I looked at the pse schematic and it looks like the valves bypass mufflers. Wouldn't that decrease back pressure and increase horsepower. Porsche doesn't claim power increase What do you think?

I haven't noticed any power increase after the pse was installed on my base 991. Similarly, pushing the button hasn't produced any kick in the seat power increase feeling. But then again I don't have a heavy foot an am always impressed by the car's power.

 

Actually... if you look at first line in the left column (of attached) you'll see that it does improve torque ... which in my experience is almost impossible to do without seeing an increase in hp as well... they just don't specify how much.

But in the end it's physics/fluid dynamics and the increase of hp/torque derived from a less restrictive flow beyond the cats is always going to be a precarious balance between gain in hp vs. loss of torque and vise versa.
In order to balance the loss of pressure associated with the increased capacity to evacuate exhaust gases one also has to increase the supply of air intake and fuel...
The richer fuel settings are actually suplied curtousy of the sport+ dfi mapping but increasing the air-intake requires a higher flow filter.


Real changes are seen when switching to 200 cell cats however the significant drop in back pressure is said by Porsche engineers to cause a build up of carbon...

Hope that answered your question.

 

That is the diagram I reviewed and I did not know that the torque increase would yield hp increase. I took physics for liberal arts majors at Villanova 40 years ago and only remember that a cute girl sat near me.

 

Ha! I love the focus on what's important!

By the way, its good to know that little tidbit of info for when I get t the track in two weeks.

 

I think her younger sitter was sitting next to me!
That said my educational exposure to physics was limited to how it relates to Architecture... and those damn bra clasps!
I have however gained an awful lot of knowledge experience for my passion for customizing (motorbike, cars, boats, planes.. any and all big boy toys).

My physics comments was more based on the fact that from a physics point of view it does not make any sense that an after market system has those 25 HP gains derived from just creating a higher flow exhaust system compared to the zero gains always referred to with Porsche PSE.
Sure Porsche has the disadvantage that they have to abide by regulatory bodies inhibiting their free reign on dB and emissions (plus image constrictions) but because the PSE system utilizes highly complicated flow and patterns designed specifically to be integrated with the ECU, DFI, throttle mapping, etc I'm always skeptical...

That said I've designed my own exhaust system (for my 991 C4S) utilizing the PSE as a base but adding a set of valves and chambers while opening up/inter connecting existing ones... mind ya this additional work is purely to increase the pleasure derived from that incredible exhaust!

So perhaps someone with a physics/engineering background (who didn't have a hottie sitting next to him ) could jump in provide an alternative view but until then all you've got is this one... by a guy called "psycho"...
I know... not confidence inspiring!

 

I don't know if the PSE offers more power, but I do know for certain that when I hit the PSE button the car feels faster, better, cooler......

Oh, and while that cutie in my physics class would have loved it, my wife doesn't

 

I must have ended up with that cutie - and yes you are right, she does love it...
In fact - before mine was delivered, I talked more about it than she did. Now that we have had it for 6 or 7 weeks, she talks more about it than I do.
I find myself driving the Merc while she takes the Porsche to do some "urgent" groceries shopping. Heck, she has even NAMED it (no, don't ask, I'm embarrassed).

Rainier

 

It seems to say that it improves the torque curve, not the peak torque, which would explain why the car feels faster yet the quoted torque (which is always the peak torque) stays the same. Probably higher torque is accessible at lower RPMs. Would be interesting to see a dyno graph with the PSE on vs off.

Sorry Rainier, now you have to tell us the name!

 

My wife has named all her cars for as long as I can remember.

Her M6 is "Lola".

Her new 991S is "Stella".

 

See, I don't think I've ever named a car. I just silently approach it, smile, and get in. Anyway...the rationale that the torque curve is improved slightly while the peak remains the same sounds right to me. I would bet if you asked Porsche is peak hp is increased, they might give you an answer like +0-5 hp gain, depending on production variation.

 

Here's an explanation of torque v horsepower FWIW:

http://www.epi-eng.com/piston_engine...and_torque.htm

Link accessed 2013-2-11.

I found the examples below Figure 2 particularly interesting.

 

Yep, both the base and S torque curves are kind of lumpy without it.

ChuckJ

 

I do ?
Well, she reckons it looks like a frog (well, I can kinda see that).
When the car started up first, her comment was "Sounds more like a Bullfrog".
Jeremia is a Bullfrog. (Remember the song ?)
So now she calls the car "mia".

I wish to add in my defence that I call the car "Porsche" and have never uttered this name.

I told you you shouldn't have asked...

Rainier