Why BMW Chose DCT for the Z4 35is

[Mark]

I thought this was a very interesting note posted by BimmerFile

With the release of the Z4 35is BMW will be offering only one transmission; the DCT. Our understanding is that the manual 6 speed Z4 (specifically the clutch) can’t handle the torque that comes with the engine upgrade in the car.

Read the rest: http://www.bimmerfile.com/2009/12/15...h-the-z4-35is/

[BlueZ4AZ]

So, then all of us with a 35i with DCT are OK to go get an aftermarket Flash for the same amount of Torque and HP BMW is offering with this new package, with absolutely no worry of it voiding any warranty, because essentially what BMW is offering is the EXACT same thing the flash does??????

But it just seems it won't work out that way, will it?

Because it's all about the $$$$$. If BMW says the flash won't void the warranty, then half of all potential 35i owners will spend $750 on the flash after they buy their car, instead of opting for an overpriced 35is.

I can hear the BMW service manager now...."Yeah, we just don't know what will happen with someone elses software"

[Mark]

Unfortunatly, I dont think it will ever be the case that an OEM will condone an aftermarket add-on. No matter what any engineer tells them the limits are, the lawyers wont let something like that happen

[matt_435xi]

Originally Posted by MarkE90M3

Unfortunatly, I dont think it will ever be the case that an OEM will condone an aftermarket add-on. No matter what any engineer tells them the limits are, the lawyers wont let something like that happen

DINAN

[Chuck76]

I don't get it. Wasn't it Dinan who stated that the DCT was not able to handle the extra torque in their test flash for the z4? I'm not choosing sides on DCT vs 6MT. Just trying to get the facts here.

So what do 6MT need...a heavy duty clutch upgrade?

--Chuck

[tiborakos]

Originally Posted by MarkE90M3

I thought this was a very interesting note posted by BimmerFile



Read the rest: http://www.bimmerfile.com/2009/12/15...h-the-z4-35is/

Is there a possibility for a "BMW Performance engine kit" for Z, like the 135/335 after all??

[mrboon]

Originally Posted by BlueZ4AZ

So, then all of us with a 35i with DCT are OK to go get an aftermarket Flash for the same amount of Torque and HP BMW is offering with this new package, with absolutely no worry of it voiding any warranty, because essentially what BMW is offering is the EXACT same thing the flash does??????

But it just seems it won't work out that way, will it?

Because it's all about the $$$$$. If BMW says the flash won't void the warranty, then half of all potential 35i owners will spend $750 on the flash after they buy their car, instead of opting for an overpriced 35is.

I can hear the BMW service manager now...."Yeah, we just don't know what will happen with someone elses software"

yeah bmw wont be happy, but we can be. It only means that the DTC can handle it

[Toodeep]

I don't believe for a minute that the 6MT couldn't handle the same power/torque with headroom to spare. BMW must have their reasons but they came from the Marketing department not Engineering.

[termigni]

Originally Posted by Toodeep

they came from the Marketing department not Engineering.

exactly.

[deshields]

Originally Posted by Toodeep

I don't believe for a minute that the 6MT couldn't handle the same power/torque with headroom to spare. BMW must have their reasons but they came from the Marketing department not Engineering.

Originally Posted by termigni

exactly.

Are you guys claiming to know more about the mechanical components of the Z4 then BMW themselves now? Come to us with facts and reasons why you believe this to be true, or is it the same belief as the toothfairy?

I think its fairly clear why what BMW says is true.

Many of these cars will be gobbled up by the US market, where people are known for being not the best of drivers and don't treat the mechanicals of their cars very well ("I get oil changes, yea I take care of my car, duh"). With that said, the 6MT clutch probably can handle the torque just fine, but after years of a typical US driver pounding and dropping the clutch it will likely fail prematurly. Then these same drivers who don't take the time to really take care of their cars will jump onto the internet and start complaining about failing this and failing that. BMW is smart to overengineer their components with a high level of wiggle room so that these kinds of things don't happen.

So in this case, BMW deemed that DCT, with its superior finesse in clutch actuation then your typical driver, will likely last a whole lot longer and so its better suited for a performance car like this.

PS Why do you think launch control was deactivated for the US market.

[Vintage]

Yes, it did come from marketing and not engineering . . . does that confirm that the DCT can't handle too much extra torque??? I guess so . . . I am a little confused.

[hokie4life03]

Originally Posted by Toodeep

I don't believe for a minute that the 6MT couldn't handle the same power/torque with headroom to spare. BMW must have their reasons but they came from the Marketing department not Engineering.

+1

BMW is one of the only manufactures that offers a 6MT in almost every model. They can't phase that out, in favor of DCT.

[Memphis1]

if the DCT is untouched from it's M3 version, then the max torque is 600Nm that's 440 lb-ft.

Getrags' info:

"has a torque capacity of 600 Nm and helps reduce the model’s 0-100 km/h acceleration time by 0.2 seconds compared with the standard manual gearbox."

[numba1guju]

Im pretty sure BMW's marketing department was told to say that(by engineering department) as I highly doubt they would lie about something like the 6MT...yeah marketing prob dont know squat about the cars they speak of so someones gotta give em their facts

[citrixscu]

Originally Posted by Toodeep

I don't believe for a minute that the 6MT couldn't handle the same power/torque with headroom to spare. BMW must have their reasons but they came from the Marketing department not Engineering.

+1

Isn't it usually the other way around? There was a post about BMW moving away from DCT and toward autoboxes because of tq limitations. It seems odd that they would claim that the 6MT could not handle the extra torque. I wonder what implications this has for those who think this motor will be placed in the new E92 335 LCI...unless they plan on offering DCT with that model as well, which would be even more interesting.

[TotalPower]

BMW also put automatic transmission in the 335d for the same reason.

I think it has to do with the CDV burning out a clutch too fast on an manual car. All you'd need is a heavy duty clutch and pressure plate IF you needed it on a car w/o the CDVPOS.

[vase330]

Originally Posted by deshields

Are you guys claiming to know more about the mechanical components of the Z4 then BMW themselves now? Come to us with facts and reasons why you believe this to be true, or is it the same belief as the toothfairy?

I think its fairly clear why what BMW says is true.

Many of these cars will be gobbled up by the US market, where people are known for being not the best of drivers and don't treat the mechanicals of their cars very well ("I get oil changes, yea I take care of my car, duh"). With that said, the 6MT clutch probably can handle the torque just fine, but after years of a typical US driver pounding and dropping the clutch it will likely fail prematurly. Then these same drivers who don't take the time to really take care of their cars will jump onto the internet and start complaining about failing this and failing that. BMW is smart to overengineer their components with a high level of wiggle room so that these kinds of things don't happen.

So in this case, BMW deemed that DCT, with its superior finesse in clutch actuation then your typical driver, will likely last a whole lot longer and so its better suited for a performance car like this.

PS Why do you think launch control was deactivated for the US market.

Of course BMW is not an after market tuner. The tuners can push the envelope to the edge and sometimes over the edge. BMW has to leave a safe enough headroom because there is such a thing as warranty claims too. If you go to a tuner, you get your power and a prayer. That's just the way it is. I agree with your assessment here.

[Wraith.]

Launch control is deactivated for the US market??

[Merefield]

Originally Posted by TotalPower

BMW also put automatic transmission in the 335d for the same reason.

I think it has to do with the CDV burning out a clutch too fast on an manual car. All you'd need is a heavy duty clutch and pressure plate IF you needed it on a car w/o the CDVPOS.

I believe my Z4M (max torque 365 Nm) has a CDV and a manual transmission!

I think that's a much lower peak torque level than the 35iS, but that begs the question - how come the Z4M is almost as quick to 60 (4.9 secs), despite that disadvantage? Its lower weight?

[Memphis1]

300 lbs lighter

[mapezzul]

Originally Posted by Toodeep

I don't believe for a minute that the 6MT couldn't handle the same power/torque with headroom to spare. BMW must have their reasons but they came from the Marketing department not Engineering.

Originally Posted by VintageBMW

Yes, it did come from marketing and not engineering . . . does that confirm that the DCT can't handle too much extra torque??? I guess so . . . I am a little confused.

Originally Posted by TotalPower

BMW also put automatic transmission in the 335d for the same reason.

I think it has to do with the CDV burning out a clutch too fast on an manual car. All you'd need is a heavy duty clutch and pressure plate IF you needed it on a car w/o the CDVPOS.

Since I am the one that knows the real reason- First, the clutch and the springs used that can not handle the torque at those load levels. The 6MT would be able to handle the torque WITHOUT the overboost function but not be in BMWs range they prefer, since engines can actually produce more HP from the factory than quoted but not less. This is also the reason with the Performance Kit. When you talk to engineers and those that have a say in the design of these products you realize it is not marketing that plays a part into these decisions, unless you consider warranty and reliability marketing. Look up the numbers for the 6MT from ZF and you will see BMW in not BS-ing

The DCT can handle more than the 6MT (period). The DCT can NOT handle the 500 ft/lbs that the V8 in the X5/X6 ///M put out (even in tweaked form).
I can't go into more details now but can say that BMW did a great job with this version of the Z4.... and when I can say more I will.

-M

[mapezzul]

Originally Posted by Merefield

I believe my Z4M (max torque 365 Nm) has a CDV and a manual transmission!

I think that's a much lower peak torque level than the 35iS, but that begs the question - how come the Z4M is almost as quick to 60 (4.9 secs), despite that disadvantage? Its lower weight?

The numbers on the Z435is are VERY preliminary. Launch Control on this model IS ACTIVE (and stated in the press release).