[Rap]

DS I agree. I have noticed a difference in the sound of the two cars.

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[flash]

tama - i never said the pipe size was inadequate. i said that press bending is a problem. the rs barn is mandrel bent.



2.5" is fine. i tried increasing pipe size and it lost a LOT of power.



the muffler is the main problem (as long as you're ok with the fitment). on naturally aspirated cars it doesn't hurt as much, and maintains the torque, but on an sc car, it limits things, and on a stage 3 sc it just isn't nearly enough

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[ds968]

Just curious, and we're talking about SC'd cars of course, is there any restriction / power difference between a catback with resonator vs one without ? My BB is without a resonator ( BB did offer both versions of catbacks for the 968 ) Not sure if resonators add a little more back pressure or not ..

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[flash]

it would depend on the resonator. a louvered one would cut power. a perforated one, not so much

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[986boxster1998]

On a related note would too much restriction in the exhaust limit supercharger boost? The boost gauge I installed doesn't show more then 4 PSI running the stock exhaust. I was thinking I probably just needed to retension the belt.

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[gbarrier]

Thanks flash for the note on the B&B. I agree that it is just a bit loud but it was almost new on the previous 968 when I bought it and it was hard to let it go with it when I sold that car so I switched the stock from my current car to that car before I sold it. Not sure I would pay the $1K it lists for.

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[flash]

actually, if anything, restricted exhaust should show higher boost readings. a boost gauge shows the net result of flow. cork things up and you get more leftover pressure which shows up on a boost gauge.



i would be looking for a leak. you would be amazed at how little it takes to lose 2 lbs of boost. i had one clamp just a touch unseated and did that.



tired valves or incorrect cam timing will do that too.

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[tamathumper]

@flash, I didn't say anything about pipe size. Are you confusing me with KRAG50? How could that happen when our avatars are so different!? <img src="/forum/images/smilies/968/biggrin.png" class="smilie" alt="" />

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[Cloud9...68]

[quote name='tamathumper' timestamp='1374255332' post='145904']

@flash, I didn't say anything about pipe size. Are you confusing me with KRAG50? How could that happen when our avatars are so different!? <img src="/forum/images/smilies/968/biggrin.png" class="smilie" alt="" />

[/quote]

Funny, I made the same mistake in another thread!

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[flash]

oops - all of those red cars look alike to me - lol

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[rxter]

OK then - I'll hold onto my pennies until a recommendation is made. I'm perfectly happy with the current performance, but would never leave the extra on the table for no good reason.

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[psuphoto]

Curious how much more awesome does it sound and how much more horse power can you expect

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[psuphoto]

[quote name='flash' timestamp='1374165465' post='145833']lol - i spoke to dynamax, and they pointed me to their website, which clearly shows that the muffler begins restricting at 193hp. on a supercharged engine, you are leaving about 15hp and 10 lb/ft on the table (yes, i tested it, but only on two cars, and with two muffler changes). besides that, you will likely blow the back end off of it, due to restriction. some of us already have.



that being said, i have not found anything else that sounds right, is quiet enough, and does not cost power



so, to answer your question, yes, but i don't know what to recommend yet. i have another muffler to st later this summer.[/quote]

can the same be said for A NON SC engine? in other words, how much world just changing the exhaust matter to a non super charged 968?

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[flash]

psu - there is NO horsepower gain with the rsbarn cat-back. but, it is the only one shown not to lose torque. all other aftermarket cat-back systems lose torque, right where most people drive the most, regardless of any minimal upper end horsepower gain. the cam overlap, and intake pulse timing create a complication with opening up the exhaust. there are countless dyno charts out there to show this.

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[bombfactory]

Flash, so on a minimally modified (chip, airbox mod) NA car, is it best to just stick with the stock exhaust? I think the only reasons I might switch to something else would be for better sound and lighter weight, but it's certainly not worth the trade-off if I'm going to lose performance.



I'm still interested in just what happens to the sound and performance of the stock muffler if the restrictor plate in front of the resonator is removed. Loss of torque? Is it louder?

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[flash]

wow - it never ceases to amaze me at how people read something that is not written, or jump to a conclusion. i'm not sure where that comes from, beyond wishful thinking, but no worries. i just find it interesting.



ok - here we go



on a STOCK car, there is no gain to be had with the rs barn, but it is the only system shown not to incur torque loss.



on a modified car, (and this includes chip, airbox, etc) the stock exhaust shows its limitations, and while the rs barn cat-back by itself doesn't gain anything, it does allow more out of the other mods, again without torque loss. the difference isn't huge, but it's there.



other systems may allow more top end gains with the other mods (and we are talking 3-4hp), but suffer increased low and mid-range torque loss, over what they did compared to with no mods, in the neighborhood of 10-15 lb/ft. this occurs centered at 3.4 - 3.7k rpm, and extends a few hundred rpm in both directions. this is particularly troublesome, as that is where most people spend the most time. it is the absolute worst place to lose torque.



weight loss will show a relative performance increase, albeit minimal. it can really add up though if you lose weight in a lot of other places too.



tone is very subjective. i like the dynamax tone (the muffler rs barn uses), and like the b&b from behind the car , but hate the b&b from inside. i'm not fond of stock either. i'm still searching for the right combination.



removal of the "restrictor plate" has been done. there is a thread about it. it does essentially what most of the aftermarket systems do. it makes it louder, fartier sounding, and suffers the same kinds of torque loss, albeit with some minimal hp gains up top. i think there was 4hp. i drove a car with this done, and it was a little bit snappier, as there was less restriction, but it wasn't any more powerful.



for clarification, when i say "up top" i mean over 5k rpm

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[kzem1]

Flash,



Specifically what Dynomax muffler do you recommend? I sent to their web site to read up on them and Porsche is not listed.

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[flash]

i don't. i tried their flapper unit. complete fail. all of the straight through mufflers i've tried are too loud. while i haven't tried theirs, it's built the same as the others, and i can't think it's going to be any different.



i need to find a baffled unit, or a reverse flow unit, that allows the flow i need, while not creating restriction.



there is a muffler i need to try, but it's pricey, and i don't have the time right now.



for the moment, i'm running a magnaflow 22" resonator and a flowmaster super50 muffler. both stainless. the pipe is 2.5" fully mandrel bent. i am going to try something with this setup first, which might quiet it down. again though, i need to find the time.



i'll let everybody know what i find out. it will be this summer some time.

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[kzem1]

Thanks for the info. I look forward to hearing what you find out this summer. I am in no rush to spend more money right now anyway. LOL

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[986boxster1998]

This thread made me decide to hold off on an exhaust for the moment; I did however take the restrictor plate out of the stock exhaust on Saturday. It opened things up noticeably and the boost gauge now shows 3 PSI instead of 4 at peak so what Flash said about the corking effect was absolutely correct. I'll be checking for leaks this coming weekend.

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