4" pipe question(HELP much confusion)
 

Hi took my car to the garage this morning(98Terzo)to see what size pipe i would need for a de-cat downpipe,it seems that the car is running from the front to the back,pipework that is 4" s in thickness!

Silly question but does that mean that the de-cat that i will need to buy needs to be also 4"?Or can it be 4" and then taper into 3"?

Its just that i have been looking at the past threads and...well i am a little confused!

Also do my98 cars need to be re-mapped or was this just an issue with JDMs?

standard pipework is 2 1/2" so if you have 4" then you have an aftermarket exhaust. 4 " is unusual as 3" is big enough for high power applications.
I would think that you may already have a decat or performance cat if indeed your pipework is 4".

my pipe work is 3" for a 330bhp wrx and i could have prob got away with 2.5".

4" sounds ridiculous, but, then again what do i know:)

unless it means a 4" tail end

Morning guys

the big pipe in question was already on the car when aquired!!..the downpipe cat is still on the car,i cannot find anything in the reciepts that i got with the car stating that an aftermarket sports cat was added..

I suspect your measuring the diameter of the pipe with the heat shields still in place?

he he he...3.5"..Good old fashioned garages,using the latest in measuring technology...EYES!!

Great cesars ghost!!..Now i can get to ordering the de-cat downpipe,spoiler to pick up next week and the roof scoop arrives next week too..

Rally slaaag....