S4 DSG Clutches

[SilverRings]

I've noticed the Audi S4 DSG clutches. They engage at low speed, when doing a rolling stop and back on throttle. I can feel them in use at higher speeds to, for a split sec here and there. Since these are clutches in the transmission, they are wear parts, right? In DSGs, do those have to be replaced at all, like a normal clutch? Do we have guys with high mileage 100k + miles without anything happening to them?

[Reckon]

I believe they are wet clutch systems so like any other 'automatic' its mostly the transmission fluid change that is required. If the clutches go bad, you are probably looking at a full replacement.

[bronz]

http://www.uspmotorsports.com/Drivet...h-Package.html

[Chris Furman]

I've noticed the Audi S4 DSG clutches. They engage at low speed, when doing a rolling stop and back on throttle. I can feel them in use at higher speeds to, for a split sec here and there. Since these are clutches in the transmission, they are wear parts, right? In DSGs, do those have to be replaced at all, like a normal clutch? Do we have guys with high mileage 100k + miles without anything happening to them?

It's a Wet Clutch system, it should never have to be replaced.

Only reason if they ever get replaced is:

1. if you start tracking the car and driving it around recklessly for most of the car's life.
2. Tune the car for massive HP / TQ gains and are abusing it.

[rgiles675]

http://www.uspmotorsports.com/Drivet...h-Package.html

And that just happened.

[chaos2984]

http://www.uspmotorsports.com/Drivet...h-Package.html

That price is such a rip off. those things should cost like 500 max. They are standard normal automatic trans clutch discs. Just the size and material change. unless that material is like carbon ceramic or something dumb expensive that price is just a rip off. There is nothing special about the design just the clutch material is all.

[S4'ed]

The DSG clutches do eventually wear-out.....

[mr shickadance]

The DSG clutches do eventually wear-out.....

eventually, but the system itself is designed that you (the car) are always rev-matching when switching gears.

over time, they will wear out, but at an incredibly slow rate given they match trans speed with engine speed near-perfectly.

[rtl5009]

^not on upshifts

[mr shickadance]

it was my understanding it's both sides of the euqaution, ups and downs

[rtl5009]

How can it rev match on an upshift? Explain.

[mr shickadance]

the same way you match on an upshift.

for example, engine and transmission are turning at 4,000 rpm

Car upshifts into 4th gear

Currently, engine speed does not match transmission speed, engine speed needs to decrease to match transmission speed.

Engine speed decreases to 3500 in order to match 4th gear transmission speed of 3500.

Once engine speed matches transmission speed, the car engages

Instead of a blip of throttle, it's no throttle.

Maybe I explained it poorly, but essentially all rev-matching is matching engine speed to transmission speed, whether that;s higher or lower is meaningless.

[mr shickadance]

more easily explained (pulled from he internet):
There is an input shaft for each clutch. Which ever gear is in use, the other input shaft is already configured for the next gear, depending on throttle input. When you signal the gear change, the transmission just applies the other clutch. Since the clutches are hydraulic, and the transmission is already in gear, the actual shift can be done very quickly.

[rtl5009]

The revs cannot decelerate as fast as the dsg shifts. It can slow shifts to match revs, but it doesn't. It shifts extremely fast. The second clutch slips during this time frame. It's the only way to slow the spinning mass in the time allotted. Revs can only fall as fast as inertia will let them. Put you car in neutral and that shows how fast revs will decelerate.

[chaos2984]

Umm first off the clutch does not rev match at all. The rev match is for the syncro's on the gears not the clutch. Plus there is no rev match going on anyways. The ecu in the trans shift the shift fork when there is no load on that gear. the even gears are on one stack and the odd gears are on another. There is really no load or rev matching going on when shifting gears. The clutch swap happens just about instantly. All it does is release pressure off one clutch and apply pressure to the other one. Its all computer controlled.

The computer takes into what is going on with the trans and engine and predicts what your going to want to have happen.

[amz]

[skiracerblah]

Which is why i drive the car in Manual Mode in bumper to bumper traffic so the tranny doesn't have to shift as often...

[mr shickadance]

The revs cannot decelerate as fast as the dsg shifts. It can slow shifts to match revs, but it doesn't. It shifts extremely fast. The second clutch slips during this time frame. It's the only way to slow the spinning mass in the time allotted. Revs can only fall as fast as inertia will let them. Put you car in neutral and that shows how fast revs will decelerate.

Most cars have built in tech in the ECU that let the revs fall artificially slowly, they can decelerate faster than you think.

[skiptowncat]

I thought the ecu slashed timing and fuel to bring the revs down quickly to make it seamless.

[sebgreen]

I don't think the S4 is a wet clutch system is it?


Sent from my iPhone using Tapatalk

[rtl5009]

Most cars have built in tech in the ECU that let the revs fall artificially slowly, they can decelerate faster than you think.

That statement is 100% false for the B8 S4

[wwhan]

I don't think the S4 is a wet clutch system is it? ....

Yes, the S4 DSG is a wet clutch.

http://www.audizine.com/forum/showth...=1#post5122523

[wwhan]

Audi New Technology 2009 – 2010, Self-Study Program 990193, see page Body20 of the PDF for the DSG:

http://www.google.com/url?sa=t&rct=j...06130839,d.cGc

[BernanksBeard]

Correct me if I'm wrong, but I understood a wet clutch uses special friction oil. And the oil is what wears out, or becomes saturated with debris and is no longer able to keep the plates clean. A well maintained dual clutch trans should not need the clutch plates replaced for the life of the trans. But if neglected, the clutches will slip much more and eventually wear out from dirty clutch plates not making perfect contact with each other, heat and stress.

Dirt bikes and motorcycles use wet clutches. Though I remember my friends replacing the clutches often on their dirt bikes... So not sure how long it would take to wear out the plates in a well maintained DCT trans...

[beckmaster]

AMZ,

Thanks for the video. I love learning new things about my car.

[wwhan]

Correct me if I'm wrong, but I understood a wet clutch uses special friction oil. And the oil is what wears out, or becomes saturated with debris and is no longer able to keep the plates clean. A well maintained dual clutch trans should not need the clutch plates replaced for the life of the trans. But if neglected, the clutches will slip much more and eventually wear out from dirty clutch plates not making perfect contact with each other, heat and stress.

Dirt bikes and motorcycles use wet clutches. Though I remember my friends replacing the clutches often on their dirt bikes... So not sure how long it would take to wear out the plates in a well maintained DCT trans...

The DSG special ATF should be replaced every 35k miles, according to the current Audi maintenance schedule.

[Luna's S4]

AMZ,

Thanks for the video. I love learning new things about my car.

Agree. I feel smarter. Thanks.

[Acejam]

The revs cannot decelerate as fast as the dsg shifts. It can slow shifts to match revs, but it doesn't. It shifts extremely fast. The second clutch slips during this time frame. It's the only way to slow the spinning mass in the time allotted. Revs can only fall as fast as inertia will let them. Put you car in neutral and that shows how fast revs will decelerate.

They can come close. Ever heard that fart noise on DSG cars when shifting at WOT? That's the ECU retarding timing, causing a small bit of fuel to dump, which results in RPM's dropping quicker and a small popping noise.

[Luna's S4]

They can come close. Ever heard that fart noise on DSG cars when shifting at WOT? That's the ECU retarding timing, causing a small bit of fuel to dump, which results in RPM's dropping quicker and a small popping noise.

Yeah, it's matching. Or close. And can exacerbate it by applying stupid throttle prior/during shift if not at WOT.

[mr shickadance]

That statement is 100% false for the B8 S4

it's true for every manual car ever.

try it yourself, drive along, and clutch-in, the revs will hold for a little bit, and slowly come down.

the engine can drop much faster than that.

Also, why are you so hostile about this, most posts here are showing you information that contradicts what your saying.

[amz]

AMZ,

Thanks for the video. I love learning new things about my car.

Agree. I feel smarter. Thanks.

NP guys. Engineering Explained is a pretty good Youtube series about cars. He puts videos up every Wednesday, I usually watch them Thursday mornings while eating breakfast. While most of his videos are accurate and pretty well done, don't watch his review of the S4...he completely misses a bunch of stuff lol. His technical stuff though is really good and easy to consume.

[rtl5009]

it's true for every manual car ever.

try it yourself, drive along, and clutch-in, the revs will hold for a little bit, and slowly come down.

the engine can drop much faster than that.

Also, why are you so hostile about this, most posts here are showing you information that contradicts what your saying.

Once the injectors shut off, the motor is working against the compression it is generating. That and what friction is present is the only things that slow the motor. Fuel injection was the last great invention here.

I'm being "hostile" cause you have no idea what you are talking about.

[mr shickadance]

Once the injectors shut off, the motor is working against the compression it is generating. That and what friction is present is the only things that slow the motor. Fuel injection was the last great invention here.

I'm being "hostile" cause you have no idea what you are talking about.

please google 'rev hang'

[damnbiker]

Back to DSG clutches: Has anyone noticed a slight slipping when going from off throttle to 75%+ throttle? I just got the APR stg2 ECU update and DSG tune and started noticing this a week after. Most apparent in 4th or 5th gear manual mode coasting along around 60mph, then floor it. The revs would jump up by about 100-200rpm, then come back down in about 1 second. You can see the tach move as well as hear it in the exhaust.

Almost like the engine torque overwhelms the clutches for a split second before the transmission realizes it needs to apply more pressure?

All manual cars I've driven (and before the DSG flash) the revs don't jump around unless you are riding the clutch pedal or something.

[mr shickadance]

prolly an issue with your DSG flash more than anything. Problem occurred after flash? if the engine is revving higher, but you are not moving any faster I would imagine the TCU is getting confused and doing something fucky with your clutches, them not holding would not likely be an issue, it's not an insane increase of power

[rtl5009]

please google 'rev hang'

That has nothing to do with rev matching upshift. You cannot rev match an upshift, the clutch slips matching revs. It is the only way to match an up shift as quick as possible, without a brake on the flywheel.

[mr shickadance]

^not true.

you can decelerate an engine much quicker than you think you can.