Exhaust

[fastgascar]

For all the exhaust guru's, will 2.5" cat back that y's into (2) 2.25" mufflers be enough to extract all the useable power out of the 2.5 Turbo motor ? Or is there still even more that can be had with 3" cat back that y's into (2) 2.50" mufflers......?

[BoxerGT2.5]

Why do you want step piping??

[fastgascar]

With the majority of the single into dual muffler system this is how I have seen it done, the factory does it this way and borla does, so my guess is there isn't any real benefit by keeping it the same all the way to the exit, I do see some restriction on the ends, but could this be to help with the TQ or is it specifically for noise?

[BoxerGT2.5]

With the majority of the single into dual muffler system this is how I have seen it done, the factory does it this way and borla does, so my guess is there isn't any real benefit by keeping it the same all the way to the exit, I do see some restriction on the ends, but could this be to help with the TQ or is it specifically for noise?

You will do fine with straight 2.5 diameter piping through out. Unless you think your gonna hit numbers like 320-350hp, you really wont need 3in diameter exhaust. In your reference to torque, if you are equating that to backpressure then the two are not related. Changing the diameter of the piping can shift peak torque but not diminish it in anyway. Typically you will see peak torque with larger diameter tubing shift to the top. What borla exhaust have you seen that used step piping? On my Rx-8 they used 3in all through out. The only other reason to use it is if there are fitament issues with certain diameters.

[fastgascar]

The goal is 320-350 @ AW. I saw the step piping from Borla on the '05 Legacy Gt, it was sitting @ the dealer, 1st one out of production, installed and ready to go. Sounded pretty good too, I had the salesman start it up and rev her up a couple of times.

[BoxerGT2.5]

The goal is 320-350 @ AW. I saw the step piping from Borla on the '05 Legacy Gt, it was sitting @ the dealer, 1st one out of production, installed and ready to go. Sounded pretty good too, I had the salesman start it up and rev her up a couple of times.

If that is your goal than you might want to consider 3in diameter from the dp back. I have yet to see the leggy borla.

[Xenonk]

The goal is 320-350 @ AW. I saw the step piping from Borla on the '05 Legacy Gt, it was sitting @ the dealer, 1st one out of production, installed and ready to go. Sounded pretty good too, I had the salesman start it up and rev her up a couple of times.

I say go with 3" all the way.. or at least 3" to 2-Y-2.5" piping. I have found out on the track that the stock exhuast is beyond restrictive, even with stock ECU parameters.. If you are hoping to hit those numbers which is way more than what I am asking for, you'll need more piping. I was hoping anywhere from 250 to 300 whp. My take will be on using a full turboback exhuast that's 3" all the way through.

Keefe

[BoxerGT2.5]

Keep in mind that you have a Turbocharged car. The rules apply differently than a N/A car. What comes out downstream from the turbo is not as important as say the exhaust manifold. N/A engines would not do as well with large diameter pipes. You could put a 5in diameter HKS pipe on a TC supra but I wouldn't do it on a 350hp N/A Camaro. I would just try and stay consistent and not step too much or bottleneck the crap out of it.

[B4_Maniac]

Agreed with the Turbo Back..that will be my final mod for my Leggy..then I will be done. I just wish one of our many tuners will hop to it and get it to market.

[chucktoo]

In the Borla did they replace the resonator after the 3rd cat or just start at the Y pipe after the resonator ?

I have yet to see a picture of the Borla - are there any around ?

[BoxerGT2.5]

In the Borla did they replace the resonator after the 3rd cat or just start at the Y pipe after the resonator ?

I have yet to see a picture of the Borla - are there any around ?

I would think it replaced the resonator cause otherwise some cutting would be needed, which defeats the purpose of a bolt on.

[chucktoo]

I was hopping it is more than just two mufflers and a real cat back.

I think that other than by visual inspection there is no way to tell the rear CAT is there since the second O2 sensor is before the CAT ?

[fastgascar]

The exhaust is a true cat back, they cannot legally touch anything from the last cat forward. It is 2.5" behind the second cat runs into a resonator 2.5" and then into the "Y" inlet is 2.5" outlet is (2) 2.25" which it then goes into (2) 2.25" mufflers.

[chucktoo]

Where can I buy one ?