S3 dirty inner pipes?!

[Itguy]

Morning all

ive only had my s3 less than a week but have started to notice that the inner two exhaust pipes seem to get a lot more sooty than the outer two.

Is this something to do with the exhaust flaps being open or shut or use of dynamic exhaust sound?

they're certainly going to take some constant cleaning to look good

 

[veeeight]

Yes, due to flaps, and Autosol is your answer

 

[Battlekrapz]

Autosol with ultra fine steel wool does the trick for inner tubes.

i also thought it was due to the flaps.

 

[J6YAK]

Morning all

ive only had my s3 less than a week but have started to notice that the inner two exhaust pipes seem to get a lot more sooty than the outer two.

Is this something to do with the exhaust flaps being open or shut or use of dynamic exhaust sound?

they're certainly going to take some constant cleaning to look good

I am cleaning mine every couple of days, it really annoys me when one is dirty and the other is clean, ah well just got to be done!!

 

[geefunk1978]

this is what you need!

 

[MA3RC]

Seal your exhausts with something like FK1000p, it'll help to stop the dirt sticking. You can literally just wipe them down and they'll be clean again

 

[CraigI]

Poor Boys

 

[Soulboy]

this is what you need!

View attachment 28933

I like that look. What have you done?

 

[Battlekrapz]

He changed his exhaust to a permentantly dirty one .

 

[geefunk1978]

Milltek black cerakote trims, look amazing and no worries about polishing!

 

[Toadoftoadhall]

If you read the latest Top Gear Magazine which includes a review of the new Golf R - it explains that the two inner pipes are used all the time and the outer pipes only come in to play above 2500rpm
With the Golf R being such a closely related cousin of the S3 this would explain what's happening. I notice exactly the same on on my new S3.

Other useful technical info in there that I haven't seen anywhere else about the S3 - includes that the haldex 4x4 system can shift up to 100% of power to front or back as needed.

 

[veeeight]

- includes that the haldex 4x4 system can shift up to 100% of power to front or back as needed.

Ahhhh. There's a bit of clever Haldex marketing speak in there, in reality you cannot have more that 50% of the drive going to the rear in a Haldex car.

You can have all the useful traction (100% at the rear) in some situations (eg: both front wheels on a skating rink, both rear wheels on Tarmac), but there will never be more than 50:50 drive split F:R.

More geeky explanation here:
http://www.audi-sport.net/vb/a3-s3-...3-how-much-power-rear-wheels.html#post2025194

 

[Spacemarine]

in reality you cannot have more that 50% of the drive going to the rear in a Haldex car.

What is the physical meaning of "drive"? You should not use this word, as it is not clear what it means. The clear words are "torque", "power", "speed", "force", etc.

If the Haldex is open, there is no torque delivered to the rear wheels.
If the Haldex in engaged, the speed of the front and rear wheels is the same (because they are connected). The amount of torque that goes to the rear wheels depends on the friction coefficient of the underground. But since the wheels are connected, you won't be able to spin the rear wheels without spinning the front wheels, even tough you can deliver 100% of the torque to the rear wheels.

 

[veeeight]

"Drive" means how the driveline is split, between front and rear.

50:50 out of the take off shaft out of the gearbox. Identical rotational speed, or drive, front axle/rear axle. Both "axles", "driven" the same.

You say that "torque" is clear, yet Haldex themselves muddy the waters by using "torque" in a specific (marketing) way.
See the other thread.

 

[Toadoftoadhall]

Thanks V8 - very good info and massively helps my understanding of the haldex quattro system in my S3

 

[Spacemarine]

Identical rotational speed, or drive, front axle/rear axle. Both "axles", "driven" the same.

So by drive you mean rotational speed? Ok, I'm with you on hat.

You say that "torque" is clear, yet Haldex themselves muddy the waters by using "torque" in a specific (marketing) way.
See the other thread.

I read the other thread. Basically he says "Haldex refer to "Torque" in marketing terms as "applied torque against a surface", rather than the more generic definition of Torque." However, he fails to explain, how it differs from the generic definition of torque and what the generic definition of torqe is (in his mind). Because as far as I can see it, the term "Torque" is used correctly by Audi. Torque in general is the tangential force times the distance of this force to a rotational center. If the rotational center is the center of the wheel and the force is the tangential force between the tire and the road, then the torqe is equal to the force that is transmitted from the tyre to the road. So I don't see any fault or misleading "markting" here.

 

[veeeight]

If you accept that Torque is the Force required to rotate an object about an axis -

then taking the example of your tyre above, whether its on ice, or on tarmac, that force is still being exerted or applied (by the engine/gearbox) on that wheel/tyre, regardless of whether its on ice, or tarmac.

Except in Haldex world, where they introduce the concept of "useful" torque - so if it grips (tarmac) - then the "useful" torque = 100%. If it slips (ice) - then the useful torque = 0%.

However, in pure terms, the engine/gearbox is still producing a force, about an axis, so even though the car is on ice, it's incorrect to state that there is zero torque.

I think it comes down to perspective, or frames of reference.

 

[Spacemarine]

If you accept that Torque is the Force required to rotate an object about an axis -

At least that is what every physicist and engineer agrees on. (I'm a physicist btw.)

that force is still being exerted or applied (by the engine/gearbox) on that wheel/tyre, regardless of whether its on ice, or tarmac.
[...]
However, in pure terms, the engine/gearbox is still producing a force, about an axis, so even though the car is on ice, it's incorrect to state that there is zero torque.

You are mistaken with these two statements. If the car is on ice, the torque of the engine will decrease. This is obvious because suddenly the engines speed increases, because suddenly the load is missing. On ice, you can get the same tyre-speed (slipping tyre of course) with much less throttle, because much less torque is needed for that kind of (tyre-)acceleration.

If the engine were to continue delivering the same amount of torque, even though you would suddenly drive onto ice, the engine would rev up until it hits the limiter.

 

[veeeight]

Except that the front "axle" and rear "axle" are coupled together,

So in Haldex example, front of the car on ice, rear of the car on tarmac, the torque exerted by the engine/gearbox on the front and rear "axles" will be identical (as they are coupled together).

So in this instance you would not get the reduction in torque.

 

[Spacemarine]

So in Haldex example, front of the car on ice, rear of the car on tarmac, the torque on both front and rear "axles" will be identical (as they are coupled together).

No, only the speed will be indentical, not the torque.

 

[veeeight]

There is only one engine/gearbox !

You're not suggesting (as Haldex do) that the front "axle" has zero torque !

 

[Spacemarine]

Did you even watch the video that you linked? If you didn't, please do. If you did, please watch again. It is very well explained there. The engaged halex acts like a locked differential in which the speed on both exits is the same, but the torqe depends on the underground.

You're not suggesting (as Haldex do) that the front "axle" has zero torque !

Yes I do, because that is what is actually happening. Please watch the video.

 

[veeeight]

I understand what you are trying to say.

All that you say about a car driving onto ice and getting a torque reduction and engine revs rising is true.

However that is not what we are discussing. We are discussing one rotational force, split evenly across two axles. And if you place different mu surfaces for both axles, you will not get the engine revs rising as you suggested for all 4 wheels in your post above (because the rear wheels are still gripping).

Front wheels on ice, rear wheels on tarmac, the front wheels will still be spinning, so there is still a rotational force being applied to the front wheels, therefore the torque being applied by the engine/gearbox cannot be zero, as Haldex claim. Something is turning those front wheels.

If there is zero torque on the front wheels, why are they spinning? There is still a force about a rotational axis going on !

 

[Spacemarine]

If there is zero torque on the front wheels, why are they spinning? There is still a force about a rotational axis going on !

You only need a torque to keep a wheel spinning if you have to compensate for friction or if you want to change the speed of the wheel. When there is no force that acts on the wheel, it will just keep spinning freely forever. (But I'm sure you know that, right? The is THE basic foundation of physics, the preservation of momentum!)

 

[veeeight]

Indeed.

The torque is not "zero", as Haldex claim !!

There will always be resistance, even in low mu surfaces such as ice !

 

[Spacemarine]

The torque is not "zero", as Haldex claim !!

Ok, so if you want to be very precise, it is not zero, that's true because there is always some friction. So the torque can not go 100% to the rear axle, maybe only 99.5% to the rear axle and 0.5% to the front axle to compensate for the omni-present friction.

But for all practical purposes, 99.5% can be regarded as 100%.

 

[veeeight]

Even that isn't the full story though, in the video example, the percentage torque that he demonstrated across a locked diff, was dependent on the load, mu, and force applied by the gearbox - not just frictional losses.

So while the marketing blurb that Haldex put out may say that 99% of the torque may be transmitted to the rear - in actual reality, when (in everyday road or track driving) are you ever going to find yourself with zero friction on the front wheels, while the back wheels are on tarmac?! In this instance, its a pure hypothetical marketing situation !

The "proper" quattro or Torsen 60/40 split is a much more useful tool !

 

[Spacemarine]

in actual reality, when are you ever going to find yourself with zero friction on the front wheels, while the back wheels are on tarmac?! In this instance, its a pure hypothetical marketing situation !

That is true, but it was YOU who brought up the ice that we have been discussing since 12 posts

The "proper" quattro or Torsen 60/40 split is a much more useful tool !

You have any evidence, that it actually brings any driving advantage? Like better handling? Or better times on a race track?

 

[Battlekrapz]

From dirty inner pipes to the physics behind quattro, what's next, quantum mechanics? . I'm sure itguy got more than he bargained for .

 

[veeeight]

That is true, but it was YOU who brought up the ice that we have been discussing since 12 posts

Actually, it was you who started it with the lack of misleading Haldex marketing in post #16,


Plenty of evidence out there of the advantages of the drivability of Torsen systems, especially in rallying. Especially over Haldex.

 

[veeeight]

From dirty inner pipes to the physics behind quattro, what's next, quantum mechanics? . I'm sure itguy got more than he bargained for .

Ha. Still, better than being judgemental about people with PP's

Or even discussing the difficulties of switching off start/stop !!!!!

 

[Itguy]