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[brine04]

OK here's the deal I have an 81.5mm forged lsvtec with stock sleeves running an hx35. I can either fab a 3" or use my existing 2.5" RSR exhaust. Explain why I should spend the time/effort/money fabbing a 3".

[Dirty_Mech_Style]

i would be very interested in inputs, pre fab 3'' exhaust for a decent price are non-existent for da's.  i did the same thing you did, Columbia Mandrel bending only had a 2.5 dp flange so i fab'd everything hot and cold 2.5.  Ill rock it till it wont flow anymore, take a note from the dsm guys, they've made impressive numbers on 2.5

[Minor Threat]

I would do a 3 inch DP and leave the rest, and see where you're at.

Is the RSR muffler chambered or straight through?

How high you revving it? I find exhaust restrictions get a lot more apparent when you're trying to rev to the moon.

[bouncinofftherevlimiter]

My f22 clusterfuck with HX35 ran into serious back pressure issues with a straight thru 2.5" down pipe back and a 3" down pipe at like 14LB FWIW....

if you are going to take the effort to do anything, go as big as you can, can't really over do it with a turbo car...

[dvst8r]

Being that you will drive it like twice, on a basemap with pump gas, and like 10psi, and then will sell it. Obviously fab the 3" as you need the practice. 

[ratcityrex]

I guess it depends on what your end goal is. I have pretty much the same setup as you. 81.50mm (8.5:1 comp) ls vtec head and hx35. I was able to pick up a China 3" cat back off eBay for $115 shipped. I added another resonator in because I wanted it real quiet. It not to loud, but I'm gonna chop the rice cannon off it in the next month or so and put a 3" straight through magnaflow on.

But like your girl said, bigger is better... Go big or go home!

[brine04]

The RSR is straight through and madtyte jdm it pretty much goes straight under the car and avoids all the bullshit turns at the end. Only revving it to 8000rpm as I only have gsr cams. Already have a 3" downpipe. If there was cheap 3" exhaust available I would do that but there isn't so it will be a bit of fab work. Don't really have a goal in mind just going to see what it can do on pump 94. All the turbo piping is 3". If I build exhaust it will have a huge resonator or two and the vibrant flat black stealth muffler.

[turbohf]

60mm on a forged Y8. only looking to make 250whp... but it was on there with my turbo B20. didnt feel like it should have an issue making over 300+.

if the shit you have is straight threw, be a lazy ass and just rock it till its an issue.... like me lol.

[Teg2boo]

I'm also tempted by the 3" even if I already have a 2.5" installed. Only problem would be the downpipe of course. It's only 200$ shipped on ebay for 3" catback...

Just cut the fartcan and put something smaller with better sound. That's what I did with my ebay N1 2.5", just cut the fucker and put el cheapo cherry bomb turbo muffler.

I don't like the sound when the car is NA tho... It's too loud without turbo, but I don't like noise so you can judge yourself...


This is with 2.5" and cherry bomb turbo muffler:
Integra 92 LS stock internal turbo at 10psi 0 to 190km/h

I can't find the link on canadiantire website, but they used to sell the muffler for 35$ and they have a 3" form. It fits pretty well under 90-01 teggies.

[highroller54]

N.N. my eg rsr exhaust was 60mm and a chambered muffler. I loved the exhaust but I wouldnt run it on a turbo car. I'm not sure what car your building now though.

[DSharp]

Ive got a 2.5" exhaust and a big resonator that appears to be closer to 2.25 ID.  I made 376 whp and 335 wtq with a hy-35 and a f22.  I would eventually like to ditch that shit and go bigger.

[The_Beave]

Turbos work by controlling the expansion of fluids flowing through them. (Compressed gasses are considered fluids.) A certain volume of gas enters and is expanded in a controlled manner, allowing the gases to impart their energy (there are also thermal and pressure wave effects happening, too) to the turbine wheel which does work on the compressor wheel. Allowing for maximal expansion post turbo increases the pressure differential pre and post turbo, which makes the system more efficient, which is a good chunk of the reason why bigger is certainly better (with some caveats left in for minimizing turbulence which hurts flow tremendously in expanding volumes), giving the effects of faster spool and more power overall.

There IS a risk of compressor surge, though, but there are many factors that come into play with each particular turbo design.

[NoPistons!]

  For spool and back pressure characteristics  a cutout would be a cheap, quick solution.  You'd still be able to evacuate exhaust gas quickly from the turbine vs letting it cool and slow down as it moves the length of a full exhaust. 

http://www.jegs.com/p/JEGS-Performance-Products/JEGS-Cast-Iron-Exhaust-Cutouts/1287065/10002/-1

Heat it up and weld some v bands to it, dump the shorty exhaust wherever you can put it.