Downpipe Questions

[pwayzjellyroll]

I did some searching but had trouble finding exactly all the answers I was looking for and understanding what I read. So here they are.

1. How do I determine what size down pipe I need?

2. My exhaust is 2.25 inches I believe with a high flow cat does the brand matter or just the flange size?

3. From what I can tell there are ones that hook up to and ones that eliminate the cat, if I decide to eliminate the cat will I throw CEL'S? A friend of mine used to have a 2g eclipse without a cat, and it had CEL's all the time and he said they were because of that.

4. Are they bolted on or welded? Or either or, because brining it to an exhaust shop is not ab big issue.

5. Brand advantages? It seems alot of them have the same size piping and what not, what determines a good and a bad one?

 

[McFox]

Your downpipe will drop from the turbo down to right about under your engine. You'll want to get under your car and see what the current flange set-up is and get a matching downpipe flange.

I've never heard of a downpipe eliminating a cat. There is a thing called a test pipe which replaces the cat with straight piping. However if you do remove your cat you will throw a CEL.

I think most are bolted. I had a leak so I ended up welding the DP to the exhaust. Whatever you want.

 

[paoconno]

No, becouse your car is OBD 1 you will not throw a check engine light due to eliminating the cat. So you now have many more options.

APEXi, Megan, punishment racing, Thermal research. These are all great companies and make a great bolt on downpipe that eliminates the cat.I personally would go with a megan or punishment racing 3 inch downpipe along with a 2.5 inch tubular O2 housing (2.5inch downpipe is available very cheap on punishments site). They are of great quality and will provide enough flow for 450whp at least.

No you will not need to weld on your exhaust, just bolt it up and go. shouldnt take more than an hour to put it on.

One thing you will need research is to make sure the downpipe will bolt up to your catback. I would recommend an megan catback if your in the market, N1 style and sounds great. Also, it will not run you $500+ like a new APEXi will.

hope this helps.

-Paul

 

[McFox]

No, becouse your car is OBD 1 you will not throw a check engine light due to eliminating the cat. So you now have many more options.

Damn it. Over looked that one.

Ya, what he said.

 

[pwayzjellyroll]

No, becouse your car is OBD 1 you will not throw a check engine light due to eliminating the cat. So you now have many more options.

APEXi, Megan, punishment racing, Thermal research. These are all great companies and make a great bolt on downpipe that eliminates the cat.I personally would go with a megan or punishment racing 3 inch downpipe along with a 2.5 inch tubular O2 housing (2.5inch downpipe is available very cheap on punishments site). They are of great quality and will provide enough flow for 450whp at least.

No you will not need to weld on your exhaust, just bolt it up and go. shouldnt take more than an hour to put it on.

One thing you will need research is to make sure the downpipe will bolt up to your catback. I would recommend an megan catback if your in the market, N1 style and sounds great. Also, it will not run you $500+ like a new APEXi will.

hope this helps.

-Paul

Now the fact that the piping for my exhaust is 2.25 I believe does this have no affect on the downpipe as long as the flanges are the same size?

http://www.hopupracing.com/meradopimiec.html

For this megan racing downpipe, it eliminates the cat from what I can tell? Then I just have to have the proper flange to go from that to my exhaust system, and if they are different sizes is it possible to get it welded without any issues? Or will the size difference between my exhaust pipes and the down pipe cause some type of issue.

Also are there gains to running without a cat as to with? What about sound wise, louder/fartier/more obnoxious? It's got a nice deep tone to it right now that doesn't make it sound stupid so how much would it alter this?

 

[paoconno]

There are 3 ways for your downpipe to work for your exhaust currently on your car: either the flanges are the same and they bolt up, you cut the flange off of one and weld on a matching flange, or you cut both flanges off and run a reducer from 3 or 2.5 inch to 2 1/4 (can be made at any half decent exhaust shop).

As for removing the cat- performance wise- only positives can come from this (aside from boost creep). faster spool up, more total exhaust flow= more power potential. you wil definitely see gains from eliminating the cat.

Sound- depends on your definition of obnoxious- yes, it will be louder all the time and WOT it is going to roar- i feel it sounds awesome and much better then a car with a cat on it.

** i would recommend you get a cat-less back that at least matchs the pipe diameter of your downpipe. attaching a huge downpipe to a 2 1/4 inch exhaust is going to be a bottle neck and limit the performance gains of your new downpipe. but that is of course if you have the funds for a new exhaust.

another option is to purchase an exhaust cut out from summit racing- then you can the benefit of an open exhaust when you want it and not have to spend several hundred on a cat back.

 

[pwayzjellyroll]

There are 3 ways for your downpipe to work for your exhaust currently on your car: either the flanges are the same and they bolt up, you cut the flange off of one and weld on a matching flange, or you cut both flanges off and run a reducer from 3 or 2.5 inch to 2 1/4 (can be made at any half decent exhaust shop).

As for removing the cat- performance wise- only positives can come from this (aside from boost creep). faster spool up, more total exhaust flow= more power potential. you wil definitely see gains from eliminating the cat.

Sound- depends on your definition of obnoxious- yes, it will be louder all the time and WOT it is going to roar- i feel it sounds awesome and much better then a car with a cat on it.

** i would recommend you get a cat-less back that at least matchs the pipe diameter of your downpipe. attaching a huge downpipe to a 2 1/4 inch exhaust is going to be a bottle neck and limit the performance gains of your new downpipe. but that is of course if you have the funds for a new exhaust.

another option is to purchase an exhaust cut out from summit racing- then you can the benefit of an open exhaust when you want it and not have to spend several hundred on a cat back.

Yeah I actually think the piping is 2.5 now is there an easy way I can check this? Also I decided that I won't be running without a cat seeing as those will just be ticket's I can't afford. So this being the case how do I know which ones to use that will not require the removal of the cat and which ones will?

 

[kmoore]

I got one downpipe for you... http://www.roadraceengineering.com/eclexhaust.htm. (scroll down)
/thread

But seriosly for the price you get a great downpipe and it is a true 3". Now, as paoconno said (good information BTW), you may need to get a reducer to fit the 2 1/4" catback. Although (what I would do), and really it's the right thing to do, is to replace that 2 1/4" pipe that is on your catback with 3" piping so there are no restrictions what so ever. I would also recommend going catless because of the additional flow that you gain with the testpipe.

Now the RRE downpipe only bolts up to an Apexi catback, Espelier catback, or RSR catback so what catback system you have depends on this downpipe. Although, you could always weld the proper flange on the downpipe if you want to keep your piping from your catback (although I would trash it and get 3")

RRE all the way

 

[paoconno]

Road Race makes great products and will allow you to get basically any combination downpipe ( 2.5 or 3 inch, cat delete or not, mild steel or stainless)

As for measuring you exhaust piping on you car- very easy to do if you are decent with some math. Use the Circumferance of a circle fomula. Circumferance (distance around a circle)= Diameter X pi (roughly 3.14....) so what you will need to do is go under you car and take thin strip of paper and wrap it around your piping. mark on the paper where it meets. Go measure from one end to the line you drew- thats your circumferance. then divide it by pi (3.14)- this will give you your Outside Diameter. Then subtract around 1/4 inch to get the inside piping diameter.

Hope this wasn't too confusing.