Gutted cats VS straight pipe
Gutted cats VS straight pipe
Tomorrow we are suposed to gut my cats, I wanted to know what is the difference between gutting the cats or replaceing them with a test pipe?
Basically does it matter which way we go.
Basically does it matter which way we go.
Yea I was told that if we gutted them it would still look legit for emissions inspections. But then my son told me that the large expansion area and then shrinking the exhaust path back down could be bad.
Lexus Champion
Joined: Oct 2001
Posts: 3,417
Likes: 0
From: el clinico magnifico
Originally Posted by morris
Yea I was told that if we gutted them it would still look legit for emissions inspections. But then my son told me that the large expansion area and then shrinking the exhaust path back down could be bad.
Id say if you had the time and money, get some test pipes made up that you can bolt right in. That way, when you need to smog the car, you can bolt the stock cats back into place. And test pipes are going to flow better anyways 
I'm short on cash right now and I'm getting it done for free, so beggars cant be choosers on top of that I'm trying to solve what we think is a backpressure problem that is effecting the supercharger. So it is all experimental at this point, sort of see what happens type of thing.
I just was trying to see if there were any serious negative aspects of the gutting process.
I just was trying to see if there were any serious negative aspects of the gutting process.
Trending Topics
Lead Lap
Joined: Dec 2003
Posts: 753
Likes: 0
From: New Jersey
morris im not too familiar w/ FI but i am w/ cars. Guttin the cat will release back pressure. Do you need more back pressure or less. On my car i did a 3" piping cat back exhaust and i dont have enough back pressure only because im doing FI in the near future, so backpressure is good, at times, and at times bad. I can assume u need less back pressure so yea that would do the job. So would bigger exhaust piping. u should just remove all piping from the cat to the muffler and see if the car is any faster, that can tell you if its back pressure or what.
P.S: MAKE SURE WHOEVER GUTS THE CAT WEARS A MASK!!!
P.S: MAKE SURE WHOEVER GUTS THE CAT WEARS A MASK!!!
ClubLexus Stories
Celebrating Lexus & Toyota from Around the Globe
8 Tips for Improving Your Hybrid or Plug-in Hybrid's Efficiency!
Michael S. Palmer
10 Best Lexus Models No One Remembers
Joe Kucinski
TRD Off-Road Premium: Best 2026 4Runner, Except This One Thing
Michael S. Palmer
Top 10 Lexus & Toyotas to Drive Before You Die!
Joe Kucinski
Top 10 Lexus/Toyotas With The LEAST 5-Year Depreciation
Joe Kucinski
Lexus LC500 Convertible Auction: A Preview of Rising Values?
Brett Foote
GX 550 vs TX 550: Best 3-Row Luxury Lexus Family Hauler
Michael S. Palmer
9 Best Lexus Models You Can Buy for Half Price (And 1 You Shouldn't!)
Joe Kucinski
2026 Lexus NX Buyer's Guide: Models, Features, Prices & More!
Brett Foote
Basically it appears that my Supercharger stops spinning freely as we get up in rpm's we are hoping that the cause is excess back pressure caused by the cats. See this link post 13 for details https://www.clublexus.com/forums/sho...2&page=1&pp=15
The theory is that hte exhaust back pressure is backing up into the intake side and creating resistance to the blower.
A few times one of teh cats was throwing codes.
The theory is that hte exhaust back pressure is backing up into the intake side and creating resistance to the blower.
A few times one of teh cats was throwing codes.
Lead Lap
Joined: Dec 2003
Posts: 753
Likes: 0
From: New Jersey
i think i understand, so basically the RPMs freeze or slowly increase at certain points. Yea definitly back pressure in one way or another. It might be too much back pressure due to a clogged cat. over 200k miles think its too much back pressure.
Well the way it is manifesting it self is that the blower pulley stops spinning as the boost increases this causes the belt to start slipping and the coggs get ripped off the belt. We are hopoing that the backpressure is making it hard for the impeller to turn.
Lexus Champion
Joined: Feb 2001
Posts: 3,124
Likes: 32
From: Texas
Originally Posted by morris
Well the way it is manifesting it self is that the blower pulley stops spinning as the boost increases this causes the belt to start slipping and the coggs get ripped off the belt. We are hopoing that the backpressure is making it hard for the impeller to turn.
The stock cats are VERY expensive. Gutting them is not easy and will not give you the results you are looking for. The car will be louder and will loose low RPM reponse and torque. The noise increase will be tinny and booming. This is NOT recommended.
Obviously headers and 2.25" pipes with a racing Y or X pipe is the correct solution. Getting the cats gutted for "free" will end up being one of the more expensive options you could choose and the results will not be what you hoped.
Have some test pipes made or better yet pull the cats off the car and have dual 2.25" pipes with a quality X or Y pipe installed.
Well let me ask you this does it sound like pulling the cats or replacing them with pipes will help with the actual problem of the supercharger not wanting to spin?
Lead Lap
Joined: Dec 2003
Posts: 753
Likes: 0
From: New Jersey
Well if you're trying to get rid of backpressure, then it should help. Depending how clogged the cat is in the first place, depends how much back pressure its sending. I agree on the headers, talk to LXOGOOD he just picked up OBX headers for like $300