3" exhaust outcome on N/A
 

So I've searched, and can't seem to find anything on it, so a little insight would be helpful. Here's the deal...

I want a single exit exhaust and there's no compromise on that. So far, everything on the market doesn't suit my needs (either ugly, sound like shit, or, more importantly, HEAVY).
Seemingly when all hope was lost, Tomei Powered has released their titanium single(s) as if on cue and at a perfect price point. Unfortunately, they only make either 60mm or 80mm piping (2.36"/3.14"). I feel the 60mm won't flow enough over stock to be worth it, and I'm worried about lack of backpressure causing me to actually lose power/tq with the 80mm.

My question is, if I run aftermarket header with 2.5" overpipe/front pipe to the 80mm piping for the cat-back, would that create a recipe for disaster? I plan on getting a tune as well, if that makes any difference.

I have zero experience with N/A.

More noise and weight. The tune will help adjust the flow. Its a good setup to do if you plan on turbo later. I'll be running a JDL UEL into a full Nameless 3" exhaust (downpipe/midpipe/axleback) and don't expect to have any issues when tuned and NA. Just awesome Subaru rumble loudness.

I think if we had a higher redline like Honda's it would help out. Our engine seems to flatten out near 7000rpms. Maybe a 3" exhaust would help this out? I dunno. Supposedly we loose low end torque but gain hp in the upper rpms with a larger exhaust. Might benefit some but hurt others. Maybe someone can chime in or test this out.

You won't lose torque due to "lack of backpressure" with a big exhaust. Big myth, that...

But then again, I seriously doubt that a 2.36" exhaust would be holding a 7400rpm 2.0L NA motor back.

Put it this way, the 6.0 liter V8 in my FD makes 465rwhp through a 3" OD single exhaust. I don't think a 2.36" exhaust is going to be a problem for you.

I would assume anything larger than stock will give enough flow to not lose power.

Also back pressure is not the issue it's scavenging and gas velocity. At the catback section this is a none issue. Buy what sounds/looks good if your staying na

I spoke to someone ( can't remember name) at Nameless about their 3" overpipe/midpipe coming soon and related power loss and they didn't expect to see powerloss with this setup. I also know from trolling s2k forums as I had planned to buy one before the snap decision to buy the FRS, that 3" actually lost power in some cases.

Most of the s2k dyno plots I've seen after a 3" showed higher flow rates but lost tq on the low end.

I just don't want to drop $1k and it be worse off.

I don't have a degree in fluid dynamics, but I do know that gas velocity changes with piping diameter, shape, angle and whether it stays uniform throughout i.e if there sections where the pipe changes in diameter like stepped runners.

I also know that cat-backs generally don't do much until forced induction comes into play and at much higher numbers. I wasn't so much concerned with cat-back power loss, I was more talking about the combination as a whole. Like I said, I don't have much experience with n/a and their heavy reliance on such aspects. I'm just used to slapping on something that would flow the most.

The tomie exhaust is pretty straight and mandrel bends so 2.38 should be plenty for na.

A 3inch dp might cause some issue's but not the catback.

Sounds like the real question is: how much would you gain if you already had a 2.38" installed, then upgraded to a 3"? If you don't gain anything (and especially if you lost) then opt for the 2.38". Give your driveshaft some personal space.

Isnt T1R has dynoed their 3" single exhaust and still make tq and hp?

my bad...the T1R exhaust is only 2.75"
http://www.ft86club.com/forums/showthread.php?t=31988

I'm thinking the same, want to get the 80mm for my NA set up

Also, the Tomei 60R weighs 5.9lbs less than the Tomei 80. That's 36.7% lighter for the same price.

Do you have a video clip of your exhaust setup? I'd be interested in hearing it. How is the drone on the full Nameless 3" btw?

Header and exhaust still being built. Been waiting 1+ months on both. Well worth it though.