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23109VC · 04-20-2009, 04:03 PM

I have a 2000 2.7L 5 speed.

I have desnorkeled and have a pedro muffler. my headers and midpipes are stock.

I am thinking of adding an exhaust/header setup. I like how my car sounds now, but wouldn't mind more power.

I have seen the dirt cheap chinese headers on ebay - I've read some threads here where people have liked them, others said they were too loud, or threw CELs...

I believe my car has cats in both the headers and midpipes. I believe my O2 sensors read before/after the front/primary cats and that's it. So if I remove the midpipes to cat delete pipes - I still have the cats up front and my o2 sensors won't know the difference - BUT, I've read that of the two sets of cats - the fronts are the more restrictive ones... not sure if that is true or not.

SO - if I want to maximize power - then I should get rid of the headers and put on some that have NO cats, but then relocate my O2 sensors to after the secondary cats... which migh require some welding, adding extension to the O2 wiring, and installing some bungs onto the midpipes.....

I could just blow a big chunk of change and buy a full NHP system that has cats in the headers and in the midpipes..they claim they are high flow cats... but I'd rather not blow big $$ on a sysstem if I don't have to.

my goal is to maximize performance, but do it on a budget.

what is the consensus here?

am I beffer off getting rid of the front/primary cats or the secondary cats? is one more restrictive than the other?

I live in CA and so I must run some kind of catalytic converter - while the visual might mater which one I have - I kinda think I could squeek by as long as there is SOME cat on the car. so many smog stations are ignorant about porsches and they see so few cars they will have no clue if I am supposed to have one or two sets... as long as it has some on it, and it passes the sniff i'll be okay.

I Just smogged the car, so i'm good for the next two years anywya.. so screw it. but i don't want to run catless as that is illegal and would be a big nasty fine if I was to be caught - so I have no desire to do that.

so - do I get rid of the front set or the rear set? will one make more of a difference in power gains? will one or the other being removed affect the noise level / sound of the exhaust?

the cheapest route I can think of right now is to add cheap chinese headers - $100 or so - and then reroute some of the O2 sensors rear of the secondary cats... then I still have two cats - but I have a high flow header on the engine.

will that make my car louder? crazy loud?

if I opted to get the NHP heders that have "hi flow" cats in them - will it really make any power - or is the fact that there is a cat in there going to clog it up a log more than the chinse headers. i would have to think that NO cats in there is going to obviously flow the best, and even a 'high flow" cat has to have a bunch of restriction...

suggestions? also - is all this a big waste of money? i mean, how much hp will I pickup on a 2.7 by doing this???

also - would I need to redo my ECU to take advantage of this? are those chips any good? i know they are not cheap - i have seen them and I belive most of them are $1000+ just to get a new flash. unless it makes a noticabel gain in power - that's a lot of money...

okay - another questio - do those chips help on a stock car??? or are they only good after you do intake/exhaust/etc

thanks!!!

04-20-2009, 04:03 PM	#1
23109VC Registered User Join Date: Mar 2008 Location: CA Posts: 726	Header/exhaust question I have a 2000 2.7L 5 speed. I have desnorkeled and have a pedro muffler. my headers and midpipes are stock. I am thinking of adding an exhaust/header setup. I like how my car sounds now, but wouldn't mind more power. I have seen the dirt cheap chinese headers on ebay - I've read some threads here where people have liked them, others said they were too loud, or threw CELs... I believe my car has cats in both the headers and midpipes. I believe my O2 sensors read before/after the front/primary cats and that's it. So if I remove the midpipes to cat delete pipes - I still have the cats up front and my o2 sensors won't know the difference - BUT, I've read that of the two sets of cats - the fronts are the more restrictive ones... not sure if that is true or not. SO - if I want to maximize power - then I should get rid of the headers and put on some that have NO cats, but then relocate my O2 sensors to after the secondary cats... which migh require some welding, adding extension to the O2 wiring, and installing some bungs onto the midpipes..... I could just blow a big chunk of change and buy a full NHP system that has cats in the headers and in the midpipes..they claim they are high flow cats... but I'd rather not blow big $$ on a sysstem if I don't have to. my goal is to maximize performance, but do it on a budget. what is the consensus here? am I beffer off getting rid of the front/primary cats or the secondary cats? is one more restrictive than the other? I live in CA and so I must run some kind of catalytic converter - while the visual might mater which one I have - I kinda think I could squeek by as long as there is SOME cat on the car. so many smog stations are ignorant about porsches and they see so few cars they will have no clue if I am supposed to have one or two sets... as long as it has some on it, and it passes the sniff i'll be okay. I Just smogged the car, so i'm good for the next two years anywya.. so screw it. but i don't want to run catless as that is illegal and would be a big nasty fine if I was to be caught - so I have no desire to do that. so - do I get rid of the front set or the rear set? will one make more of a difference in power gains? will one or the other being removed affect the noise level / sound of the exhaust? the cheapest route I can think of right now is to add cheap chinese headers - $100 or so - and then reroute some of the O2 sensors rear of the secondary cats... then I still have two cats - but I have a high flow header on the engine. will that make my car louder? crazy loud? if I opted to get the NHP heders that have "hi flow" cats in them - will it really make any power - or is the fact that there is a cat in there going to clog it up a log more than the chinse headers. i would have to think that NO cats in there is going to obviously flow the best, and even a 'high flow" cat has to have a bunch of restriction... suggestions? also - is all this a big waste of money? i mean, how much hp will I pickup on a 2.7 by doing this??? also - would I need to redo my ECU to take advantage of this? are those chips any good? i know they are not cheap - i have seen them and I belive most of them are $1000+ just to get a new flash. unless it makes a noticabel gain in power - that's a lot of money... okay - another questio - do those chips help on a stock car??? or are they only good after you do intake/exhaust/etc thanks!!!