2008 135i steptonic transmission HP limit?

[BadOneThreeFive]

Anyone know what the HP limit is for the steptronic transmission on this car? I heard it was 450. is this true?

[pAuLoZe]

Good question ....

[RnmEvo9]

Torque is the force that can destroy motors and transmissions. Just how much of it to do it to destroy those components I have no idea.

[Freon]

Horsepower can be an issues as well due to heat, but I tend to think that is more related to the engine stress than transmission stress. Usually people talk about torque capacity on transmission and other driveline components. On slushboxes you can heat up the ATF which can be power related as well. Not sure if the automatics have ATF temp sensing or not.

How much rear tire you have will play a big role as well. You can probably run a car with more power and torque on street tires than on race slicks since the tires will have their own limits that can keep stress on the transmission, axles, shafts, etc. lower. The catch 22 being without enough traction extra power and torque may not be very useful.

No good answers on this, and it definitely doesn't boil down to just a single torque number across the board for all cars and situations.

[rader1]

Originally Posted by RnmEvo9

Torque is the force that can destroy motors and transmissions. Just how much of it to do it to destroy those components I have no idea.

This is totally true... but for some reason almost all drivetrain parts are rated by horsepower, and I can't figure why

[GeeRam]

Originally Posted by rader1

This is totally true... but for some reason almost all drivetrain parts are rated by horsepower, and I can't figure why

Most of the gearbox manufacturers I've seen quoting data, rate their gearboxes with a torque rating rather hp....?

ZF, Getrag, Asin-Warner all give torque capacity design ratings.

The ZF GA6HP19Z 'Steptronic' used in the 135i (and 335i) has a nominal 400Nm torque rating IIRC.

[Jeef Beef]

Yep, ZF rates the GA6HP19Z at 400nm max. Plenty of people running tunes on it though with no reported issues.

[135Dan]

I have asked this before and remember from somewhere the limit on the step is 450NM. Why would the performance pack boost to 450NM on the step while preserving warranty if the ZF was limited to 400NM? Have I missed something somewhere?

Dan

[Dackelone]

Originally Posted by Jeef Beef

Yep, ZF rates the GA6HP19Z at 400nm max. Plenty of people running tunes on it though with no reported issues.

FYI 400 Nm = 295 Ft/Lbs

Most of the N54 tunes put out around 500 Nm. Some as high as 550 Nm.


And... some people still believe in BMW's lifetime fluids. lol IF I were running an A/T I would be changing my fluids often (30 to 40K miles).


Dackel

[rader1]

Originally Posted by GeeRam

Most of the gearbox manufacturers I've seen quoting data, rate their gearboxes with a torque rating rather hp....?

ZF, Getrag, Asin-Warner all give torque capacity design ratings.

The ZF GA6HP19Z 'Steptronic' used in the 135i (and 335i) has a nominal 400Nm torque rating IIRC.

And I stand corrected. I'm new to the bmw/euro tuner world. I'm used to gm/ford small block parts, and all the parts I've purchased/researched in relation to transmission and driveline are hp rated(clutchs, input shafts, synchros etc. With the exception of driveshafts, I've seen several driveshafts rated in ft lbs)

[GerryL]

Originally Posted by Dackelone

FYI 400 Nm = 295 Ft/Lbs



And... some people still believe in BMW's lifetime fluids. lol IF I were running an A/T I would be changing my fluids often (30 to 40K miles).


Dackel

Its the lifetime of the warranty. Once thats done, your future failures are their income.

[Jeef Beef]

Originally Posted by Dackelone

FYI 400 Nm = 295 Ft/Lbs

Most of the N54 tunes put out around 500 Nm. Some as high as 550 Nm.


And... some people still believe in BMW's lifetime fluids. lol IF I were running an A/T I would be changing my fluids often (30 to 40K miles).


Dackel

Most of the dynos I've seen with just tune (PROcede or JB4) read about ~430nm atw. That's a fair bit over the apparently 'limit' set by ZF.

I wonder what our stock clutches for 6MT are rated at.

[1speedbike]

Not sure what the real limit is, but plenty of people have been pushing 500 Nm on their 335i's for thousands upon thousands of miles with no real transmission issues.. Though there are the odd few with transmission issues that have and some that haven't even tuned their car.

[BadOneThreeFive]

Thanks for all the input guys. Who knows what the real limit is. Guess it depends on the conditions as far as the amount of heat and the kind of tires you are running makes a difference. I'm assuming it all comes down to how you drive your car and of coarse the amount of power and torque you are pushing out of that N54. I can see if your pushing around 500Nm torgue and running slicks at the track and launch your car hard enough you can definitely snap something. I looking to put in a few grand in some more mods (DPs, intercooler, meth injection, JB4) and Im just worried that if i start going above 450 HP+ that im gonna start breaking some stuff in the drive line. Right now my car has about 360 WHP and so far so good. Ill just take it easy and i wont launch my car so hard when i get in the 400 range.

[Jeef Beef]

Keep in mind 400nm is the TORQUE rating. Just a tune can put you well north of 550nm.

The torque converter and the overheating ATF are probably the first signs of tranny failure when you put too much power thru it.

[GeeRam]

Originally Posted by Robertbenson30

Thanks for all the input guys. Who knows what the real limit is. Guess it depends on the conditions as far as the amount of heat and the kind of tires you are running makes a difference. I'm assuming it all comes down to how you drive your car and of coarse the amount of power and torque you are pushing out of that N54.

Exactly.

The manufacturers 'limit' of 400Nm is their serviceability 'limit' deduced over extended use to meet the 'design life' of the car at all the extremes envisaged by the manufacturer in normal conditions... i.e. 100k running over a 6-8 year period or more say for example. It's not an ultimate design limit.
Of course, 9 time out 10, putting much higher torque levels of 500+Nm through it won't intially break the 'box, but, it's likely that it won't last as long as the manufacturer designed it last. Whether it reduces the life to 2, 3 5 or however many years is anyones guess.

[Dackelone]

Originally Posted by Jeef Beef

I wonder what our stock clutches for 6MT are rated at.

The guy at Digi-Tech tunning over at the 'Ring told me that 550Nm is about the max the clutch can take, He also said that it is better to chip a car with low miles then with higher miles. He said once you go over 550Nm the first thing to go is the clutch.

[BerkTechnology]

Other than the HPFP, BMW has built a pretty stout platform. No real weak points in the drivetrain have surfaced as of yet.

To answer your question you can throw any bolt-on you want, and the tranny will take all of the abuse.

Our car has been heavily raced for over 3 years now and I have had zero issues. We do change all of the fluids once a year though.

[J. Dub]

I'd like to know if anyone knows the limits now that it's 2015?

[135Pats]

Originally Posted by J. Dub

I'd like to know if anyone knows the limits now that it's 2015?

Provided you take care of it (solid mounts, frequent fluid swaps etc) it holds at least 500WTQ without issue. North of 550WTQ it's a coin flip. There are some big WHP cars that play fine with the automatic on "short" pulls. It's the 2-3-4-5 pulls where you are loading everything up for a long time...that's when things can get ugly.

Mine is fine @25PSI, which is probably around 630-650WHP/525WTQ? Something in that ballpark. But i'm rarely WOT through 5th gear. That's moving.

[J. Dub]

Originally Posted by 135Pats

Provided you take care of it (solid mounts, frequent fluid swaps etc) it holds at least 500WTQ without issue. North of 550WTQ it's a coin flip. There are some big WHP cars that play fine with the automatic on "short" pulls. It's the 2-3-4-5 pulls where you are loading everything up for a long time...that's when things can get ugly.

Mine is fine @25PSI, which is probably around 630-650WHP/525WTQ? Something in that ballpark. But i'm rarely WOT through 5th gear. That's moving.

This is great info. Thanks Pats. Do you have a build thread on your car?

[dsocold]

dunno the rating, but for reference my transmission went south at 89k miles with only about 20k of those miles being cobb stage 1 sport tuned.. it was slipping in any gear, uninstalled cobb recieved new tranny under cpo now it shifts Perfect