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SOUL | GT3 Side Muffler Bypass Vs Center Muffler Bypass Explained

Old 12-03-2018, 04:32 PM
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Default SOUL | GT3 Side Muffler Bypass Vs Center Muffler Bypass Explained

Hello Everyone,

My name is John Gaydos, and I’ve been an active Rennlist member and Porsche owner for many years while in the aftermarket performance industry. I've seen a lot of threads weighing the differences between side muffler bypass pipes and center muffler bypasses exhausts and wanted to dive into the differences. Sound is very subjective - side muffler bypass pipes might meet your goals better than a center bypass, vice versa, or it just might be that a full header replacement would be a better match. Either way, an educated decision is the best decision so I’m going to get into the side muffler vs center muffler delete as that seems to be a popular topic.

The GT3 exhaust design consists of three components (headers, side mufflers, center muffler) – the last two are often compared and considered as the best return on investment when it comes to mod time and cost – but which is the best solution for you?









You can see how much of a difference there is in sound restriction between valves open and valves closed. The distance the exhaust travels, the piping diameter, and the number/size of chambers and baffling it goes through all contribute to a restriction in sound level and cabin presence with valves closed, or a lack thereof in the valves open condition.

With valves closed, the factory side mufflers have a larger volume area, longer distance to travel, and a smaller 50mm tubing diameter in which to do it than the factory center muffler. With valves open, the factory side mufflers have a shorter distance to travel (air gap) between the 63mm entry pipe and exit pipe than the factory center muffler. This helps explain the differing sound characteristics between the side and center muffler deletes below. Most aftermarket CMB will forgo the factory chambered design for a straight through flow path, yielding the more aggressive exhaust note - like our design below.



SOUL CENTER MUFFLER BYPASS EXHAUST
MSRP:
$845-$849
Weight savings: 11 lbs
Click for Product Page








Center Muffler Bypass exhausts (CMB) have a more raw, deep, aggressive exhaust note than side muffler bypass pipes. Regarding the cabin presence and overall sound level, they are typically quieter with valves closed, and louder with valves open. This also causes them to have a much more intense transition from the valves closed to open position. Some people do not like that aspect of the center muffler bypass. You can run a CMB and disable vacuum or control the factory valves with a valve controller to have the valves open at all times. Some CMB's will allow you to change the tips as well.

Our CMB is a cost effective solution for a more aggressive sound with customizable tips for a unique look.Each system is made from mandrel-bent T304L stainless steel tubing. Mikalor Supra Heavy-Duty W4 Clamps are included to mount the system to the vehicle (also included to mount Single Wall tips). Projection welding spots, swinging bridge, high-strength stainless steel bolt and the exclusive design of the captive nut and trunnion offer superior clamping forces and longevity. AccuSeal clamps are included to connect the exhaust to the side mufflers. We offer a variety of exhaust tip options ranging from double wall tips to attractive single wall stainless steel tips. For 991 GT3 exhaust applications, we recommend 4″ tips to fill out the bumper, but 3.5″ tips are available by request. 991.2 GT3 tips are slightly longer as a result of the change in the bumper.

Yes, we do customization! For an additional cost, we have the ability to PVD coat these tips black AND if you want to support your business, if you want to support a cause, if you want to stand out....given there is space we have the ability to apply custom lettering/logos to the single wall tips. Examples: " I LOVE" / "MY WIFE" or "PDK RULES" / "MANUAL DROOLS" or "PORSCHE" or "SMOKIES GT"












Side Muffler Bypass pipes (SMB) are smoother and more exotic in pitch, akin to the factory exhaust note but uncorked and much livelier with a better tone. It is not quite as loud as a center muffler with valves open, and with valves closed it is not quite as quiet. However, it still has minimal drone characteristics due to routing the exhaust through the more restrictive top entry of the factory center muffler with valves closed. SMB’s also have a much smoother and less notable transition from valves closed to open vs a CMB. Also for reference, our non-valved SMB’s offer essentially the exact same sound as our valved SMB’s in the valves open position. Eliminating the valves saves an additional 3lbs which is ideal for more dedicated track cars that don’t need PSE functionality.
We utilize a dual inlet design for our side muffler bypass pipes that utilizes both the upper and lower entry to the center muffler. This bleeds off pressure into the top of the center muffler, more evenly distributing the pressure and promoting the life of the factory center muffler. We also utilize a flex pipe in the upper pipe to prevent fatigue and to allow for easier installation. I have yet to experience a factory center muffler fail when used with a dual entry side muffler bypass and factory headers, including dozens of GT3’s with thousands of track miles at Sebring during my time building GT cars in Florida.
Additional Weight and Heat Benefits of Side Muffler Bypass Pipes

Side muffler bypass pipes are an underrated modification, especially for track enthusiasts. Side muffler bypass pipes have two distinct advantages over a center muffler bypass from a performance perspective – weight and heat. A center muffler bypass saves around 10lbs of weight off the rear of the car while dual entry side muffler bypass pipes save about 35-38lbs depending on whether or not they contain valves. Side muffler bypass pipes also rid the car of a notable amount of heat soak just inches off the rear tires. This helps with more consistent / cooler tire temps at the track, especially if idling or warming up the car in the pits / paddock prior to going out for a session.



SOUL VALVED SIDE MUFFLER BYPASS PIPES

MSRP: $1,395
Weight savings: 35.4 lbs / 16 kg (44.9 lbs vs 9.5 lbs)
Click for Product Page

SOUL SIDE MUFFLER BYPASS PIPES

MSRP: $945
Weight savings: 38.3 lbs / 17.3 kg (44.9 lbs vs 6.6 lbs)
Click for Product Page
Why choose SOUL for your upgrades?








LIFETIME WARRANTY: Enjoy your SOUL exhaust parts with confidence on both the street and track as they are covered by our Lifetime Warranty. Yes, we mean it...a full warranty for track use! Our team will quickly work with you to resolve any issues or answer any questions that you may have.
PACKING: We foam pack every product to ensure your components arrive in perfect condition.
CUSTOMER SERVICE: We are standing by to help in any way we can - pre sale and post sale, just let us know. No customer left behind, ever!
.
That all said, I invite any questions as an open/friendly discussion on this topic. We have some future GT3 products in the works and cars coming in for comparison videos. Until then I look forward to working with you!
.
Best Regards,

John Gaydos
Performance Specialist
PCA National Instructor
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Last edited by Soul Performance; 01-14-2019 at 08:00 PM.
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Old 12-03-2018, 05:26 PM
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Jimmy-D
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But what about the loss of low-end torque with the side bypass?

A lot here do not track so on the street that may be a disadvantage
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Old 12-03-2018, 05:46 PM
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Originally Posted by Jimmy-D View Post
But what about the loss of low-end torque with the side bypass?

A lot here do not track so on the street that may be a disadvantage
Jimmy I have yet to see any third party or reputable manufacturer dyno results showing a gain or loss of performance with any side muffler bypass pipe design. The same goes for a center muffler delete, save for perhaps Akra's dynograph. Point being, there is little to no data to support any loss or gain of performance via bypass pipes. Most everyone I've seen that has stated or believed such gains or losses have done so via their own butt dyno. Personally, I've never felt any notable loss or gains on any center or side muffler bypass pipe I've ever driven. I also know from experience that an illusion of loss or gain in the low end can be created by gains or losses over factory elsewhere in the powercurve. Therefore, I'm making no assumptions nor claims in regards to performance until there is more reputable third party data provided to the community on the topic. In time, I aim to try and arrange that to settle my own curiosity but I expect it to be negligible as I always have. If people want a noticeable power increase, they have to ditch the factory headers. Otherwise you have to look at the sound, weight, and heat benefits of the various bypass pipes or catback systems to make a decision.
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Old 12-03-2018, 06:04 PM
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Bravo John...
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Old 12-03-2018, 06:18 PM
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Great post John - the cutaway diagrams really do paint a picture of what's happening - appreciate you taking the time to post this up.
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Old 12-03-2018, 07:23 PM
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Alan C.
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John, Thanks for the details.

Examples: " I LOVE" / "MY WIFE" or "PDK RULES" / "MANUAL DROOLS" or "PORSCHE" or "SMOKIES GT"
'SMOKIES GT'
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Old 12-03-2018, 07:47 PM
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Originally Posted by cox1974 View Post
Bravo John...
Thanks Cosimo : ) You keeping out of trouble over there? lol

Originally Posted by Ducati1199 View Post
Great post John - the cutaway diagrams really do paint a picture of what's happening - appreciate you taking the time to post this up.
Thanks for the kind words. And it's no problem, I've been meaning to do it for years and finally just snagged a 997.2 GT3 side muffler and center muffler to cut apart as they share the same part numbers as the 991 GT3.

I assume you know Ducatis well, PM me your thoughts on mid-2000s Monsters if you have some time.

Originally Posted by Alan C. View Post
John, Thanks for the details.


'SMOKIES GT'
​​​​​​I thought you might like that one Alan
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Old 12-03-2018, 08:32 PM
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Great explanation!
Fair pricing.
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Old 12-03-2018, 09:36 PM
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What about doing both the side muffler bypass as well as the center muffler bypass? I don't really care about having the valves and I like my exhaust loud. Thanks!
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Old 12-03-2018, 09:49 PM
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John, with the valves open, would oem flow go through both the loud and quiet path in the side mufflers?

Edit: if I want OEM quiet with valves closed and ear piercing loud with valves open, what should I do?

Last edited by garudatwo; 12-03-2018 at 10:04 PM.
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Old 12-04-2018, 12:04 AM
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Thanks John for doing this. I need to get something for my .2 gt3. Christmas specials coming?!?!
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Old 12-04-2018, 12:13 AM
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​I have previously run SOUL PP race headers on my GT4 and sport cats on my 991.2 C2S Cab. I enjoyed those so much that I kept pushing John to get an early set of the SOUL valved SMB's for my new GT3RS. I think I ended up with the first production setup and installed them over Thanksgiving weekend.

This product like the others that I have purchased from SOUL is top notch quality. The ship time was fast and the packaging was great. The finish of the products is very nice and clean. The customer service is second to none, which anyone who has worked with John will attest to as well. It doesn't get better than this.


I am no mechanic by any means, but have installed a couple Porsche exhausts over the years. I would rate this job as a 4/10 in the difficulty range. All combined it took me a solid 5-6 hours solo to install it. It was very straightforward, and everything matched up perfectly.

The sound of this setup is just about perfect for me. I would rate the stock exhaust at a 6/10 in terms of the loudness that I personally desire at full throttle. The SMB's took it to a 8.5/10. They made the tone slightly deeper, but really kept the exotic sound of the stock car. I can't notice any drone with valves open or closed. In retrospect, I probably would have gone with the non valved SMB's given that I press the PSE button first thing after I start the car, and this car isn't a DD for me. I think I could easily have a phone call on my way home from work with the PSE on with no issues.

For me this modification fulfilled my desires of maintaining the stock exhaust quality but making it louder while dumping some weight and heat soak from the rear of the car. I really don't think you can beat the combined quality, value, and customer service that the SOUL products provide.









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Old 12-04-2018, 10:49 AM
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That is the first LG I've seen with those color wheels. Looks great and it's nice to see something besides the black ones.
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Old 12-04-2018, 11:26 AM
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Originally Posted by mdrums View Post
Thanks John for doing this. I need to get something for my .2 gt3. Christmas specials coming?!?!
No problem Mike : ) No plans for Christmas, but I'll give you a shout today to discuss. It's been awhile I look forward to catching up

Originally Posted by TRAKCAR View Post
Great explanation!
Fair pricing.
Thanks Peter! Lunch on me next time we're at Sebring together, and yes that is a bribe to see more details about a certain house Steve and I still talk about haha.

Originally Posted by onehogwild2006 View Post
What about doing both the side muffler bypass as well as the center muffler bypass? I don't really care about having the valves and I like my exhaust loud. Thanks!
Hey me too, that's right up my alley haha. I can assure you it will have a cabin presence at cruising speeds, but whether or not it is "manageable" is very subjective depending on the person. If you're up for an adventure, I'd say give it whirl! And you better get some tunnel runs videos, that is mandatory
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Old 12-04-2018, 11:34 AM
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Originally Posted by krell View Post
That is the first LG I've seen with those color wheels. Looks great and it's nice to see something besides the black ones.
thanks krell! i really like the silver wheels on it. i took off the black "GT3RS" side script for the clear bra, but am thinking i will put a new one soon.
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