Catalytic Converter without A.I.R. System
03-26-2012, 09:44 PM
#1
Instructor
Thread Starter
Catalytic Converter without A.I.R. System
Is there a problem with having a catalytic converter on your car without the A.I.R. System working? What problem will this cause?
03-27-2012, 12:05 AM
#3
Le Mans Master
The A.I.R. system pumps fresh air into the exhaust manifold and directly into the cat until the engine warms up. This gets the cat going to burn off the excess fuel that was not burned during combustion.
Removing the system may delay the start of the cat operation.
Removing the system may delay the start of the cat operation.
03-27-2012, 01:14 AM
#4
Race Director
The A.I.R. system pumps air into the catalytic converter to help keep it hot and burn off as much "junk" as possible. I don't think it would make much difference. It might affect emissions, which could be important depending on what your state does for emissions checking.
The ECM controls where the air goes from the A.I.R. pump. From what I've seen of the ECM code, it directs the air to the converter about 90% of the time.
The only other problem that might arise is that the ECM adds a fudge factor to the O2 sensor reading to compensate for the extra air in the exhaust manifolds when it sends the air there. I think it only does that when you're decelerating and the fudge factor is pretty small, so it's probably not a problem.
The ECM controls where the air goes from the A.I.R. pump. From what I've seen of the ECM code, it directs the air to the converter about 90% of the time.
The only other problem that might arise is that the ECM adds a fudge factor to the O2 sensor reading to compensate for the extra air in the exhaust manifolds when it sends the air there. I think it only does that when you're decelerating and the fudge factor is pretty small, so it's probably not a problem.
03-27-2012, 05:24 AM
#5
Instructor
Thread Starter
Thanks. I had read in an earlier post from several months ago that if you don't have the A.I.R. System working with the catalytic converter, it will cause the catalyst inside the converter to melt down and fail. I've been running with a catalytic converter on my car for about six months without the A.I.R. System and I haven't had any problems, however I only drive the car on the weekends and usually less than 50 miles.
03-28-2012, 02:25 AM
#7
Race Director
The cats on our cars are two stage. The front half does "stuff" and the rear half does "other stuff". The air goes into the rear half. That's why the little tube is in the middle (just hooked mine up last week, so that's why I know. PITA Oetiker clamp...).
There are probably web sites that can tell you what "stuff" means, but I don't feel a need to know that "stuff", so I can't tell you.
There are probably web sites that can tell you what "stuff" means, but I don't feel a need to know that "stuff", so I can't tell you.
03-28-2012, 09:55 AM
#8
Its about the substrate design and the fact that the whole cat does not need to be running at 2000 degrees, which desgtroys them quicker. The front half is a scrubber and the back half is the burner that does need the air supply. 90s chevy trucks were different than these cars....
You CAn run a cat without the air system but one of 2 things will happen...
it will cook and melt internally OR or it simply clog and plug up because it never got hot enough without fresh air to lite off and burn the crud out as it should.
I don;t understand why people still believe they need to remove the air system on street cars...it does nothing to reduce hp and it actually does clean up exhaust and help manage emissions without any sacrifice in performance,. An additional 6 lbs of hardware for clean exhaust? Even Forrest can figure that one out,...
You CAn run a cat without the air system but one of 2 things will happen...
it will cook and melt internally OR or it simply clog and plug up because it never got hot enough without fresh air to lite off and burn the crud out as it should.
I don;t understand why people still believe they need to remove the air system on street cars...it does nothing to reduce hp and it actually does clean up exhaust and help manage emissions without any sacrifice in performance,. An additional 6 lbs of hardware for clean exhaust? Even Forrest can figure that one out,...
03-28-2012, 12:06 PM
#9
Race Director
Its about the substrate design and the fact that the whole cat does not need to be running at 2000 degrees, which desgtroys them quicker. The front half is a scrubber and the back half is the burner that does need the air supply. 90s chevy trucks were different than these cars....
You CAn run a cat without the air system but one of 2 things will happen...
it will cook and melt internally OR or it simply clog and plug up because it never got hot enough without fresh air to lite off and burn the crud out as it should.
I don;t understand why people still believe they need to remove the air system on street cars...it does nothing to reduce hp and it actually does clean up exhaust and help manage emissions without any sacrifice in performance,. An additional 6 lbs of hardware for clean exhaust? Even Forrest can figure that one out,...
You CAn run a cat without the air system but one of 2 things will happen...
it will cook and melt internally OR or it simply clog and plug up because it never got hot enough without fresh air to lite off and burn the crud out as it should.
I don;t understand why people still believe they need to remove the air system on street cars...it does nothing to reduce hp and it actually does clean up exhaust and help manage emissions without any sacrifice in performance,. An additional 6 lbs of hardware for clean exhaust? Even Forrest can figure that one out,...
That said, I had motivation to remove the AIR because my pump was failing, it's bracket broke, and I've converted to a less-than-daily driver as much for show as go....
When converters fail or when people want a performance upgrade, many will seek out aftermarket "performance" converters. Compared to our original L98 units, they might be different in configuration. That's because some Corvettes (IIRC 86-91) came with pre-cat fronts and main cat center. I believe this config was designed to remove NOx with the pre-converters and carbon with the main converter.
When swapping to performance converters, you'll find most (if not all) are now 3-way units where NOx and carbon can/will be removed with a single piece. Plus, they may be less dense (fewer cells/inch) to allow more exhaust flow.
This typcially comes at a cost if more "chemical dip" is needed to meet an adequate level of chemical conversion. IOW, good performance converters cost more than cheap-ineffective ones. OTOH, stock converters may cost the most.
With the exception of California (and possibly a few municipalities), I think you would find there is some allowance for degrading systems. IOW, they (often) don't expect 20-yr-old cars to have as good emissions as it's new equivalent did. That means a new performance converter will often out-performance the piece of crap that's still sitting on your car. Plus, there can be a performance benefit -- by removing a more restrictive part of your exhaust.
In reality, the decision comes down to what you feel is right an/or what you think is best. If you believe a conversion to a performance converter (with or w/o) the existing AIR system will provide as good or better "cleaning" than the worn-out stock one, I think it's something that people should feel acceptable to do. OTOH, if you just like to punch-out or drop cats to be cool or get 12 more HP from an aging ICON, I think it's a stupid idea.
If you can't afford a new cat, buy a different car. If you think your cool or creating some hp/tq monster, that's a delusion. With the way pollution is headed, no one need feel so compelled to gain power that they should ignore any semblance of responsibility to the environment.
Obviously, this goes beyond the scope of the original question -- unless people are reading and trying to figure out the best solution to their aging cars. As you can tell, in some cases, I believe you would end up with a more efficient and cleaner vehicle if you consider a complete conversion to a more modern converter setup.
Of course, that ain't going to be cheap. But neither is owning an older Corvette.
05-24-2015, 10:23 PM
#10
Cruising
Member Since: May 2010
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CATS, Pre-Cats & Older Corvettes
I hear where you're coming from -- as I normally advise people to leave converters on their car. Too many want to drop converters and run mufflers (only) under the pretext of improving performance. But, you can run converters w/o mufflers and achieve the same result with cleaner emissions. (Plus converters muffle!)
That said, I had motivation to remove the AIR because my pump was failing, it's bracket broke, and I've converted to a less-than-daily driver as much for show as go....
When converters fail or when people want a performance upgrade, many will seek out aftermarket "performance" converters. Compared to our original L98 units, they might be different in configuration. That's because some Corvettes (IIRC 86-91) came with pre-cat fronts and main cat center. I believe this config was designed to remove NOx with the pre-converters and carbon with the main converter.
When swapping to performance converters, you'll find most (if not all) are now 3-way units where NOx and carbon can/will be removed with a single piece. Plus, they may be less dense (fewer cells/inch) to allow more exhaust flow.
This typcially comes at a cost if more "chemical dip" is needed to meet an adequate level of chemical conversion. IOW, good performance converters cost more than cheap-ineffective ones. OTOH, stock converters may cost the most.
With the exception of California (and possibly a few municipalities), I think you would find there is some allowance for degrading systems. IOW, they (often) don't expect 20-yr-old cars to have as good emissions as it's new equivalent did. That means a new performance converter will often out-performance the piece of crap that's still sitting on your car. Plus, there can be a performance benefit -- by removing a more restrictive part of your exhaust.
In reality, the decision comes down to what you feel is right an/or what you think is best. If you believe a conversion to a performance converter (with or w/o) the existing AIR system will provide as good or better "cleaning" than the worn-out stock one, I think it's something that people should feel acceptable to do. OTOH, if you just like to punch-out or drop cats to be cool or get 12 more HP from an aging ICON, I think it's a stupid idea.
If you can't afford a new cat, buy a different car. If you think your cool or creating some hp/tq monster, that's a delusion. With the way pollution is headed, no one need feel so compelled to gain power that they should ignore any semblance of responsibility to the environment.
Obviously, this goes beyond the scope of the original question -- unless people are reading and trying to figure out the best solution to their aging cars. As you can tell, in some cases, I believe you would end up with a more efficient and cleaner vehicle if you consider a complete conversion to a more modern converter setup.
Of course, that ain't going to be cheap. But neither is owning an older Corvette.
That said, I had motivation to remove the AIR because my pump was failing, it's bracket broke, and I've converted to a less-than-daily driver as much for show as go....
When converters fail or when people want a performance upgrade, many will seek out aftermarket "performance" converters. Compared to our original L98 units, they might be different in configuration. That's because some Corvettes (IIRC 86-91) came with pre-cat fronts and main cat center. I believe this config was designed to remove NOx with the pre-converters and carbon with the main converter.
When swapping to performance converters, you'll find most (if not all) are now 3-way units where NOx and carbon can/will be removed with a single piece. Plus, they may be less dense (fewer cells/inch) to allow more exhaust flow.
This typcially comes at a cost if more "chemical dip" is needed to meet an adequate level of chemical conversion. IOW, good performance converters cost more than cheap-ineffective ones. OTOH, stock converters may cost the most.
With the exception of California (and possibly a few municipalities), I think you would find there is some allowance for degrading systems. IOW, they (often) don't expect 20-yr-old cars to have as good emissions as it's new equivalent did. That means a new performance converter will often out-performance the piece of crap that's still sitting on your car. Plus, there can be a performance benefit -- by removing a more restrictive part of your exhaust.
In reality, the decision comes down to what you feel is right an/or what you think is best. If you believe a conversion to a performance converter (with or w/o) the existing AIR system will provide as good or better "cleaning" than the worn-out stock one, I think it's something that people should feel acceptable to do. OTOH, if you just like to punch-out or drop cats to be cool or get 12 more HP from an aging ICON, I think it's a stupid idea.
If you can't afford a new cat, buy a different car. If you think your cool or creating some hp/tq monster, that's a delusion. With the way pollution is headed, no one need feel so compelled to gain power that they should ignore any semblance of responsibility to the environment.
Obviously, this goes beyond the scope of the original question -- unless people are reading and trying to figure out the best solution to their aging cars. As you can tell, in some cases, I believe you would end up with a more efficient and cleaner vehicle if you consider a complete conversion to a more modern converter setup.
Of course, that ain't going to be cheap. But neither is owning an older Corvette.
