IEMaestro

I currently have the Greddy SP2 axle back exhaust on my IS350, but I want a little more sound and horsepower. Will removing the secondary cats give me what I want? What are the pros and cons of removing the secondary cats? Are they easy to remove? Would I be able to do it myself, or should I go to a shop? Thanks for your time and info!!

radicalrev

iTrader: (2)

i believe the gain is either o to 1 HP...lol...pros - louder... cons- illegal....hahahaha...

go to a muffler shop and do it...

IEMaestro

Thanks radicalrev. Why is it illegal?

phil9892

iTrader: (1)

Even though we have 4, we're not suppose to remove any catalytic converters as most shops would get fined if they were caught removing them. If I remember correctly, you'll get fined too for removing them in some states if not all. I guess it depends on where you live have emissions testing as well.

IEMaestro

Thanks for the info phil!

caymandive

iTrader: (2)

Check out my dyno in my signature. I did a before and after of the secondary cats. Peak power isn't much, but you gain some nice power all through the curve until around 5700rpm where it stayed about the same.

You will also pick up some nice sound as the Greddy and Tanabe are a bit on the quiet side. http://youtube.com/watch?v=D-d8IlLwkUo

radicalrev

iTrader: (2)

any1 remove the secondary cats AND the resonator at the same time?? I only heard people removing the sec. cats only but not both....

combfilter

iTrader: (3)

according to your sig you are in CA. I wouldn't touch my cats if i lived in CA for a gain of around 3hp (which isn't @#% on a 300hp car). That's a huge no-no out there. Here in TX its still a no-no, but they are not as strict as CA. I bet you'd have a hard time even finding a shop out there to do it.

combfilter

iTrader: (3)

one guy said he did in the after market ex\haust thread based on other designs. He said "i like" and gernby asked what he "liked".... I think he came back and said it was too loud and he was going to get his resonator put back or something. Not sure why you would remove the resonators though?

carchitect

iTrader: (1)

I have a Lexus HKS exhuast on mine. I'm debating about making a custom mid-pipe to replace my OEM one. I'm planning on making it a slight bit larger diameter than the OEM one and making an x-pipe configuration to it. The pipe will be a straight shot. The OEM resonator and secondary cats won't be on there anymore. The stuff will need to be made of 304SS so i'm still researching the flanges and orings (for the Lexus HKS exhuast]s mufflers) I'm going to need to get this done.

radicalrev

iTrader: (2)

thinking that removing the resonator will make the exhaust sound louder?? I got my secondary cats removed already with the Tanabe. But the difference is not that noticeable...so i want to make the Tanabe louder by removing the resonator replacing with another straight pipe...

caymandive

iTrader: (2)

You really don't think that with the secondary cats out that it's not all that much louder!? Aside from it getting louder, I did notice that the slight drone that was inherent to the Tanabe under slight load was pretty much eliminated when I pulled the cats and it really opened up the sound in the higher rpms. I think when you pull that large resonator that it's going to get really aggressive sounding, but won't gain any power. You'll also shed a few lb's which is a good thing. Definitely get some video and leave feedback when you do this. I'm curious.

Also instead of making another hack to the stock exhaust system, why not just have the exhaust shop make you all new piping from the tanabe all the way up to the primary cats? Heck then you can basically swap it back to stock anytime you want. Just a thought.

radicalrev

iTrader: (2)

well i did notice it in high rpms ...not much on lower rpm...yes..i did notice the drone is less now on the freeway on constant 2.5K rpm...

yeap, not looking for any gains...just the sound....but still thinking of going intake or removal of the resonator...

hahaha..new piping = more $??

passnu2

iTrader: (33)

what about the Megan mid pipes? this will replace that whole area and pretty much give you what you are looking for. ???

radicalrev

iTrader: (2)

yeap...that would be it...borla too...