Secondary Cat Delete
05-01-23, 06:44 AM
#1
Advanced
Thread Starter
Secondary Cat Delete
Hey all, I did some searching around the forums and found lots of debates about deleting ALL the cats, but I’m interested in specifically how the car SMELLS. I want to keep the main catalytic converters coming off the exhaust manifolds, but eliminate the large cat downstream. Can anyone comment on how eliminating this one affects the smell coming out the exhaust?
I use my car mostly as a date car with the wife. A cat less car is out of the question because of the stink that comes from that. If deleting the 3rd cat will cause a drastic increase in stink, then I’m out.
Appreciate your feedback boys!
Nick
I use my car mostly as a date car with the wife. A cat less car is out of the question because of the stink that comes from that. If deleting the 3rd cat will cause a drastic increase in stink, then I’m out.
Appreciate your feedback boys!
Nick
05-01-23, 09:55 AM
#2
Pole Position
I had mine taken out (along with both resonators) on my SC400 and I never noticed a bad smell... I also passed emissions here in CO just fine with only the two primaries. Getting rid of that and adding a nice catback really wakes up some lovely sounds from those 1UZ's!
05-01-23, 05:45 PM
#3
I can't speak for the V8 models but I know high flow aftermarket cats are what many people with all but the most powerful JZ turbo cars do. Totally catless is smelly as hell. My first car was so old it was made before cats were required... and I held my breath every time I started and got out of that car. I actually WANTED aftermarket cats installed even though it was a 60's carbureted model before EGR which probably wouldn't heat them up quite enough.
JZ turbo cars often delete the #1 cat in favor of a downpipe and then have a high flow secondary cat installed in the easier to service (and fabricate pipe for) stock #2 cat location.
I would imagine that a similar approach might be the way to go for a 1UZ car, just with a two high flow cats instead of one.
But... unless you've already done extensive forced induction modification to your 1UZ Nick I don't think this will do much to free up power. Removing those secondary resonators on the stock rear exhaust pipes even with stock mufflers definitely changes the exhaust note night and day.
...
Also other than rich exhaust smell from old cats, cold cats or fewer than the stock number of cats is still secondary to any elimination of the fuel vapor charcoal canister system that controls and alleviates fuel smell as the car is parked. Definitely leave all that hardware in place. Even catless highly modified SCs retain all of those components.
....
As far as which high flow cats to go with... Magnaflow is the biggest industry player as is any of the companies owned by Airtek. Random Technology used to offer great high flow cat options for Supra MKIVs and I think they at least offer universal high flow cats.
There might be some other current aftermarket high flow cat options on Supraforums threads. Everything like this will be custom selected and fitted for a 1UZ car so that is where I would start looking for other universal fit high flow options to have welded in to all new piping or the factory piping.
Until you have forced induction in the mix I do not think going with an exhaust pipe diameter larger than stock will do very much. Since that will reduce back-pressure it will probably reduce low end torque while your engine is naturally aspirated.
JZ turbo cars often delete the #1 cat in favor of a downpipe and then have a high flow secondary cat installed in the easier to service (and fabricate pipe for) stock #2 cat location.
I would imagine that a similar approach might be the way to go for a 1UZ car, just with a two high flow cats instead of one.
But... unless you've already done extensive forced induction modification to your 1UZ Nick I don't think this will do much to free up power. Removing those secondary resonators on the stock rear exhaust pipes even with stock mufflers definitely changes the exhaust note night and day.
...
Also other than rich exhaust smell from old cats, cold cats or fewer than the stock number of cats is still secondary to any elimination of the fuel vapor charcoal canister system that controls and alleviates fuel smell as the car is parked. Definitely leave all that hardware in place. Even catless highly modified SCs retain all of those components.
....
As far as which high flow cats to go with... Magnaflow is the biggest industry player as is any of the companies owned by Airtek. Random Technology used to offer great high flow cat options for Supra MKIVs and I think they at least offer universal high flow cats.
There might be some other current aftermarket high flow cat options on Supraforums threads. Everything like this will be custom selected and fitted for a 1UZ car so that is where I would start looking for other universal fit high flow options to have welded in to all new piping or the factory piping.
Until you have forced induction in the mix I do not think going with an exhaust pipe diameter larger than stock will do very much. Since that will reduce back-pressure it will probably reduce low end torque while your engine is naturally aspirated.
05-02-23, 04:37 AM
#4
Advanced
Thread Starter
Any drone issues?
Nick
05-02-23, 04:41 AM
#5
Advanced
Thread Starter
I can't speak for the V8 models but I know high flow aftermarket cats are what many people with all but the most powerful JZ turbo cars do. Totally catless is smelly as hell. My first car was so old it was made before cats were required... and I held my breath every time I started and got out of that car. I actually WANTED aftermarket cats installed even though it was a 60's carbureted model before EGR which probably wouldn't heat them up quite enough.
JZ turbo cars often delete the #1 cat in favor of a downpipe and then have a high flow secondary cat installed in the easier to service (and fabricate pipe for) stock #2 cat location.
I would imagine that a similar approach might be the way to go for a 1UZ car, just with a two high flow cats instead of one.
But... unless you've already done extensive forced induction modification to your 1UZ Nick I don't think this will do much to free up power. Removing those secondary resonators on the stock rear exhaust pipes even with stock mufflers definitely changes the exhaust note night and day.
...
Also other than rich exhaust smell from old cats, cold cats or fewer than the stock number of cats is still secondary to any elimination of the fuel vapor charcoal canister system that controls and alleviates fuel smell as the car is parked. Definitely leave all that hardware in place. Even catless highly modified SCs retain all of those components.
....
As far as which high flow cats to go with... Magnaflow is the biggest industry player as is any of the companies owned by Airtek. Random Technology used to offer great high flow cat options for Supra MKIVs and I think they at least offer universal high flow cats.
There might be some other current aftermarket high flow cat options on Supraforums threads. Everything like this will be custom selected and fitted for a 1UZ car so that is where I would start looking for other universal fit high flow options to have welded in to all new piping or the factory piping.
Until you have forced induction in the mix I do not think going with an exhaust pipe diameter larger than stock will do very much. Since that will reduce back-pressure it will probably reduce low end torque while your engine is naturally aspirated.
JZ turbo cars often delete the #1 cat in favor of a downpipe and then have a high flow secondary cat installed in the easier to service (and fabricate pipe for) stock #2 cat location.
I would imagine that a similar approach might be the way to go for a 1UZ car, just with a two high flow cats instead of one.
But... unless you've already done extensive forced induction modification to your 1UZ Nick I don't think this will do much to free up power. Removing those secondary resonators on the stock rear exhaust pipes even with stock mufflers definitely changes the exhaust note night and day.
...
Also other than rich exhaust smell from old cats, cold cats or fewer than the stock number of cats is still secondary to any elimination of the fuel vapor charcoal canister system that controls and alleviates fuel smell as the car is parked. Definitely leave all that hardware in place. Even catless highly modified SCs retain all of those components.
....
As far as which high flow cats to go with... Magnaflow is the biggest industry player as is any of the companies owned by Airtek. Random Technology used to offer great high flow cat options for Supra MKIVs and I think they at least offer universal high flow cats.
There might be some other current aftermarket high flow cat options on Supraforums threads. Everything like this will be custom selected and fitted for a 1UZ car so that is where I would start looking for other universal fit high flow options to have welded in to all new piping or the factory piping.
Until you have forced induction in the mix I do not think going with an exhaust pipe diameter larger than stock will do very much. Since that will reduce back-pressure it will probably reduce low end torque while your engine is naturally aspirated.
For this particular instance however, I’m going to leave the stock manifold cats in place, and just remove the secondary cat, located downstream in the middle of the car. My only debate now is straight pipe or replace with a resonator. I don’t want to go through the trouble and have it still be too quiet, but I also don’t want to regret it by having a ton of drone.
Nick
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KahnBB6 (05-02-23)
05-02-23, 05:04 AM
#6
Advanced
Good morning Nick,
I don't know what others are talking about, BUT on my '93 300 I got rid of my cats and installed headers and a cat less mid pipe. I already had a stainless rear exhaust on the car. No odors and I picked up several MPG. I could not be more satisfied. My car has 198k+ miles and runs like a Champ, of course no turbo which will not ever happen at my age. I am still scratching my head on this odor problem. Odors always come from a bad cat or running too rich etc. but not by deleting cats. What would be left to cause an odor.
The only problem I have is now my car is a little too loud (which I love) for my wife and too low with my suspension.
Best of luck,
Bill
I don't know what others are talking about, BUT on my '93 300 I got rid of my cats and installed headers and a cat less mid pipe. I already had a stainless rear exhaust on the car. No odors and I picked up several MPG. I could not be more satisfied. My car has 198k+ miles and runs like a Champ, of course no turbo which will not ever happen at my age. I am still scratching my head on this odor problem. Odors always come from a bad cat or running too rich etc. but not by deleting cats. What would be left to cause an odor.
The only problem I have is now my car is a little too loud (which I love) for my wife and too low with my suspension.
Best of luck,
Bill
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RXRodger (05-02-23)
Trending Topics
05-02-23, 07:06 AM
#8
Advanced
t2d2,
The one on my mid pipe was definitely a cat. I believe you are thinking father back. Toyota calls the pipe that connects to the cat at the exhaust manifold the mid pipe. This cat has all the shielding which to my knowledge you will never see on a resonator unless someone knows better.
Bill
The one on my mid pipe was definitely a cat. I believe you are thinking father back. Toyota calls the pipe that connects to the cat at the exhaust manifold the mid pipe. This cat has all the shielding which to my knowledge you will never see on a resonator unless someone knows better.
Bill
05-02-23, 08:20 AM
#9
Advanced
Thread Starter
05-02-23, 08:24 AM
#10
Advanced
Thread Starter
Good morning Nick,
I don't know what others are talking about, BUT on my '93 300 I got rid of my cats and installed headers and a cat less mid pipe. I already had a stainless rear exhaust on the car. No odors and I picked up several MPG. I could not be more satisfied. My car has 198k+ miles and runs like a Champ, of course no turbo which will not ever happen at my age. I am still scratching my head on this odor problem. Odors always come from a bad cat or running too rich etc. but not by deleting cats. What would be left to cause an odor.
The only problem I have is now my car is a little too loud (which I love) for my wife and too low with my suspension.
Best of luck,
Bill
I don't know what others are talking about, BUT on my '93 300 I got rid of my cats and installed headers and a cat less mid pipe. I already had a stainless rear exhaust on the car. No odors and I picked up several MPG. I could not be more satisfied. My car has 198k+ miles and runs like a Champ, of course no turbo which will not ever happen at my age. I am still scratching my head on this odor problem. Odors always come from a bad cat or running too rich etc. but not by deleting cats. What would be left to cause an odor.
The only problem I have is now my car is a little too loud (which I love) for my wife and too low with my suspension.
Best of luck,
Bill
Since I’m not after power, but instead a bit more theater, I won’t take the chance and eliminate the manifold cats and risk that smell coming back. My eventual setup will incorporate high flow cats.
Nick
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Bimmerbill (05-02-23)
05-02-23, 10:02 AM
#11
Pole Position
I do believe that third unit is indeed a cat (it was on my '96, but I'm not sure where that car came from originally). You'll definitely pick up some sound and since you'll be retaining the other two cats along with a nice catback exhaust I don't think you'll have any issues with drone. I never had any issues with smells either - the two primary cats seem to do most of the heavy lifting in the emissions department. Get rid of that bad boy, start it up, and let us know what you think!
05-02-23, 10:04 AM
#12
t2d2,
The one on my mid pipe was definitely a cat. I believe you are thinking father back. Toyota calls the pipe that connects to the cat at the exhaust manifold the mid pipe. This cat has all the shielding which to my knowledge you will never see on a resonator unless someone knows better.
Bill
The one on my mid pipe was definitely a cat. I believe you are thinking father back. Toyota calls the pipe that connects to the cat at the exhaust manifold the mid pipe. This cat has all the shielding which to my knowledge you will never see on a resonator unless someone knows better.
Bill
Shielding alone doesn't tell you it's a cat. Some mufflers and general exhaust pipes also have heat shields. You would need to cut it open and look inside to verify it's a cat based just on visuals.
05-02-23, 10:24 AM
#13
Advanced
I give up. I just know what I have experienced and that is all.
Bill
Bill
05-02-23, 11:07 AM
#14
This is the best I've managed to find, but it takes a few subsequent searches to piece things together:
https://parts.lexusstevenscreek.com/...ust-components
17410-50080 is the Federal (non-CA) version and is sometimes titled converter and amplifier, other times just front pipe. 17410-50090 is the CA version and is titled pipe assembly. If I remember right, the mid-pipe is also referred to in some schematics as the sub-cat.
I think having converter in the name of the Federal version is what confuses things. It obviously differs from the CA version, so that should tell you it's probably not a cat. (Because, what else would differentiate them?) Having amplifier in the name also hints strongly at it being a resonator.
05-02-23, 03:59 PM
#15
Advanced
Let me start by saying that I did not assume anything. I took my mid pipe with cat off myself with the help of a friend since I am cripple, I do try to do everything I possibly can do and not depend on other people(friends). The person helping me was a personal friend who is retired now (still does a little work on the side). He has been doing muffler/mechanic work for 50 years. He confirmed that it was a cat, just like I knew it was. I am 84 and have been working on my personal cars since I was 15 when got my first car which I still own.
The diagrams you reference are all SC400 with two pipes coming from the engine. You missed the whole point of the conversation since my car is a SC300 with only one single mid pipe. To go back and explain again, I removed my exhaust manifolds with cat and installed headers then later I removed my mid pipe with cat on the end and installed a Supra mid pipe without a cat. I also do not have any odors, maybe it is the gas i am burning here in Mobile.
I have made this as plain as I can.
Bill >>
The diagrams you reference are all SC400 with two pipes coming from the engine. You missed the whole point of the conversation since my car is a SC300 with only one single mid pipe. To go back and explain again, I removed my exhaust manifolds with cat and installed headers then later I removed my mid pipe with cat on the end and installed a Supra mid pipe without a cat. I also do not have any odors, maybe it is the gas i am burning here in Mobile.
I have made this as plain as I can.
Bill >>