exhaust questions

[StraightOuttaCanadaEh]

Okay after much deliberating I decided not to go FI and stick to naturally aspirated glory.

According to a diagram I found on the internet, our exhausts go

headers -> overpipe -> front pipe -> mid pipe -> muffler

Q1: Now, is "muffler" the catback, or does the catback include the mid-pipe? Cause I have the catback covered.

Q2. I should probably keep everything the same diameter right? Don't want a 3" pipe to go into a 2.5" pipe, as it might cause a bottleneck and slow things down, correct?

Q3. Which of these pipes are catted on our cars?

Q4. Which do you recommend upgrading for gains with an OFT tune combined? All? Just a couple?

Q5. Does it matter what the order of catted/non-catted pipes is? For example, a catted header, non-catted overpipe, or vice versa. I'm guessing having an uncatted pipe go into a catted pipe would create a bottleneck, wouldn't it?

Q6. Am I right to assume that the more of these pipes you replace, the louder the car will get?

Thanks!

[BigTuna]

I'm assuming the diagram below is the one you found?

Originally Posted by StraightOuttaCanadaEh

Okay after much deliberating I decided not to go FI and stick to naturally aspirated glory.

According to a diagram I found on the internet, our exhausts go

headers -> overpipe -> front pipe -> mid pipe -> muffler

Q1: Now, is "muffler" the catback, or does the catback include the mid-pipe? Cause I have the catback covered.
The muffler is it's own piece and is the large canister at the back of the car. A catback includes the midpipe.

Q2. I should probably keep everything the same diameter right? Don't want a 3" pipe to go into a 2.5" pipe, as it might cause a bottleneck and slow things down, correct?
Correct, trying to avoid any diameter changes is best. 2.5" is plenty for a NA car, whereas a lot of the FI guys end up running a 3"

Q3. Which of these pipes are catted on our cars?
Header and Front pipe

Q4. Which do you recommend upgrading for gains with an OFT tune combined? All? Just a couple?
Header. The others will give you slightly more on top, but header will give you the most.

Q5. Does it matter what the order of catted/non-catted pipes is? For example, a catted header, non-catted overpipe, or vice versa. I'm guessing having an uncatted pipe go into a catted pipe would create a bottleneck, wouldn't it?
Cats are bottlenecks in themselves. For max flow, delete them both. I have a catless header and the stock (catted) frontpipe. The order though, I don't think matters.

Q6. Am I right to assume that the more of these pipes you replace, the louder the car will get?
Yes. The muffler does the most to quiet the system though.

Thanks!

[churchx]

A1: "catback" are all exhaust parts, that come after catalizator (1st one in header, 2nd one in front-pipe). So midpipe+muffler. There are also "axlebacks", that are just mufflers.
A2: not necessarily. Stock is smaller diameter then 2.5, and 2.5" should be sufficient for most "reasonable" applications, including NA & forced induction to 300hp imho. Not much to gain, and 3" will be noticeably louder.
A3: see A1.
A4: depending on goals & budget. With unlimited budget all. With minimal budget - catless headers, if performance main priority, catback, if want different sound/loudness.
A5: there are usually more gains to be had from catless header. Decatting secondary (in frontpipe) on the other hand may work well with stock tune, due second O2 sensor being before it, thus no problems with CELs.
A6: depends with what you replace. There are some catbacks that might be stock-quiet or even maybe quieter? (eg. Q300 / Ace's Lagunaseca). Loudness will be increased from: going larger diameter piping, removing cats, removing resonators, less muffling mufflers (or removing them). Turbo will quieten exhaust, rest being same.

Check opening post of this sticky theme., good read.

[KnightRyderx2]

Q1: Now, is "muffler" the catback, or does the catback include the mid-pipe? Cause I have the catback covered.

Muffler is just the axle back area, the large box you see when looking under from the rear bumper. Cat back includes the mid-pipe and muffler sections. When its name is (whatever)back they are talking about the system rear of the area, i.e. header back would start at the over pipe and including everything rear of that.

Q2. I should probably keep everything the same diameter right? Don't want a 3" pipe to go into a 2.5" pipe, as it might cause a bottleneck and slow things down, correct?

Yes.

Q3. Which of these pipes are catted on our cars?

Header and front-pipe. Only the one in the header is monitored and may throw a CEL if taken out. The front-pipe is not monitored, no CEL if taken out.

Q4. Which do you recommend upgrading for gains with an OFT tune combined? All? Just a couple?

Headers and maybe mid-pipe will give the most. The rest will have very little additional power. The rest would mostly be for sound quality and volume control.

Q5. Does it matter what the order of catted/non-catted pipes is? For example, a catted header, non-catted overpipe, or vice versa. I'm guessing having an uncatted pipe go into a catted pipe would create a bottleneck, wouldn't it?

Just FYI, there is no cat in the mid-pipe.

No, it doesn't matter. But, if you have a cat in the front-pipe, you cannot monitor it and you may throw a cell (this is moot with a tuning solution). Also you will not be able to run Stage-2 on OFT since you still have a cat in the system.

Q6. Am I right to assume that the more of these pipes you replace, the louder the car will get?

Somewhat, yes. The Muffler or cat-back will control volume level and sound quality. The front-pipe will add some volume but mostly it will contribute rasp and/or drone considering the combination or lack of resonators and a cat. The header will change the sound and add a bit of volume and rasp depending on if it is catted or not and what quality of material is used.

[StraightOuttaCanadaEh]

Thanks guys. Huge help!