perfect, i will let dave know.

 

I don't think the AH mufflers are different here - it's more to do with the difference between the standard 'S' and 'non-S' mufflers. You are absolutely right that on a 997S, 'straight-through' mufflers/resonators don't make much (if any) power by themselves as the standard 'S' cans are quite free-flowing. The story is different for a non-S 3.6 however. IIRC, the internal design of the 3.6 muffler is completely different (and more restrictive) than the 'S' design. Replacing the mufflers on a non-S 997 (or 3.6 996 for that matter) with a good aftermarket design has always been good for 10BHP or so.

It would be interesting to see if the 3.6 benefitted from fitting standard 'S' mufflers (and tips, they're bigger diameter and will flow better). As the 'S' muffler/tip combo is more free flowing, there's no reason why a 3.6 shouldn't pick up some power from doing this. And there are hundreds of standard 'S' mufflers lying around and available for almost zero money.... Anyone like to try this?

 

Ian,

You brought up a good point here.

 

Possibly, but it's highly speculative IMO until someone dynos it. Remember, folks are putting on hacked stock cans and PSE mufflers and not picking up any noted gains. I also think too, if doing this did provide an inexpensive performance gain there would be tons of posts on the "swap 997 for 997S muffler mod" topic, but I don't see mention of it anywhere (and the 997S cans would be going for a lot more $$ on the used market!).

I've seen the inside of a 997 muffler (but not an S muffler), and the AH muffler design is clearly visible from the outside- They seem completely different to my eyes, AH is completely straight through and factory is chambered with offset inlet / exit pipes. Can you explain to me how they are the same? I'm just trying to understand your comparative perspective.

Overall I think there is some good logic to your point, if non-S and S mufflers are indeed different internally, one would think that putting S mufflers on a non-S car would show improvement.

 

I'm pretty sure the part numbers for S and non-S mufflers are identical.

Actually, this was not true.

here are the part numbers:

997 - 997.111.221.03 and 997.111.222.03
997 S - 997.111.421.04 and 997.111.422.04

 

Gundo- from one obervation the non-S muffler exit pipe is "squashed" narrower at the end than the S exit pipe. So that would probably warrant a different part number.
I'll always be scratching my head why Porsche did that??

 

So here are the latest results from todays dyno run-

1st run was with stock mufflers, kn intake and no rss plenum.
2nd and 3rd runs were with AfterHours mufflers, kn intake and no rss plenum.
I wanted to see what additional gains the plenum was giving me at the previous dyno testing. It is clear to see that the plenum does indeed improve performance numbers.

My stock muffler run was 257 TQ and 296 HP without the plenum.
My stock muffler run was 273 TQ / 313 HP with the plenum.
-So a net gain of 15 TQ / 17 HP at the wheels with the plenum, stock mufflers and kn intake, not too bad for just a couple of minor mods.

In both dyno sessions (with and without the plenum installed) the AH exhaust added an average 11 TQ / 11 HP additional gain over the stock mufflers.
With the plenum and the AH pipes together, I estimate a total avg. gain of 26 TQ / 28 HP.
So this confirms my feeling that the car feels much stronger overall with both of these mods.
This is my best attempt at trying to accurately document everything, which I hope helps others who are considering either of these parts for their pcar.

BTW I got pulled over today on the way back from the dyno.... by some guy in a minivan wildly waving me down. Turns out he has a 997 and wanted to know where I got my exhaust because it sounded so awesome!! LOL how is that??

Todays dyno chart (no RSS plenum installed):




Last weeks dyno runs (with RSS plenum):

 

guys there is no difference between non s and 's' mufflers internally. The only difference is the tip of the mufflers where the tips are attached. They are a different size so that you can not interchange the tips without some modification to keep the 2 models distinct from one another.

 

Sorry if I didn't make my point as clearly as I should. The point I was trying to make wasn't about 'S' mufflers vs AH - my comments on the possibilitiy of the 'S' muffler giving an increase was just an afterthought! The point I was making was that the gains shown by the AH mufflers aren't different from other straight-through, aftermarket designs. It's down to the fact that the 3.6 seems to benefit well from the fitment of straight-through mufflers, in a way that the 3.8 doesn't. Most straight-through designs give around 10BHP on the 3.6. The added adantage of the AH seems to be very light weight. I would doubt the AH will give as much of an improvement on an 'S', just as other aftermarket mufflers don't.

 

Hi Ian- Good points indeed. All I honestly know so far is data from this product on my car. What is overall of note to me is the gain in both TQ and HP, not just HP alone. For a muffler swap alone it does seem better than expected.
I don't know of any other straight-through designs for 997 to compare. When I was shopping around, M&K and Jubily/Zero Int'l make a similar system but only for 996 (AFAIK).
Can you post up some mfr info on the other 997 straight-through systems you are aware of?

I'd love to see some dyno numbers from an S for comparison, could very well be less of a gain since the 3.8 is fairly optimized as-is. I guess we'll have to wait until someone out there with an S + AH pipes throws their car on the dyno.

 

If it's a straight through design, why not save a few bucks and go with a muffler bypass? I would guess the sound is very similar.

 

Not from my experience- I ran with bypass pipes for a few days before finding the AH mufflers. Bypass pipes dropped TQ numbers on my car and only added a couple hp up top. This would seem consistent with other posts I've read here that the flat six likes some backpressure. I think the AH introduces some backpressure by running a length of pipe equivalent to the overall run of the factory mufflers, and a couple of turns, along with the two resonator sections. This is just my speculation.
Sound was very mean at WOT, but sounded bad (IMO) at idle / off idle. Couldn't even hear myself think in the car. Was a fun experience though just so I knew what others were talking about with using them.

 

Kurt,

Nice post and dyno! We were wondering what you have been up to? Well documented post. Congratulations on the power gains, and thanks for the postive mention.

Mike
SP/RSS

 

Thanks Mike- Just been working like a dog and goofing around with car mods on my free time. I've been contemplating trying out your bored-out 997 TB, do you think it might offer any additional improvements?

 

Both Fabspeed's and AWE's mufflers are straight through designs