Could anyone confirm for me the factory size of the GSL's exhaust?

The reason I ask..

On mine, from the headers back it's a 2" pipe until it reaches the center muffler then into 2.5" to the rear (aftermarket pipe taken from a GSR)

Obviously 2.5" was a bit of a joke when I had it fitted. So this Saturday I'm having a new system fitted, & don't know whether I go a full 2" or 2 1/4" ? As I'm not sure if 2" is the factory size or not for a non turbo...

Cheers.

Both the GSL and GSR were a 2 inch system..........

Shit, is that so!? Bloody hell

So 2 1/4" would be a suitable upgrade then for it?

Or save some coin & just replace the 2.5" rear pipe with 2" again but retain the high flow rear muffler + the already fitted headers.

Not sure what is going to benefit more for an N/A

The headers are actually "tuned length"......this ensures exhaust is released in the engines firing order improving efficiency (rather than dumping into a un-efficient cast manifold)..........the small 2 inch system will increase back pressure therefore "strangling" power, I would go for a 2 1/4 inch system on the N/A.........this will ensure max flow without loosing bottom end response due to volumetric efficiency levels. (Exhaust temp)

Great, thanks a lot Andrew! Very insightful as always.

2 1/4 it will be then.

I can only imagine how messed the system is at the moment with the current combination

Keeping the 2.5" rear muffler shouldn't hinder anything?

It shouldn't..........as it's at the "colder" end of the exhaust.........are you running the factory camshaft?

No worries, saves me on a new muffler

And still running the factory camshaft, is it worth replacing on the 4G37/anything available?