Williampreza's Kamaitachi: NA BRZ The "Easy" Way

[tehShirt]

@Williampreza looks great! Initial thoughts?

And they probably corrected something after I called them multiple times and they tried to make it sound like my fault haha.

[mistople]

Originally Posted by Williampreza

Some of the threads regarding the Corsa exhaust plus headers have led me to question my plans about adding headers at all.

I haven't done an exhaustive search, but my impression is that the Corsa sounds much better by itself than it does with headers. I couldn't find a UEL pairing that sounded better than a Perrin or MXP after a quick poke around. Interested in what you find here.

I do wonder what an A350 would sound like with the Corsa..

[StraightOuttaCanadaEh]

Originally Posted by mistople

I haven't done an exhaustive search, but my impression is that the Corsa sounds much better by itself than it does with headers. I couldn't find a UEL pairing that sounded better than a Perrin or MXP after a quick poke around. Interested in what you find here.

I do wonder what an A350 would sound like with the Corsa..

Have you heard this one though? Corsa+Gruppe-S, combo I'll be going for

[ame="http://youtu.be/fQ2NO-Z1ai8"]http://youtu.be/fQ2NO-Z1ai8[/ame]

[mistople]

Originally Posted by StraightOuttaCanadaEh

Have you heard this one though? Corsa+Gruppe-S, combo I'll be going for

That one sounds pretty cool! I'd be interested to hear some in-cabin or drive-by recordings. Not that the camera mics ever do these justice

Seems a bit more aggressive than the JDL + Perrin I'll likely go for. Any idea of how loud that setup will be?

[StraightOuttaCanadaEh]

Originally Posted by mistople

That one sounds pretty cool! I'd be interested to hear some in-cabin or drive-by recordings. Not that the camera mics ever do these justice

Seems a bit more aggressive than the JDL + Perrin I'll likely go for. Any idea of how loud that setup will be?

No idea, sorry. All I know is if you wanna keep the volume relatively simple, leave the oem overpipe and front pipe in place

[Williampreza]

Originally Posted by tehShirt

@Williampreza looks great! Initial thoughts?

Well, my wife and I went out last night and nobody complained. That's even after quite a bit of extra driving because our favorite restaurant went out of business (retirement) and we had to drive around deciding on a substitute.
Lower end rpms are completely acceptable. The only notable difference was that, particularly when at intersections in heavy weekend traffic, I kept looking around for the car with the aftermarket exhaust, only to remember that it's me.

Wide open is a blast and the overall effect is exactly what I was looking for. Now that the exhaust is installed, I can hear exactly which frequencies are missing relative to the 308 benchmark, but I knew it wouldn't be perfect.
I am probably going to see how far I can get the car with tuning, intake manifold work, and E85, before committing to headers. The dB level is right where I want it.

[scottman]

If you are worried about the inside of your intake manifold, may I recommend looking into getting a pcv catch can.
2cents

[Williampreza]

Originally Posted by mistople

I haven't done an exhaustive search, but my impression is that the Corsa sounds much better by itself than it does with headers. I couldn't find a UEL pairing that sounded better than a Perrin or MXP after a quick poke around. Interested in what you find here.

I do wonder what an A350 would sound like with the Corsa..

Yeah, the A350 was part of my original plan. We'll see how I feel after a few months, when everything has settled in.

[Williampreza]

After a brief chat about intake manifolds with my local tuner (I was still trying to source a local extrude hone or manetic abrasive honing shop), I came away with an interesting notion. He pointed out to me that the stock aluminum manifold for the new twins has an inherent design flaw from a flow perspective. The intake charge enters the plenum from the front, the plenum is more or less rectangular, and the runners are arranged longitudinally along the path of airflow. So, basically, the front two cylinders/runners get cleaner air than the back two.

Now, I don't know how much of a difference this actually makes in real life. But I started flipping through a couple books and the internets and I noticed a conspicuous trend. If you look at high performance intake manifolds, they are all designed to account for even air distribution between different cylinders. Even the STI manifold has a different way of directing air to the runners:



So... what's this all about? Well, now I'm toying with the idea of modifying an intake manifold by chopping the throttle body off, welding up the side where it once was and moving the throttle body to the top. I measured... Kinda... It might fit.

I'm thinking something along the lines of an old school single-plane manifold.

[Whiskerz]

I'd be interested to see how that would go. In general I'm not sure how much there is to be gained on NA from intake mods, but I'd imagine if anything works that will be it.

[new2subaru]

Originally Posted by Williampreza

After a brief chat about intake manifolds with my local tuner (I was still trying to source a local extrude hone or manetic abrasive honing shop), I came away with an interesting notion. He pointed out to me that the stock aluminum manifold for the new twins has an inherent design flaw from a flow perspective. The intake charge enters the plenum from the front, the plenum is more or less rectangular, and the runners are arranged longitudinally along the path of airflow. So, basically, the front two cylinders/runners get cleaner air than the back two.

Not sure if you've seen this but it's a good read.

http://www.ft86club.com/forums/showthread.php?t=82479

[Williampreza]

Originally Posted by new2subaru

Not sure if you've seen this but it's a good read.

http://www.ft86club.com/forums/showthread.php?t=82479

Yeah, I wish that had worked out for them. The way they've got that designed, it looks like they're aiming for high rev power, probably beyond 7400rpm.

My hope is to find a bit of power still hidden in the stock manifold. It's also likely that, for the stock redline, there is none left. That would mean I need to increase the rpm range, which would require cracking open the front cover and pulling the heads/valvetrain (in order to make any effective AND safe changes).

Eventually, I'm going to get brave enough to pull this pristine intake manifold off my engine and get some measurements.

[Williampreza]

Here's the shape of what I'm thinking...

[Williampreza]

A quick note:

I got to take the car out for an East Tennessee backroad drive. This exhaust system is perfect. Total fizzy feelings running through my nervous system when I wind it out. Didn’t record. Don’t care.

Highly recommend.


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