Any1 know how to use the Launch Control?

[cdeslandes]

Originally Posted by ttuner

1. buy a real manual
2. put it in 1st gear
3. rev engine
4. drop the clutch

problem solved! lol.

+1

[tranquility]

So you have to shift yourself or leave it to the rev limiter to automatically shift when it redlines?

[BMWZ4]

No shifting required. DCT does the work.
Dave

[Dr Stig 2]

It shifts automatically until you either lift off from full throttle or change gears manually...

Its all in the manual which you can download (manually). Pun intended.

[tranquility]

Originally Posted by Dave Marien

No shifting required. DCT does the work.
Dave

So it shifts at redline?

[Memphis1]

yes

[Dr Stig 2]

Fast, yes, but in true launch control, the flag appears on the central LCD display...

[teagueAMX]

Originally Posted by tranquility

So it shifts at redline?

One thing you see all the time on Youtube and M5board videos is people rev'ing their engine right to the red line. It's hard to really know any different without some experimentation on a dyno, but horsepower seldom peaks right at redline. The readline after all is simply the manufacture’s “do not exceed” point and has nothing to do with horsepower.

Below is a N54 TT chart showing horsepower (dashed line) and torque (heavy black line) curves.

I drew a red vertical line to illustrate the horsepower peak at around 6000 RPM, and two blue lines indicating the width of the peak, which is from about 5800 RPM to about 6200 RPM. Notice the engine was tested to it’s 7000 RPM redline.

Clearly, this chart shows it’s a waste of time to rev the engine to the redline and in fact shifting at around 5800 is your best bet - it saves engine wear and tear, too. Power begins to decline right after 6200 RPM well before the 7000 RPM readline.

.

[richard in NC]

The fastest acceleration is to maximize the total for the entire length of time. One downside to short shifting is ending up at a lower RPM the next gear. With such a broad torque peak on the 35i, it doesn't matter too much but it could.

[teagueAMX]

Gee, I don't think we called it short shifting when I was drag racing street cars back in the mid-1970's. Seems to me we wanted to get the lowest ET.

You're correct of course Richard and it requires a bit of experimentation to hit the right RPM for shifting to the next gear. My point is that most people aren't really aware that horsepower drops in the upper RPM region, so you could actually go slower by rev'ing to the redline.

[richard in NC]

Somewhat related, I read a road test of the new Buick Regal "sport sedan". The car has a 2.4 I4 and 180hp, 0-60 in 9 secs, hardly a sport sedan. Anyways, it has a 6500 rpm redline, a 6700 rpm HP peak, and a auto trans that refuses to allow revs over 6200 RPM. Why bother tuning to a 6700 RPM peak? With a torque peak of 172 at 4900 RPMs, there is a VERY narrow range of power. Hardly an exciting combo.

[tranquility]

Originally Posted by teagueAMX

One thing you see all the time on Youtube and M5board videos is people rev'ing their engine right to the red line. It's hard to really know different without some experimentation on a dyno, but horsepower seldom peaks right at redline. The readline after all is simply the manufacture’s “do not exceed” point and has nothing to do with horsepower.

Below is a N54 TT chart showing horsepower (dashed line) and torque (heavy black line) curves.

I drew a red vertical line to illustrate the horsepower peak at around 6000 RPM, and two blue lines indicating the width of the peak, which is from about 5800 RPM to about 6200 RPM. Notice the engine was tested to it’s 7000 RPM redline.

Clearly, this chart shows it’s a waste of time to rev the engine to the redline and in fact shifting at around 5800 is your best bet - it saves engine wear and tear, too. Power begins to decline right after 6200 RPM well before the 7000 RPM readline.

.

Thx for the chart and explanation. If launch control indeed shifts @7k, then perhaps it is not the fastest launch time? I wonder if someone on this forum can test launching and shifting at diff revs to see if there is really a diff in times.

[teagueAMX]

Originally Posted by tranquility

If launch control indeed shifts @7k, then perhaps it is not the fastest launch time?

That's precisely my point. Launch Control is good because it reconfigures all the electronic nanny controls. An example is that some cars need a little wheel spin to keep RPMs in the right range during launch, whereas regular traction control will not allow wheel spin. The n54 a lot of torque so that's not much of a problem, however.

I would suggest using Launch Control but pick your own shift points.

If a person is really serious about launching and top performance, then a LSD (limited slip differential) is a must.

[Mr. ///M3 RD]

Knowing you can do it is good enough for me. I would never ever treat my toy that way

Just me ... you all do it if you like, I get my kicks out of just looking at teagueAMX's chart.

Cheers,

Rolf-Dieter

BTW, if you do it quite often make sure a new set of rear tires are on order or stand by

[tranquility]

^True, our launch control is not as robust as Porsche's, as an example. Just not on the same level. One can really beat that Porsche's engine to death and it keeps in ticking.

[richard in NC]

Originally Posted by tranquility

^True, our launch control is not as robust as Porsche's, as an example. Just not on the same level. One can really beat that Porsche's engine to death and it keeps in ticking.

It's not the motor that gets abused during launch control, its the drivetrain.
BMW motors can certainly take high revs all day long. I know, I've done it on track, and some on the road. At Virginia International Raceway is a sharp 180 followed by a 3/4 mile straight. In my 550i, I was foot to the floor 40mph to 135mph lap after lap, redlining 2nd, 3rd, & 4th. I did that (plus the whole 3.25 mile lap) for 10 laps a session for 7 sessions a weekend, That's 210 redline shifts without the slightest indication of abuse.

[tranquility]

Originally Posted by richard in NC

It's not the motor that gets abused during launch control, its the drivetrain.
BMW motors can certainly take high revs all day long. I know, I've done it on track, and some on the road. At Virginia International Raceway is a sharp 180 followed by a 3/4 mile straight. In my 550i, I was foot to the floor 40mph to 135mph lap after lap, redlining 2nd, 3rd, & 4th. I did that (plus the whole 3.25 mile lap) for 10 laps a session for 7 sessions a weekend, That's 210 redline shifts without the slightest indication of abuse.

Thx for the clarification; so how come your drivetrain held up?

[richard in NC]

Originally Posted by tranquility

Thx for the clarification; so how come your drivetrain held up?

Its hard launches from a dead stop that abuse the drivetrain, because of the sudden shock of torque into the system. If the tires don't give (and spin), something else may... Shifting at redline doesn't hurt it, especially in higher gears. As long as the transmission can handle it, and the Sport Automatic in the 550i or the DCT in the Z4 seem well able to do so.

[tranquility]

Originally Posted by richard in NC

Its hard launches from a dead stop that abuse the drivetrain, because of the sudden shock of torque into the system. If the tires don't give (and spin), something else may... Shifting at redline doesn't hurt it, especially in higher gears. As long as the transmission can handle it, and the Sport Automatic in the 550i or the DCT in the Z4 seem well able to do so.

Ic. Thx.

[teagueAMX]

Hey richard,

Seems I remember from somewhere on the x6 forum, that the car's computer records the number of Launch Control launches. I could never get a definitive answer if that was a warranty issue based on the number of launches.

Do you recall that discussion?

[Darbs330]

Originally Posted by teagueAMX

Hey richard,

Seems I remember from somewhere on the x6 forum, that the car's computer records the number of Launch Control launches. I could never get a definitive answer if that was a warranty issue based on the number of launches.

Do you recall that discussion?

Reading that made me curious... so I did some searching and found this thread from the M3 Forum...

#6 seems to have a lot of interesting info on the subject...

http://m3forum.net/m3forum/showthread.php?t=286107

Don't know if it's true or applicable to the e89... but it seems plausible...

(Edit: I also came across this cautionary tale about "launching" too often. I guess it really can lead to a 'bent tranny')

http://www.autoblog.com/2008/10/13/c...owners-busted/

[teagueAMX]

Originally Posted by Darbs330

Reading that made me curious... so I did some searching and found this thread from the M3 Forum...

#6 seems to have a lot of interesting info on the subject...

http://m3forum.net/m3forum/showthread.php?t=286107

Don't know if it's true or applicable to the e89... but it seems plausible...

(Edit: I also came across this cautionary tale about "launching" too often. I guess it really can lead to a 'bent tranny')

http://www.autoblog.com/2008/10/13/c...owners-busted/

Good research Darbs, thanks.

But after reading the data I'm pretty much back were I started. It sounds like some manufactures have an issue with it (Nissan), but it "appears" that BMW does not keep an eye on it.

You'll note one of the comments from the forum link you provided, sort of down at the bottom, a guy mentioned he talked with his BMW Service Manager and who said it was a myth.