clutch heat issues

B8 S4
#75

a camera would be a good investment on top of the charger.

I forgot how much did your battery weigh. and how is the clutch now that you got more miles on it.

#76

Clutch update

I haven’t had much time to drive the car. I’m still under 100 miles on the new clutch, but they’re hard city miles where driving 500 feet is 6 shifts.

The self adjusting clutch mechanism is pretty bizarre. Sometimes it moves the travel all the way to bottom of the pedal, like if I’ve been sitting at a traffic light. Then when I start driving it moves back to the normal spot. I’ve been in the habit of leaving the car in gear at a red light with the clutch pedal depressed, just to keep things normal. I wonder if I disconnect the clutch switch bypass if it will start acting normal again. Since I didn’t do the work, I don’t even know what to reconnect.

In spirited driving the car seems to do great. I can rev 1st gear all the way out, pop the clutch into 2nd, and it grabs like an on/off switch as I get back in the gas. If it works like this for an entire track session, I got what I paid for. Which is a motorsports clutch that acts a little wonky from a start in 1st gear.

But then a few minutes later everything goes to shit. The engagement point moves back to the bottom. The car is hard to get in gear. The clutch pedal travel is like air for the first 40%, then catches, then sticks at the bottom.

It looks somewhat ridiculous breaking this clutch in on city streets for hours, but there is so much weird shit going on in SF that I hardly stand out.

http://uploads.tapatalk-cdn.com/20160806/9cdf80de57cba8c6ff1335fc5c2e5491.jpg

#77

I wonder if I need a new clutch vacuum assist line.

[quote]There is a known problem on early delivery RS4s with the clutch vacuum assist line. This needs to be replaced. Basically the line is too week and colapses, pinching off the vacuum. One way to see if you have the problem safely is to place your transmission in neutral and depress the clutch petal twice rapidly in succession. If you have the problem, on the second press, the clutch petal will stiffen up and be almost impossible to press to the floor. But, any kind of change in clutch operation on the 2nd press is a problem.
[/quote]
It is back at the shop and we are going to try:

1/ reset hall switch to normal
2/ bleed slave line again

Any of you guys see anything else we should replace? Obviously we have done the master, the slave, the line in stainless steel, the throwout bearing, the pressure plate.

Maybe the actual over center spring on the pedal? I know the spring makes the clutch-in effort easier, but it also serves the function of returning the pedal.

http://www.jimellisaudiparts.com/showAssembly.aspx?ukey_assembly=746646

http://www.jimellisaudiparts.com/images/parts/Audi/fullsize/670721250.jpg

#78

Checking the vac assist line is a good place to start. Testing it wouldnt be a bad idea.

You can bleed the line and that might not be another bad thing to test.

#79

Does anyone have the vacuum system diagram for the B8?

What’s my worst case scenario with his job? Hook up the heavy duty clutch to the OEM dual mass flywheel?

#80

Looks like we have a brake (clutch) fluid leak. My guess would be the clutch master. If it’s in the bell housing I’m in trouble.

#81

That is worth looking into. a leak would obviously not be helpful.

The flywheel isnt going to change anything so I wouldnt go down that path.

#82

So maybe the slave cracked when I breaking it in. If so, replace here:

http://i64.tinypic.com/1zvyate.png

Here is the OEM clutch master:

http://i65.tinypic.com/qyclj7.png

The current wisdom is to modify it as such to move it closer to the firewall, so the hall switch bypass is not needed:

http://i66.tinypic.com/24l7whf.png

#83

That should put it a lot further in.

#84

This helps me reason about the problem better.

http://i63.tinypic.com/rjfggm.png

#85

I got confirmation it is indeed the slave cylinder that is leaking. So we are replacing the slave. Then we’ll pull apart the engine bay again, mod the clutch master so it inches forward, disconnect the hall switch grounding hack, and hopefully everything works normally again.

I don’t care if the slave cylinder becomes a consumable part. I’ll gladly replace it after every track weekend. I just want it to work while I’m out there.

#86

why would you do all that modding if a slave will fix it?

#87

Because it is dumb to leave the hall switch grounded and the finite state machine permanently confused. It injects wonky behavior. The reason the slave cylinder broke is because the clutch will only travel 70% of the way. Push it 75% and the slave sacrifices itself under massive force.

Fixing the master will allow full pedal travel as god intended.

#88

Clutch slave cylinder was replaced yesterday. Pedal feel is back to normal. Today they are doing the clutch master cylinder mod. The hope is that moving the cylinder’s top dead center 1cm closer to the firewall will allow the clutch pedal pivot to do the last 1" of travel (without resistance), and properly disengage the clutch safety switch. The caveat is the clutch return point might also move down 1", as we aren’t changing the amount of fluid displaced in the system.

If this works, all of the time I have invested on car forums will have paid back in one miracle of homebrew re-engineering to push these entry level lux german sedan platforms to peak performance.

Of course the original reason we pulled the clutch apart was to use a stronger friction disc and a stronger pressure plate, so it can withstand the full 25 minutes of track abuse. We haven’t cleared that hurdle yet.

I am testing at Sonoma Raceway (full course, not drag strip) on Thursday, August 25. In fact if anyone here actually wanted to meet up, I could probably swing the Sonoma drag strip on Wednesday August 24 in the evening.

http://www.sonomaraceway.com/track/wednesday_night_drags/

#89

Good for you west. keep us all posted. I would be interested in hearing how this plays out. This clutch switch issue seems to be a big one.

Sounds like you are checking off all the boxes here and should have all the little issues sorted out with the clutch system and a nice sporty clutch

#90

Hey, I’ve got a Black B8 6MT S4 myself and have about 7 days at Thunderhill under my belt – unfortunately on the last day someone’s GoPro fell off and then bounced off my hood at close to 100 mph on the front straight
Left a big indention and cracked the paint :’(

I’m wondering if I should just a get a CF hood like yours or maybe just buy your old one if you still have it?

I’m going to go to Sonoma for the first time September 10-11 and then again with the Golden Gate Audi Club in October

#91

SonnyDeez you are in luck. Contact my friend Cynthia at Classic Auto Body in Berkeley (510) 526-0310 to schedule an appointment with that hood. You should let them install it since they stored it for free and by some miracle did not discard it.

You can give me whatever it is worth to you. I should note it’s Phantom Black Metallic, not flat black.

#92

http://uploads.tapatalk-cdn.com/20160823/3d8deac0d10bdd506b6e55ccf573a2ac.jpg

Did the clutch master trim hack but the car still won’t start on its own without the hall bypass. So I’ll have to live with an EPC light - no chimes, no CEL.

#93

The car seems to run and drive well. Occasionally first gear is a little bit notchy but then it goes away. The pedal seems to travel a normal amount again. The real test is Thursday.

#94

The clutch did pretty well at the track today.

GOOD:

  • 4/3/2 downshifts are perfect
  • the clutch doesn’t stick on downshifts
  • it engages much faster
  • shifting is less “busy” in technical sections of the track
  • granny shifting is over for me

BAD:

  • 3 times the clutch wouldn’t grab 4th gear (and I have to try again)
  • I had to notch some gears rather than just “throwing”
  • the starter motor takes 2 tries to start the car
  • sometimes first gear is sorta hard to get into on the street after

Overall this is an improvement. The car has some new quirks that I can live with. I’m faster.