74goldtarga

My 2014 has stock headers and side-mufflers along with a Sharkwerks center bypass (I don't own the stock center unfortunately). It sounds fantastic. My car gets most of it's use at the track but I do drive it on the street occasionally. It is said that the side-mufflers retain heat particularly behind the rear tires - I'm wondering if anyone could really tell a difference in tire performance on track after removing the side mufflers?

As far a sound is concerned, the car is pretty loud with the valves open which is fine most of the time - with the valves open are the side-mufflers totally bypassed or is exhaust still routing through the mufflers themselves (and heating them)?

If I want to replace my current system I'm considering a few options:
1. Side-muffler bypass with Sharkwerks CMB - lightweight and loud. Pretty inexpensive.

2. Fabspeed catback competition X-pipe - also lightweight and loud and inexpensive - not sure if this is louder or similar loudness to option 1??

3. Soul performance valved side-deletes with their GT3 center muffler - a bit more expensive - only makes sense if there is a real-world difference (rather than theoretical) in rear tire performance gained at the track by removing the side mufflers.

4. Full Dundon setup with long-tube street headers / side-deletes / muffler. This is what I want and I have no doubt it is good value for the money but it's more than I want to spend for the 2014 so it isn't a current option.

Lastly - what are peoples' experiences with catless race headers and coding out the errors for track use? I am assuming you need a tune to run these in all cases? I am not interested in a tune while I have a 10 year engine warranty but may consider doing this after the warranty is up.

Thanks for all suggestions.

Seth Thomas

This is the setup I had on my 991.1 GT3 RS so I can comment on it. No CEL ever with this setup. A tune was never needed with the race headers. The only issue with the race headers vs the catted headers is the smell of exhaust gas when stopped at a red light. You definitely want to have the air recirculate activated for those times.

Larry Cable

I have the Soul valved bypass with OEM Center ... takes a huge amount of weight off of the back of the car... I'd probably go with the Soul "quieter" center since Ca sound is an issue.

JCviggen

1. Will be very loud. If that's not an issue for a car that mostly drives on track it seems the obvious way to go.

Personally as an alternative to 1. I'd look for something like a used (or even new) IPE catback which in 1 piece holds valved side deletes and a silencer on each bank which makes it reasonable to drive with valves closed. It sounds good too.

2. Basically just straight piping things from the cats back with no valves or resonators of any kind, so again very loud. I'd rather have something like the IPE I just mentioned or sell/swap your CMB and get a stock muffler plenty of them around and then add a side bypass. I'm not sure why getting a stock center isn't an option since the main issue seems to be that you didn't get one with the car. They don't cost much used and are fine for track duty if you don't go catless.

3. Not a bad solution, but the Soul center muffler doesn't do much a used OEM does not and costs 3x. Personally I'd say the weight loss from ditching the sides is a bigger deal than the tire temp but I don't have any real world data.

4. Is absolutely the worst value for money, as is usually the case with the toppest of tiers solution. This will give you the most power but if the car is mostly being tracked then you'll probably have to get the cats replaced somewhat regularly and I am not a fan of catless race header solution on any car that spends any time on the street at all. I've done it and it's just not good. Anyway solution 4 is only relevant if budget is no consideration because the improvements are not in line with the extra cost versus some of the other solutions.

74goldtarga

JC thanks for the excellent reply. Despite the theoretical weight savings from removing the side mufflers - in an ideal location - I’m not sure it matters enough if the tire temp issue with the side-mufflers is also only a theoretical rather than practical one. I’m probably not a good enough driver (and I’m not too bad) to notice a 40lb drop.

I can get an OEM and use side-deletes if the muffler won’t blow out. I appreciate the recommendation against race headers since you have tried it. A used OEM muffler with side-deletes is still a $3K investment without an increase in power or much reduction in weight over my current setup which is why I am hesitant - in that case the only benefit is shedding the heat-sink purportedly due to the presence of the side mufflers.

JCviggen

If you're happy with your current solution (not looking for more power or sound) then don't sweat it, the rear tire temp thing is not a drastic change if you delete the sides so you can just keep using it the way it is.

Meraki Autoworks

We have done a lot of the Soul units that you described, adding onto your current system will be pretty loud. We can work you a deal on a Soul unit.

-Josh

Rod27

the 40lb in the rear makes a bigger difference than you might think. My last 991.2 RS felt quicker with Fabspeed straight pipe than my current 991.2 RS which only has center delete. The sound also wasnt enough for me with just the center. The car wasnt an "event" to drive on weekends, not enough crackles and pops on decel either. Valved side deletes going on friday so ill let you know what it feels like and if my above opinion stays.

Tugboat 996

Has anyone done #3 with the Soul CMB instead of the stock center? I am assuming very loud.

Larry Cable

I haven't but they have 2 variants a "louder" and a "quieter" relative to OEM.

tdmgt3

I kept the oem side mufflers on my setup. GMG Center Bypass, GMG WC-EVO long tube headers (catted), and then a Soul valve controller. It's loud as hell when open but quiets down decently when closed. And you get a nice power bump from the headers.

74goldtarga

So that's a question - the GMG headers are a bit more expensive than most options but less so than Dundon - the Dundon headers are the longest it would appear with the GMG maybe second and all others a similar design to stock. Is the power gain from the equal length, extending the length from stock, the new Catalytic convertors, or some tuning magic - or all of the above. I know the Dundon claim the biggest power bump and their reputation at least backs this up - physics, however, does not discriminate and it's possible there are other good options. As far as I can tell all manufacturers other than Dundon have header designs that are intended to mate up to the stock side mufflers (or side-deletes that replace the stock sides). The Dundon system replaces both the stock headers and side-deletes to match up to stock center exhaust or the Dundon center exhausts if I am seeing things correctly.

GMG and others are 304 stainless, Kline Innovation is Inconel or 304SS. Dundon is a different stainless alloy 321SS.

Do the side-mufflers rob power or just add weight and heat?

markiegt3

Dundon gives power due to header length and freer flowing 200 cell cats. I have no tune.

Good bump in mid range torque.

Bit boomy between 1800 - 2800 revs under load.

V happy with the Dundon setup (street) with standard rear box. Great sound

3RSJ

Dundon is really expensive but high quality stuff. Catless headers is going to be super loud and the smell really bad. Soul Performance is good but not cheap. Id go with the sharkwerks side bypass.

PCarOMFS

I have the Soul non-valved side muffler bypasses and center muffler bypass. They call it their competition modular exhaust. It’s very loud when you’re on full throttle and reasonable at cruising speeds but it has quite a bit of drone around 2000 rpm. My car is 90% track so I don’t mind it, but if I spent any extended amount of time street driving, I would go with valved side muffler bypasses and the new Soul center muffler. This should keep things civil enough on road trips yet loud and fun when you want to wring it out.