I tried but I could not find anywhere the information about RS4's horsepower when the S button is turned off. For example, the M5 has 400HP without the M button. With it has 507Hp. Does someone know how much horsepower the RS4 has in the normal (without the S) regime?

 

Sorry, but I doubt if there's any measurableHP diffy. All it does is quicken the throttle map and open the muffler flap.

 

which adds power...

 

I don't think it adds to total HP - just ramps up quicker.

 

from what i understand the S button has little or nothing to do with HP and more with fuel mapping and exhaust gas flow....thus making it a more responsive drive....which might be too jerky when just cruising around town slowly...so the give you the option.

 

With the S mode it engages the dual exhaust (aka "opens the flap"), switches the tune, and lowers the ride height. The reason they have the flap is to improve economy when driving normally, if you can drive an rs4 normally.Suspension lowers for better response and handing and the ecu changes from more response as well, not sure if there is really a HP gain but there could be, would make sense that there would be

 

The problem high performance manufacturers face is increasing problems with noise regulations. A 4.2 V8 should sound like a 4.2 V8 but this would upset all the rules and they'd never gget the car approved.

So the easy solution is to have an adjustable exhaust that under certain conditions (ie - the ones not covered by the noise police) bypasses the second stage of muffling hence giving a proper exhaust note.

The throttle response is just a feature of the the drive-by-wire throttle - by default the throttle is slightly non linear allowing (for example) the first 50% of pedal travel to only cover the first 30% engine throttle opening. This makes it much easy to drive normally and not have the car zooming off down the road with the slightest control input. However, 100% pedal is 100% throttle - so no difference in engine performance. I've no idea why BMW limit the output but suspect it is more to do with preserving engine life. On the BMW it reduces the rpmredlineand thereforereduces the maximum engine output when the "400bhp" mode is selected (the default).

Pressing the sport button simply changes these parameters - it (as far as I know) doesn't change the ride height but instead alters the damper settings and 4wd power distribution ever so slightly.

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The Sport Button does NOT have anything to do with ride height - the suspension of the car simply makes ride heightadjustment impossible without changing out the springs and/or dampers.

Regardless of the Sport setting, the caralways remains dual exhaust. The dual mufflers have oval-shaped tips, but inside those oval tips there are two outlets to each muffler, one contains the vacuum-operated butterfly valve (flap). With Sport on, theflap opens and allows exhaust to flow unrestricted from both outlets on each side of the car.

On a practical matter, I have about 6000 miles on my RS4. The first several thousand, I had the muffler flaps disabled (open at all times) and drove without Sport mode (off), For the second couple of thousand miles, I returned the flaps to operational and pushed the Sport button every time I started the car. Recently, I once again disabled the flaps (always open) and do not use the Sport Button. I can tell you, the care is far, fareasier to clutch/shift with SPORT OFF. So I'm convinced the best solution is to disable the flaps and drive with SPORT OFF. There's also some antidotal evidence that doing so reduces fuel dillution issues in the oil because of the "accelerator pump" effect of the quickened throttles in Sport Mode.

So, my advice is to disable the muffler flaps and "just say NO" to Sport Mode.



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Hey Elevens,question.

So I know your a "no go" on the S mode button, butwhat you are saying your preference is: keep the exhaust flaps open for "sound" & "flow" by using your technique and not engaging the S mode buttonfor mapping & response???

 

Exactly right. Mechanically defeat the exhaust muffler flap, thenleave Sport off.