lowbee

There were some interesting discussion on a CAT pipe group buy post I started a few days ago regarding straight pipe versus X-pipe. I'd like to restart that discussion in this new thread even though the Group Buy was taken down due to the shop offering the Group Buys wasn't a registered vendor on this forum. Enough said about the group buy and I'd like to hear why people prefer X-pipe over straight pipe.


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Initially x-pipe look more appealing to me because it looks sexy (and different from OEM) plus it is shown to flow more CFM due to scavenging effect; however, digging into this some more I found that flowing more CFM for a naturally aspirated engine is not always a good thing. I've been looking at CAT pipe options and come across a few reviews on different 997 forums, my research leads me to believe that the straight CAT pipe give the best of both worlds in term of low-end torque and sound. My research leads me to conclude that x-pipe will be louder at below 3500 rpm and you lose in the neighborhood of 25 lb-ft of torque down low which is something I want to avoid. So IMHO if you want the car to be loud from 2000-7000 rpm and don't mind LOSING around 25 lb-ft of low-end torque, x-pipe is for you; however, if you want the car to be loud only from 4000 -7000 rpm then I think going with straight CAT pipe might be a better choice.

The following reviewer from another forum tested both straight CAT pipe and CATLESS x-pipe with dyno chart reaches a similar conclusion
https://www.pistonheads.com/gassing/topic.asp?t=1276180


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FVD developed a U-shape CAT pipe for 997.1 and claim that it will prevent losing low-end torque
https://www.fvd.net/us-en/21011125/9...-u-design.html



I think I will go with straight pipe unless I learn something new in this discussion because I would hate to losing any low-end torque for a primary sound enhancing mod....


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roman944

if this is a cat discussion, maybe someone can explain to me how this works - we have downpipes - then cat pipe or x-pike - then muffler? so when buying a fabspeed exhaust I would buy mufflers and x-pipe or cat pipe?

sorry don't mean to derail

from little research, I think general population that drives their car on street every day would probably care more about the sound then potentially loosing a couple horses at the limit

cwheeler

For me, the engine is meant to be driven at high RPM. That's when the thing comes alive. Losing HP at 3000 doesn't mean much as I don't drive down there once the car is warmed up. Moreover, the exhaust note is better, with the X-pipe.

Cw

vern1

Lowbee, I went through the same process as you and went with the AWE straight pipes for the same reasons.

A few comments though. I dont think the cats are just loud above 4k. I have headers, cats and gundo and it is plenty loud at all rpm's

Roman994, i would disagree on the statement as you are not losing HP at the limit (as you should gain at the limit as its a freer flowing system) but rather its the torque you lose and people do care about that (25ft/lbs is material). The torque curve is much more relevant to the everyday drivability and "quickness" of the car. Re Fabspeed, I dont know what kind of car you have but Fabspeed will sell you components or the full system - check out their website

cwheeler, also disagree with this. You have to get through 3k rpm to get to the higher rpm's and the torque (not HP as you claim) you lose at that part of the curve is critical to your performance. Why would you want to give up TQ?? There is no benefit/tradeoff that the crosspipe provides to offset this loss that I am aware of. Also i dont think the exhaust note is "better" with the crosspipe. The straight pipes provide an outlet directly from each bank and generally provide a lower, more throatier sound. I consider that "better" but of course this is subjective

Cheers

roman944

maybe what I said kind of came out wrong? someone who is looking for more performance then aesthetics/sound is going to care more about the drop in hp/tq then the other

think of what kind of gains you get with just a sound modification vs actual exhaust system? that's all

vern1

Well i hear ya but if you just want some more sound then the gundo will do that for a couple of hundred bucks. But we are talking about cats here and once you are looking to purchase cats then its a significantly larger cash outlay and you want sound AND performance. At least i certainly did

lowbee

Ideally, I'd like a setup that a bit louder than stock under 4K and goes louder and louder as the RPM climb

If there is gain to be had great but I sure don't want to lose what's there now

vern1

Well i am also in TO if you want to hear mine at some point. Do you already have gundos? They make it louder than stock but the addition of 200 cell cats takes it up another notch

The combo definitely screams as the revs climb....

lowbee

Great, I might just take you up on your offer. Do you come out to the PCC or PTN meets ? I have DesignTek muffler from Design911 in the UK, it's a tad louder than stock and works out perfect for me.

You Tube

I am hoping the CAT pipe will free up so HP at the top end because I do feel like the car is making more effort up high but I also want to sacrifice as little torque in the low-end as possible. I will deal with how the car sound once I am happy with how it drives and that might involve doing something with the muffler once the CAT pipes are in.

vern1

Sorry what are those meets? Can always try and drop by to one depending on where they are. I am in the Beaches

Assuming you are looking at 200 cell cats it will free up the top end for sure. It will definitely be louder than what you've got. I also have a few other mods (4.0 L, gt3 TB, IPD plenum, x51 headers, that may contribute a little more sound to my set up as well)