I am curious whether anyone has had a custom exhaust made that has dual pipes for the full length, i.e., no Y-pipe. It seems odd to me that the pipes go from dual to single to dual again in stock configuration.

 

I do.... My car has custom made headers, down pipes, high flow cats, X-pipe, duals back to a couple Apex-i mufflers. It cost an insane amount of money to get it done.

 

Any particular reason you installed an X-pipe as opposed to running straight duals?

 

Its recommended to have a balance pipe for engines that has 2 banks of cylinders for scavenging. Scavenging is when the exhaust pulses helps increase exhaust velocity for efficiency, therefore, more performance.

 

Second that about x pipe, its dyno proven as well to add hp. I had my friend at exhaust shop cut at cats, run 2 1/4 dual piping back to x pipe then dual 4" magnaflows to polished oval tips and sounds beautiful. Whole thing cost me $300. Magnaflows (2)$69 ea., x pipe $35, dual polished tips cut from my wifes stock g37 coupe muffler free dollars thank u baby

 

My butt dyno told me the X-pipe added HP

 

When I had my 1uz twin turbo set up I had true dual, no cats, no x pipe. It was too loud and didn't sound all that good to me. I later added the x pipe, made all the difference in the world in the way the car sounded. Any good muffler shop can do it for a decent price

 

So is it for sound only? I asked some local muscle car guys and they told me the purpose of the x-pipe was to alter the sound characteristics, not to add more power. They said a lot of muscle cars have headers that are not equal on each side, so the X-pipe helps to balance them out and sound better. I am curious if anyone has done a before/after dyno with and without an x-pipe.

 

I have had the S&S headers, 100cell cats, full dual 2.5 stainless exhaust with X-pipe, burns stainless resonators and GReddy Evo2 rear section on my car since 2006.

This is the best sounding setup I have tried - I have tried 4-5 other setups and they all had issues.

The X-pipe adds power and makes it sound better as well - you can easily google the theory.

 

XPipe design IIRC came out of NASCAR (Dr. Gas), nothing to do with noise, but to increase scavenging of the opposite exhaust pipe. A Y-pipe does much of the same, think of it as a very long X pipe, but most y-pipes remain single where our 2GS4's go into a muffler than then back into dual. So there is lots of room for improvement there. The Y pipe properly designed has a higher scavenging effect, but if the pipe is too small/large it will affect power.

I read on (I think Lextreme) that the size of of the Y-pipe on the GS/LS is critical to power. Larger will increase PEAK power, but it hurts the midrange everywhere. And the gains aren't much either.

So be careful on increasing pipe size, and if you can have a long X (almost like 2 pipes welded together for a short distance, say 6-9 inches instead of the typical x-pipe 2-3 inches) it has a stronger effect. And might be a good replacement for the first muffler in the 2GS4.

If you want noise, great sounding noise, go true dual with no balance pipe/X-pipe. Will have more power than stock y-pipe/muffler. A well designed X is still best for power.