Front pipe installed = WTF

[FR-S Matt]

Originally Posted by solidONE

Currently running the factory cat back exhaust. I plan on fabricating my own single sided cat back system. I'm debating whether to use 2.75" tubing or 3" from the mid pipe back and if I should install a 2.5" overpipe or modify the 2.75" front pipe to include a 2.75" over pipe section. Waiting on the n/a people to post up some dynos with their 3" cat-backs and header-backs.

All the combos of diameter I'm considering:

1. 2.5">2.75">2.75"

2. 2.5">2.75">3"

3. 2.75">2.75">2.75"

4. 2.75">2.75">3"

Or maybe even

5. 2.5">2.75">2.5" to maybe keep exhaust velocities up.

Leaning toward 1. and 2. right now since most of the collectors on the ends of the headers tend to be 2.5" or maybe smaller. Plus it's probably not a good idea to go too big right after the header.

My main concerns are of course peak output, but I don't want to loose too much <4000rpm and partial throttle power. This doesn't seem to be much of a problem as all of the exhaust options from stock has pretty much seen increase in the low to mid range with and without a ECM tune. Also, I don't want it to be obnoxiously loud.

3" > 3" > 3"

Man up!

[Jason@DSG]

Originally Posted by solidONE

Currently running the factory cat back exhaust. I plan on fabricating my own single sided cat back system. I'm debating whether to use 2.75" tubing or 3" from the mid pipe back and if I should install a 2.5" overpipe or modify the 2.75" front pipe to include a 2.75" over pipe section. Waiting on the n/a people to post up some dynos with their 3" cat-backs and header-backs.

All the combos of diameter I'm considering:

1. 2.5">2.75">2.75"

2. 2.5">2.75">3"

3. 2.75">2.75">2.75"

4. 2.75">2.75">3"

Or maybe even

5. 2.5">2.75">2.5" to maybe keep exhaust velocities up.

Leaning toward 1. and 2. right now since most of the collectors on the ends of the headers tend to be 2.5" or maybe smaller. Plus it's probably not a good idea to go too big right after the header.

My main concerns are of course peak output, but I don't want to loose too much <4000rpm and partial throttle power. This doesn't seem to be much of a problem as all of the exhaust options from stock has pretty much seen increase in the low to mid range with and without a ECM tune. Also, I don't want it to be obnoxiously loud.

It depends what your future plans are. If you are going to stay N/A, you can keep it at 2.5" after the front pipe and the flow should be perfect (depending on how you fabricate the exhaust).

If you have plans on going forced induction, my experience is limit the backpressure at all costs! I have 1.75" runners, 3" turboback on my car to dual 3" exits.

Also, you'll only ever have the efficiency of what's coming out of the engine. If everything is 2.5" up front, no matter how big you go on the back end you'll only ever really be as efficient as 2.5". Now, that being said, based on the FR-S/BRZ engine platform, 2.5" is actually a perfect size for flow versus pressure etc.

To each their own! I'd probably run 2.5" the whole way with headers.

[Jason@DSG]

Are you running an intake on the car?

[solidONE]

Right now I'm running an AFE r5 drop in. I don't plan on going fi in the near future. After I get a decent amount of n/a power I will be saving my monies for proper suspension (4-5k range on dampers alone) Only after then will I consider forced induction.

I also have to consider "rules" for certain time attack competitions i'd like to enter and I'm not nearly fast enough to try to challenge the guys in modified classes yet. This means I'll be limited to catted headers, maybe cams when someone releases them, intake exhaust and tune. I'd still like to see what a 3" exhaust can put down on a N/A tune before I decide.

[BRZ NA]

Does the front pipe has an o2 sensor that need to be fix?after u install aftermarket ones?

[whitefrs]

Originally Posted by BRZ NA

Does the front pipe has an o2 sensor that need to be fix?after u install aftermarket ones?

no 02 sensor

[roddy]

No. both O2 sensors are in the header/manifold. One before the 1st cat and one after it. When eliminating the cat in the header, welding in a bung after the cat in the front pipe (for re-location of the 2nd sensor) might be an option though. I haven't done this yet, so hopefully someone who has will post up.

[BRZ NA]

Originally Posted by whitefrs

no 02 sensor

So there is only one o2 sensor which is located at the header for this car?

[whitefrs]

Originally Posted by BRZ NA

So there is only one o2 sensor which is located at the header for this car?

one is in the manifold and the other one is in the stock header

[BRZ NA]

Originally Posted by whitefrs

one is in the manifold and the other one is in the stock header

Manifold? Not the exhaust manifold right cause the header is the exhaust manifold

[whitefrs]

Originally Posted by BRZ NA

Manifold? Not the exhaust manifold right cause the header is the exhaust manifold

Lol
I kinda messed up
Manifold/header is the same

O2 sensor--- Cat---O2 Sensor



Sent from somewhere

[FR-S Matt]

When you tune the car, normally you delete the second 02 sensor and the one bung in the header becomes the primary.

Option two is moving the secondary bung back to the front pipe meaning you need O2 wire extensions to move it back that far. So far, option 1 is the most common one as you have seen most front pipes don't come with O2 bungs in them. Any exhaust shop can add one though.

[BRZ NA]

Originally Posted by FR-S Matt

When you tune the car, normally you delete the second 02 sensor and the one bung in the header becomes the primary.

Option two is moving the secondary bung back to the front pipe meaning you need O2 wire extensions to move it back that far. So far, option 1 is the most common one as you have seen most front pipes don't come with O2 bungs in them. Any exhaust shop can add one though.

Good to know thx

[leicaboss]

I legit wasn't expecting anything.

I replaced my Nameless Axleback with a Perrin 2.5" Res'd Catback and added a Berk Catted Front Pipe (HFC).

While I'm sure the catback gave me some gains over stock system/axleback - I HIGHLY doubt it did what the front pipe is doing. Mine's catted but the throttle response difference is huge to me, most definitely noticeable. I wasn't even trying to look for it, I basically had zero expectations for bolt ons. Now I'm super psyched for headers....