This is great! Thanks for writing it up. Really looking forward to the dyno and sound clips of that Akrapovic.

 

Hey ajw45, did you dyno the Akrapovic GT4 Exhaust, and were you able to compare track dB levels?

 

I actually bought ajw45's akra exhaust. I have it mated to cargraphic headers (catted high flow) and have a gt3 throttle body and ipd plenum.
Here is the dyno graph from BBi after a tune (ap unit) on california 91 octane. It has stock, AP over-the-counter, and then the custom tune.
Obviously your results will vary based on dyno/gas/alignment of moon.

I like that I can still maintain the PSE functionality for when driving in neighborhoods, and yet friends say the car sounds really nice when spirited driving with the exhaust open.
I don't have any db results as the only track days I did had limits of 103db (which I didn't break). No drone with either the exhaust open or closed. Its my only car for the past 2 years (thanks covid).

 

Thanks ProgrammerCat.
How's tonal quality, and loudness both with valves shut and open, compared to the PSE?
I have Dundon race headers without catalysts, wondering if valve closed could be more quiet than the PSE.
There's an upcoming HPDE at a track with a 92dB limit, so I may have to zip tie the valves shut, use Track Nanny or the Soul remote.
The exhaust was listed as discontinued, but looks like they made another batch.

 

I heard ajw45 went to prison after a lengthy manhunt involving a series of ramen shop robberies in queens

 

Hmm, my very un-scientific ranking would be:

Stock Headers + Stock PSE = 92db
Stock Headers + Akra = 93~94db
Cargraphic Catted + Akra = 95~97db
Dundon Race Exhaust = 100db+

I have heard the Dundons from another GT4 owner. I have no doubt you can squeeze more performance from a full race exhaust but it comes at a much louder resulting exhaust. It is noticeably louder than stock while I feel the Cargraphic + Akra hangs close enough to stock.
I have also heard that even stock Headers + PSE fails 92db at Laguna Seca, so all these numbers may be higher than expected.

I will also mention that the Akra being Titanium has a more "tin" like sound to it. It is a preference I prefer (my previous '05 STi also had a full TI exhaust) but it is not for everybody. I think with some of the race exhaust setups, you are closer to a rumbling how the race porsches sound.

 

I bought the Dundon headers to help smooth out the power band, and the sound level increase is a plus, at least off track.
It appears the Akrapovic's shape has more space inside than the PSE, and therefore more muffling potential, if the valves remain closed above the ~3.5K RPMs they'd normally open at.
Good point about the tone of Ti compared to SS, I'm not sure I'd have a problem with that though, the F6 will never sound like a V8 so may as well go the other way.