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The one thing that seems favorable with regard to the Akra rear box is that it scavenges drone quite well, which is not unexpected given it looks like the OEM rear box. . . they both are really big 'mufflers' that scavenge drone
Mufflers do not just scavenge drone, but also decibels . . . again, not surprising the Akra rear box does not appear to produce much, if any, more decibels over the OEM rear box
So, at the end of the day, between the OEM and Akra rear box . . . does one or the other produce a tone you prefer? Even if I enjoyed the Akra tone, $8K new or $6K used is a HEFTY price for a subtle difference from OEM rear box.
The Akra OAPs seem popular but, honestly, OAPs are just link pipes that do not take rocket science to get right. Decide if you want resonated or non-resonated and pick your brand . . . I think the least expensive I have seen are the Flat6 link pipes and people seem routinely satisfied with the impact they have on their exhaust setups.
Is there a big jump in volume when the valves open? I wonder if that cheap collar mod would work / be effective on this rear section. I have that on the stock section now and it is a killer mod for the money. Mine is set so I *just* hear a difference between valves open and closed. Now when the valves do fully open I don't notice it as much and it is still tame at low speeds.
There is a noticeable difference between the valves closed and open, not HUGE but it's obvious. How does the collar mod work exactly? Thought it basically kept the valves open.
Originally Posted by Avera
Mufflers do not just scavenge drone, but also decibels . . . again, not surprising the Akra rear box does not appear to produce much, if any, more decibels over the OEM rear box
So, at the end of the day, between the OEM and Akra rear box . . . does one or the other produce a tone you prefer? Even if I enjoyed the Akra tone, $8K new or $6K used is a HEFTY price for a subtle difference from OEM rear box.
The Akra OAPs seem popular but, honestly, OAPs are just link pipes that do not take rocket science to get right. Decide if you want resonated or non-resonated and pick your brand . . . I think the least expensive I have seen are the Flat6 link pipes and people seem routinely satisfied with the impact they have on their exhaust setups.
Avera
There is definitely a difference in both tone and volume, especially the latter. OEM setup is supposed to be 91 dB and Akra Slip On (with stock GPF) is 98 dB. There is certainly a decent price difference, but if you want to get OAP and a good pair of tips (Akra, JCR) you're looking at over $2k already. A used Akra Slip On can be found in the marketplace for an average of $5k, lower if you check daily and are patient. Found mine for a very good price but did take me a year. I believe there are two sets for sale in the marketplace.
There is a noticeable difference between the valves closed and open, not HUGE but it's obvious. How does the collar mod work exactly? Thought it basically kept the valves open.
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No!, if you want the valves open there are easier ways (like just unplugging the line). The collar lets you tweak how open you want them, when they’re trying to close. Here’s where I have mine, it just keeps them open a little when closed, and it made a good difference. I can hear the exhaust valves closed now. I was just wondering if this would have a similar impact for you since the OEM box and the Akra appear to share a similar concept.
No!, if you want the valves open there are easier ways (like just unplugging the line). The collar lets you tweak how open you want them, when they’re trying to close. Here’s where I have mine, it just keeps them open a little when closed, and it made a good difference. I can hear the exhaust valves closed now. I was just wondering if this would have a similar impact for you since the OEM box and the Akra appear to share a similar concept.
Got it, thanks for the video. The Akrapovic Slip On also used OEM valves so there is a possibility it can be done. Haven't seen the car on the lift after the install so I don't know unfortunately.
My 2 cents on the Akra.....it follows the same design philosophy as the OEM. The valves closed route is muffled and the open valve route is just dumped individually on each side.
While I know sound/tone is very subjective the dumping of each individual cylinder bank without a complete mixing of exhaust gases is what makes all 4.0 liter 718 sound so...dare I say...un-Porsche.
I had one that I tested with the rest of the stock system and with the Dundon street headers/OAP.
The first one was Ok but didn't like the tone. The second one was horrible with drone and just amplified a sound I didn't like.
BTW...I also had problems with the muffler developing fissures on the center section. Was taken care via warranty but the material is very thin.
My 2 cents on the Akra.....it follows the same design philosophy as the OEM. The valves closed route is muffled and the open valve route is just dumped individually on each side.
While I know sound/tone is very subjective the dumping of each individual cylinder bank without a complete mixing of exhaust gases is what makes all 4.0 liter 718 sound so...dare I say...un-Porsche.
I had one that I tested with the rest of the stock system and with the Dundon street headers/OAP.
The first one was Ok but didn't like the tone. The second one was horrible with drone and just amplified a sound I didn't like.
BTW...I also had problems with the muffler developing fissures on the center section. Was taken care via warranty but the material is very thin.
“ . . . the dumping of each individual cylinder bank without a complete mixing of exhaust gases is what makes all 4.0 liter 718 sound so...dare I say...un-Porsche.”
I have heard you state this before. I do not possess any special expertise pertaining to tone production when it comes to exhaust acoustics. With that acknowledged, I do not understand how the lack of cylinder bank mixing tends to produce the ‘un-Porsche’ tone?
For example, as you know, I just removed a JCR Race Pipe that produced a high-pitched/wailing tone. Yet, the exhaust gases from the left and right never ‘mix’ in the Race Pipe. Conversely, I do not know what happens inside the OEM rear ‘box,’ but wonder if the gases ARE mixed inside? If not, why would Porsche construct such a large ‘box’?
The Akra seems to have similar architecture to the OEM rear box which, in my mind, would explain why they both produce a similar low-pitched/rumbling tone.
In short, is it possible you have it backwards? The ‘mixing’ of exhaust gases is what produces the ‘un-Porsche’ tone?
As to the drone, I have yet to hear anyone with Dundon components who does not report significant drone with any rear box option other than the OEM rear box. This is why I have settled on the OEM rear box with my Dundon components.
Finally, with respect to Akra ‘fissuring’ you observed . . . when Akra came out with their setup for the G8x (M3/4) there were numerous complaints by forum members on Bimmerpost of early breakdown. Not surprisingly, Bimmerpost deleted all threads as they developed on the topic. . . apparently not good for sponsorship if you allow forum members to report quality issues.
“ . . . the dumping of each individual cylinder bank without a complete mixing of exhaust gases is what makes all 4.0 liter 718 sound so...dare I say...un-Porsche.”
I have heard you state this before. I do not possess any special expertise pertaining to tone production when it comes to exhaust acoustics. With that acknowledged, I do not understand how the lack of cylinder bank mixing tends to produce the ‘un-Porsche’ tone?
For example, as you know, I just removed a JCR Race Pipe that produced a high-pitched/wailing tone. Yet, the exhaust gases from the left and right never ‘mix’ in the Race Pipe. Conversely, I do not know what happens inside the OEM rear ‘box,’ but wonder if the gases ARE mixed inside? If not, why would Porsche construct such a large ‘box’?
The Akra seems to have similar architecture to the OEM rear box which, in my mind, would explain why they both produce a similar low-pitched/rumbling tone.
In short, is it possible you have it backwards? The ‘mixing’ of exhaust gases is what produces the ‘un-Porsche’ tone?
As to the drone, I have yet to hear anyone with Dundon components who does not report significant drone with any rear box option other than the OEM rear box. This is why I have settled on the OEM rear box with my Dundon components.
Finally, with respect to Akra ‘fissuring’ you observed . . . when Akra came out with their setup for the G8x (M3/4) there were numerous complaints by forum members on Bimmerpost of early breakdown. Not surprisingly, Bimmerpost deleted all threads as they developed on the topic. . . apparently not good for sponsorship if you allow forum members to report quality issues.
Avera
The JCR does mix both banks....the tubes in the middle are connected.
If you look at GT3s and 981 GT4 they both use a mufflers that mixes both banks. That's why they sound so good.
Due to the diffuser design on the 718s the center exit was not possible.
When you dump each bank individually, you do decrease the backpressure but you are basically having two separate 3 cylinder engines....and that's the reason for the sound these cars have (coupled with a muffler that's designed to control drone).
All the rear sections I like have some type of mixing but then they are not that great in handling volume tone, probably the exception is the Kline system since it has those resonators on the OAP.
Perhaps I do not understand what you are referring to exactly - so please correct me if I am wrong - when you state the banks merge (and mix) where the pipes meet at center?
If so, the only thing I see are the two pipes coming together and soldered together at the meeting point. There does not appear to be any pipe openings (mixing) and, if there are openings beneath the soldering, the amount of mixing would be minuscule and of no apparent consequence.
Again, I could be wrong, but I do not see any evidence of mixing in either my 70mm Race Pipe or the 63mm Race Pipe (pics below)
Aside from the above observations and associated questions, it does not intuitively make sense to me that the merging of gases would produce a higher-pitched/wailing tone. To me, just the opposite would be true; the merging of exhaust gases would produce turbulence. In this latter regard, I think the less than desirable tone produced by the OEM and Akra rear boxes is because they DO mix banks that produce turbulence. By contras, the Race Pipe does not appear to merge/mix and, I would assume, it is the freer/faster exhaust gas flow that produces the higher-pitched/wailing tone?
Again, I could be wrong and happy to be corrected/educated on the matter.
Perhaps I do not understand what you are referring to exactly - so please correct me if I am wrong - when you state the banks merge (and mix) where the pipes meet at center?
If so, the only thing I see are the two pipes coming together and soldered together at the meeting point. There does not appear to be any pipe openings (mixing) and, if there are openings beneath the soldering, the amount of mixing would be minuscule and of no apparent consequence.
Again, I could be wrong, but I do not see any evidence of mixing in either my 70mm Race Pipe or the 63mm Race Pipe (pics below)
Aside from the above observations and associated questions, it does not intuitively make sense to me that the merging of gases would produce a higher-pitched/wailing tone. To me, just the opposite would be true; the merging of exhaust gases would produce turbulence. In this latter regard, I think the less than desirable tone produced by the OEM and Akra rear boxes is because they DO mix banks that produce turbulence. By contras, the Race Pipe does not appear to merge/mix and, I would assume, it is the freer/faster exhaust gas flow that produces the higher-pitched/wailing tone?
Again, I could be wrong and happy to be corrected/educated on the matter.
Avera
That area in your photos is open so gases can flow from side to side.
The sound is bad because you are missing firing cylinder sound on each outlet and creates a tone that previous GTs didn't have.
Take the JCR, BCFab, some Cargraphics, Kline...people rave about the tone/sound because these designs incorporate the mix of both banks.
Dumping the open valve path independent on each side is cheaper to manufacture and creates the sound most of us are not happy with.
I do agree that the amount of gas mixing on the JCR could be improved.
That area in your photos is open so gases can flow from side to side.
The sound is bad because you are missing firing cylinder sound on each outlet and creates a tone that previous GTs didn't have.
Take the JCR, BCFab, some Cargraphics, Kline...people rave about the tone/sound because these designs incorporate the mix of both banks.
Dumping the open valve path independent on each side is cheaper to manufacture and creates the sound most of us are not happy with.
I do agree that the amount of gas mixing on the JCR could be improved.
Ok, I admittedly do not know what lies beneath the Race Pipe soldering . . . and accept that I am wrong
In addition to wishing I could actually visualize the opening underneath the soldering on the Race Pipes, I wish I could see what is underneath the big tin 'boxes' with the OEM and Akra rear boxes. I wonder why they have all the pipes enclosed in that 'tin box' if not to allow exhaust gases to merge inside at some point?
I think a common "mistake" is that only the "high pitched wail" is the sound of a Porsche - IMO that sound is actually the exception.
Thankfully, I actually prefer the lower, throatier tone to the wail. Not that I would ever drop $8K on an exhaust system anyway. Just not where my priorities are.
Thankfully, I actually prefer the lower, throatier tone to the wail. Not that I would ever drop $8K on an exhaust system anyway. Just not where my priorities are.
$8k plus you've got to move the valves LOL - a bit of salt in the wound.
11-07-2022, 07:02 PM
