TT-S4

Yes, that is part of my plan to better understand what is going on.
How a particular person responds to certain vibrations is definitely subjective.
For me, I've always hated steering wheel vibration, it just bothers me as I'm very sensitive to it.

I recall from my other S4 test drives that I did not notice the differences in idle speed going from D to S mode.
But, it's possible I didn't notice because there wasn't much or any noticeable difference in those S4s.
Even with my S4 I didn't fully notice the idle increase in S mode until I had my S4 for about 2 months.

I've also read that Audi tweaked the AT software, and thus operation of the AT, for the 2019 model year S4s.
If that is true I will contact Audi and demand that software, if indeed it improves the AT's performance.
For that I also need to start with some test drives of 2019 S4s.

The best scenario would be if there is something that could be fixed.
I would even like it if an Audi tech could simply cancel out the idle RPM increase in S mode, that would be the best for what I would like.
I have no use for an increased idle speed in a car with a torque converter AT.
In the A4 with the DSG the same idle increase happens with the same roughly 200rpm.
But in that model it works well as the actual clutch is decoupled from the engine at idle.

Audi could have easily adjusted the throttle trim response in S trans mode, so that the off idle response is a touch quicker, yet still retain the smoother low idle rpm.
The increase in idle speed in S mode with this type of AT is effectively pointless, and worse, it's a waste of gas.
I have felt NO increase in any performance parameter from this idle increase.
I've also been searching the web trying to find some technical explanation as to why Audi did this, and for what effect and use.
If you find or have found something, please let me know.

jlarke

FWIW, I was stopped at a light in my 2019 S4 and changed my drive mode from auto to dynamic, which also put the transmission into S. The extra rpm were not perceptible through the steering wheel.

jondin2000

I agree 100% it makes no sense why Audi did that....i just can't see any benefits from such high RPM. On top of that this car feels so uncomfortable and rough to drive it in S mode all the time.

mplsbrian

Glisse

Because it is a B-cycle engine.

TT-S4

No difference in any exhaust mode.
Thanks for the suggestion.

TT-S4

Please explain what you mean by that.

The B-cycle is a modified "Miller cycle".
The B-cycle, "Budack cycle" closes the intake valves sooner than Miller cycle, before the completion of the intake stroke.
This allows a higher compression ratio without altering piston stroke. It's an excellent idea and increases engine efficiency, by increasing power without the need to burn more fuel for the increase.

Given that tuning, I still do not see a benefit to increasing the idle speed in relation to changing the trans operation mode.
If an increased idle is beneficial to running B-cycle, then it would benefit the efficiency in all trans modes.

Perhaps I am missing something, which could very well be the case.
What benefit is there to increasing idle rpm due to going to a "sport" setting on an Auto trans due to a B-cycle engine?

Glisse

The increased idle is a benefit when not running in B-cycle, as there would be a torque hole below 1350rpm. When in S mode, the transition from 900rpm to boost (1350rpm) takes milliseconds. The benefit of the B-cycle is that it lifts engine torque below boost, and Audi is leveraging this in D mode so that the car spends as much time as possible with the engine running off boost. This is, of course, primarily to provide the lowest possible emissions, and consumption numbers during test cycles. And of course, the other obvious benefit is that the engine can also operate in Otto cycle. Just to be clear, neither B, Miller nor Atkinson cycles "increase" power - their benefits is that they can increase efficiency of the fuel burn at partial loads. They all lose power (as in bhp/kW etc) vs the Otto cycle.

The irony is that much of the emission/fuel consumption (in the case of carbon dioxide, these two are intrinsically linked) certification numbers listed for the car are based on being driven in B-cycle mode. But the power / torque / performance numbers are when the car is being driven in Otto cycle mode. Or D mode and S mode respectively, depending on throttle inputs. The switching between the cycles, which is enabled by the variable valve timing system and the direct injection control system is based on both engine load and engine speed, and who knows how Audi are programming this - they certainly don't talk about it, nor is it obvious in any of the patents. Speaking of which, a number of patents have also been filed at the US patents office by Audi AG relating to teams involving Dr. Budack, who himself is / was (after last year's VAG upheaval, many Audi engineers are gone / repurposed) a long standing employee at Audi's Ingolstadt engineering base. Virtually all the patents and media coverage relate to the first B-cycle engine produced, which was the EA888 Type3-B 2 litre 4 cylinder engine. But you seem interested, and you can see many of the patents here:

https://patents.justia.com/inventor/ralf-budack

But I was just responding to your comment as to why there is a higher idle speed in S mode. None of this really helps address your vibration issue. And whilst there is obviously an increase in sound at the higher idle speed, like all the others that have posted (and your earlier experiences), I have never encountered the level of vibration you have described and I have driven at least 5 different cars with this engine, as well as owning two of them. And given this vibration issue seems very specific to a 900rpm idle speed, and not experienced in any other conditions, it seems to be some sort of harmonic resonance. It may be a calibration issue with the transmission. As a left field suggestion, try pulling the fuse on the Soundaktor, your manual will show the fuse position, and there is no harm from taking out the fuse and disabling the Soundaktor. Unlike BMW, who pipe engine sounds through the speaker system, Audi use a vibration device which is positioned just below the windscreen. This may be causing the issue you describe. Good luck.

As an aside, the BMW N55/B58/whatever inline 6 cylinder engine with the ZF8HP is one of the sweetest combinations of engine / transmissions around. In my opinion, the most attractive feature of the F3x series. But the ZF8HP is a modular design and there are many different versions. The BMWF3x use a ZF8HP-45, whilst the B9 S4 is using a ZF8HP-55. But within the model series, there are many variants. IIRC, an F3x RWD uses a different version than is used in xDrive. The model used in the B9 S4 is specifically designed for the self-locking centre differential that is attached at the rear of the transmission. You aren't comparing an apple to an apple.

Audi have been using the ZF8HP series for as long as BMW, just not as ubiquitously. The C7 RS6 / RS7 used a ZF8HP-90, the transmission the new M5 has just moved to. As I have posted elsewhere, Audi now only want to use self-locking centre diff quattro with the ZF8HP. The new C8 A6 and A7 being release in the US are using the EA838 you have, but with a dual sequential S tronic transmission. And quattro Ultra. If you have a good relationship with your Audi dealer, try and get a test drive just out of interest.

The behaviour with the ZF8HP in the B9 is a deliberate programming choice by Audi, and it is to deliver optimum certification numbers in Euro 6 / 6D. If you read a bit more broadly than just local media, you will see that there are issues appearing with all new Audi that have been certified against the new (Sept last year) WLTP, which most of the world are adopting. This is being mentioned both in reviews and in forums. There is a very large thread in one of the German forums outraged at what Audi has done with the 3.0TDI engine used in the new C8 models (the EA838, as used in the S4 is not yet certified, and was pulled early last year) - post certification for Euro 6D-temp (Sept last year), Audi have made a huge torque cut to this engine below 2000rpm - which also uses the ZF8HP and "real" quattro, in D mode. Sound familiar? I would say out of all the people in that 44 page thread who had test driven the car anecdotally 25% indicated they would still buy the Audi, 25% the BMW 5 series, and 50% the Mercedes E class, in terms of 6 cylinder diesel engines. Given this was a specific 8 A6 forum, that is atrocious.

Audi are panicking to reduce their fleet certification averages, and seem to be making some very poor engineering decisions in terms of throwing out driving dynamics in the process. But then, many of their engineers are gone. Either out the building or working on EV. And in management terms, they are acting like a headless chicken. Building a car that is horrible to drive to bring down your fleet emissions average is more likely to just reduce the size of your fleet, but the people making these decisions are more arrogant than they are smart!

Rather than hope for a 2019 S4 with anything other than a few trim or colour changes to signify a new "model year" for the benefit of dealers, what you should hope for given your general concerns is that Audi reverse engineer cars for the US market. Which is suddenly more important to Audi AG than it has been before. I don't think they will though, more likely to see engines and drivetrains "frozen" with older versions, as they did with the Q7 in the US. Given the latest versions appearing from the factory, you should be thankful.

I like my B9 models, but then I never drove my earlier Audis in D mode either