Adding test pipe to stock exhaust system
Razorlab, which particular test pipe was used? I am also curious about one thing... if the stock exhaust is 2.5 in, would using a 3 in test pipe not cause turbulence in the exhaust flow? I would tend to think that by having a smaller diameter open up to a larger diameter and then shrink back down to a smaller diameter again that it would hurt exhaust gas velocity when compared to a constant diameter, such as by using a 2.5 in test pipe.
I know that people back in the day used to gut their cats thinking that it would boost performance, but it actually caused a power loss because the exhaust gas would get caught in the large chamber of the gutted cat and circulate, creating back pressure and causing a reduction in exhaust gas velocity as a result.
Granted, the difference in diameter is much greater in a gutted cat, but if I planned on keeping the stock exhaust for stealth/noise factor, would it be beneficial to use a 2.5 in test pipe to match the diameter of the stock exhaust, or would the difference be negligable? Thanks for any info or advice. Oh, and nice work man; it seems like this boost pill is the shiznit!
I know that people back in the day used to gut their cats thinking that it would boost performance, but it actually caused a power loss because the exhaust gas would get caught in the large chamber of the gutted cat and circulate, creating back pressure and causing a reduction in exhaust gas velocity as a result.
Granted, the difference in diameter is much greater in a gutted cat, but if I planned on keeping the stock exhaust for stealth/noise factor, would it be beneficial to use a 2.5 in test pipe to match the diameter of the stock exhaust, or would the difference be negligable? Thanks for any info or advice. Oh, and nice work man; it seems like this boost pill is the shiznit!
Thread Starter
Joined: Aug 2003
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From: Mid-Hudson, NY
Razorlab, which particular test pipe was used? I am also curious about one thing... if the stock exhaust is 2.5 in, would using a 3 in test pipe not cause turbulence in the exhaust flow? I would tend to think that by having a smaller diameter open up to a larger diameter and then shrink back down to a smaller diameter again that it would hurt exhaust gas velocity when compared to a constant diameter, such as by using a 2.5 in test pipe.
I know that people back in the day used to gut their cats thinking that it would boost performance, but it actually caused a power loss because the exhaust gas would get caught in the large chamber of the gutted cat and circulate, creating back pressure and causing a reduction in exhaust gas velocity as a result.
Granted, the difference in diameter is much greater in a gutted cat, but if I planned on keeping the stock exhaust for stealth/noise factor, would it be beneficial to use a 2.5 in test pipe to match the diameter of the stock exhaust, or would the difference be negligable? Thanks for any info or advice. Oh, and nice work man; it seems like this boost pill is the shiznit!
I know that people back in the day used to gut their cats thinking that it would boost performance, but it actually caused a power loss because the exhaust gas would get caught in the large chamber of the gutted cat and circulate, creating back pressure and causing a reduction in exhaust gas velocity as a result.
Granted, the difference in diameter is much greater in a gutted cat, but if I planned on keeping the stock exhaust for stealth/noise factor, would it be beneficial to use a 2.5 in test pipe to match the diameter of the stock exhaust, or would the difference be negligable? Thanks for any info or advice. Oh, and nice work man; it seems like this boost pill is the shiznit!
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From: Rhode Island
In RI and apparently other States as well, emmissions inspections for AWD vehicles use a tailpipe "sniffer" test at 1500 and 3000rpm; if you use a test pipe in these States , your car will fail emmissions.
Now the technical question is, is there a high flow Cat that is better than the OEM Cat? Works has committed, some time ago, that the OEM Cat is quite large. Are there any redesigned after market Cats' of similar size that increase flow further that (1) improve performance relative to OEM and yet (2) enable our X to pass emmisions (OEM internals but aftermarket mods e.g., intake, Cat back, FMIC, etc)?
Later, Ken
AMS Intake&Exhaust
Iveytune (322 all around; dynojet)
Robispec K&W
Now the technical question is, is there a high flow Cat that is better than the OEM Cat? Works has committed, some time ago, that the OEM Cat is quite large. Are there any redesigned after market Cats' of similar size that increase flow further that (1) improve performance relative to OEM and yet (2) enable our X to pass emmisions (OEM internals but aftermarket mods e.g., intake, Cat back, FMIC, etc)?
Later, Ken
AMS Intake&Exhaust
Iveytune (322 all around; dynojet)
Robispec K&W
In RI and apparently other States as well, emmissions inspections for AWD vehicles use a tailpipe "sniffer" test at 1500 and 3000rpm; if you use a test pipe in these States , your car will fail emmissions.
Now the technical question is, is there a high flow Cat that is better than the OEM Cat? Works has committed, some time ago, that the OEM Cat is quite large. Are there any redesigned after market Cats' of similar size that increase flow further that (1) improve performance relative to OEM and yet (2) enable our X to pass emmisions (OEM internals but aftermarket mods e.g., intake, Cat back, FMIC, etc)?
Later, Ken
AMS Intake&Exhaust
Iveytune (322 all around; dynojet)
Robispec K&W
Now the technical question is, is there a high flow Cat that is better than the OEM Cat? Works has committed, some time ago, that the OEM Cat is quite large. Are there any redesigned after market Cats' of similar size that increase flow further that (1) improve performance relative to OEM and yet (2) enable our X to pass emmisions (OEM internals but aftermarket mods e.g., intake, Cat back, FMIC, etc)?
Later, Ken
AMS Intake&Exhaust
Iveytune (322 all around; dynojet)
Robispec K&W
Bigger and it is a metallic.
Also the emission part.
If you do a HFC and other power mods + TUNE it. most likely you will pass , and even get a better numbers then a stock evo.
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From: USA
In RI and apparently other States as well, emmissions inspections for AWD vehicles use a tailpipe "sniffer" test at 1500 and 3000rpm; if you use a test pipe in these States , your car will fail emmissions.
Now the technical question is, is there a high flow Cat that is better than the OEM Cat? Works has committed, some time ago, that the OEM Cat is quite large. Are there any redesigned after market Cats' of similar size that increase flow further that (1) improve performance relative to OEM and yet (2) enable our X to pass emmisions (OEM internals but aftermarket mods e.g., intake, Cat back, FMIC, etc)?
Later, Ken
AMS Intake&Exhaust
Iveytune (322 all around; dynojet)
Robispec K&W
Now the technical question is, is there a high flow Cat that is better than the OEM Cat? Works has committed, some time ago, that the OEM Cat is quite large. Are there any redesigned after market Cats' of similar size that increase flow further that (1) improve performance relative to OEM and yet (2) enable our X to pass emmisions (OEM internals but aftermarket mods e.g., intake, Cat back, FMIC, etc)?
Later, Ken
AMS Intake&Exhaust
Iveytune (322 all around; dynojet)
Robispec K&W
Most states do their emmisions testing the same way, but there are always exceptions. It doesn't even just depend on the state, but the city. Some cities don't require emmissions testing at all, while others are very strict. Charleston, SC doesn't require emmisions at all. Neither does Rifle, CO. Places in Cali are on the other end of the spectrum; they are very strict.
Worth noting is the fact that any vehicles newer than 2005 are exempt from emmisons testing altogether, if not permanently then for several years so even if you did put on a test pipe in a strict state that has an emmissions testing center with an AWD dyno, you wouldn't have to bother for several years from now anyway, and once the day came, all you would have to do is put your cat back in for that day. It's an easy install/uninstall.
Last edited by STi2EvoX; Nov 29, 2008 at 06:15 PM.
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From: Rhode Island
True, but when they run the sniffer at 1500 and 3000 rpms, the engine has to be under load i.e. on a dyno. Most emmisions places use a 2WD dyno that an AWD car can't be run on for testing this (not the same type of dyno used for tuning; it's just rollers for the car to drive on basically). I went to get my emmissions test done on my old STi, which had a catless turbo back, and they couldn't run it on the dyno so all they did was check the OBD2 port for CELs (I had the CEL for the cat disabled permanently with access port since I was using a test pipe) and I of course passed with flying colors.
Most states do their emmisions testing the same way, but there are always exceptions. It doesn't even just depend on the state, but the city. Some cities don't require emmissions testing at all, while others are very strict. Charleston, SC doesn't require emmisions at all. Neither does Rifle, CO. Places in Cali are on the other end of the spectrum; they are very strict.
Worth noting is the fact that any vehicles newer than 2005 are exempt from emmisons testing altogether, if not permanently then for several years so even if you did put on a test pipe in a strict state that has an emmissions testing center with an AWD dyno, you wouldn't have to bother for several years from now anyway, and once the day came, all you would have to do is put your cat back in for that day. It's an easy install/uninstall.
Most states do their emmisions testing the same way, but there are always exceptions. It doesn't even just depend on the state, but the city. Some cities don't require emmissions testing at all, while others are very strict. Charleston, SC doesn't require emmisions at all. Neither does Rifle, CO. Places in Cali are on the other end of the spectrum; they are very strict.
Worth noting is the fact that any vehicles newer than 2005 are exempt from emmisons testing altogether, if not permanently then for several years so even if you did put on a test pipe in a strict state that has an emmissions testing center with an AWD dyno, you wouldn't have to bother for several years from now anyway, and once the day came, all you would have to do is put your cat back in for that day. It's an easy install/uninstall.
Later, Ken
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Anyway, to get back on topic: Brian, would you consider making a 2.5 in resonated test pipe for those of us that plan on working around the stock exhaust? The gains from just a reflash, especially when coupled with the test pipe and your boost pill upgrade, are good enough for many of us, especially considering that the car will still be quiet. At my age, I want the power but not the noise, so this would be the best option for me. Now, I don't know if GST does any fab work, but if you guys won't be making one then do you know where I could find one? Thanks.
Thread Starter
Joined: Aug 2003
Posts: 14,092
Likes: 1,090
From: Mid-Hudson, NY
Anyway, to get back on topic: Brian, would you consider making a 2.5 in resonated test pipe for those of us that plan on working around the stock exhaust? The gains from just a reflash, especially when coupled with the test pipe and your boost pill upgrade, are good enough for many of us, especially considering that the car will still be quiet. At my age, I want the power but not the noise, so this would be the best option for me. Now, I don't know if GST does any fab work, but if you guys won't be making one then do you know where I could find one? Thanks.
I can attest to this. I replaced my CAT with a 3” high flow cat from COBB. No discernable increase in noise but a noticeable increase in power (measured with a Butt Dyno).
Solenoid capacity
Hey Razor,
Are you at wide open on the boost solenoid valves at 7000 RPM and it still will only support 20.5 psi ? Can you put a pill in that will get it to hold 23 or 24 psi solid to 7500 RPM? I mean peak out at 24 psi and hold 24 psi till 7500 RPM or is that beyond the flow characteristics of the turbo and pneumatic solenoid control system.
Brian
Are you at wide open on the boost solenoid valves at 7000 RPM and it still will only support 20.5 psi ? Can you put a pill in that will get it to hold 23 or 24 psi solid to 7500 RPM? I mean peak out at 24 psi and hold 24 psi till 7500 RPM or is that beyond the flow characteristics of the turbo and pneumatic solenoid control system.
Brian
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I think that's beyond the flow characteristics of the turbo, but he'd know better than I would. Hell, the improvement from stock to a tune is great, and the improvement from tuned to tuned+pill is impressive as well. I'd be totally satisfied with these levels of boost, because you can still make power from timing as boost drops, especially in the 4b11.
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