[ImUrGoDaK]

saw this function listed on the canadian website. what is that? and is it on cars made for the states too?

[shimshimhada]

Yeah, I think all BMWs are equipped with this. It's a little annoying, but you get used to it.

[shimshimhada]

I'm not sure if they are equipped on the M cars though.

[E90Fleet]

Most new cars have them these days

The spring system inside the clutch keeps the clutchplate at the same position even as it wears down sothat the engagement point is always at the same point throughout the clutches life

In other words the point at witch the clutch engages on your clutchpedal will always remain constant trhoughout the clutches life.

It also makes the clutch easier to push in
Best place to see the difference is if you try and press in the clutch of a 80's Porsche Turbo and the latest ones. The old ones are almost impossible to push in and the new ones are ligth as a feather.

All due to the SAC technology

BMW have used them for many years now

[E90Fleet]

Originally Posted by shimshimhada

Yeah, I think all BMWs are equipped with this. It's a little annoying, but you get used to it.

No, you are thinking of the Clutch Delay Valve

[akhbhaat]

The self-adjusting clutch is an annoying piece of unnecessary overengineering which has a tendency to fail prematurely and force an expensive clutch job early in the car's life. Its practical use is next to nothing. Tell me if you actually notice the engagement point moving one inch over the course of five years? It also ruins clutch feel.

In the 3 series, the SAC is accompanied by another monstrosity; the dual-mass flywheel. The dual-mass flywheel is essentially two flywheels strapped together (heavy) and mediated by a piece which allows a limited about of slip between the two...the whole deal is mated to a single solid hub clutch disc. The two "seperate" flywheels move slightly independently of one another in such a way that allows them to soak up engine vibrations...the end result is absolutely no chatter - and really shitty throttle response (especially when attempting to rev match).

With the laggy drive-by-wire (and I say laggy because over time it "adjusts" - completely unnecessarily - to your driving style, which means that a week of soft commuting means that the car has temporarily adjusted throttle inputs for soft driving - WHY?), that's just inexcusable.

When the completely unabused self-adjusting clutch in my E46 suddenly began to slip with a mere 38,000 miles on it (a good portion of that being highway mileage), I tossed out the whole damn thing (along with the god awful dual-mass flywheel) and installed an 8.5 lb aluminum flywheel from UUC with a non-self adjusting sprung hub E34 M5 clutch disc and pressure plate.

The result? World-class feel, grip, and engagement properties...with only a tiny bit of chatter which only really occurs after the car has been driven hard. Totally transformed how the car feels to drive. Truly awesome.

So awesome, that if I buy an E90, I'm going to be extremely tempted to rip out the POS stock setup right away (I couldn't STAND the featherweight clutch feel and vague engagement of the stock E90 clutch when I test drove it - almost made me want to buy automatic!) and put another LWF and E34 clutch in there.

[shimshimhada]

Originally Posted by E90Fleet

No, you are thinking of the Clutch Delay Valve

I thought that the SACs were equipped on cars with the CDV.

[E90Fleet]

Originally Posted by shimshimhada

I thought that the SACs were equipped on cars with the CDV.

2 totally different things that have nothing to do with each other.

Most european cars have SAC's but not all have CDV

[shimshimhada]

Originally Posted by E90Fleet

2 totally different things that have nothing to do with each other.

Most european cars have SAC's but not all have CDV

Do the M models have SACs?

[obLu]

I'm generally not a fan of self-automagical-do things for me-anything. Drive by wire in itself isn't bad, just don't massage the data ... let it go to the ECU raw and quit having it adjust to my driving "style". Not a big fan of dual mass flywheels either; haven't seen an older performance car yet with a dual mass that didn't need it replaced because it failed and resulted in an expensive clutch replacement.

SAC ... big whoop, why? Why does everything need to be automagical now? Where's the pratical upside? SAC doesn't produce the lighter clutch effort btw. What's wrong with the engagement point moving so that you know it's getting to be about time to replace it? Why does that need to be hidden from me until it just finally fails?

Rain sensing wipers, why? On the e90 they pretty much suck anyway, how hard is it to flick the wiper stalk? Automatic headlights? How hard is it to turn a switch once when I get in the car and once when I exit? Ooooh that's a real effort saver that one is.

Okay, I'll go take my metamusil now, eat some prunes and quit crabbing.

[E90Fleet]

Originally Posted by shimshimhada

Do the M models have SACs?

Yes




Another thing it does is help save the clutch from people who rest their foot on the lutch pedal.

[E90Fleet]

Originally Posted by obLu

I'm generally not a fan of self-automagical-do things for me-anything. Drive by wire in itself isn't bad, just don't massage the data ... let it go to the ECU raw and quit having it adjust to my driving "style". Not a big fan of dual mass flywheels either; haven't seen an older performance car yet with a dual mass that didn't need it replaced because it failed and resulted in an expensive clutch replacement.

SAC ... big whoop, why? Why does everything need to be automagical now? Where's the pratical upside? SAC doesn't produce the lighter clutch effort btw. What's wrong with the engagement point moving so that you know it's getting to be about time to replace it? Why does that need to be hidden from me until it just finally fails?

Rain sensing wipers, why? On the e90 they pretty much suck anyway, how hard is it to flick the wiper stalk? Automatic headlights? How hard is it to turn a switch once when I get in the car and once when I exit? Ooooh that's a real effort saver that one is.

Okay, I'll go take my metamusil now, eat some prunes and quit crabbing.

Remember a few years after SAC's were introduces ( yes they have been around a while) there was a article stating cars comming in for clutch repairs droped around 90% in Germany

If you dont like Rain Sensors or Auto headlights dont order the option or tell your local BMW importer not to put it on as standard. But may people want the toys

[akhbhaat]

Anybody know if the E90 has the dreaded CDV?

[Broken1]

Originally Posted by akhbhaat

Anybody know if the E90 has the dreaded CDV?

It does have a CDV...but for the life of me - I can't figure why poeple hate it so much. My shifts are butter smooth, and I've never had a problem. Maybe I just don't know any different

[rebelfocus]

Originally Posted by Broken1

It does have a CDV...but for the life of me - I can't figure why poeple hate it so much. My shifts are butter smooth, and I've never had a problem. Maybe I just don't know any different

Same here. I am majorly impressed with the clutch feel and smoothness of the gear changes (especially with a torquey diesel engine which is often the most difficult to get right).