I had a 3" single exhaust with a cheap muffler made when I went turbo. It was at the end of the process and funds were a little tight so nothing special.

But damn is it loud. Obnoxious is the best word for it.

The plan has always been to replace the back end with a split and twin mufflers but so far I haven't got around to it.

I have the chance to pick up an Invidia 70mm twin system. Not only that but the previous owner replaced the front resonator with a bigger Lukey unit to reduce the sound.

Will going from a 3" straight through exhaust to a 70mm (6.2mm smaller diameter) Invidia have much effect power wise?

 

Without means to quantifing muffler performance or the losses from piping.

Assuming all else is equal there will be no difference.

 

less sound/drone and most likly same performance. DO IT.

 

Just turn the boost up 0.1 psi to compensate.

 

i wanna say you'd lose a few horses.. but u should be ok.. make sure u check the afr just because sometimes it throws off a lot

 

Absolutely loving the Invidia. It has a custom resonator/mid-muffler and is nice and quiet.

 

6mm may seem like nothing but its actually a 16% reduction in area. Not insignificant IMO. Whether or not you are flowing enough air for that to help, hurt, or do nothing I don't know.

 

Any loss of power is not noticeable on the bum dyno. It actually feels like an increase because the car still has plenty of power but doesn't make a great deal of noise making it.

I'll retune soon and we'll see if there is any loss. Mind you, I've had a new turbo, new exhaust and readjustment of the tappets since my last tune.