Catalytic Converters And Headers

[alero_ecotec]

so basically i want to do a custom exhaust by the end of the summer.....im going to do 2.5 in piping to the camaro dynomax super turbo muffler.........now since im doing larger piping im going to get a high-flow catalytic converter...probably a dynomax super converter b/c the price is right......this brings me to my 1st question, i can get a 2.5 in converter that's 13.25 inches long for 54 bucks....but they have a 18 inch long converter that's 120 bucks....what's the advantage to the longer converter, and is it worth a crap load of extra money (i doubt it personally)........my next question is that sometime in the future im planning on getting some pacesetter headers with ceramic coating, should i have any trouble fitting these in if i put on a custom exhaust?...i have an ecotec by the way

[Redog]

Mmmmm, you post an interseting question.

A cat is a cat, I'm sure you can find the size you want, you'll just have to shop around. I suggest Summit Racing (http://www.summitracing.com) to find the cat, but do the headers you want come with a cat?, If they do it will be easier to hook up custom exhaust.

[alero_ecotec]

im pretty sure they do not come with a cat...........i've been told that the headers will hook up to the stock cat fine....so if the aftermarket cat is in the same place shouldnt it hook up fine too?

[Redog]

I would think so.

I suggest getting an O2 sim. off PFYC to keep that pesky SES light off

[alero_ecotec]

where does the O2 sim fit into

[AleroSS]

Ignore the comment about the o2 simulator, because there is no o2 sim offered for our cars (by our cars, I mean us ecotec owners), and your only option is either A: set off a CEL due to an obdII incompatible cat, and not knowing when something that REALLY is throwing a CEL light is actually happenin, or B: getting an OBDII compliant/compatible Cat, and leaving the stock o2 sensors (both of them) in the exhaust in their appropriate places. ALSO, if you are planning on staying NA (naturally aspirated) I would recommend only steppin it up to 2.25 as you will be losing back pressure, and may suffer more losses than gains with the oversized exhaust. HOWEVER, if infact you will be increasing performance on the car, make sure that the mods planned, will warrant a 2.5" exhaust.

Cheers,
Landon

[alero_ecotec]

i hear alot of different things about backpressure however......there's alot on here who say that less backpressure will not kill you at all..helps infact..i cant remember who, but im searching for the post now

[AleroSS]

Well youre partially right, backpressure isnt what is important per say, but rather EGV (Exhaust Gas Velocity) but the two normally go hand in hand. However, unless you are runnin a turbo under the hood, you certainly do need EGV/Backpressure, in order to maintain a decent amount of "pull" all across your powerband. Go over on Jbody.org and see what the J body owners have found using 2.5" on their NA ecotecs for the best feedback.

[alero_ecotec]

aleroSS, i searched around a bit on jbody and i understand what you're talking about now..........so, if i go with 2.25 inch piping will my local exhaust shop be able to fit that to the super turbo muffler that has a 2.5 inch inlet?.....or, also, would i just be better off going with something like this exhaust (http://www.horsepowerfreaks.com/price/Oldsmobile/Alero/performance/Exhaust/Exhaust_Systems) ??

[Grouch]

Originally posted by alero_ecotec@Jun 26 2005, 12:54 PM
aleroSS, i searched around a bit on jbody and i understand what you're talking about now..........so, if i go with 2.25 inch piping will my local exhaust shop be able to fit that to the super turbo muffler that has a 2.5 inch inlet?.....or, also, would i just be better off going with something like this exhaust (http://www.horsepowerfreaks.com/price/Oldsmobile/Alero/performance/Exhaust/Exhaust_Systems) ??
Quoted post


Yes they will. But why don't you just go with 2.5-inch pipes? It has been dyno proven that you still get a bit better results with 2.5 over 2.25. Same set up I have 2.5-inch pipes from the catback with the superturbo muffler. Nice combo. ;)

[alero_ecotec]

also, would it be ok to stick with the stock cat because when i looked up the price of a OBDII compliant flowmaster that had dual sensor hookups it was going to run me 200, and that's a crap load of money for just a converter.......and if i dont get an OBDII i will throw a code correct?

[alero_ecotec]

ahhh i knew there was a veteran on here who always said that 2.5 is better than 2.25....now i really dont know what to do

[AleroSS]

Im leery of these "dyno results" especially whether they pertain to the ecotec specifically. Certain cars, and certain motors respond differently to different sizes, so without seeing these dyno results Im gonna have to wave the BS flag until I see proof. Im not disputing the fact, I just need to see proof first. There are a number of variables that have to be factored into that statement before just accepting it as a fact. Such factors include header upgrade? crush bent or mandrel? choice of muffler? cat convertor? etc etc If you are going with a crush bent system, and its not one of the nicer benders, you will be able to get away with 2.5" however a lot of the newer/nicer benders barely crinkle the inside edges of the bend, and alow for flow results closer to the mandrel (but not an equal flow to mandrel)

Also, as I posted in another thread in here " GM actually supplies a rather good cat with their cars. The shame being that they only allow for a small inlet and outlet for gases to pass thru. If you find someone who can enlarge the openings, youd be saving yourself a nice pocketful of change, and be able to run the stock cat on a larger diameter exhaust with decent results."

They can flare out any piping to go from 2.25 to 2.5, and when it comes to fitting your muffler(s)

[alero_ecotec]

well......i dont know, on jbody they really have a strong stance on 2.25 being a better size if you're staying NA....and at this point in time, being that im a poor college student, im definately staying NA....my goal is eventually 200 hp NA, and from talking to some people on ecotecpower.org and talking a bit back and fourth with mantapart i've decided it can definately be done...but this wont happen untill i start taking loans for dental school, where i can just tack on an extra 5 grand a year for car money :thumb: .....so what are the openings on the stock cat? 2.25 or smaller?

[alero_ecotec]

also, am i going to need a resinator, the guys over on j-body are using one......... getting an OBDII compliant/compatible Cat, and leaving the stock o2 sensors (both of them) in the exhaust in their appropriate places. does that mean there are 2 o2 sensors in the cat.....or one in the cat and one somewhere else?

[AleroSS]

There is one 02 sensor in your exhaust manifold or just a lil downstream of it, the other is just after the cat convertor.

cheers