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Which Cat-back Is Less Restrictive ?

cobrAA

By cobrAA,
in Engines & Forced Induction

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cobrAA Mentor

cobrAA

Posted
Posted (edited)

I have a dilemma. I've been reading about cat-back for the last 2 weeks. I have to swap my RS*R Exmagt2 for either:

1. a 3' non straight pipe cat-back ( I.E: Magnaflow XL turbo) + Swap the downpipe for an Aftermarket.

http://www.magnaflow.com/02product/shopexd...ain&id=8264

xl02.jpg

Or

2. The OEM cat-back which is 2.5' but straight pipe + adding a Y pipe with a electric open-valve ( cutout) just before the cat. But I'm afraid it will be way too loud to run it on the street and won't use it enought to make it worth the hassle.

006-2.jpg

EchappementOEMGTR2.jpg

3. Varex cat-back with the butterfly valve but is there any backpressure problem with this exhaust because if you close the valve it will only have a 1 inch hole?

VarexDiagram.png

Which one should be less restrictive?? a 3 inch 3 chamber system or a 2.5' straight free-flowing..

For the moments, I'm fairly stock ( approx. 340whp) but I plan on upgrading the turbo( -5) and go to the 450ish whp marks and I don't want to loose like 50 HP because of those exhausts.

Edited by cobrAA
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R31Nismoid Grand Master

R31Nismoid

Posted
Posted
waits for nismoid's normal exhaust answer :P

''you can have a quiet exhaust which IS fairly well flowing"

:teehee: Nah i've got a better one! :P

450rwhp - you have the wrong wrong wrong turbo choice. The choice you want is the Garrett -9s!!!!!

Not really on topic, but needs to be said as far too many people are poorly informed about turbo selection.

Varex - Crap. They sound dreadful. I've not heard one car fitted that sounds any good. Must be the materials used, they just give off a woeful exhaust note.

OEM - Crap... OEM is like the pinnacle of restriction. You can't hope to make 330rwkw with a 2.5" exhaust.

Magnaflow - NFI, but just looking at the design i cannot see how that's going to flow at all well.

Why don't you just build a proper 3" straight through system?? It will 100% be under 90dB if done right.

Hell even off th shelf jap systems are under 90dB and you can get them 2nd hand for $600-$800 worst case.

Ideally you want a 3.5" system for the power goal, but you will "get away" with a 3" if you must, without question, be legal.

3.5" is a bit harder to get to legal without some love :bunny:

cobrAA Mentor

cobrAA

Posted
  • Author
Posted
:P Nah i've got a better one! :thumbsup:

450rwhp - you have the wrong wrong wrong turbo choice. The choice you want is the Garrett -9s!!!!!

Not really on topic, but needs to be said as far too many people are poorly informed about turbo selection.

Varex - Crap. They sound dreadful. I've not heard one car fitted that sounds any good. Must be the materials used, they just give off a woeful exhaust note.

OEM - Crap... OEM is like the pinnacle of restriction. You can't hope to make 330rwkw with a 2.5" exhaust.

Magnaflow - NFI, but just looking at the design i cannot see how that's going to flow at all well.

Why don't you just build a proper 3" straight through system?? It will 100% be under 90dB if done right.

Hell even off th shelf jap systems are under 90dB and you can get them 2nd hand for $600-$800 worst case.

Ideally you want a 3.5" system for the power goal, but you will "get away" with a 3" if you must, without question, be legal.

3.5" is a bit harder to get to legal without some love :P

The problem is to be legal I have to have a non-straight through system( excepting the OEM) or else I will get a exhaust ticket and will have to go to court to fight it( something I'm freakin tired to do)

Cosa Community Regular

Cosa

Posted
Posted (edited)

I read an article in HPI where they tested an OEM catback against after market on an R32 GTR with mild mods. Had 3" from turbos to the cat back.

In the article they CLAIMED they made 2kw more with the OEM.

Edited by Cosa
PM-R33 Grand Master

PM-R33

Posted
Posted
Varex - Crap. They sound dreadful. I've not heard one car fitted that sounds any good. Must be the materials used, they just give off a woeful exhaust note.

Not entirely true. The rear mufflers/cannons might not sound the best, but i use one of their universal ones underneath the car to keep the car quite when needed (99% of the time its opened) and you would never pick something wasn't right on the car when it is opened. When it is shut its just quite as all hell. Im getting a 3" straight pipe to bolt on and off to replace the varex when needed due to the Varex weighing half a million kg's and sitting quite low.

cobrAA Mentor

cobrAA

Posted
  • Author
Posted
Not entirely true. The rear mufflers/cannons might not sound the best, but i use one of their universal ones underneath the car to keep the car quite when needed (99% of the time its opened) and you would never pick something wasn't right on the car when it is opened. When it is shut its just quite as all hell. Im getting a 3" straight pipe to bolt on and off to replace the varex when needed due to the Varex weighing half a million kg's and sitting quite low.

Yeah, my valve would be open 99% of the time. the 1% will be when I see a police. It is that heavy?

Do you have a sound clip of that varex :worship: ?

Parag0n Mentor

Parag0n

Posted
Posted (edited)

All those catbacks look shit to be honest.

Get something fabricated, will probably end up coming out on top in both price and performance.

If you're paranoid about the loudness of your car get some mid mufflers / resonator or just baffle the shit out of a box and call it your exhaust.

Edited by Parag0n

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