Exhaus system: cat or no cat, that is the question

mocpac · Post by **mocpac** » Sun Jun 18, 2006 3:35 am

Well Im about to put the new header in a couple of weeks. But now Im not sure about to put a performance magnaflow cat or just leave a straight pipe. Here is the deal.

*Header (4-1), perfromance cat, hi flow resonator, hi flow muffler, complete exhaust system 2¼ (stock 2").

I know that the cat can make some restriction but I'm aware about the noise, and a little about the emanations (save the planet, save the wales). Now, I will put just one cat and increace the pipe size, and this cat is "performance, suposed to restric less. Do you think this will make a notable restriction or diference? By what I read, a complete cat system (streight pipe from header to muffler) can give you from 20 to 35 hp depends the car. So what you think

Nubira2.2 · Post by **Nubira2.2** » Sun Jun 18, 2006 8:01 am

the goal of a performance exhaust is to reduce backpressure

by this the engine will be able to generate more power because less power is being wasted pushing exhaust gases through exhaust system

increasing the exhaust pipes diameter will reduce back pressure and if you are using a high flow cat and resonator they will still give backpressure but less than the OEM ones

the hp and tq agains will be determinated by the efficiency of the OEM exhaust system against your new one

i think 4-1 header, 2.25 pipe with a single high-flow cat and resonator will be more efficient and will keep your car quiet

woo · Post by **woo** » Sun Jun 18, 2006 1:14 pm

no back pressure= no torque while too much = no power. There is a ballance. Every mechanic i have spoken to and every exhaust shop and my friends who have found this, say that on non turbo cars, cannon mufflers are a load of crap

mocpac · Post by **mocpac** » Sun Jun 18, 2006 1:45 pm

woo wrote:no back pressure= no torque while too much = no power. There is a ballance. Every mechanic i have spoken to and every exhaust shop and my friends who have found this, say that on non turbo cars, cannon mufflers are a load of crap

so +1 for the cat?

kinkyllama · Post by **kinkyllama** » Sun Jun 18, 2006 6:14 pm

I take it you have the 2.0?

If I were you I'd go with 2" piping since your deleting a cat and having hi-flow everything else. Even that maybe not enough restriction. I doubt the stock ones 2" though... my forenza was much smaller than that.

mocpac · Post by **mocpac** » Sun Jun 18, 2006 6:44 pm

Yesp in the 99 to 2003 nubiras the pipe is 2" in the 98 is 1.75" why dont know, my teory is that the car was made with the 1.6L engine so whn they swap the engine and put the 2" never change the pipe until 1999.

Any how. the cat is performance not hi flow just the resonator. BETO, and nubira2.2 have a straight pipe and no have problems. Nubira2.2 have a 1.75 and beto a 2"

Nubira2.2 · Post by **Nubira2.2** » Sun Jun 18, 2006 10:26 pm

my car has 2" pipe with no cayt and resonator

and a magnaflow center-corner muffler

with the 2.2L engine and it works fine

mocpac · Post by **mocpac** » Mon Jun 19, 2006 1:43 am

my fault