SMG Gearboxes

[_Nathan_]

Can you recommend a Cerametallic friction plate please?

I'm fitting a gearbox cooler to mine, the main issues I had were 5th to 4th downshifts crunching, not sure if that could be because I was changing down a bit early in the braking sequence and the SMG logic can't cope with the 4.1 final drive? Got an overrev to 8436rpm on one crunchy downshift.

[NZ_M3]

'The Gorilla' ... Steve never said what brand of clutch he's using - you are assuming that he uses a Sachs race clutch pack.

The factory OEM clutch kit is made by LuK, not Sachs - get your facts right

The self adjusting mechanism on the pressure plate doesn't change the distance that the clutch slave actuator moves when the clutch disc is worn - the adjustment is done via a spring mechanism internally of the friction contact plate, the fingers on the pressure plate moves the same distance throughout the life of the clutch pack. What changes is the take up point which is what the automatic adjusting mechanism is doing. And it is also what the clutch reinitialisation does when the car's hooked up to the GT1 - it reinitialises the take up point not the disengagement point - that is constant.

What you are saying is incorrect - as the disengement of the clutch is the same - so when the hydraulic shifts gears the clutch will always be disengaged. It is the take up that causes issue with aftermarket clutch packs (go and read the American forums, it has a detailed analysis on why high clamping pressure plates causes issues).

[The Gorilla]

Hi,

Hi- NZ_M3 - I do not agree with what the ''Americans' have to say
on this issue, sorry.

If I remember correctly you also dismissed the rear turret reinforcement
rings from the Z3, saying they would make no difference ?

The SAC Clutch is a bad design, go ask any E39 M5 owner or Forum
on SAC standard clutch which is the same poorly designed component.

The wear in the clutch is adjusted via a nylon strip within the SAC
pressure plate, so as to try and compensate for the wear in the disc.
This was designed to make the engagement travel of pressure plate
to clutch the same as the disc wears.

Of course as these two components wear and the SAC tries
to keep the distance bewteen disc and flywheen the same the
travel distance of the hydraulics increases as the disc is worn.

Once a slight mis-alignment starts to ocurr due to wear etc, then
the acctuators still function on pulse signal, inputs etc,
and the pump is told shift, it has no way to compensate for any
slight mis-alignment or wear 'ie slack' in the system.

On a manual car the SAC clutch adjustment when worn is
to a degree compensated by the driver inputs, and the shift
pattern to an extent can be altered to suit.

Shimmy- I do not think that re-programming the Gear box ECU/Software
would make much difference once the clutch has worn past a certain
point, go to the Hewland website explains a lot about gearboxes.

Nathan- The Sachs uprated Pressure Plate and the uprated Clutch
Disc used with Standard Dual Mass Flywheel have brought about
quite good results.
Some who use their cars for Track and Road run the Sachs Pressure plate
and the standard S54 Clutch Disc as a compromise.

NZ_M3- I do not think I assumed anything on Steve Gills clutch.

Regards,

The Gorilla.

[_Nathan_]

thanks.

My car isn't used on the road any more so happy to go with the uprated disk and pressure plate if you've used it with SMG without issue.

Don't suppose you know the part numbers? Sorry to be a pain.

[The Gorilla]

Hi,

Nathan- Sach Uprated Cover is 083082 999791
fits the std Dual Mass 240mm S54 Flywheel.

Make sure it is S54 as the S50/ B30/32 are also 240mm
but have a Pressure Cover bolt pattern that is not quite the same,
and do not fit the S54 Flywheel.

You will have to check with Sachs as I think they have
changed the Part numbers on the Discs ?

Their Organic Disc which is good for 570nm / 422 lb/ft
was part number- 891964 999978 and is a little better than
the std OEM BMW Clutch Disc.

As a note of interest a lot of the Diesel BMW's at 525cc and larger
run the same clutch disc as the M3 but with just a different centre
mount.

As the Diesels make far more Torque lower down the rev band,
its interesting the loads the standard OEM disc can take.

I run a Gearbox oil cooler, but much for the wear on the
Transmission components at higher temps,
than making the clutch operate better.

Regards,

The Gorilla.

[_Nathan_]

Thank you.

Did you weld seperate take offs for the pipes in to the box or adapt the filler hole and sump plug to accept return and pump feed respectively, trying to weigh up the best way of doing it versus trying to do it cheaply

[NZ_M3]

Originally Posted by The Gorilla

Hi,

Hi- NZ_M3 - I do not agree with what the ''Americans' have to say
on this issue, sorry.

Fair enough - I don't agree with everything they have to say about the M3s - but majority of them know more about the SMG system than you do I must say. But I'll entertain.

Originally Posted by The Gorilla

If I remember correctly you also dismissed the rear turret reinforcement
rings from the Z3, saying they would make no difference ?

And I still say they make no difference - a stress induced failure will take time - time will prove me right that if you run a full coilover setup on the rear of the E46 coupe chassis without a full cage or the likes to spread the load then it's only a matter of time before the rear shock tower tears itself apart.

Originally Posted by The Gorilla

The SAC Clutch is a bad design, go ask any E39 M5 owner or Forum
on SAC standard clutch which is the same poorly designed component.

I agree - I never said the Self Adjusting Clutch was a good design (made worse by the Clutch Delay valve that BMW insists on putting in their cars) - I am simply saying your technical explanation is incorrect ... the forums are for sharing information, and I am simply pointing out inaccuracies that you are putting across. For example your explanation below of how the Self Adjusting mechanism works - it couldn't be further from the truth

Originally Posted by The Gorilla

The wear in the clutch is adjusted via a nylon strip within the SAC
pressure plate, so as to try and compensate for the wear in the disc.
This was designed to make the engagement travel of pressure plate
to clutch the same as the disc wears.

The self adjusting mechanism works off a spring and ramp ring design - i.e. it rotates in or out to compensate for the wear:

Here it is directly from the manufacturer - as I said, the OEM clutch pack is made by LuK

Originally Posted by LuK SAC 1

Since clutches are subject to wear during use in the vehicle, LuK, as the first clutch manufacturer, put a great deal of effort into developing a type of wear compensation system for the clutch, and put it in production in 1995. The self-adjusting clutch SAC uses a load sensor (sensor-diaphragm spring) to activate its wear compensation by turning a ramp ring. This compensation mechanism has made it possible to decrease operating loads. The compensation for the clutch wear has also made it possible to increase the clutch service life by about 1.5 times without any significant change in the operating load over the service life. The wear adjustment system of the SAC – consisting of the sensor-diaphragm spring (load sensor) and the deep-drawn steel adjuster ring – is characterized by very high functional precision. Since a harmonic operating load curve is required in addition to comfortable clutch operation, the SAC was created with the capacity to be tuned to specific vehicle characteristic curves. One of the mechanisms that makes this possible is the compensation spring, which can generate the flatter characteristic curves that are frequently desired.
The newly developed SAC II.

provides a further optimization of the system. Here, the load sensor is not comprised of a second diaphragm spring, but rather of the sensor fingers formed from the main diaphragm spring and special tangential leaf springs with a decreasing characteristic curve.

Originally Posted by The Gorilla

Of course as these two components wear and the SAC tries
to keep the distance bewteen disc and flywheen the same the
travel distance of the hydraulics increases as the disc is worn.

Once a slight mis-alignment starts to ocurr due to wear etc, then
the acctuators still function on pulse signal, inputs etc,
and the pump is told shift, it has no way to compensate for any
slight mis-alignment or wear 'ie slack' in the system.

On a manual car the SAC clutch adjustment when worn is
to a degree compensated by the driver inputs, and the shift
pattern to an extent can be altered to suit.

Wrong again .... If what you are saying is true, then as the clutch disc wears the distance required to 'disengage' (or open) the clutch should be shorter (i.e. it takes less pedal travel to disengage the clutch as there's less material between the pressure plate ring and the flywheel due to the clutch plate wearing down). The opposite would be true when closing the clutch or engaging the clutch as there's a larger space for take up - that is why when clutch wears out the clutch pedal take up point (or bite point) is higher in a traditional 3 pedal manual car.

I can assure you that the hydraulic clutch slave actuator pushes the clutch in (to disengage) the same distance everytime through out the whole life of the clutch - the software initialisation only adjusts the take up point (i.e. to engage the clutch) ...

Here directly from the SMG training manual:

Originally Posted by SMG training manual

The Clutch Slave Cylinder is an innovative and new feature of the SMG II. The component consists of a slave cylinder with an integrated sensor housing. The sensor termed PLCD (Permanent Linear Countactless Displacement) measure clutch release travel

Originally Posted by The Gorilla

Shimmy- I do not think that re-programming the Gear box ECU/Software
would make much difference once the clutch has worn past a certain
point, go to the Hewland website explains a lot about gearboxes.

Again wrong as above.


I am aware that Sachs has brought out a new clutch pack that works on both manual and SMG vehicles - I've yet to try it or read the specs on it - but my suspicion is that it has an uprated friction plate rather than an increased pressure plate clamping force. But I'll need to read the specs to be sure.

[The Gorilla]

Hi,

Nathan- on the Gearbox oil cooler in and out feeds
I used the bottom drain plug for the feed out,
and the side plug for the return.

Banjo fitting for feed out, with the lug cut down to
keep the fitting as close to the box as possible,
and a new blanking bush for the side, with a Goodridge alloy T
so that I could run my Gearbox temp sensor as well.

NZ_M3- Your entitled to your views and opinions, but please
read and understand what I have said.

By the way I beleive the manufactures of the Titanic said it
was, quote, '' Unsinkable''.

Regards,

The Gorilla.

[shimmy]

dear Gorilla and NZ_M3

i do find both of your threads and posts very interesting and full of technical info that most of us here, and tbh most of the BMW specialists we know would not understand

however you both seem to constantly disagree with each others techinical opinions on nearly every subject even subjects that can only have one answer

now i am not a mechanic or even a person with car knowledge more than a few skils like changing brake pads and wheels and occassionally a disc or two, but i am qualified as a Project Manager and understand when i am being fed bullshit on a monumental scale.

So for my peace of mind and so i get some sleep without worrying if my rear turret is gonna split or if my chassis is gonna twist or if my gearbox and clutch is gonna piss itself all over the floor can which ever one of you that is guessing (note my careful choice of words) please stop and let the other tell us the truth!

[_Nathan_]

Thanks very much - that was the answer I was hoping for (as it doesn't involve too much labour!).