What does the Sport Button do on the 997.2 GT3? On my previous 997 TT it worked through the ECU to increase boost pressure and also changed the sensitivity of the accelerator pedal; not sure what parameters changed but the car was noticeably jumpy. On the GT3 it appears that only the exhaust note is different - change in internal baffles; and Porsche claims better mid-range torque.

On a related topic, the exhaust system on the turbo was anemic whereas the GT3 is just about perfect especially in Sport Mode.

 

I believe it wakes up the exhaust and throttle response. Like a power button.

 

Would alter the engine parms to bring the Hp/Tq in a bit earlier on the RPM scale, also makes the throttle response.....well, more responsive. Basically does an alternate mapping in the ECU for you. (Will also stiffen the suspension, unless you push the button that looks like a shock absorber to just have the engine mgt working w/o the suspension). Also, as was said, opens up the exhaust.

I personally like driving with SPORT most of the time, accept possibly on a highway stretch to make it a tad less bumpy. (Not that its all that bad anyway)

 

Changing exhaust back pressure by changing baffle position in the exhaust system (probably lowering back pressure) would change both the location of the torque and therefore the hp curves, and also their magnitude even without remapping the ECU. You think they also remap the ECU which they probably do - wish I could find a technical or workshop manual to describe the details.

I know from prior experience in building an exhaust system for a 1960 Ferrari that you need a certain amount of back pressure to create torque - I had built wide open large diameter pipes that sounded great but the engine generated very little power; I then reduced the diameter significantly to increase back pressure and therefore increase torque (first lesson in tuning an exhaust). I suspect that Porsche has all the design software to optimize these variables; although the aftermarket guys can always find a way to improve (?) on the performance.

Like you, I drive mainly with the Sport button active except on the highway. Huge improvement over the 997 TT.

 

I believe youre spot-on...... The exhaust does not come full open until about 3700rpm because supposedly there is a hp/tq loss in the lower rpm range if left open. (Back to your backpressure item)..........which makes sense.

All-in-all it is purely amazing the hp they get from a 3.8L engine.

 

Supposedly Sport "on" also relaxes the reigns of PSM and TC, giving you a bit more freedom without turning them off completely. That's what I was told at Porsche Silverstone Experience centre and had a chance to experience the difference at their wet surface section.

 

It is true, PSM (since I don't have a 997.2 GT3, my car doesn't have TC and cannot comment on it) doesn't interfere so much with your driving anymore

 

It's interesting that the Sport button may reduce the interaction of the PSM - I wish that Porsche would publish more complete manuals for their cars. As an enthusiast I would like to know how everything works in much greater detail that what is supplied in the Owner's Manual. Unfortunately my dealer who is one of the largest in the Northeast U.S. is clueless on this type of information. Thanks for the feedback!

 

That is only the case on the Carrera models, not on the GT3.

AFAIK on the 997 MK2 GT3 it only alters the throttle response and makes sure the valves in the exhaust open from 4000rpm and approx 50mph onwards.

Since I have the Carnewal valve remote control the valves on my car are always open. I played with the Sports button and honestly I can't tell when it is on or not.

 

Here is an explanation for the Mk I. Not sure about Mk. II:

Sport off: idle - 4K RPM, the exhaust flows through all three mufflers. Above 4K RPM, the exhaust bypasses the two side mufflers and flows through the rear muffler only.

Sport on: at idle, the exhaust flows through rear muffler only. Above idle - 3K RPM, the exhaust flows through all three mufflers. Using light throttle from 3K - 4K RPM, the exhaust will continue to flow through all three mufflers. Apply moderate - heavy throttle above 3K RPM and the exhaust flows through the rear muffler only. Above 4K RPM, the exhaust flows through the rear muffler only.

Sport off/Sport on/Plug pulled: same sound over 4K RPM.

Sport off/Sport on: same sound 'just above idle' - 3K RPM.

Plug pulled: valves are open from idle - redline. The exhaust flows through rear muffler only. It is louder than either Sport-off/Sport-on in the 'above idle' - 3K RPM range. It's a purer sound.. no valves opening or closing, so no sudden changes in volume/tone. There is resonance/drone from 2K - 3K RPM, however.

 

What do you mean by "plug pulled" - pulling a relay that activates the values? My car is a Mk. II and it acts very similar to how you described your car. I also notice the slight drone probably from 2600 - 2800 RPM; I will pay attention but I think it's present in either mode. Car has to be fully warmed up to notice it, I noticed it today after a two hour drive whereas I had not noticed it prior - this is a new car to me after coming out of a 997 TT.

 

are we sure it alters throttle response?

 

I don't believe it alters throttle response, it probably effects torque as the back pressure through the exhaust is changed. On the standard Carrera and on the Turbo, it does alter the throttle response - at least that's my experience with these cars.

 

I tried to look up the Sport mode in the owner's manual,

It didn't mentioned anything about remapping the ECU or changing throttle response, at least not in the owner's manual.

In my experience, I indeed didn't realize the throttle response changes in my GT3 between the Sport mode On and Off. The only difference I could feel was the exhaust note was louder when the car was stop and when the rpm was above 4,000-ish.

On the other hand, when I drove my 997.1 C2S, it was very obvious that I could feel the throttle response was remapped between the Sport On and Off modes, because whenever I was in bumper-to-bumper traffic I would turn-off the Sport mode so to be easier to moderate my speed following the car in front of me.

Regards,

 

You don't need the backpressure really. You need to keep the velocity high and the backpressure low.
If you enlarge the diameter of the Ferrari exhaust pipes from 40mm to 50mm then the cross section increases from about 12.5 cm2 to 19.5cm2.
That is of over 50% !
It also means that the air speed inside the 50mm pipe is over 50% slower than the airspeed inside the 40mm pipe.
A slow airspeed has a negative impact on the scavenging effect so you'll loose hp / tq at low rpm.
The best exhaust is the one with the smallest pipe ( high velocity ) and the lowest backpressure.
Hope this helps and sorry for the OT.