is my car losing power?

[SCL_///M3]

Hi all,

when i first got my car (brand new with 10km on her), i used to be able to chirp the tires on partial throttle upshifts from 1->2->3rd gear at 5500rpm, in DCT S4 or S5 setting. i had followed the break in instructions, never floored the throttle, never exceeded 5500rpm. now that my car has 6000km and i just cant seem to be able to chirp the tires on upshifts from 2 to 3rd gear, even shifting at 8200rpm with full throttle, in S5 setting. sometimes the tires don't chirp even on an upshift from 1st to 2nd gear.
what gives? is my car losing power? i checked the onboard diagnostics and everything seems fine. tires are fine too.
has any of you experienced the same thing?
another problem i have come to notice is that my car has difficulty with tractions on take offs. unless i'm every soft on the throttle in 1st and 2nd gear, any hard input would induce wheel spins (traction light goes off) even in second gear at around 4000rpm. the only solution i got is to switch on the MDM setting. I don't remember having such a problem when the car was new.
any thoughts?
thanks in advance for any input.

[sameh]

Aren't you saying 2 opposite things. Too much power even on medium rpm that ties spin BUT "not much power" as your shifting on full rpm!!!!

[kmarei]

how many miles on the tires?

[smmmurf]

Originally Posted by kmarei

how many miles on the tires?

word, tires need at least 500 street miles to break in

[SCL_///M3]

Originally Posted by kmarei

how many miles on the tires?

4000 kms on the tires. had some problem with the original tires and had them replaced at 2000 kms break-in service.

[mdosu]

i'm thinking tires too...it's the biggest variable to your "measurement of power."

For a more scientific way, try dynoing the car once a year on the same dyno with the same settings to see if you've lost power.

[SCL_///M3]

Originally Posted by mdosu

i'm thinking tires too...it's the biggest variable to your "measurement of power."

For a more scientific way, try dynoing the car once a year on the same dyno with the same settings to see if you've lost power.

correct me if i'm wrong, but as the tires go bald, shouldn't it be easier to make them chirp on high rpm upshifts as they have less traction?

[330CIZHP]

DCT is supposed to be "automatic smooth" by design without jerks, chrips etc.

So at 8400 rpm, you would not be able to get a chirp out since "shift shock" is the first thing required to induce a "chrip". Since there is no "shift shock" in DCT due to the smoothness from the clutch already loaded with the next gear, it will not chirp.

You could even get a 100 HP manual car to chrip from 1st to 2nd if you slam the clutch in hard enough so chirping is never a measure of how much power a car is putting down.

The reason why you were able to get a chirp before at 5500 rpm were because the tires were too new and did not have the compound fully "broken in". Secondly, the flywheel (especially light one's) have far less inertia at lower rpms than higher rpms, which is why "shift shock" in extremely fast shift speed is far easier to induce in the midrange than high rpms due to the much more rapid change in flywheel speed.

Think about a lightweight wheel turning at 50 rpm. It will go through much rapid changes in speed than when it is turning at 300 rpm since the inertia introduced at higher rpms is far greater than the at lower rpms.

[andrew270681]

Im with 330CIZHP.

The DCT box is designed to be smooth etc.

I have a Manual and sometimes its a pain in the ass (but shitloads of fun) trying to keep the power down when changing gear especially when im changing gear fast.
The DCT is designed to keep the power down which in turn means that you will accellerate more efficiently.

[e1000]

The upper level drivelogic shift modes (D5, S5, S6) will absolutely have a noticeable transition between upshifts under full throttle. It's not smooth at all.

[330CIZHP]

Originally Posted by e1000

The upper level drivelogic shift modes (D5, S5, S6) will absolutely have a noticeable transition between upshifts under full throttle. It's not smooth at all.

I don't doubt it is not noticeable. Still, the smoothness feels far closer to automatics than it does to manuals.

Remember, the whole design philosophy of DCT centers around shifting so butter smooth that mid-corner it does not cause any chirps, wheelspin or shocks in order to prevent upset of the chassis balance front to back while turning.

That was the biggest design philosophy BMW sold the DCT on over the previous SMG.

[mkoesel]

Originally Posted by e1000

The upper level drivelogic shift modes (D5, S5, S6) will absolutely have a noticeable transition between upshifts under full throttle. It's not smooth at all.

Yes.

Originally Posted by 330CIZHP

I don't doubt it is not noticeable. Still, the smoothness feels far closer to automatics than it does to manuals.

I would have to respectfully disagree with that suggestion based on my experience with the three types of transmissions. As you know the DCT uses clutches vs. a torque converter. The way the transmission of power happens is actually very similar to a manual transmission.

Remember, the whole design philosophy of DCT centers around shifting so butter smooth that mid-corner it does not cause any chirps, wheelspin or shocks in order to prevent upset of the chassis balance front to back while turning.

That was the biggest design philosophy BMW sold the DCT on over the previous SMG.

Its worth reading up on the past discussions about the "surge" and how it actually makes for better acceleration. I am pretty sure I recall that this has been measured and proven scientifically. Swamp, lucid, Bruce and others have analyzed this in pretty minute detail as I recall it.

What I am saying is that the transmission is deliberately designed not to shift as smoothly as possible because that would not allow for the best performance.

[e1000]

Originally Posted by 330CIZHP

I don't doubt it is not noticeable. Still, the smoothness feels far closer to automatics than it does to manuals.

Remember, the whole design philosophy of DCT centers around shifting so butter smooth that mid-corner it does not cause any chirps, wheelspin or shocks in order to prevent upset of the chassis balance front to back while turning.

That was the biggest design philosophy BMW sold the DCT on over the previous SMG.

It's really not the case. Partial throttle is absolutely near transition-less. I think you're mistaking the BMW principal that DCT is supposed to deliver constant power, vs smooth power delivery. Again, in upper level drivelogic modes at full throttle, the shifts are absolutely noticeable. It is in NO WAY smooth.

[e1000]

Here's a fine example:

Notice how the 1-2 shift produces some wheelspin? You can also faintly hear the 2-3 shift makes a small chirp. Also notice that the camera shakes during those shifts. These are NOT smooth shifts.

[mrkbbd]

Also the new software program on it causes significantly less wheelspin between shifts

[mfeltiii]

Tire temperature (i assume it is cold now in Canada) may play a role in your new lack of traction from a dig as well.