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-   -   Cat bypass pipes (https://rennlist.com/forums/991-turbo/1114666-cat-bypass-pipes.html)

AirBusPilot 11-25-2018 08:46 PM

Cat bypass pipes
 
https://soulpp.com/product/porsche-9...-bypass-pipes/

Anyone ever use these? I have a Cobb on order (thanks Sam @By Design). I'm' not planning on changing my exhaust, but in order to run stage 2 I need to at least get rid of the cats.

Thanks.

Tfk 11-26-2018 02:26 AM

Ideally, with the cobb stage 2 map, you'd want to be running race cats (100-200 cell), paired with OEM or aftermarket muffler.
That said, you Can run the stage 2 map with these catless downpipes.
Catless DP's should yield ~5-10whp more than race cats.
If/when you get exhaust/o2 sensor codes, you can clear them with the Cobb AP.

pepinozaur 11-26-2018 07:08 AM

I run custom made cat bypass pipes, car runs great, Managed to do 5.9s 60-130 in cool weather using 94octane pump gas. 991.2TTS with glass sunroof and FAL etc.
Thanks Sam for the info, really helpful guy :) He let me know that the oem muffler isnt so restrictive and tried these pipes. I do have other cars - 996tt with external gates and alpha10+ gtr with full 4"pipes to get the racecar type exhausts.
If you want your car to be quiet enough, this is the way to go. Still, if you are looking for more raw sound, like GT3.. this isn't going to be aggressive enough for you

Stef from Europipe put some numbers recently
OEM muffler with test pipes (catless): 0.14 Bar

To put the low back pressure into perspective here is some more data:
OEM muffler with OEM cats: 0.35 Bar
OEM cats with a 65mm straight pipe (no muffler): 0.29 Bar


https://cimg7.ibsrv.net/gimg/www.6sp...a7b94d24fa.jpg

AirBusPilot 11-26-2018 08:11 AM


Originally Posted by Tfk (Post 15454621)
Ideally, with the cobb stage 2 map, you'd want to be running race cats (100-200 cell), paired with OEM or aftermarket muffler.
That said, you Can run the stage 2 map with these catless downpipes.
Catless DP's should yield ~5-10whp more than race cats.
If/when you get exhaust/o2 sensor codes, you can clear them with the Cobb AP.

So, the Cobb AP can permanently clear a CEL due to the missing cats as it comes from Cobb?

Thanks.

AirBusPilot 11-26-2018 08:12 AM


Originally Posted by pepinozaur (Post 15454772)
I run custom made cat bypass pipes, car runs great, Managed to do 5.9s 60-130 in cool weather using 94octane pump gas. 991.2TTS with glass sunroof and FAL etc.
Thanks Sam for the info, really helpful guy :) He let me know that the oem muffler isnt so restrictive and tried these pipes. I do have other cars - 996tt with external gates and alpha10+ gtr with full 4"pipes to get the racecar type exhausts.
If you want your car to be quiet enough, this is the way to go. Still, if you are looking for more raw sound, like GT3.. this isn't going to be aggressive enough for you

Stef from Europipe put some numbers recently
OEM muffler with test pipes (catless): 0.14 Bar

To put the low back pressure into perspective here is some more data:
OEM muffler with OEM cats: 0.35 Bar
OEM cats with a 65mm straight pipe (no muffler): 0.29 Bar


https://cimg7.ibsrv.net/gimg/www.6sp...a7b94d24fa.jpg

Fantastic info, thank you!

Tfk 11-26-2018 08:23 AM


Originally Posted by AirBusPilot (Post 15454798)


So, the Cobb AP can permanently clear a CEL due to the missing cats as it comes from Cobb?

Thanks.

Afraid not.
The CEL/fault code is triggered by running catless.
The Cobb can Temporarily clear the CEL/fault code(s). But for as long as you're running catlless with stock/cobb ots tune, the codes will reappear again and again.
You can erase them again or leave them be.
The way the car drives won't change.
Apart from the CEL/fault code, there's no real harm done.
Granted, you could optimize the tune further for the catless downpipes - to bump up power/effeciency - but there's nothing wrong with you sticking to any of the cobb ots stage 2 maps.

For what it's worth, power wise, my 3" race exhaust paired with equal length tubular headers didn't really yield any power/performance benefit over my previous setup; OEM everything paired with catless downpipes.

If you're after sound, then it's a Very different story.

good luck

AirBusPilot 11-26-2018 08:33 AM


Originally Posted by Tfk (Post 15454808)
Afraid not.
The CEL/fault code is triggered by running catless.
The Cobb can Temporarily clear the CEL/fault code(s). But for as long as you're running catlless with stock/cobb ots tune, the codes will reappear again and again.
You can erase them again or leave them be.
The way the car drives won't change.
Apart from the CEL/fault code, there's no real harm done.
Granted, you could optimize the tune further for the catless downpipes - to bump up power/effeciency - but there's nothing wrong with you sticking to any of the cobb ots stage 2 maps.

For what it's worth, power wise, my 3" race exhaust paired with equal length tubular headers didn't really yield any power/performance benefit over my previous setup; OEM everything paired with catless downpipes.

If you're after sound, then it's a Very different story.

good luck

How will the car sound with stock muffler/no cats?

Thanks.

Randyc151 11-26-2018 08:43 AM

What 100-200 cell racing cats are you guys running? I'm looking for them right now, prior to going with a Cobb tune for track use.

Tfk 11-26-2018 08:52 AM


Originally Posted by AirBusPilot (Post 15454814)


How will the car sound with stock muffler/no cats?

Thanks.

Stock-like..
The tone is identical. But at a higher volume.
The pops and bangs do become more pronounced.

AirBusPilot 11-26-2018 08:53 AM


Originally Posted by Tfk (Post 15454825)
Stock-like..
The tone is identical. But at a higher volume.
The pops and bangs do become more pronounced.

That may be enough, for me. Thanks.

Tfk 11-26-2018 08:54 AM


Originally Posted by Randyc151 (Post 15454819)
What 100-200 cell racing cats are you guys running? I'm looking for them right now, prior to going with a Cobb tune for track use.

HJS cats seem to be the benchmark if memory serves correctly.
Most of the reputable catted aftermarket exhausts use HJS cats.

Tfk 11-26-2018 08:58 AM


Originally Posted by AirBusPilot (Post 15454826)


That may be enough, for me. Thanks.

I thought so too at first.
Apparently not.

More than volume, the 991tt needs help with tone in my opinion.
Speak to Sam about Kline.
Kine addresses the tt's tone very well. And they have many different volume levels as well.


SamboTT@ByDesign 11-26-2018 11:21 AM

Hi Air, gentlemen,

my pleasure the access port should be waiting for you when you get back and I’ll be here for you if you need some support getting it installed and set up to its full potential! Regarding the bypass bypass it’s a great option for those who are not looking for too much sound or perhaps not quite ready for a full exhaust system. Through extensive testing and independent results we’ve seen between 10 and 20 hp and 20 and 30 pounds of torque gained by running the bypass on the stock exhaust system. This is about 80% of what you get from changing the entire exhaust until you start getting into upgraded turbo chargers and more pressure than we see that if it’s from changing the whole system. It’s a good intermediate option for some as is the sport Cadillacs in place of the original they all have their place and pros/cons.

Randyc151 11-26-2018 02:59 PM


Originally Posted by SamboTT@ByDesign (Post 15455038)
Hi Air, gentlemen,

my pleasure the access port should be waiting for you when you get back and I’ll be here for you if you need some support getting it installed and set up to its full potential! Regarding the bypass bypass it’s a great option for those who are not looking for too much sound or perhaps not quite ready for a full exhaust system. Through extensive testing and independent results we’ve seen between 10 and 20 hp and 20 and 30 pounds of torque gained by running the bypass on the stock exhaust system. This is about 80% of what you get from changing the entire exhaust until you start getting into upgraded turbo chargers and more pressure than we see that if it’s from changing the whole system. It’s a good intermediate option for some as is the sport Cadillacs in place of the original they all have their place and pros/cons.

What sport cats do you like, Sam?

pfl 11-26-2018 03:18 PM

I’m running straight pipe from turbo back, no cats, no muffler. Car is very loud on cold start. After cold start, in normal mode it is relatively quiet at low speed only when not on throttle or barely touching throttle.

If if I get into boost, in any mode, it gets loud quick.


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