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My flame suit is on in preparation for the chokemaster speeches heading my way. That being said, I had a Jones Exhaust Full Boar chambered muffler installed on my ‘00. It’s a little quieter than I was expecting but all and all I like it. On the hwy I can’t hardly hear it over the wind noise. 😂
I think it sounds close to my 'stock' exhaust. Certainly not too loud from what you have shown. As long as YOU like it, be happy with your choice.
Yeah it’s not much louder than stock but it’s louder and deeper. I don’t have an 80 series flowmaster to compare it to but I’m guessing it’s probably on par since they’re both chambered and have the same dimensions. I imagine a transverse Magnaflow straight through type muffler would be even quieter at idle since they generally are than tbe chambered type all else being equal. As far as liking it, overall I do but it’s a mixed bag. I kinda was hoping for a little louder, but on the other hand it’s a little easier to make long rides than a car with single chamber mufflers. Do these things (4th gen) have resonators as well as cats or just cats?
It sounds very similar to my '02 Z28 when it was stock with just an 80-series FM. It's really not a loud muffler when combined with stock manifolds and cats, but if you move to an ORY (with or without headers) it gets A LOT louder (and raspy). For a bit more volume you could move to a single chamber version (like an FM 10-series, or equivalent) and it still wouldn't be stupid loud as long as you keep the cats - but then you'd only have one tailpipe (some folks do this, using just a single turndown tucked up into the bumper and it actually looks very nice on a Z28/SS/Formula, but not a Trans Am with the bumper cutouts for tailpipes). If you wanted to do two opposing mufflers and true duals, it would get very costly and require some modifications to fit over the axle.
The stock 4th gen F-body LS1 exhaust system consists of two cats (one per side) and one transverse muffler, no resonator(s). For base V8 models (Z28/Formula) the muffler is longer and has 2.25" outlets, for SS/WS6 the muffler is shorter and uses 2.75" outlets. All models use a 2.75" I-pipe and the same Y-pipe/cats/manifolds for a given model year. Only exceptions would be a Firehawk or SS optioned with SLP upgraded exhaust, in which case the I-pipe is 3" and obviously a different muffler (SLP dual/dual) was used and, of course, the 1998 SS/WS6 cars with the single outlet muffler.
It sounds very similar to my '02 Z28 when it was stock with just an 80-series FM. It's really not a loud muffler when combined with stock manifolds and cats, but if you move to an ORY (with or without headers) it gets A LOT louder (and raspy). For a bit more volume you could move to a single chamber version (like an FM 10-series, or equivalent) and it still wouldn't be stupid loud as long as you keep the cats - but then you'd only have one tailpipe (some folks do this, using just a single turndown tucked up into the bumper and it actually looks very nice on a Z28/SS/Formula, but not a Trans Am with the bumper cutouts for tailpipes). If you wanted to do two opposing mufflers and true duals, it would get very costly and require some modifications to fit over the axle.
The stock 4th gen F-body LS1 exhaust system consists of two cats (one per side) and one transverse muffler, no resonator(s). For base V8 models (Z28/Formula) the muffler is longer and has 2.25" outlets, for SS/WS6 the muffler is shorter and uses 2.75" outlets. All models use a 2.75" I-pipe and the same Y-pipe/cats/manifolds for a given model year. Only exceptions would be a Firehawk or SS optioned with SLP upgraded exhaust, in which case the I-pipe is 3" and obviously a different muffler (SLP dual/dual) was used and, of course, the 1998 SS/WS6 cars with the single outlet muffler.
Thank you sir. I wonder if a set of “high flow” cats would make it noticeably louder? On other cars I went from no cats to “high flows” (short cats basically) and the exhaust was noticeably quieter, and on another car I removed two of the four cats and replaced the other two with high flows and it was noticeably louder. The bulk of the louder was probably due to having two less cats than before though. I guess I’ll have to crawl under and see how big the stock ones are. The high flows are 11.” My luck I’d prob end up with the same amount of sound and a check engine light.
Thank you sir. I wonder if a set of “high flow” cats would make it noticeably louder? On other cars I went from no cats to “high flows” (short cats basically) and the exhaust was noticeably quieter, and on another car I removed two of the four cats and replaced the other two with high flows and it was noticeably louder. The bulk of the louder was probably due to having two less cats than before though. I guess I’ll have to crawl under and see how big the stock ones are. The high flows are 11.” My luck I’d prob end up with the same amount of sound and a check engine light.
The factory cats are pretty small to begin with, here is a picture of the 2000-'02 style (which I think covers your model year...if not just let me know and I can post a pic of the 1998-'99 style, which has a larger passenger side cat):
Certain "high flow" cats, especially the really small metallic substrate ones, might make it a bit louder but probably not enough to justify the cost or hassle, plus the possible SES light issues you mentioned. With that in mind, you could also just delete the O2 codes with a basic custom tune (mail order would be fine for this), or even a simple set of O2 simulators, and then just delete the cats entirely. If you remove them completely (such as going with an ORY or installing a bypass pipe) you will not only get more volume but also a very loud rasping sound in the low to mid 2k rpm range with that muffler. It's sort of like a Kazoo on crack...lol, this is an unfortunate result of the Y-pipe configuration (catless true duals wouldn't have this problem).
On the other hand, if you simply gut the cats and then reinstall the hollow shells, you'll get a noticeable volume increase without the horrible rasp (I know this from personal experience with the Flowmaster version of this chambered muffler, I did this on my '00 WS6 like ~20 years ago). Actually, this was one of my favorite setups in terms of sound; had great volume with that hollow/tinny muscle car sound and NO rasp (unlike when I went to a proper bypass pipe...that's when the rasp began). But the hollow cat shells aren't the ideal setup in terms of flow (not that it's any worse than ungutted cats though). I imagine you'd be very happy with the volume, tone/overall characteristics of this setup - and it's cheap (assuming you can still get the cats unbolted from the manifolds without breaking a stud - that was easy when these cars were new, but at this point it's more of a challenge); they can then be gutted with a crow bar, etc. Another option would be to go with a complete ORY (or cat bypass pipes) and then install small bullet mufflers in the Y-pipe (probably best to go with a whole new Y-pipe here, as it will be more difficult to fit any sort of resonator/muffler in the flattened portion of the driver's side Y-pipe) to help reduce the rasp while still getting better volume. Said bullet muffler/resonator could also be fitted into the I-pipe for additional rasp reduction, if needed.
Obviously, all of these cat delete options will only work if you live in an area without an actual sniffer test. If it's OBD scan only that's no problem with tuning or O2 sims, but there's no way to fool an actual exhaust sniffer.
The factory cats are pretty small to begin with, here is a picture of the 2000-'02 style (which I think covers your model year...if not just let me know and I can post a pic of the 1998-'99 style, which has a larger passenger side cat):
Certain "high flow" cats, especially the really small metallic substrate ones, might make it a bit louder but probably not enough to justify the cost or hassle, plus the possible SES light issues you mentioned. With that in mind, you could also just delete the O2 codes with a basic custom tune (mail order would be fine for this), or even a simple set of O2 simulators, and then just delete the cats entirely. If you remove them completely (such as going with an ORY or installing a bypass pipe) you will not only get more volume but also a very loud rasping sound in the low to mid 2k rpm range with that muffler. It's sort of like a Kazoo on crack...lol, this is an unfortunate result of the Y-pipe configuration (catless true duals wouldn't have this problem).
On the other hand, if you simply gut the cats and then reinstall the hollow shells, you'll get a noticeable volume increase without the horrible rasp (I know this from personal experience with the Flowmaster version of this chambered muffler, I did this on my '00 WS6 like ~20 years ago). Actually, this was one of my favorite setups in terms of sound; had great volume with that hollow/tinny muscle car sound and NO rasp (unlike when I went to a proper bypass pipe...that's when the rasp began). But the hollow cat shells aren't the ideal setup in terms of flow (not that it's any worse than ungutted cats though). I imagine you'd be very happy with the volume, tone/overall characteristics of this setup - and it's cheap (assuming you can still get the cats unbolted from the manifolds without breaking a stud - that was easy when these cars were new, but at this point it's more of a challenge); they can then be gutted with a crow bar, etc. Another option would be to go with a complete ORY (or cat bypass pipes) and then install small bullet mufflers in the Y-pipe (probably best to go with a whole new Y-pipe here, as it will be more difficult to fit any sort of resonator/muffler in the flattened portion of the driver's side Y-pipe) to help reduce the rasp while still getting better volume. Said bullet muffler/resonator could also be fitted into the I-pipe for additional rasp reduction, if needed.
Obviously, all of these cat delete options will only work if you live in an area without an actual sniffer test. If it's OBD scan only that's no problem with tuning or O2 sims, but there's no way to fool an actual exhaust sniffer.
How was the exhaust smell without cats? I had a car with an ORX and it was like riding around in a gas pump until I added high flow cats. I’m kind of on the fence about turning the rear O2 incase since the P0420 type codes are pretty generic and can be caused by numerous things. For example, not long after getting this Camaro I cleaned the IAC and I reused the old o ring and it gave code that code. It wasn’t really running rough either so I wouldn’t have known I had a problem if the light didn’t come on.
How was the exhaust smell without cats? I had a car with an ORX and it was like riding around in a gas pump until I added high flow cats.
Much of this is a matter of personal perception. I'm used to dinosaur cars like my '71 and '74 that never had cats in the first place; to me, that smell is a normal part of operating a vehicle with an internal combustion engine. With that said, the smell is a lot stronger when you have a cam with increased overlap (which is pretty much any aftermarket cam). On my '00 WS6, I first deleted the cats and drove it that way for probably a year, then I installed an aftermarket cam and the smell was noticeably stronger due to increased overlap/more raw fuel entering the exhaust. When the engine was stock, the catless smell was much less noticeable.
Another example... my '71 Nova (355ci SBC) has an aftermaket Crane cam, so more overlap than stock, and the exhaust smell is much stronger than my '74 Cutlass (350ci SBO) with a completely stock cam. Neither car has cats, but the smell from the '74 is much weaker as the cam and engine are stock.
Modern SEFI engines (such as your LS1) generally run pretty lean at idle and part throttle, so as long as the engine is in a good state of tune and the cam is stock, the smell from a catless exhaust shouldn't be overpowering by any means. But, make no mistake, if you are someone who is highly sensitive to anything other than an odorless exhaust then you will certainly notice the cat delete even in this application, however it's not really something you should notice from inside the car as long as you have tail pipes exiting at the rear bumper.
Originally Posted by Y2K_Frenzy
I’m kind of on the fence about turning the rear O2 incase since the P0420 type codes are pretty generic and can be caused by numerous things. For example, not long after getting this Camaro I cleaned the IAC and I reused the old o ring and it gave code that code. It wasn’t really running rough either so I wouldn’t have known I had a problem if the light didn’t come on.
P0420/P0430 are only tripped by the PCM recognizing an undesirable reading between the front and rear O2 sensors for a given period/condition as preset in the factory tune. The 2000-'02 cats are known to be failure prone (GM issued a TSB concerning this and actually extended the factory warranty on these cats to something like 10 years/120k miles - a notice regarding such was mailed to original owners many years ago, but the extension is obviously now expired for all examples), so P0420/P0430 is pretty common to be seen. The fact you saw this code after servicing the IAC was most likely coincidental, especially if there were no idle irregularities present (which would indicate that any vacuum leak from this O-ring would have been very small and well within the range of which the IAC could compensate). FWIW, I have removed/serviced LS1 IAC motors before without replacing the O-ring and never had an issue, they typically don't fall apart or become damaged upon removal unless it's a very high mileage engine or perhaps has been removed many times. What is more likely is that your original cats are somewhat marginal at this point, and you may likely see one or both of these codes again in the future even if all else is running properly (again, specifically because these cats are failure prone - the issue lies with coatings that wear off the substrate thus diminishing the effectiveness of the cat).
The only purpose of the P0420/P0430 is to monitor the oxygen storage capacity (i.e. "filtration" efficiency) of the respective cat; these two codes serve no other purpose nor do they help indicate or diagnose problems other than that which would be directly related to the cat or, on rarer occasion, the respective rear O2 sensor - neither of which would matter if the cats were deleted.
Much of this is a matter of personal perception. I'm used to dinosaur cars like my '71 and '74 that never had cats in the first place; to me, that smell is a normal part of operating a vehicle with an internal combustion engine. With that said, the smell is a lot stronger when you have a cam with increased overlap (which is pretty much any aftermarket cam). On my '00 WS6, I first deleted the cats and drove it that way for probably a year, then I installed an aftermarket cam and the smell was noticeably stronger due to increased overlap/more raw fuel entering the exhaust. When the engine was stock, the catless smell was much less noticeable.
Another example... my '71 Nova (355ci SBC) has an aftermaket Crane cam, so more overlap than stock, and the exhaust smell is much stronger than my '74 Cutlass (350ci SBO) with a completely stock cam. Neither car has cats, but the smell from the '74 is much weaker as the cam and engine are stock.
Modern SEFI engines (such as your LS1) generally run pretty lean at idle and part throttle, so as long as the engine is in a good state of tune and the cam is stock, the smell from a catless exhaust shouldn't be overpowering by any means. But, make no mistake, if you are someone who is highly sensitive to anything other than an odorless exhaust then you will certainly notice the cat delete even in this application, however it's not really something you should notice from inside the car as long as you have tail pipes exiting at the rear bumper.
P0420/P0430 are only tripped by the PCM recognizing an undesirable reading between the front and rear O2 sensors for a given period/condition as preset in the factory tune. The 2000-'02 cats are known to be failure prone (GM issued a TSB concerning this and actually extended the factory warranty on these cats to something like 10 years/120k miles - a notice regarding such was mailed to original owners many years ago, but the extension is obviously now expired for all examples), so P0420/P0430 is pretty common to be seen. The fact you saw this code after servicing the IAC was most likely coincidental, especially if there were no idle irregularities present (which would indicate that any vacuum leak from this O-ring would have been very small and well within the range of which the IAC could compensate). FWIW, I have removed/serviced LS1 IAC motors before without replacing the O-ring and never had an issue, they typically don't fall apart or become damaged upon removal unless it's a very high mileage engine or perhaps has been removed many times. What is more likely is that your original cats are somewhat marginal at this point, and you may likely see one or both of these codes again in the future even if all else is running properly (again, specifically because these cats are failure prone - the issue lies with coatings that wear off the substrate thus diminishing the effectiveness of the cat).
The only purpose of the P0420/P0430 is to monitor the oxygen storage capacity (i.e. "filtration" efficiency) of the respective cat; these two codes serve no other purpose nor do they help indicate or diagnose problems other than that which would be directly related to the cat or, on rarer occasion, the respective rear O2 sensor - neither of which would matter if the cats were deleted.
The IAC & P0420 might have been a coincidence I guess. Prior to replacing the o-ring I cleared the code a couple of times but it came back on right away. It was also idling like it had a tiny vac leak. I replaced the o-ring the code & cleared the code & the light hasn’t came back on since, and this was back in March.
The IAC & P0420 might have been a coincidence I guess. Prior to replacing the o-ring I cleared the code a couple of times but it came back on right away. It was also idling like it had a tiny vac leak. I replaced the o-ring the code & cleared the code & the light hasn’t came back on since, and this was back in March.
I guess I misunderstood the bolded part based on what you said here:
Originally Posted by Y2K_Frenzy
It wasn’t really running rough either so I wouldn’t have known I had a problem if the light didn’t come on.
^ This led me to believe that the code appeared with no other symptoms.
If the vac leak was not within the capability of the IAC to control, then significant unmetered air would have been entering the system thus causing lean O2 values to necessitate additional fuel. But if the leak was big enough that the IAC was no longer in control of idle speed, then you should have seen something like a P0507 (idle hang), or if it was really big then it wouldn't want to idle at all. Regardless, this shouldn't trigger a P0420 by itself. At the very least, if the IAC issue somehow caused such an odd fueling situation as to be the only factor in tripping this code, then it would have also tripped P0430 (other bank) as both cats should have been affected equally by macro fueling changes related to unmetered air that would have been seen by both banks of front O2 sensors (since air drawn from the IAC will reach both banks of the engine equally).
More likely, the bank 1 cat (P0420) is marginal and something about the fuel trim changes of the unrelated IAC condition just caused it to trigger a code during that period. If there was no other underlying issue with the bank 1 cat then P0430 (bank 2) should have also been tripped.
I guess I misunderstood the bolded part based on what you said here:
^ This led me to believe that the code appeared with no other symptoms.
If the vac leak was not within the capability of the IAC to control, then significant unmetered air would have been entering the system thus causing lean O2 values to necessitate additional fuel. But if the leak was big enough that the IAC was no longer in control of idle speed, then you should have seen something like a P0507 (idle hang), or if it was really big then it wouldn't want to idle at all. Regardless, this shouldn't trigger a P0420 by itself. At the very least, if the IAC issue somehow caused such an odd fueling situation as to be the only factor in tripping this code, then it would have also tripped P0430 (other bank) as both cats should have been affected equally by macro fueling changes related to unmetered air that would have been seen by both banks of front O2 sensors (since air drawn from the IAC will reach both banks of the engine equally).
More likely, the bank 1 cat (P0420) is marginal and something about the fuel trim changes of the unrelated IAC condition just caused it to trigger a code during that period. If there was no other underlying issue with the bank 1 cat then P0430 (bank 2) should have also been tripped.
The idle issue w the old baggy o-ring was subtle. So subtle that I thought maybe that it was in my head until the check engine light on. If it was someones first time to drive the car they probably wouldn’t have noticed anything out of the ordinary. So on that one kinda thank goodness for the CEL. I found a letter in the glovebox notifying the PO about the cat failure saying to bring it in to get new cats if the cel comes on. I guess she never had it done. If the cats go bad I’ll prob either replace them with cheap high flows & a mail order tune if it comes out the same or cheaper than stock cats. I don’t think I’m going to go cat-less though due to the scent.
12-27-2022, 10:13 PM
Sound Clip $50 80 series knock off 
With that said, the smell is a lot stronger when you have a cam with increased overlap (which is pretty much any aftermarket cam). On my '00 WS6, I first deleted the cats and drove it that way for probably a year, then I installed an aftermarket cam and the smell was noticeably stronger due to increased overlap/more raw fuel entering the exhaust. When the engine was stock, the catless smell was much less noticeable.