Removing the cats?
Lexus Champion
Joined: Feb 2001
Posts: 3,124
Likes: 32
From: Texas
Folks, the stock cats ARE high flow!!! 
In fact the Magnaflow "high flow" on that link are lower flow than the stock cats! Follow the Magnaflow link to the metal subtrate cats which are more expensive and higher flow. The stock cats are metal substrate (except for newer 430 engines, forget which year that change was made).
With dual high flow cats there is no noticeable peak loss and in fact a noticeable low range loss. This is due to the cats working like a one way check valve. The high temperature and pressure out flow from the exhaust port flows out the cat but the reversion pulse is blocked by the cat.
Leave them on. Also, do not focus on the pipe size as it is the core size that matters. Look at the Magnaflow metal substrate cats and notice they all have the same core regardless of "pipe" size.
Despite the cracking problems with the early runs on the headers they are still the best exhaust mod available for power AND the very important driving feel.
In fact the Magnaflow "high flow" on that link are lower flow than the stock cats! Follow the Magnaflow link to the metal subtrate cats which are more expensive and higher flow. The stock cats are metal substrate (except for newer 430 engines, forget which year that change was made).
With dual high flow cats there is no noticeable peak loss and in fact a noticeable low range loss. This is due to the cats working like a one way check valve. The high temperature and pressure out flow from the exhaust port flows out the cat but the reversion pulse is blocked by the cat.
Leave them on. Also, do not focus on the pipe size as it is the core size that matters. Look at the Magnaflow metal substrate cats and notice they all have the same core regardless of "pipe" size.
Despite the cracking problems with the early runs on the headers they are still the best exhaust mod available for power AND the very important driving feel.
going from a high flow cat to a test pipe will only give you a gain of 1 hp. I read this on a mag where they tested diffrent types of cats and that was the result. Also, if you plan to remove your cats, you will have to be tuned or you will run lean and get a cel.
Thread Starter
Pole Position
Joined: Oct 2004
Posts: 3,398
Likes: 15
From: Maryland
Hey Kev. I removed my cats originally and I just couldn't bear the smell on a regular. Especially with all the stop and go traffic here in NYC. I eventually put a high flow cat and it made a world of difference in the way it smells, LOL.
Like GSteg said if anything just switch to a high flow cat.
Nick, the point of hollowing out your cat is to pass visual inspection. Your basically gutting out the cat which is the same thing as removing them.
For those interested, I went with the magnaflow 3" high flow cat. I got it for under $80 shipped. They have EPA compliant & CARB certified OBDII Catalytic Converters up to 3" inlets.
You can get them from www.hottexhaust.com. They are also having some sale going on where all items are discounted 10.5%. They offer free shipping on orders over $50, no sales tax and here's the coupon code so that you can get an additional 10% off.
At checkout use the code : hottsavings
Like GSteg said if anything just switch to a high flow cat.
Nick, the point of hollowing out your cat is to pass visual inspection. Your basically gutting out the cat which is the same thing as removing them.
For those interested, I went with the magnaflow 3" high flow cat. I got it for under $80 shipped. They have EPA compliant & CARB certified OBDII Catalytic Converters up to 3" inlets.
You can get them from www.hottexhaust.com. They are also having some sale going on where all items are discounted 10.5%. They offer free shipping on orders over $50, no sales tax and here's the coupon code so that you can get an additional 10% off.
At checkout use the code : hottsavings
GSTeg, on a high power turbo car(400hp-ish) having a cat can cause up to a 40-50hp hit in horsepower figures. Pretty soon, with me pushing past 600hp the cat in place will cause an even bigger restriction in power. I'm all for cleaner air so that's why I'm gonna install a high flow cat...well when I have the money to do so(a high quality highflow isn't cheap) lol . I also have the electric dump so I can just open up the exhaust when I need maximum power. Then when I'm cruising I can close the dump and drive around and be ok with a big hp loss 
. I also have the electric dump so I can just open up the exhaust when I need maximum power. Then when I'm cruising I can close the dump and drive around and be ok with a big hp loss 
So I'll just have to "get around" it each year.
Hey Kev. I removed my cats originally and I just couldn't bear the smell on a regular. Especially with all the stop and go traffic here in NYC. I eventually put a high flow cat and it made a world of difference in the way it smells, LOL.
Like GSteg said if anything just switch to a high flow cat.
Nick, the point of hollowing out your cat is to pass visual inspection. Your basically gutting out the cat which is the same thing as removing them.
For those interested, I went with the magnaflow 3" high flow cat. I got it for under $80 shipped. They have EPA compliant & CARB certified OBDII Catalytic Converters up to 3" inlets.
You can get them from www.hottexhaust.com. They are also having some sale going on where all items are discounted 10.5%. They offer free shipping on orders over $50, no sales tax and here's the coupon code so that you can get an additional 10% off.
At checkout use the code : hottsavings
Like GSteg said if anything just switch to a high flow cat.
Nick, the point of hollowing out your cat is to pass visual inspection. Your basically gutting out the cat which is the same thing as removing them.
For those interested, I went with the magnaflow 3" high flow cat. I got it for under $80 shipped. They have EPA compliant & CARB certified OBDII Catalytic Converters up to 3" inlets.
You can get them from www.hottexhaust.com. They are also having some sale going on where all items are discounted 10.5%. They offer free shipping on orders over $50, no sales tax and here's the coupon code so that you can get an additional 10% off.
At checkout use the code : hottsavings
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Verdad Gallardo
Driver
Joined: Feb 2015
Posts: 136
Likes: 1
From: BC
Hey Kev. I removed my cats originally and I just couldn't bear the smell on a regular. Especially with all the stop and go traffic here in NYC. I eventually put a high flow cat and it made a world of difference in the way it smells, LOL.
Like GSteg said if anything just switch to a high flow cat.
Nick, the point of hollowing out your cat is to pass visual inspection. Your basically gutting out the cat which is the same thing as removing them.
For those interested, I went with the magnaflow 3" high flow cat. I got it for under $80 shipped. They have EPA compliant & CARB certified OBDII Catalytic Converters up to 3" inlets.
You can get them from www.hottexhaust.com. They are also having some sale going on where all items are discounted 10.5%. They offer free shipping on orders over $50, no sales tax and here's the coupon code so that you can get an additional 10% off.
At checkout use the code : hottsavings
Like GSteg said if anything just switch to a high flow cat.
Nick, the point of hollowing out your cat is to pass visual inspection. Your basically gutting out the cat which is the same thing as removing them.
For those interested, I went with the magnaflow 3" high flow cat. I got it for under $80 shipped. They have EPA compliant & CARB certified OBDII Catalytic Converters up to 3" inlets.
You can get them from www.hottexhaust.com. They are also having some sale going on where all items are discounted 10.5%. They offer free shipping on orders over $50, no sales tax and here's the coupon code so that you can get an additional 10% off.
At checkout use the code : hottsavings
Also, dor you notice power gain or loss? Thanks for reviving an old thread!
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