[Eric_Oz_S2]

I want to get rid of my cat converter. The way I see it there are two options:



1. Test pipe

2. Install a silencer like this one:



http://www.promaxmotorsport.co.uk/produc...-only.aspx



My question relates to the sound difference. I'm reasonably confident option 2 will keep the sound as it is or similar - which I like from my rear Dansk silencer and cat converter at the moment.



My question then is will option 1 increase cruise noise or result in a drone? Is option 1 likely to push the total noise up considerably or will it just increase marginally.



So if anyone has installed a test pipe in their 968 - let me know what your opinion of the change was.



Thanks



Eric

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[flash]

this relates only to the 968 cat, which, according to everything i can find is specific to the 968, and very different than the previous S2 cat.



removal of the cat will absolutely change the tone. it will get raspier, louder, and sound like it has a "hole" in it. this is due to the change in velocity. the cat really slows things down. if you look at the profile of the entry, they worked it to change the speed and tone. even a resonator in there won't do the same job. i've been playing with exhaust tone stuff for a long time now on this car. it's amazing at how even little things change the tone of this system. i am still playing with it to try to kill a "kazoo" sound when it's cold, and lower the note (not the level)

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[jws]

Flash, now that I have my ride I am like all (or most) new toy owners, I want to noodle with it. I would like you to give me your long time ownership advice. I live in a state where we don't have any emissions testing so anything is ok! What would be the best system in your opinion from the head to the tailpipe. I am 52 so I really don't want to sound like I am going 10,000 mph while I am sitting at a stop light but on the other hand if it sounds nice some noise is a good thing. Also pulling the cat would be a no brainer so take that in consideration in your recomendation.

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[flash]

this car responds like no other i've ever dealt with when it comes to exhaust. the things you would do to just about any car, do not work on this one, and actually mess things up. i've spent many thousands of dollars and a lot of time trying and testing things. it has been a long and frustrating process, with results that surprised me.



pulling the cat will NOT help anything useful. in fact, it will result in odd running conditions, likely early O2 sensor failure, and a loss in low and midrange torque. leave the cat in there.



as for behind that, there is really no magic to any cat-back. the only advantage to buying a full system is that you don't have to spend the day at the muffler shop.



if you decide to do it yourself, you can use a 2.5" diameter mandrel bent pipe. larger diameter pipe than 2.5" results in major low and mid torque loss. it is important though that it is not a standard press bent pipe like you would get at the cheap muffler shops, as the press bends present turbulence. mandrel bending will cost you twice what press bending does, but it works.



mufflers are a very subjective thing. there are many ways to go. some of them will cost you torque. some of them will cost you upper end hp. some just sound nasty.



i don't have any "perfect system" recommendations. even mine is a little bit louder than i want (that mark seems to be a moving target as i get older). i have a couple of things to try yet, but i haven't had time. it's the best i've come up with though, and the tone is good. it's a magnaflow super 50, with a 22" flowmaster perforated resonator.



the dynomax muffler is the smoothest sounding, and does not result in loss of torque, but it does have a horsepower limit, where it begins restricting things. more than one of us has blown it apart.



the b&b will give you a couple of upper end hp, but at the cost of low and midrange torque. it is the lightest of the bunch though.



the flowmaster super 50 has the best flow, but resonates a bit more than some would like (the stainless one resonates more than the mild steel one too). a 20" or better perforated (not louvered) resonator must be used with it to maintain power.



the sebring straight through sounds great, but results in a torque loss at 3400rpm, like all straight through mufflers on this car



the magnaflow mufflers that fit all result in power loss and really loud sound



the zoomers that fits is the same as the magnaflow



the cargraphic system loses power and is heavy



i've played with a few other odd ball mufflers, but can't recall their names right now.



i hope that helps

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[kzem1]

Do you have the part numbers for the correct super 50 and the resonator. It seems there are multiple options on the site under that muffler. I am going to sound stupid but I assume a 22" perforated resonator is a separate piece available on the same site? Sorry for my ignorance. Just looking around.

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[flash]

different company on the resonator (note: magnaflow and not flowmaster)



i'll have to pull the part number for the muffler and get back to you

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[kzem1]

Oops. Hense the ignorance part.

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[MCL968]

Thanks for the info, Flash. I have seen this with 911's, where they came from the factory so well engineered that changing things resulted in torque losses or flat spots in acceleration. It's good to know that this is not the place to look for significant gains in HP.

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[jws]

Yea, I also really appreciate the info! I enjoy bouncing ideals off of people that know what they are writing about. It saves allot of time and that is something you can never get back once it's gone. That is what's nice about forums like this were the subject matter a particular car and not just a generality. Thanks' again!!!!

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[flash]

yup - i have to hand it to porsche on the exhaust. they did a LOT of engineering on it. they slowed things down in there twice. there is a reducer just before the cat, and a restrictor in the resonator, both of which are designed to slow down the gasses to balance with the cam overlap and sound requirements. it may leave a few upper end hp on the table, and it may weigh a ton, but it does do its job.



to date i don't like any of the packaged systems. either they don't fit right, and hang too low, or they come apart, or they lose power, or they sound like crap. that's why i still have the stock system in the white car.

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[Cloud9...68]

To me, the major advantage of an aftermarket cat back is that it cuts out 30-40 pounds. Can't remember the brand of mine (hurt my back pretty bad recently, so I don't want to bend down and read it right now), but I really like the sound, and I haven't detected any loss of power anywhere, although I changed so much on my car (freshly rebuilt engine, took out about 200 lb) that it isn't a fair comparison.

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[flash]

you can pretty much figure that any straight through muffler (as opposed to a baffled or reverse flow) will cost you a good 10 lb/ft of torque in the middle. some more. some also down low. some will give you a small amount of upper end hp in the trade. to show it fairly easily, you need to either put it on an eddy current or load generating dyno, or drive around, never going above 4k rpm, and test acceleration in 4th gear or better (lower gears accelerate too quickly to give good comparisons)

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[ds968]

[quote name='flash' timestamp='1381513146' post='150611']

never going above 4k rpm, [/quote]



Whaaat ?! That's just crazy talk man, don't listen to him folks and take MY advice : never let that engine drop BELOW 4k rpm..ever..not even when you pull out of the garage ! <img src="/forum/images/smilies/968/3gears.gif" class="smilie" alt="" /> <img src="/forum/images/smilies/968/tongue.png" class="smilie" alt="" />

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[DaveN]

I back in so this is going to be a real challenge! Thanks for the exhaust specs Flash. As you may remember, my pipe/muffler fit poorly and met the road through the mountain a few times. I have straightened it a bit since I returned home but the pipe and muffler have dents so replacement is inevitable. Too bad there isn't a mandrel bender within 300 Km's of my place <img src="/forum/images/smilies/968/sad.png" class="smilie" alt="" />

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[flash]

that is the biggest problem. more than once i have thought about knocking out a tail pipe for sale, and letting others figure out what muffler to use. i just never got around to it.



press bending costs power though. on an sc, it can be as much as 20hp

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