Launch hesitation

[watoowatoo]

This is my first automatic car and for a long time this is something I need to figure out:
Every time I press the gas pedal for fast start from stand still there is about less than a second with no response what so ever, not even little rpm change, until the moment the car actually engages. Even when I start from full manual mode in 1st gear.

Anyone else notices this pause or hesitation? Could you explain the reason?

[dmlgc]

turbo lag.
http://en.wikipedia.org/wiki/Turbocharger
section 8.2

[watoowatoo]

What I am referring to is different than throttle response and delay of power. More like transmission engagement delay.

" Conversely on light loads or at low RPM a turbocharger supplies less boost and the engine acts like a naturally aspirated engine."

Seems like engine doesn't act at all let alone the naturally aspirated part.
Put the gear in M1 mode. push the throttle fast for quick start and for about half a second no action.

[archwerks]

As much as we all need to Blast Off from the red light once in a while, to show the old lady in the Corolla that u r in a big hurry, U cannot expect to do that everytime from a stop, in a 5000 lb. beast without some electromechanical protection/delay built into the system. I used to do that a lot in a mercedes sedan & end up paying for a few transmission coupling repairs.
For those requiring instant speed of immediate afterburner kick, I suggest a lighter vehilcle like the M3 GTS.

[watoowatoo]

Originally Posted by archwerks

As much as we all need to Blast Off from the red light once in a while, to show the old lady in the Corolla that u r in a big hurry, U cannot expect to do that everytime from a stop, in a 5000 lb. beast without some electromechanical protection/delay built into the system. I used to do that a lot in a mercedes sedan & end up paying for a few transmission coupling repairs.
For those requiring instant speed of immediate afterburner kick, I suggest a lighter vehilcle like the M3 GTS.

After some digging figured you are right. There is actually a purposeful delay to give time to transmission to engage under full throttle. Simple solution is actually NOT to floor the gas pedal for faster start so that engagement happens instantly under lighter load!
I found this on M3 forum guys in M3 have same experience almost:
http://www.m3post.com/forums/showthr...68#post3690868

[Hamed]

As if you were talking about how i feel towards my car (X6 35i) .. which I am getting disappointed little bit of its performance !

For me..not only from stand...even during crusing...giving the car a FULL kick down..there is this delay..which really pisses me of ! (I had a V8 american car..it used to FLY when I do that) .. thats why I am pissed of with my car !

What to do ?

[jfewins]

Originally Posted by Hamed

As if you were talking about how i feel towards my car (X6 35i) .. which I am getting disappointed little bit of its performance !

For me..not only from stand...even during crusing...giving the car a FULL kick down..there is this delay..which really pisses me of ! (I had a V8 american car..it used to FLY when I do that) .. thats why I am pissed of with my car !

What to do ?

get a procede. It will help substantially. Next time, don't order a 6 cylinder engine for a 5500 lb car.

[archwerks]

The best thing to do do is test drive the vehicle for at least an hour or 2, so the engine is fully warmed up, & drive it as hard as you can for throttle & handling response. Then test drive another vehicle as reference or comparison.
In this case maybe compare it w/ the X6M or the Cayenne Turbo.
Everyone values different driving dynamics differently.
Especially if u intend to track ur vehicles for fun.
The search for the Ultimate continues...

[watoowatoo]

Originally Posted by Hamed

As if you were talking about how i feel towards my car (X6 35i) .. which I am getting disappointed little bit of its performance !

For me..not only from stand...even during crusing...giving the car a FULL kick down..there is this delay..which really pisses me of ! (I had a V8 american car..it used to FLY when I do that) .. thats why I am pissed of with my car !

What to do ?

35i is no TTV8 or muscle car. But still I surprised quite a few V8s out there. In D mode it takes it too easy to save fuel. Doing 50km/h it's already in 4th gear in D which is sluggish with slow kick down to 2nd. But in sport mode reaction is quite impressive I would say. On the highway TT comes alive no complain there. Whatever I drive I try to learn how to keep her happy all the time!

[archwerks]

Originally Posted by watoowatoo

35i is no TTV8 or muscle car. But still I surprised quite a few V8s out there. In D mode it takes it too easy to save fuel. Doing 50km/h it's already in 4th gear in D which is sluggish with slow kick down to 2nd. But in sport mode reaction is quite impressive I would say. On the highway TT comes alive no complain there. Whatever I drive I try to learn how to keep her happy all the time!

Those who are auto mechanical engineers / or deal with dyno readings can perhaps elaborate.
The way I see this torque vs. power output graph seem to indicate that the engine "sweet spot" is @ roughly 3750 rpm, where the torque line intersects the output line.

[Hamed]

At rpm 3500+ .. here is when the Turbo starts operating...this is what a friend told me..who is a specialist in tunning BMW's...!!

[archwerks]

I doubt the turbos start that late.

[m3_p0wer]

try launching the car by holding the brake and gas i always do that great launch at 2000 rpm or just hold the brake and push full throttle and release the brake immediately

[Rac10000]

Originally Posted by archwerks

I doubt the turbos start that late.

They turbos definitely don't start spooling at 3500 RPM ... Peak torque happens at just 1300 RPM and peak boost for the N54 is 0.4 bar (5.8 psi) ... Assuming you go full throttle from a stop light I would bet the turbos are pushing full boost by 1300-1500 RPM. The delay that some of you are noticing is most likely due to the traditional automatic transmission.