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Old 02-28-2018, 12:26 PM
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OverBoosted28
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Default Back pressure


Over the weekend I learned how sensitive our cars are with reduction of flow in exhaust. Had my street tail pipes on, and got dinked for 96.5 db (MRLS). Stuck my MC baffled tail pipes on, and was at 89 db. Sounds good right? Wrong! The previous event, I had a slight hesitation around 5k and up, going up the hill, and through front straight. Figured plugs might be tired, and extra boost is overwhelming spark. Didn’t get to plugs, and car had felt really good on drive to track. Next session with baffles, immediately notice my “hesitation”. So I end up short shifting the rest of Saturday, and most of Sunday. Last session Sunday afternoon, I figured I’d pull baffles, and see if I can get by sound. Immediately felt like I replaced 50 ponies, nursed it up the hill past sound (at 89 db), and ran my personal best pal time. The baffles I had been using are more so, spark arrester, than a muffler. Wouldn’t have thought it would have had such an impact on boost.
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Old 02-28-2018, 08:12 PM
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Mike J
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Just so I understand (since I do not remember what baffles you are running and if they are more restrictive than the stock pipes, or they are part of the custom crossover?) is that a more open exhaust downstream of the cats felt like more power and less hesitation, or do I have it backwards?

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Old 03-01-2018, 12:18 AM
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This is what I was using. Just a bolt, and nut, holding them in end of straight 997 tips I made. Cans are pretty much free of any packing, and no cats.







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Old 03-01-2018, 12:21 AM
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I was just stunned, that such a small amount of restriction, made such a noticeable loss in power. Easily at least 25-30+ hp loss, because it felt like 50 hp.
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Old 03-01-2018, 11:58 AM
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I guess it makes sense - probably the turbos naturally give the engine all the back pressure it needs, so anything downstream of the turbo should be as free-flowing as possible - less resistance in this area, it allows for more pressure differential across the turbo and thus better spin up and higher flow. I went with this theory when I built by exhaust, using 3" tubing right through to the mufflers - but I need to finish that system, I go to 2.5" tubing after that since I am using gutted mufflers. Yet another project on the list ... ;-)
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Old 03-01-2018, 08:13 PM
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You need these for Laguna " Fister Fangs "

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Old 03-02-2018, 12:22 PM
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Been there, done that. Was wanting to avoid sheering skin off my shins ��
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Old 03-02-2018, 03:08 PM
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Old 03-04-2018, 01:03 PM
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Default PIPES

SOLD

I have some AWE Dump pipes, I dont need, if anyone wants cheap PM, Stole these Pics off google, there in the garage somewhere.... $400




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Old 03-04-2018, 07:15 PM
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Originally Posted by AC/911's View Post
I have some AWE Dump pipes, I dont need, if anyone wants cheap PM, Stole these Pics off google, there in the garage somewhere.... $400



Nice tips!, they appear to be copies of the oe GT2Evo ones
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Old 03-04-2018, 09:30 PM
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They look loud ! Not so good for 89 db
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Old 03-05-2018, 09:59 PM
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SOLD

Never had them on, loud I'm sure, the "pea shooter" design is to tone down a bit, But how much??

I'm gonna give em' to my polisher & ebay for a good Chunk$, They were like $1200 new years ago....



.

Last edited by AC/911's; 03-07-2018 at 11:38 PM.
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