I have been doing a lot of research on the design of exhaust systems and I have come to some conclusions that might not be too popular: the normally aspirated 350 Z doesn’t benefit from either large diameter tubing or true dual exhausts.

The reasons are: gas velocity and gas temperature. Either larger tubing diameter or dual paths for the exhaust gases will both produce lower pressures, lowered gas temperatures and slower flow. High exhaust temperature is good because hot gases are low in density, retain more energy, and flow better and faster.

As we all know, cool air is dense air (remember your cold air intake) is great on the intake side, and it is exactly what you need to avoid on the exhaust side. This is why racers wrap their headers with insulation: to keep the exhaust gases as hot as possible throughout the entire system.

Big tubes and dual paths both lower velocity, lower temperatures and just don’t help. With our relatively small displacement 3.5 motors, we just don’t need 3” duals. The original equipment exhaust system is very appropriately sized and very well designed for our cars. This is why so little additional horsepower is realized with aftermarket systems.

Additionally, big tubing and duals are bigger, heaver and more difficult to package. We need less weight and bulk, not more. I examined a Stillen 3” dual system laid out on the floor at a local shop. It looked like it would be perfect for a 426 Hemi Cuda. It was extremely impressive to look at. It was also huge and really heavy.

A system that reduces weight and bulk, maintains gas velocity and temperature at stock levels, and sounds nice is all good. But big, heavy, complex, slow flow systems are a step backwards.

Big V8’s and turbo’s with high boost pressure are a different matter.

Just my 2 cents worth. Am I wrong?

 

not really a good idea to run dual 3" on a stock Z/G. you could get away with a 2.5" system though if a properly designed cross pipe was used, like mine, lol. stillen and borla are the only other manufactures making H pipes in their systems for the Z. we took it a step further and hand making X pipes, that are for superior to the H pipe. the purpose is to create a low pressure in the opposite tube as the exhaust pulse travels past from the other bank. proven technology for years, just expensive to make.
but don't take my word for it, do an internet search on H and X pipes and the benefits. yes both our 3" and 2.5" duals run the X pipe.

 

3" is broken dont buy it, 2.5" is fixed was broken now working. good luck

 

All I know is stillen's dual dyno'd the highest gains on an N/A Z.

 

I am in the process of installing the Borla TD system including the headers. Does anyone have this setup on a N/A Z? They say that it is 12lbs lighter than the stock setup on their page..

 

because of the H pipe, lol

 

?

 

yeah, wtf?

 

HUH?

 

I propose a BAN

 

I second that proposal.