I just got he rrm turbo and ive been told several times that it is better to get a 2.5" catback instead of a 2.25" with a turbo. How much of a difference will it make as in hp and torque numbers?

 

almost nil as you still have the stock cat right?

cause then you would need a 2.5 test pipe to a header with a 2.5 outlet flange. dont worry about it. it wont make much of a difference at all.

 

i did get a test pipe from jaime as well but i havent measured it to see if its 2.25 or 2.5. if i used that as well witha 2.5 catback will it hen make a diff?

 

remember, you're removing one of the cats when you put your downpipe in, so you have reduced the backpressure or the cat.

what you want to look at with your exhaust setup is exhaust velocity. Certain diameter exhaust piping works best for certain cars. In the case of the lancer, it's been a common thing to see 2.5" systems on turbo lancers because it works best for exhaust velocity.

What you'll want to do is get a high flow cat, or a test pipe and mix it up with a 2.5" catback for maximum effect. Also, your downpipe should be 2.5" as well.

 

yeah, but how much of a diff will that really make? i want to know how much hp and torque diff there would be with the 2.5 setup?

 

you'll see an increase in overall horse, but a decrease in low end torque. for exact figures, I don't have them

 

dont worry about back pressure. that is only true in a non-turbo car. the turbo will provide all the back pressure you need.

 

so guro do you know how much a diff it would make?

 

yep, zippo!!!!!!!! lots of guys run turbo's with the test pipe. the actual turbine provides the back pressure you need.

as for the test pipe and 2.25 vs 2.5 it is still minimal at best. you arent running super high boost so 2.25 is just fine. now if you dont have your cat back yet and are looking to go custom then go 2.5 cause you can. if you already have the 2.25 catback then dont worry about it as you wont see gains worth the cost.

 

just straight pipe the ***** from the turbo back. that'll solve everything

 

ok cool, i dont have any exhaust right now so my next question: guru you dont have an exhaust at all, how much would i gain overstock from getting 2.5?

 

a good amount. i dont have exhaust at all either but i have the magnaflow catback waiting to be installed.

you will gain like 10 ponies or so on a turbo car.

 

really?!?! nice. i really dont like the sound of an exhaust on an import bc i live in major hick country and ppl think you are a ricer if you have exhaust. i want to be quiet. thanks for all the info guru.

 

sure, i recomend the magnaflow catback for quiet. i head one of my friends turbo's with header, test pipe and the magnaflow catback and it sounds really quiet yet you get nice gains. either order that one from RRM or just get a custome 2.5 made with a magnaflow muffler.

 

buschurs 2.5 comes with an optional magnaflow muffler now too