what size piping for custom exhaust

SC Titan · 03-08-2005, 06:08 PM

Got a question for any one out there who can give me factual information and not just opinions. Im going to be installing a new custom exhaust on me CC Le. I know to go at least 2.5" but was curious as to wheather going larger would result in a loss or greater gain in performance. Also one other quasetion: Im stuck on my deision as to go with the borla or jba muffler. I am planning on installing jba headers given everything works out financially if that makes any difference on muffler decision. All opinions would be greatly appreciated.

johnszcz · 03-08-2005, 06:21 PM

Performance must be the reason for it as why else go to the expense.

Sammy Sandbag · 03-08-2005, 07:06 PM

I'd save your money on those JBA headers, you'd be better off waiting on the Nismo full headers or just sticking with your factory manifolds. Pipe size depends on the set up. If you were going single all the way through I'd say 3", dual I'd say 2.25-2.5".

Tim Sloper · 03-08-2005, 07:08 PM

If you are going to go with a custom exhaust system make sure you are using piping with mandrel bends. You will not find mandrel bent pipe at 99% of the exhaust shops out there. Also, don't confuse the smooth bends you will find with mandrel bends. A mandrel bent pipe will maintain the diameter of the pipe all the way through the bend. This is not what you will get at your typical exhaust shop. You will get a smooth bend but if you look at it closely you will see that the diameter throughout the bend is less than that of the rest of the pipe. A 2.5" pipe becomes a very restricted pipe and your custom exhaust will be worse than what you started with.

You can get mandrel bent pieces from places like Summit Racing or Jegs which you can cut as necessary to fit your application.

As for headers... unless you are going to install a set of long tube headers (not sure any exist yet) you will be wasting your time and money. Shorty headers are of little to no benefit over the stock manifolds. You just can't get the scavenging effects out of shorties that you will out of properly designed long tubes.

The last point I'd like to make relates to the notion of low-end loss of torque with aftermarket exhaust systems. When it comes to anything past the manifolds/cats you will NOT lose low end torque with a free flowing catback setup. I don't know why that notion keeps comming up but unfortunately it does. If you could lock the torque converter and do a before/after dyno run across the entire RPM band you would not see a loss of low end torque. If you did it would purely be due to the air/fuel calibration not being optimum for the new setup not because a free flowing catback inherently causes you to lose anything at the lower RPM band. Header sizing is a different area that can have an impact on torque output but at this point in time it is not something the Titan community has to worry about. Backpressure in an exhaust system is BAD.

Tim

**loufish** · 03-08-2005, 09:50 PM

As a guy who worked at an muffler shop for almost 10 years...you plumb your toilet with pipe, you fab your exhaust with "tubing"....

SC Titan · 03-08-2005, 10:36 PM

Thanks for all of the feedback. Looks like i will be waiting on the headers till some one comes out with something other than shorties. As for the choice of jba vs borla mufler...can i get some feedback from people who have used either or both, and which seems to get better results overall. Thanks again