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Discussion Starter #1
Im thinking of modifying my exhast this weekend.
I orginally planned to buy a stillen downpipe and a new ATR cat back system. However, I've been reviewing the post's on this messageboard and as far as I can tell it is a waste of money since apparently you will only gain power by releasing the exhast gas that is restricted by the precats and main cat.
Does the stillen Downpipe eliminate both precats and the main cat, or just the front precat??
Would I be better off to just keep my stock exhast and downpipe and just drill out both precats and the main cat?? Im on a tight bidget, so anything I can do to save money will help. I want the exhaust to be loud, but not so annoying that I can't hear my stereo driving down the road, but most of all I wan't the extra 20-30 horses this mod can supposedly give us.
Also, can I drill out all my cat's without screwing up the ECU??

Please Help!!


Black 97VR4
Current mods include: K&N FIPK, HKS MBC @15 psi, 20%Window tint and brow, Two 10" JL 10W0 Subs in custom box and a 400watt Coustic Amp.
 

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Large Member
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6,164 Posts
You could do that.. it is a lot of work though, to gut the cats. I'm fairly sure the ATR will eliminate both precats completely. You also need to remember that just the design of the downpipe makes a difference, too. The stock downpipe is just plain restrictive, gutted cats or not. An aftermarket downpipe will flow much better, and give you better performance. But there is nothing wrong with just gutting your cats, esp. since you have a low budget..
 

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Vr-4 Evr
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2,027 Posts
no you want to get a downpipe because the piping size of the stock DP is to small. You will get more HP gain by just adding a downpipe alone with cats then a stock DP with no cats. Best thing to do is a downpipe and no cats=)
 

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The Wizard Of Aaahhhhh's
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1,596 Posts
The stock downpipe is F-shaped and is restrictive. An ATR, Stillen, Alamo, or any other aftermarket one is Y-shaped and flows alot better. As far as I know, the Stillen DP replaces the front precat and the main cat. The ATR does not replace any of the precats, but can be ordered to replace the main cat, or bolt up to the main cat. I have the complete ATR system on my car. I gutted the precats and ordered the ATR DP to replace the main cat, and bolt up to the ATR cat back. The flow is simply awesome. :)


Chris
 

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Senior Member "Go Pig Go"
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3,086 Posts
the atr dp does not eliminate any of the pre-cats....the stillen eliminates the front pre-cat. An aftermarket DP flows much better than the stock dp......it'll help spool the turbos much faster than the stock dp.
 

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Discussion Starter #6
I've heard gutting the rear cat is a huge PITA...
Looks like im gonna have to break out my pneumatic drill!!


So, will I achieve the same amount of Horsepower by bolting a stillen DP on with my stock cat-back still in place and drilling out the remaining rear pre cat as I would If I replaced the whole exhaust system? From what I have read you really don't get any performance gains from a cat back system at all, and I can't really afford to buy a cat-back system right now anyway. Has anyone tried this?? How does it sound??

p.s. Thanks alot for you're quick replies.. I love this messageboard...:D
 

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The Wizard Of Aaahhhhh's
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1,596 Posts
The DP and gutted precats will definatly help, but the stock catback is still pretty restrictive compared to an aftermarket one like ATR or Borla. The stock muffler is a POS in my opinion (at least the active exhaust muffler is). If you just install a DP and gut the precats, I think you will see a pretty good noticable difference. If you want to have the most free flowing exhaust either go with a custom setup or an ATR catback.
Search for a guy nemed Ruiner on here. I think he ran his car with an ATR DP for a while before he goy his catback. Try to PM him or email him and see what kind of a difference the DP alone made. I did mine all at once, so I really don't know.


Chris
 
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