Im curious about something. Ive heard the stock exhaust is about 61.5mm. Now isnt the idea of an exhaust, bigger pipes = better flow, which is the why the 70mm exhausts produce the most power. How can an exhaust smaller than stock produce more power? Is most of the power lost in the twin loop muffler design?

And also another question regarding the HKS exhaust which is 60mm and known to lose power. Is it because of the 60mm piping or the big "resonator" in the back? What exactly is it in the exhaust that makes the noise, if a smaller exhaust can be so much louder than oem. What would stop someone from taking the hks mufflers and putting them on the 61.5mm exhaust and have a noise similiar to the hks without the power loss.

I understand a single 60mm exhaust with less bends and weight can smooth out the air flow and put less weight on the car, but it just seems so odd to me than they would make exhausts smaller than stock.

 

I have the Megan drift spec single. And from my experience my 60mm single made a little extra power on the top end over the stock exhaust. Just my $.02

 

if what you say is true and the stock exhaust system is 61.5 mm, then:

70 mm single >> 60 mm single > 61.5 mm dual > 60 mm dual (HKS = loss of power?)

you also have to remember that the stock is a dual exhaust system, which splits the air flow into two different directions and into even small diameter piping. at least with the 60 mm single, it's all a consistent flow through and no tapered piping. this is probably why you see a small increase (when going with a single 60 mm over the stock 61.5 mm dual.