AirtoMud

I own a 2015 S5 Coupe Prestige 6 speed maunual with an AWE S-FLO carbon intake, AWE Stage 2 tune w/ smaller pulley and AWE resonated touring exhaust. The car really moves! Several days ago, I changed the driving mode to Auto for the first time. In normal driving I didn't really notice much of a difference in performance but when I decided to "get on it" a few times, and even with normal Autobahn driving, I noticed the clutch slipping and noticed the burned clutch smell when I got out of the car. At first I was confused as to what was wrong with my car since it only has 22K miles on it. I don't seem to have this problem in either Comfort or Dynamic modes. Has anyone seen this before? Until I figure out a solution, besides never putting into Auto mode, I guess I'll just stick between the other two modes.
Just to answer any haters- Yes, I know how to drive a manual very well. Any answers would be great!

superswiss

Honestly, I don't see how the driving mode would make a difference here. The only relevant adjustment here is the throttle map. Comfort and Auto have the same throttle map, Dynamic has a more sporty throttle map. The most likely issue here is that you've got too much torque for the stock clutch. The stock clutch is a known weak part. It isn't made to withstand much more than stock power and torque.

You are learning the lessons of tuning. Once you start bumping up the engine power, the other parts start showing their limits. If you want a more powerful car, then do it right and beef up the rest of the car to keep up with the additional power.

Glisse

Pretty weird. Assuming the car is still not doing this in Dynamic mode nor Comfort mode, and only when cycling in Auto mode (where it simply cycles between the Comfort and Dynamic throttle maps as determined by sensor settings reported to the ECU), it can only be due to an ECU software problem relating to torque delivery.

With the S-tronic transmission, the ECU cuts (feathers is probably more correct) torque at the change point to limit stress on the clutch packs (there are two) and drive shafts. I don't know whether they do something similar with manual transmission cars. The ECU obviously knows when you are changing gear via clutch actuation and transmission shifts, but it can't know how long the shift will take. So I don't see how this could take place for manual cars. The main reason Audi do this with S tronic is because of the very fast upshift speed, 8ms, which creates significant static torque shock. I'm sure you drive a manual very well, but not with 8ms shifts

I would ask AWE if there is anything in their code that might be causing this.

It could be coincidental, as it is possible from the sound of your modifications that you are exceeding the torque rating for the OEM clutch pack, although I do not know what that is. You can buy heavy duty clutch kits for the B8 S4, which are rated to around 400ft-lb (standard engine is 325ft-lb) which are suitable for road use and the existing flywheel. Going higher is likely to require a new flywheel, and not be so pleasant to drive on the street.

Of course, if the car really is still fine in Dynamic or Comfort, maybe not worry about it until the clutch needs replacement? Which sounds like it may not be far away given your modifications and driving style. Brake replacements will also not be too far away, I would have thought.

I dislike Auto mode myself, and never use it. Good luck.

AirtoMud

Thanks for the info Superswiss. I didn't think there was a connection between the driving modes and the manual transmission but found it to be a strange coincidence. Again, I don't have any problem with comfort or dynamic modes... The car drives fine now. I agree with your statement about too much power/torque for some stock parts. I've tuned other cars in the past and have had to deal with them as well! LOL.

Do you have any recommendations for a good aftermarket clutch? How about expected cost to have it installed? The car sees mostly Autobahn miles and some city driving. I don't want this to be a track car. Thanks again for the reply!

AirtoMud

Thanks for the reply Glisse! It is weird... Any recommendations for parts/installation costs?

Glisse

I didn't realise you were in Germany, as when I saw AWE assumed you were in a US car. Possibly it is a US car, and you bought it over with you. That makes it a bit tougher.

Sachs make a heavy duty clutch kit for your car (engine code should be CGWC, but if 2015 S5 means US sales model year, don't use that. Europe uses production year), and lifts torque rating to around 550Nm (400ft-lb). As they say this is 15% higher than OEM (and there's a fair chance Sachs make the OEM clutch components), that suggests the OEM clutch is rated around 350ft-lbs:

Verstärkte Kupplung ZF Sachs Kupplung 3000950918 für Audi S4 (B8) - 3000950918

I doubt if the OEM part from Audi would be much cheaper. In the US, places like JHM and ECS sell heavy duty clutch kits. The prices for ~400ft-lb versions are higher than this ZF Sach's kit, which is including the 19% tax in Germany

The good news is that most cars sold in Europe are manual transmission cars. So every garage knows how to change a clutch, and order ZF Sachs parts. The bad news is nearly all these manuals are for the smaller engined, base model cars. You've probably noticed the cultural difference where Europeans associate manual transmissions with cheap cars, whilst Americans associate it with performance cars.

All the major Audi tuners in Germany base their development work on the assumption the car will be using a dual sequential gearbox or ZF8HP, not a manual. So you might have to hunt around a bit to find the right sort of shop to do the clutch work, and maybe Frankfurt has more options? I've never been to Wiesbaden, although given the size of the US military base there, I assume there must be some demand in the local area, or perhaps Frankfurt, for "specialty" car services? After market modifications in the EU require certification, and Germany is particularly strict. So some places may freak out when they see your car, and refuse to work on it.

Hopefully, the slipping was just an aberration relating to that particular scenario of temperature/torque delivery/hard driving, etc.

AirtoMud

Thanks for the info Glisse! It is a US spec car that was purchased in Germany. It cranks out just under 400ft-lbs with 93 octane, which I use 99.999% of the time, and just over 400ft-lbs on race fuel. Do you think I would be fine with the clutch you referenced or look for a slightly higher rated one? I don't drive the car very hard but like to know I can if the opportunity arises. I also don't want to have to address clutch issues often.

Thanks again!

Glisse

Well, I hope you are using 98RON in Europe, LOL!

The problem with higher rated clutches is they will become less pleasant to drive. As the clamping force goes up, so does pedal pressure. The higher the friction co-efficient of the plate material, the more the clutch becomes "grabby". Horrible in heavy traffic. And if you go too much higher in torque ratings, you will need to use a new flywheel, and they are expensive. Those systems are really intended for track driving, sustained use at high temperatures, etc. Not what you need.

I don't think your outputs are crazy - the 3.0TDI puts out about the same amount of torque. And you will be surrounded by B8 TDI's using MTM or ABT tunes with >450ft-lbs. The S tronic DL501 is rated at 439 ft-lbs (but it can manage torque delivery). Just the fairly rare manual transmission's clutch happens to have a lower torque rating than anything else in the drive train.

I think the Sachs heavy duty unit would be fine, and as I said, probably no more expensive than Audi's ~350ft-lb OEM clutch kit.

19hole

I'm sure you drive a manual very well, but not with 8ms shifts

There isn't a transmission out there that will shift in 8ms. The state of the art in dual clutch transmissions are those used in the current F1 cars and they still need 50ms to shift.

superswiss

Yeah I didn't think it was 8ms, but neither does F1 use dual clutch transmissions. F1 uses seamless gearboxes. They shift without a clutch. They cut ignition briefly while the dog rings disengage from one gear and bind to the next gear resulting in only 0.3ms of power interruption. The transmission has a single clutch that's operated manually via two buttons on the steering wheel and is only used to start and stop and in an emergency. The first button gets the clutch right to the bite point and the second button gives the driver fine control over engaging the clutch, so there is some driver skill involved in getting out of the hole. Dual clutch transmissions are prohibited by F1 regulations.