Aftermarket Exhausts?

[Draco-REX]

Well, looks like the cat in the manifold is the primary cat.

Found this in another thread (ignore the red arrow):


The downstream O2 sensor is immediately after the first cat. The second cat is completely un-monitored. So moving the primary downstream will require extending the second O2.

EDIT: Yay! Looks like those stupid little tips are removable. It's a little ricey, but it seems we can replace them with something bigger to fill out the bumper cutouts.

[MtnDrvr86]

Originally Posted by Draco-REX

Well, looks like the cat in the manifold is the primary cat.

Found this in another thread (ignore the red arrow):


The downstream O2 sensor is immediately after the first cat. The second cat is completely un-monitored. So moving the primary downstream will require extending the second O2.

EDIT: Yay! Looks like those stupid little tips are removable. It's a little ricey, but it seems we can replace them with something bigger to fill out the bumper cutouts.

Yes! Walmart exhaust tips here I come! hahaha or not...

[Gardus@Supersprint]

I think we could use the room for the 2nd cat for the headers and place the sports cats even more downstream.
I need to see if the pre-cat sensor wire is long enough for the header design I have in mind, it would be a hassel to extend both the cables.

I see there is a resonator on the centre section...guess this car really tends to drone.

If all the components have flanges how it looks like in that drawing a modular system will be easy to make, with no cut in the stock one.

Depending on the room available around the rear diff we could put a Y-pipe where the centre silencer is and use two separate mufflers with longitudinal piping, but that would mean an axle back won't be available.

To answer Grip Ronin about the stock system:
Design of the header and the sequential cats id because of the gas regulations.
The centre silencer (or resonator) is to avoid drone.
The rear box is designed to be cheap. The silencer is a not a straight flow one, the pipe ends and inside there are some chambers, then the two pipes start again to reach the endpipes. Is a common design on 4 pots cars with twin exits, for example the VW Golf GTI.

[Draco-REX]

Originally Posted by Gardus

I think we could use the room for the 2nd cat for the headers and place the sports cats even more downstream.
I need to see if the pre-cat sensor wire is long enough for the header design I have in mind, it would be a hassel to extend both the cables.

I see there is a resonator on the centre section...guess this car really tends to drone.

If all the components have flanges how it looks like in that drawing a modular system will be easy to make, with no cut in the stock one.

Depending on the room available around the rear diff we could put a Y-pipe where the centre silencer is and use two separate mufflers with longitudinal piping, but that would mean an axle back won't be available.

To answer Grip Ronin about the stock system:
Design of the header and the sequential cats id because of the gas regulations.
The centre silencer (or resonator) is to avoid drone.
The rear box is designed to be cheap. The silencer is a not a straight flow one, the pipe ends and inside there are some chambers, then the two pipes start again to reach the endpipes. Is a common design on 4 pots cars with twin exits, for example the VW Golf GTI.

I've heard that a transverse muffler like that also helps to cut down on drone.

[Gardus@Supersprint]

Yes, that's true, especially with chamber mufflers.

[wcbjr]

Originally Posted by Subaruwrxfan

Yep, this is what I did with my Legacy GT when I went with a catless up-pipe.

Or remove the CEL with a reflash.

[AJ PwR]

Originally Posted by Gardus

That doesn't look very good, why so many welds, you can make that with just one bent pipe and it'll be lighter and stronger. The problem with NA engines, especialy 4 pots in small cars, it's they tend to drone. A transversally mounted mufflers helps, and doesn't really affect the power much. I've seen that HKS went for a helmotz resonator on its louder system. We use it sometimes but it's heavy. As the market will be floaded with catback exhausts coming from the same factories in taiwan and china, we'll concentrate in making the best header+cat kit we can.

There are many welds because they can't do mandrel bending and I don't think there's other reason for it.

Well, looks like the cat in the manifold is the primary cat.

Found this in another thread (ignore the red arrow):



The downstream O2 sensor is immediately after the first cat. The second cat is completely un-monitored. So moving the primary downstream will require extending the second O2.

EDIT: Yay! Looks like those stupid little tips are removable. It's a little ricey, but it seems we can replace them with something bigger to fill out the bumper cutouts.

I have this diagram too. The secondary cat can be totally deleted but I think it's good to be resonated or else the exhaust will drone.

[Grip Ronin]

i cant imagine a Helmholtz res not having an effect on performance

[old greg]

Imagine harder.

[Grip Ronin]

lol it doesn't effect the flow? i mean its offers a passage for the fumes that is just a dead end

[Droopy]

ok why cant you collect the two exhausts on the right together and the left side together then all 4 just before the cat? wouldnt that increase flow and be less restrictive? and delete the 2nd cat altogether or create a resontating chamber there

EDIT: or would the angles be to sharp?

[Dimman]

Originally Posted by Droopy

ok why cant you collect the two exhausts on the right together and the left side together then all 4 just before the cat? wouldnt that increase flow and be less restrictive? and delete the 2nd cat altogether or create a resontating chamber there

EDIT: or would the angles be to sharp?

Has to do with firing order and scavenging.

[Droopy]

ok thanks

[StuttterButtter]

Any one know if RS-R will have a Exhaust coming out (or any other products) for the FR-S or BRZ. I have one of the Exmag's (not the GT2 Version) now and a friend has one on his 06 Evo and i love the sound. Very quiet in low RPM's but sounds great in high.