Quick update here for anyone considering a bypass style exhaust for their 991 3.4 PDK (without PSE). The AWE exhaust was installed in place of the Sharkwerks crossover pipes, which sounded great, but vibrated pretty badly at idle. Mainly in non-sport mode, but sporadically when in sport mode as well. Also, the Sharkwerks caused a groaning resonance/vibration when taking off from a stop in certain conditions. Anyways, some are more sensitive to this stuff than others, but for me it was too much. In any case, the AWE is vibrating as well, but more on that in a bit.

Last Friday I got the AWE exhaust (http://www.awe-tuning.com/991-34na-exh) installed. While other Sharkwerks owners referenced online the vibration at idle issue, similar issues were not reported on the AWE. Plus, the AWE copy on their website mentioned that their exhaust was designed specifically for the PDK. This seemed promising as in general manual transmission owners did not experience this vibration at idle nearly as much.

The guys at Infinite Auto Tech in San Jose (https://www.yelp.com/biz/infinite-au...-tech-san-jose) installed the AWE. They were really great to work with, I highly recommend them.

The AWE exhaust sounds good. The Sharkwerks seemed a little louder, with more pronounced burbles and crackles, especially at lower rpm. I liked the sound of the Sharkwerks better in this regard. However, the AWE also produces these sounds, just a bit more muted, and it takes a bit more revs to produce them. Essentially, you'd just get more popping and crackling coming off throttle at a lower rpm in the Sharkwerks, and they were a bit louder. So it was easier to produce all these cool sounds just bopping around town in the Sharkwerks, But they both sound very good.

On the flip side, as revs build, I prefer the sound of the AWE. Whereas at higher revs the Sharkwerks sounded a bit rough around the edges, the AWE produces a more refined sound as revs build. This is all subjective, so some might prefer the Sharkwerks sound, especially since it is a little louder. But I like the sound of the AWE better when I wind the engine out.

On the downside, they both produced vibration. That said, the vibration on the AWE is less severe, and really only happens when the car is not in Sport mode. Also, the AWE doesn't make that groaning noise when I take off from idle in first gear. I attribute this to the fact that the AWE also mounts very securely to the factory muffler mount, while the Sharkwerks, I believe, only mounts to the catalytic converter studs with no other mounting points. There could be another explanation as well. It simply could be due to the outside temperature, which is quite a bit warmer now with the AWE as compared to when I had the Sharkwerks installed (although this is norther cal, so we aren't talking night and day differences). On startup, these outside temperature differences could also be affecting idle speed, which I think has the biggest impact on vibration.

That all said, the AWE vibration in non-sport mode is unlivable. While not quite as severe as the Sharkwerks, it is still quite bad. So if I was to keep the exhaust, I'd have to drive exclusively in sport mode. This isn't a problem in itself, but it's certainly nowhere near ideal.

The owner of Infinite, who is very knowledgable, has reached out to AWE, and I am waiting to see if they have any recommendations.

The only difference that we can point to between sport and non-sport mode that would make a difference here is the idle speed. It's 100 or 200 rpm higher in sport. Much like a Harley V-twin vibrates at idle, then smooths out as revs come up, we think the same is happening here. The lower idle is causing more vibration, or at least vibration at a lower frequency, which is now being transferred through the exhaust system versus being eliminated with the factory muffler.

I don't believe any flaps are opening or closing with the non-PSE vehicles. And I can't think of any other difference that would explain the vibration. Sharkwerks also believed that it was the idle speed that was causing it.

It would be great if AWE comes up with a recommended fix. Hard to believe I am the only one that has, and will run into this issue, and if that is the case, then AWE and Sharkwerks should either make a change to the product, not offer it, or at least provide a caution to customers that this may happen. Sharkwerks references vibration issues for their 997.2 crossover pipes, but not on this exhaust, and to their credit, they gave me a complete refund and were awesome to deal with (great company).

For reference, AWE, when installed by one of their authorized dealers, offers a sound guarantee. I asked them specifically if they had heard of anyone having vibration issues and the person I dealt with said no. Then I asked if I could get a full refund and swap back to the stock muffler under the sound guarantee if there was an issue with vibration, and they said yes. Which is why I was sure to have it installed by their dealer.

So that is where I am now in case anyone is looking into these products for their PDK equipped 991 3.4 without PSE.

Sorry for the lengthy post.

Thanks,
Mike

 

Have had the AWE installed now for 2+ years. No vibration. Perhaps it's the tone ur not uses to.?

 

I wish it was only the tone. Definitely a significant vibration. The owner of the shop that installed it characterized it as "vibrating pretty badly" to the AWE rep. So it wasn't just me.

Mike

 

I currently have no vibration issues with AWE, but I did with Sharkwerks crossover, but both were on cars with manual trans.

 

Yup, both you and does195 (the last person who replied to this post) both have manual transmissions, which seems to be much less likely to present a problem. PDK is more likely to cause issues.

But interesting that even with manual transmission you had an issue with one and not the other. Vibration on mine was more pronounced with the Sharkwerks, so I guess that makes sense...

 

So what happened? Corrected? Curious. Maybe a loose part of bad connection? Anything else done?

 

I sent photos of the installation to AWE. They confirmed it was correctly installed, then suggested I take advantage of the sound guarantee which provides me with a full refund.

I was hoping they'd offer some troubleshooting steps or work with their installer to resolve the issue, but seems like they'd rather not deal with the headache and would rather quickly wash their hands of the problem.

I did reach out to Cobb Tuning to see if they could raise my idle in non sport mode to 800rpm in order to eliminate the vibration, but they don't have this feature yet.

So I have another couple of weeks to decide on whether to take advantage of the sound guarantee or not.

Best,
Mike

 

What is your non Sport or Sport Plus idle RPM? I installed the same system on my 2014 C2, removed it and reinstalled on my 2016 C2, no vibration to speak of.

 

I don't have Sport Plus. I only have a Sport button that is on or off. Idle without Sport on is 600rpm. Idle with Sport is 800rpm, once the car hits 160 degrees oil temp.

Yeah, I guess in the case of AWE the vibration isn't typical. Not sure what the heck is going on with my car. All I know is that it doesn't vibrate at all with the stock muffler, and it has vibrated with both the Sharkwerks and AWE bypass pipes.

 

Perhaps your idle rpm is the culprit. My car idles (non sport)at 672 RPM. If the vibration is going away in Sport (idle will be around 790 RPM), it very well be that your idle is set to low. The stock muffler may have dampened the vibration, which now is pronounced without the center muffler.

There is a very very slight vibration in my car, but nothing that anyone but me would notice.

 

Yes, I think that's exactly what's happening. I just haven't found a way to adjust idle yet. I contacted Cobb Tuning but they don't have the ability to adjust idle yet for the 991. They did say they were thinking about adding it.

 

There are a lot of folks that have installed the AWE in their cars without any vibration issues. As I have said, this is my second install. Perhaps you should visit your dealer and have them check out the idle speed, fuel/air ratio's at idle to see if this may be causing the problem. It is quite possible that there is another problem that is coming to light without the center muffler dampening the vibration. Is your car throwing any faults?

 

I am happy to have read this post. I also purchased the Sharkwerks bypass and it vibrated at idle. Sharkwerks did let me return it, but it was kinda of a pain to install it and then remove it. I did call AWE and they told me I would not have that issue with there's. So thanks for the post. I would not want to go through this again.

 

I wonder if Fabspeed would have the same problem with there x-pipe.

 

No, not throwing any faults. I could have the dealer check it, but my intuition is telling me it's normal.