• A few months ago I had PPE Headers installed as well as an ARK Grip Catback on my RC350, (I came here to post since the motors are the exact same between the IS350 and RC350, and theres no performance section on the RC side of CL). I love how it sounds for the most part, but theres still some rasp I want to get out of the system. Any ideas on what to do?

 

I'm assuming your headers eliminated the cats?

The only way, that I know of, to eliminate the raspy sound is by having stock or high flow cats. Cat-less headers with a cat-back exhaust will often have a raspy sound.

You could add some high flow cats back into your system

https://www.rr-racing.com/Lexus-IS-F...isfexcat02.htm

 

Yes, the PPE Headers are catless. My Ark Grip has 2 cats, 2 resonators, and 2 mufflers. Would it not be odd to have 4 cats in my midpipe? I want to minimize airflow restriction as much as possible too.

 

Yeah, after second thought your exhaust having the high flow cats should be enough but I am by no mean an expert with exhaust engineering so lets wait for someone with a little more experience to weigh in.

My comment was based on what was on the RR racing header page:

But your exhaust does have high flow cats, so I am unsure.

Sorry I wasn't more helpful

 

Maybe you could change your ARK resonator for some bigger magnaflow or vibrant type resonator. It will not be restrictive as a highflow cat.

 

That's actually a pretty good idea. I'm just scared that I'm going to do more damage in terms of exhaust note than good.

 

I haven't seen the ARK in real life, but it appears the "mufflers" are more like resonators? Basically just a straight pipe with maybe some materials in the walls? If so then they aren't likely doing much to change the sound aside from the attached Helmholtz resonators which are there to help with drone. The main resonators appear to be a decent size and cats should attenuate the sound, which is why I suspect the "mufflers" don't to much at all considering the ARK is relatively loud.

I changed out my 7" Tsudo resonators for 18" Vibrants and it made a fair difference in attenuating and smoothing out of the sound. They were the same 4" diameter and straight-through. ARK's appear to be at least 12" long so different bottle-style ones may not make much difference, unless you go with the UltraQuiets or similar, which have larger bodies to them. Check out the 1141, or for ultimate deadening the 17930 (mine are 1793s). All are straight-through so they won't affect airflow much if at all, yet will certainly tailor the sound and volume.

 

That's reason why I didn't go for the ARK catback exhaust system because of the two airflow restriction cats built on them. So I went with a high quality Japanese exhaust company that looks very similar but without the airflow restriction cats built on them called Apexi. I just had my PPE headers catless installed six days ago on my 2016 Lexus IS350 F Sport rwd along with my Apexi catback exhaust system and it rasp in the lower rpms. It doesn't matter what brand of exhaust you have whether it's a high-end brand or a cheap brand it's going to rasp going catless with PPE headers or any headers. But it doesn't bother me since I was looking to get the most performance out of my engine by adding the PPE headers, Apexi exhaust, RR racing tune, and the RR racing intake. Your ARK catback already came with two built on cats so I would just leave it alone and don't add anymore airflow restrictions. There's a reason why you went with PPE headers catless and ARK catback exhaust system. Now you have to ask yourself whether you want performance or just sound. That's what happens when you go catless on headers you either love it or hate it. I'm loving the way my car is performing and sounding it feels like a different beast with these great mods. But then again it is my weekend toy. 😎👍 Hope everything turned out great for you ✌