Stock exhaust manifold outlet diameter?

[jmgtp]

2001 LGT
2.5 SOHC

What is the diameter of the factory exhaust manifold where it bolts to the cat converter? Is it 2.5" ?

Ultimately, I'd like to know if a knock off Borla header will bolt to my stock cats? Are the outlets the same diameter?

Anyone try this combo? What does it sound like? I know it is the opposite most would do, since it is typical to start at the muffler and work your way back. I'm looking for a throatier sound but don't really want much additional internal/external noise. Ever hear a 350z at part throttle? Thats the volume level I'm looking for. Just that nice throaty performance sound.

Since I'd be retaining the stock cats would there be any CEL issue? Would the exhaust cool too much with the borla and force the mixture (precat) o2 sensor into open loop and lead to a CEL? I believe the CEL issue is only when replacing the cat with a high flow and the catalyst monitoring o2 sensor believes the cat has failed.

[Huffer]

A borla will fit your stock cats. Your stock cat is not 2.5" in diameter.

You may or may not have CEL with the stock cats - I don't think you will because the stock cats will reduce the flow down.

I think it's a waste of time to bolt up a Borla to the stock cats...

[Sarra]

your exhaust should be 2.25". And the borla is a replacement for just the stock manifold, you'll keep your stock cats. The OBX manifold replaces the stock cat with another resonator.

Get a high flow cat with your borla for the best results.

[jmgtp]

I'm looking for primarily a throatier, more performance oriented sound - not so much actual performance increases though that would be nice - but I don't want to increase the volume level by using an aftermarket muffler.

I was hoping the headers would give me that. I use this car as a daily driver and don't want to spend too much replacing the cats/mid pipe etc nor do I want it to be much louder than stock. I believe the headers I was looking at indicated a 2.5" outlet which is why I wanted to know the diameter of the cat inlet, which Sarra has said is 2.25" going a step down from 2.5 to 2.25 could be detrimental to flow if it inst a smooth transition so I'm not sure if a 2.5" header collector would work with the stock cats at all.

[Sarra]

The only headers I know of with 2.5" tubing are TWE's EL headers, which cost like $1,200 (according to their website).

I would suggest keeping it at 2.25" unless you have supporting mods, like cams, intake, etc.

If I were you, I would grab some Borla replicas and an SPT exhaust. It WILL be louder, but not by much, and it will sound better.