Thanks for this Serge. Was thinking about getting the clear for my white P-car and now that I see it, I think I will keep as is.

 

Nice Pics!! What a fun morning. Thanks for sharing.

 

Serge, both are showing good gains, especially Agency Power ( 3800- 4200 rpms =50 hp & +80 lbs./tq. and + 20 hp up to redline. Are they both willing to stand by their published claims? If you purchase their product, and you do a before and after dyno, same day, same conditions, same dyno and the results are markedly different how will they make you whole? If these numbers for both fabspeed and agency power are true, then the cost for benefit is excellent. I agree with you on the ability to have a loud/soft button for PSE.

 

Those LFAs are gorgeous.. your 991 isn't too bad either

 

This is in fact a very good question... I had a thread going on on Rennlist about exhaust options and I have been -very logically- warned to take the claimed numbers with a BIG grain of salt.

I also did a quick recap of some previous experience with exhaust mods and an interesting article I found on a similar topic (not the same cars, not the same exhaust, but relevant reference points).

Fabspeed Performance package (Maxflo mufflers, headers, X-Pipe sportcats, tips, ECU upgrade, Competition Intake) on my 2003 996 C2:





The results were satisfactory with a gain of 24hp at the wheels and 21 ft.lbs of torque. The dyno shows a max power of 312 hp at the wheels at 7,100 rpm and 270 ft.lbs of torque at 4,500 rpm (not too far from what Fabspeed claimed)

The significant increase in torque around 3,500 rpm is clearly noticeable and given the performance improvement and the nice sound of the exhaust, I would recommend this type of upgrade.

Fabspeed headers with sportcats on my first 991S:



No dyno data here. Fabspeed claims +17hp and +14 ft.lbs of torque to the wheels at 6500 RPM (does not mention if it is for the catless or sportcats headers though). This is probably a bit optimistic.

My subjective feedback is that it made the throttle feel a bit more responsive and there was a bit more sound (in both PSE mode). Hard to put a number on this. I liked those headers as they made the 991S feel different (read 'personalized').
I had also installed BMC air filters, but I think that the hp gain there was mostly psychological

Article about a Full Capristo Exhaust on a Cayman R:

I found the following article interesting as it underlines a few of sensible points:
-Porsche naturally aspirated engines (and their exhausts) are already optimized to perform close to their maximum potential (if anything, only emission & sound regulations as well as reported mpg are the limiting factors)
-Numbers claims by exhaust manufacturers are probably on the (very) optimistic side. In the case of this article, a remap was required to come close to the performance improvement claimed by Capristo WITHOUT an ECU tune...





Back to my original idea of doing something on my new 991S exhaust, here's where I stand:

-I have a hard time believing the performance claims of the manufacturers (especially Agency Power)
-I am not ready to go for an ECU on the 991S (and no reputable tuner has a product on the market anyhow)
-I may go once again for the Fabspeed headers as I had a positive (though qualitative only) experience with them
-If I want more sound/less weight, I may then go for another valved exhaust that would be close to PSE in quiet mode and straight pipes in loud mode.
-I have seen nices pics of 'blue flame' tips and I liked them... OK, this brings zero performance improvement.

 

Serge,
Very logical analysis and decision pathway. And you clearly know more about this than I do. But just reading your data presentation struck me a bit differently. Sound and sound functionality aside (and that is no small deal), the fact that two so similar systems gave such similar performance gains overall I found encouraging. They could be read as mutually supportive of an expectation of at least the Fabspeed performance - perhaps somewhat inherent in that design. In which case, instead of looking at them individually, you should see if the story that they tell, together, is more believable overall and worth the very similar level of investment. If they together suggest a minimum performance increase that is worth the money, than either is a good choice, for the different reasons you suggest. A true gain of 15 hp, and possibly much more, and the added torque earlyish in the power band for about $1,500. Is that worth it? With a little luck it is a 5% gain - not too bad. Not too expensive.

Just another direction on your fine analysis.

As to sound and on/off functionality, it is a big deal to me. I did not get PSE for a stupid reason - I did not realize at the time you could turn it off. My Mustang has Ford racing exhaust. It sounds great - from two blocks away! And it is always on. It gets old. These cars are much improved over my 997 in terms of noise. But they are not a quiet car as it is. This is JMHO, but I would not do anything in terms of exhaust upgrade that you can not turn down the volume.

Great thread as always!
Michael

 

You hit that nail right on the head: I had a custom exhaust system on my 2003 Mustang Cobra (headers, X-pipe, cat-backs, etc.) and after a while that drone can really get into your head, especially around 1,800 RPMs on the highway.

It was the same with the Akrapovich titanium exhaust on my ZO6, but that car had the vacuum on/off control, which I'd modified with an on/off switch.

Long story short: it's good to have a "switch."

 

Thanks Michael, this is a good point. I see we both are very logical persons



The thing that preoccupies me though is that through my -limited- research work on the topic, I found out that only Fabspeed and Agency Power (and in fact Akrapovic) are publishing full before and after dyno curve. Other manufacturers are jut saying that their design is identical and that the performance should be the same as their competitors, or that they could even not get a good dyno reading of the 991 (hence the thread I started with a question about this...). I'll keep investigating, I am in no hurry.

PS: nice new avatar, I see you are putting your new pics to good use!

 

Yep. I have tried the secondary muffler bypass on the 991. Good loud sound... but you would not hear the difference between PSE on/off anymore. You would not even hear the sound of the stereo in your car either

 

. It is almost always good to have an off switch - on a spouse, a child, the IRS (seemed timely) and and an exhaust!. It was great to meet you yesterday!

 

Tell me where to get all these switches!

 

I just love this picture. My friend just darkened it and gave this wow factor. I agree there is no rush to make a decision on the exhaust - not for that level of performance gain. The more I drive my 991, the more I am reminded of how well Porsche balanced the everyday driver with the performance car. You must be carful not to do too much for performance at the cost of its drivability - at least that would be my fear.

Be well!

 

Still looking!

 

Started a web search... Did not exactly find what I expected....

 

. Must be a fantasy book - an idle hour. What is that?