a LOT easier to instruct a novice on track with a DCT versus a 6MT. It's truly scary what some novice 6MT drivers can do...

[M3takesNYC]

Its not just the shift speed the but the gearing is much more favorable as soon as you hit 3rd for the dct. 3rd and 4th which are typical 60 mph and 3rd is the most difference of all the gears so in 3rd the dct really pulls a lot harder than the manual and shifts faster so I really notice through 3rd and beginning of 4th the dct is really noticably faster. Which is nice as 3rd is where i do almost all of my WOT pulls on the freeway

[chris s]

Originally Posted by CSBM5

Sure, why refute decades of drag racing experience? The tighter you are on the light the more likely the tighter you are on your shifts. You do realize there is a long history of shift speed time analysis in the drag racing world dating back 40+ years...

Sure i do...you also said "most manual drivers". Are we talking professional drag racers now or the BMW enthusiast who might take his car to the track now and then?

[NYBulldog]

Wasn't this about the DCT Lag issue? I remember having that issue. After a few mods and installing the Evolve-R it was a non-issue. I don't know if its a fluke but just my experience. (For the record all my cars have been stick forever and I fell in love with DCT... only after that lag disappeared)

As far as the 6MT vs DCT shift-speed discussion, it seems to be a wasted argument. A majority of "enthusiasts" couldn't shift faster than DCT... now just imagine what percentage of M3 owners could actually shift faster than DCT.

[CSBM5]

Originally Posted by chris s

Sure i do...you also said "most manual drivers". Are we talking professional drag racers now or the BMW enthusiast who might take his car to the track now and then?

I never said "most manual drivers". Seriously, read what I wrote? Here's the quote:

Originally Posted by CSBM5

A good manual driver will be way faster than 0.4 seconds. The 6MT is nowhere close to being 0.6 seconds slower in the 1/4 mile (when driven by a seriously competent driver that is ). The flip side of the coin is how well an experienced manual driver can nail a holeshot by being able to control the clutch to provide just the right amount of initial weight transfer coupled with just the right combo of clutch engagement versus throttle application for the conditions (tires, road surface, ambient temperature, etc). Said driver likely has down the ability to shift very quickly and would model in the range of 0.2 to 0.25 sec/shift.

Well, I'm not a professional drag racer, but I do have almost 35+ years of experience autocrossing, drag racing, track instructing, etc., so I suppose I'm considering myself when I consider a 6MT driver....i.e. a very experienced and competent 6MT driver which is what I was referring to in my quote above when saying a "good manual driver" and an "experienced manual driver." Note I also said "when driven by a seriously competent driver that is ".

Regards,
Chuck

[exmowner]

Originally Posted by alee0729

The shift times are just navel gazing. DCT's advantage is about consistency. Long after the manual driver is tired and shifting slower at every turn, the DCT driver will still be banging out quick shifts.

Somewhat true.. I sold my DCT for a 6sp m3 and never looked back.

The drive is so much more rewarding. Don't get me wrong dct downshifts are great but perfecting that on a 6sp puts a smile on my face

[CSBM5]

Originally Posted by M3takesNYC

Its not just the shift speed the but the gearing is much more favorable as soon as you hit 3rd for the dct. 3rd and 4th which are typical 60 mph and 3rd is the most difference of all the gears so in 3rd the dct really pulls a lot harder than the manual and shifts faster so I really notice through 3rd and beginning of 4th the dct is really noticably faster. Which is nice as 3rd is where i do almost all of my WOT pulls on the freeway

...and what I was referring to when discussing every day driving. Very few people actually track their cars but instead drive at illegal speeds and hence are subject to arrest and in some jurisdictions confiscation of their car. If they're racing another car, they can be held criminally liable for the actions of the other driver (and at least here in NC, have their confiscated car taken from them and sold at auction with no recourse). The place for fun with a car as powerful as the M3 is the track, whether it's getting road race track experience or a dragstrip. Yeah, I'm preaching to some of you I guess, but that's what you do when you're old and have seen the sad results of fast cars and street driving craziness.

[SenorFunkyPants]

Originally Posted by CSBM5

That's not purely correct. You need to read up on the detail of DCT. It is not a zero second without power interruption shift. There is a time required to transition from one clutch to the other, and power is interrupted (managed by the ECU) during that process.

Its easy to test...take a passenger, run full throttle in S2 and shift at the red line...watch your passengers head for zero movement.

[GB///M]

boys check this out...

It may answer some questions in regards to DCT vs 6MT; at least for rolling starts

[Vic311]

My reasoning is not flawed and I am certainly not the one making a fool out of themselves.

You stated the DCT is good for 25-50 HP. No matter how much subjective data and graphs you try to support this absurd statement and convince yourself.. it doesn't make it so.

Originally Posted by swamp2

I can see why you think this, but your reasoning is flawed.

Two points:

•Faster shifts make a car faster, period. The gain in a given contest is very likely close to the number of shifts multiplied by the time saved per shift.
•If a car is faster (at the same weight) one would typically conclude it has more power. In this case I have come up with an equivalent power that has the same effect as the gains from M-DCT related to its faster shifts. The amount of power does depend a bit on what contest you consider (0-60, 0-100, quarter mile, 30-160, etc.) hence why I posted a range.

Have a look at this very old and detailed post I made on this topic. This addresses the first point above. Pay particular attention to the graph. Again, there are also a PLETHORA of posts here on the forum on this idea of 25-50 hp, with plenty of PROOF of this statement. Please read up, don't make a fool out of yourself without reading those posts, both by me and other very credible forum members who have TESTED this in their supercharged M3s! Then perhaps begin your skepticism where some of these prior discussions have left off. I should refuse to continue this "debate" until you have taken this friendly and appropriate advise.

[e46e92love]

Originally Posted by swamp2

RJ: Thanks for reigniting my passion for this topic. I am also suffering as I beg to disagree - this lag is still present!

Although I have vehemently argued in the past that some sort of purposeful adaptation routine, that attempts to intelligently modify the DCT software to the user driving style, absolutely does not exist, my lag has grown from truly imperceptible to clearly present, annoying and bad enough to be borderline unsafe at times. It can be particularly bad under circumstances which also under prior software versions could cause lag. Medium, even speed, perhaps in the 40-60 mph range, gentle to medium (street level) braking, then followed by a medium throttle applied rapidly and immediately after letting off the brake. I've experienced lag which can be about 1 full second. The car simply feels as if it is completely ignoring the throttle application (and it really is).

What can we do to get some resolution to the issue? I'm long off or my factory warranty and also had a terrible go around with BMW NA not taking care of an issue that occurred just under 50k miles but ended up at the dealer at around 50,030.

Can we revisit the issue with the NHTSA? Look for a lawyer to take a class action? Letter writing campaign?

The DCT continues to amaze me with its performance, character and adjustability but as I have said prior this lag issue is like the giant pimple on the nose of the supermodel. Well of course also not covered by this analogy is that this situation is borderline or perhaps even definitely dangerous.

Are others continuing to suffer from this lag?

Cheers.

Swamp, sorry to hear of your continued troubles. I for one have had no such lag issues unless I don't consistently and accurately down shift. In other words, if I'm in 5th heading into a turn and hit the down shift paddle more than 3 times times, obviously, she will hesitate and figure out what won't blow her up: as at the speeds I'm holding in 5th, 1st or 2nd might do the trick of destroying her).

But as long as I treat it like a MT, in that I know exactly what gear I want and slecet that gear at the same point that I would when I was driving a 6MT and begin to depress my clutch, it works great.

Only issue I have had (if you can even call it an issue) is if you are down shifting while coming to a stop, if its not aggressive enough to get a throttle blip, I get this clunky sound and a slight "shutter" or roughness. But its just the gearboxes personality on that one and I don't mind that, it adds personality to this beast which I like

Hope for most this problems is gone.

Cheers,
e46e92

[Radiation Joe]

Wow!
I was just drunk typing and wanted to get in a dig at BMWNA. I started up one of our old firestorms.

In this car, I prefer a properly functioning DCT to the manual. But I do still enjoy banging out smooth fast double clutch downshifts. I absolutely hate trying to get a fast shift from 1st to second, though. Believe it or not, it took me a whole day to get used to the DCT on the track. My hands and feet had too much muscle memory from the manuals to co-ordinate myself with the paddle shifters.

[kscarrol]

^^ That's it! No more posting while drinking for you...

[WCH]

I had some lag in my '08 that was better after the update. I've never experienced any lag in my early '11.

[Dkhan23]

Go sell it then...

[Vic311]

Originally Posted by CSBM5

A good manual driver will be way faster than 0.4 seconds......Said driver likely has down the ability to shift very quickly and would model in the range of 0.2 to 0.25 sec/shift.

Very plausible..if you consider the fastest shifting transmission in a production car is now the Aventador @ 50 ms (.05 seconds), an F1 car does it in 40 ms (.04 seconds)

I'm not sure where the DCT stands with shift speeds, but I'm sure its no where near a Lambo or an F1 car

[sensi09]

Originally Posted by GB///M3

boys check this out...

It may answer some questions in regards to DCT vs 6MT; at least for rolling starts

Audi, but here's DSG vs 6mt from a dig, both with professional drivers....skip to .36sec for the race. And DSG doesn't have the programmed surge like DCT does in S4/S5 either.

[sensi09]

Originally Posted by Vic311

Very plausible..if you consider the fastest shifting transmission in a production car is now the Aventador @ 50 ms (.05 seconds), an F1 car does it in 40 ms (.04 seconds)

I'm not sure where the DCT stands with shift speeds, but I'm sure its no where near a Lambo or an F1 car

I believe there is some debate as to what constitutes an actual shift. The actual start and finish time is not universal I believe. Nevermind that the aventador still uses a single clutch and many would complain about that in e9x M3.

[sensi09]

Originally Posted by Radiation Joe

Wow!
I was just drunk typing and wanted to get in a dig at BMWNA. I started up one of our old firestorms.

In this car, I prefer a properly functioning DCT to the manual. But I do still enjoy banging out smooth fast double clutch downshifts. I absolutely hate trying to get a fast shift from 1st to second, though. Believe it or not, it took me a whole day to get used to the DCT on the track. My hands and feet had too much muscle memory from the manuals to co-ordinate myself with the paddle shifters.

Double clutch downshifts are my favorite. I don't practice launching all that much, but do enjoy trying to get quick 1st to 2nd and 2nd to 3rd shifts. Sometimes feel like an arse though doing a fast shift at decently high rpm from 1st to 2nd so usually just shift to 2nd early. Not a problem doing that in DCT though.

[e92M3C]

Why this thread turns into another DCT vs MT thread?

http://www.caranddriver.com/reviews/...le+Feedfetcher

DCT is faster in shift while MT is more involved in driving.

To each of his/her own.