Just got a 3"inlet/outlet magnaflow muffler. I'm getting custom piping done this weekend. I am trying to decide whether to go 2.5" or 3" all the way through. I am almost 100% sure I will be going turbo within the next few months. My question is should I go 2.5" now then redo the exhaust to 3" when I am turbo or just go 3" now? Will there be a significant power loss with lack of backpressure due to the bigger piping on a NA car? And will it be rediculously loud? Thanks for all the input.

 

i say 2.25 or 2.5 for n/a...really losing backpresesure with 3". get all mandrel bent piping. piping should be redone to 3" after you got the turbo.

 

yup that's what I was planning on doing..thanks for confirming my thoughts

 

Are you going to cut the exhaust after the s-pipe and weld on the custom pipe after that?

 

my custom piping will include redoing the s-pipe

 

Yeah stay away from anything larger than 2.5" until the turbo is installed. At least the 2.5 is still ok for turbo, 3" is just to get the most out of it. 3" is UBER loud at high rpms on an NA car, so I'd stay clear of it.

Good luck with your prject though.

 

i myself is getting custom exhaust done soon too. you guys answered my questions too. good stuf

 

So you aren't worried about the CEL coming on?

I'm planning on cutting the exhaust after the s-pipe (right after where it bolts up to the midpipe). That way when a aftermarket s-pipe is finally out I can just bolt it to the mid pipe.

 

2.25 is best for NA cars like everyone else said.

 

it wouldn't hurt to have 2.5 on either turbo or on na, unless your going to boost more than 6 to 8 psi. anything more, go for 3 if your boosting 12-20 psi

 

I thought the car would only throw a CEL if you are running no cat. And isn't the s-pipe going to be the same thing whether I get one made or buy one from an aftermarket company assuming they are both mandrel bent?

 

whats an s-pipe?

 

https://www.scionlife.com/forums/vie...diagram#676930

view 4th post from top

 

personally, i think you should wait until you get the turbo installed, then do the 3" exhaust. since you already know that you want a 3" exhaust, why not just wait a little bit longer? save the money that you would of spent on the 2.5" exhaust and put it towards your turbo needs.

 

still depends on the boost your doing, if you only doing 6-8 psi, then go ahead with the 2.5

 

2.5in only. Do not do 2.25in, stock is 2.25in but its crush bent. Since your getting it custom done Im sure its going to be crush bent pipes. Shouldnt hurt the flow too much but it will hurt flow.

3in is pretty big for N/A but it wont hurt back pressure much on these cars. Its a very big motor and dynos have proven good horsepower and torque gain running open header.

I have a crush bent 3in turbo-back on my Mx6. Made a huge difference even though its crush bent.

2.4L plus a turbo even on low boost needs 3in.

 

Stock is not crush bent. Stock is 2.25 mandral bent.

Backpressure being good is bull____. Look at the dyno readings for an upgraded header & exhaust on this same forum. Backpressure was reduced significantly, and both HP and TQ still rose alot.

 

While it can and will increase peak HP & TQ numbers, the more important thing to look at is how well it is distribute, especially in NA cars. If I get and extra 15 hp from 5000 rpm's to redline, but drop 10 from idle to 5000, you can keep those mods. I had a 3" on my 1.8T GTI, and even with a turbo and hi-flow cat in the way, it was still LOUD. Just rock what you got until you install the turbo.

 

This man knows what he is talking about, for best results go 2.5-3, if you plan on going turbo then 3 for sure, It will not hurt velocity, you have a 2.4l engine, you'll be fine.