Banter

I thought with turbocharger you get something for nothing - hence better mileage and more power.(and high maintenance)

As I understand the supercharger is driven by main shaft and add a little load to give you a little more power?

We had supercharger on a C series Benz and mileage was terible and it ran rough. Never liked it.

I may be completly wrong about this technology, but that is why I am asking.

Audiboy

You can't compare a small 4 cylinder turbo to a V6 mileage for example even though their power delivery is identical.

Although it's hard to argue that the supercharged 3.0 is worst than the 3.2 in gas mileage since they are almost identical.

In any case, I'm willing to believe the reason is packaging, reliability, concerns of aftermarket.
It's relatively straight forward to pack a supercharger on top of any V engine, and if running low boost, no need for extra intercooling hardware. Turbos require lots of space and plumbing. With the 2.7T on the S4's, they seem to break way before the warranty expired. This was expensive for the factory. The A6 and Alroad 2.7T's faired much better and it's probably due to better heat dissipation and owner's desire to mod (my theory). A supercharger is fairly reliable at least past the warranty period. Any turbo charged vehicle has software support to run the turbos past their efficiency range, and return them back to stock before a dealer visit. This drastically reduces their reliability, and often these cars end up at dealers for service or lease returns. Supercharges, since mechanical, need more work to increase power, and their bump is relatively conservative since the factory belt can only drive so much. Then with FSI, it really becomes a big challenge for tuners to mess up a good thing. So, they stay conservative. Anyway, that's my 2 cents.

Hokie_Audi

Doing the work on the intake charge requires that a certain amount of energy be extracted from the overall system. The penalty on an exhaust driven blower comes in the form of decreased breathing efficiency.

Banter

True, I have been doing more reading on this. A clutch driven mechanical supercharger can be more fuel efficent.

Still makes one wonder why BMW moved to Turbo charger in 5 Series and in case of Mini Cooper they dropped supercharger to Turbos?

gk1

Audi already stated they tried both turbo and supercharged V6 this time around for the S4/A6 and as others have indicated they chose the supercharger for reliability, packaging and throttle response.

From what I gather the parasitic loss of the modern supercharger is not so much to be concerned about. (Also from what I've see the Eaton TVS unit they have chosen is the most modern model available.)

Their ability to increase power 20% while simultaneously reducing fuel consumption and emissions is quite impressive. Could they have done this with turbos...probably...but as others have stated after the 2.7T warranty issues I'm sure they are shying away from gasoline multiple turbo motors in mainstream vehicles. Another option could have been an increase in displacement to allow for more power. I estimate they would need about 3.6-3.8L to get 300HP and would still come up short of the torque available in the 3.0T and I'm sure would suffer a mileage & emissions penalty.

The only puzzling part is why they did not simply make the A6 have the same 333+HP as the B8 S4? But perhaps that is more a marketing maneuver.

TVR1977

in terms of appreciable lag, etc, in my opinion the complications involved in heat management and high revving parts are hard to justify.

While superchargers do entail some parasitic power loss, it's probably not much more than turning on the a/c. Plus, the boost is completely linear since boost increases directly with increase in engine revs.

The technology is much simpler, too, as only the engines intake needs to be modified. Not involving the exhaust means no heat issues. Because of their (relative) simplicity, superchargers can be added to an existing engine design, while a turbo engine really needs to be purpose built.

Given the above, SC seems to be the way to go.

Dubliner

Just wondering whether future A6 3.0T owners can look forward to a mod upgrade to get the same specs as the B8 S4? Or maybe more?
Being able to modify is a selling factor!

gk1

Since the only way to force more air into the s/c engine is to spin the s/c faster with a smaller pulley/belt and even then there is a limit until you simply need a larger supercharger. (That will be the most interesting to see...Stage III B8 S4.)

Also IIRC a turbo car benefits more from an upgraded exhaust & downpipe... Bigger = better, but an exhaust upgrade on a supercharged motor might only be about as beneficial as on a NA motor.

Audiboy

your MBZ has a clutch. IIRC, Toyota might have used a clutch too on a previa. Haven't seen 3.0T yet

Audiboy

<ul><li><a href="https://forums.audiworld.com/fi/msgs/210.phtml">3.0T engine</a></li></ul>