Which to get? 2 or 3 way for a converter?
07-05-2002, 01:11 PM
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Which to get? 2 or 3 way for a converter?
I have noticed that a lot of people have changed their later model C4Ős *(the ones with Pre-Cats) to the Y Pipe without pre-cats...
My question is did you go with a main 2 way cat or 3 way?
Iam going to a high-flow one...and am wondering what is the difference as far as performance of the 2-way one vs. the 3-way one. Obviously the 3-way is designed to be used if you are indeed removing the pre-cats....
so....which should I be getting.....Iam looking to get the most performance and sound out of this new system...
Jeff
My question is did you go with a main 2 way cat or 3 way?
Iam going to a high-flow one...and am wondering what is the difference as far as performance of the 2-way one vs. the 3-way one. Obviously the 3-way is designed to be used if you are indeed removing the pre-cats....
so....which should I be getting.....Iam looking to get the most performance and sound out of this new system...
Jeff
07-05-2002, 03:15 PM
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Re: Which to get? 2 or 3 way for a converter? (XtremeVette)
If you want performance go with no cat.
If you have to pass emissions you want a 3 way cat (two sections). First section does NOx, second section does HC/CO (why the AIR tube in the middle of the cat).
If you have to pass emissions you want a 3 way cat (two sections). First section does NOx, second section does HC/CO (why the AIR tube in the middle of the cat).
07-05-2002, 08:00 PM
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Re: Which to get? 2 or 3 way for a converter? (XtremeVette)
Need to add to my post:
The 3-way cat is not specifically for the elimination of the pup-cats. It is simply what is required for some systems to scrub the exhaust.
Some engines / control systems will pruduce much less NOx then others. Tons of mis-information about this. For example an LT4 has valve timing that introduces exhaust gasses back into the combustion chamber, it does not need an egr valve and uses a two way cat.
The L98 system requires an egr valve and further help for NOx reduction in the cat converter. The pup cats do not reduce NOx (as I first thought), they are only useful in EPA tests as they heat up faster and reduce HC/CO sooner (maybe only HC). Once the main cat "lights up" it will work fine, just takes longer.
"Two way" cat is HC/CO. "Three way" cat is NOx, HC and CO. You need a three way cat on an L98 with stock valve timing, stock programming, and stock compression.
Why is there an AIR tube on a three way cat? Good question. Because NOx is better reduced w/o any oxygen. The stock system running correctly will allow very little O2 into the exhaust gas, so NOx is first stage in a three way cat. Now HC and CO are better controlled with the presence of O2 to help in the reaction and raise heat, so air is introduced in to the second half of a three way cat to aid in the control of HC and CO.
That's the rest of the story, as I know you didn't believe me.
The 3-way cat is not specifically for the elimination of the pup-cats. It is simply what is required for some systems to scrub the exhaust.
Some engines / control systems will pruduce much less NOx then others. Tons of mis-information about this. For example an LT4 has valve timing that introduces exhaust gasses back into the combustion chamber, it does not need an egr valve and uses a two way cat.
The L98 system requires an egr valve and further help for NOx reduction in the cat converter. The pup cats do not reduce NOx (as I first thought), they are only useful in EPA tests as they heat up faster and reduce HC/CO sooner (maybe only HC). Once the main cat "lights up" it will work fine, just takes longer.
"Two way" cat is HC/CO. "Three way" cat is NOx, HC and CO. You need a three way cat on an L98 with stock valve timing, stock programming, and stock compression.
Why is there an AIR tube on a three way cat? Good question. Because NOx is better reduced w/o any oxygen. The stock system running correctly will allow very little O2 into the exhaust gas, so NOx is first stage in a three way cat. Now HC and CO are better controlled with the presence of O2 to help in the reaction and raise heat, so air is introduced in to the second half of a three way cat to aid in the control of HC and CO.
That's the rest of the story, as I know you didn't believe me.