The truth about the smell with no cats?
11-05-2008, 03:26 PM
#42
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High flow is a good way to go, i believe the 03+ already have them.
I put a magnaflow high flow in my Camaro and loved the sound it produced. I picked up a little power but not much.
Gmctrk you are a puss and need to get over it, I actually really like driving behind old small blocks, brings back good memory's.
If the smell is too much i will take them off your hands... for free
I put a magnaflow high flow in my Camaro and loved the sound it produced. I picked up a little power but not much.
Gmctrk you are a puss and need to get over it, I actually really like driving behind old small blocks, brings back good memory's.
If the smell is too much i will take them off your hands... for free
11-05-2008, 04:24 PM
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11-05-2008, 07:35 PM
#44
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i noticed that when i had no cats before i got a tune the smell was much stronger. it seemed to be running richer. now that i have a tune the smell doesnt seem as rich as before.
11-06-2008, 12:42 PM
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just a side note, if you disable your rear O2's and you have cats you could burn up the element inside the cat faster. Our PCM's have COT which modifies fueling based on the rear O2 readings to lengthen the life of the cats 
11-06-2008, 04:56 PM
#50
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When you disable the rear O2 sensors you are eliminating the FAOSC fuel strategy.
The rear O2 sensors are used for small 1-2% fueling corrections.
The rear fuel trim corrections are learned in KAM (Keep Alive Memory).
Internally this system is known as Fore Aft Oxygen Sensor Control (FAOSC). Note that FAOSC learns and reacts very slowly because the catalyst, with its large/slow oxygen storage and release characteristic, is part of the control loop.
Rear O2s if you will are a fine tune of the commanded fuel flow but are very much part of the model used in the PCM's math to correct AFR for closed loop.
In the trucks after 1996 the cats flow quite well.
If I were looking for a long lasting high flowing cat, I would look to the 2500HD dual 3" cats. these cats are designed by GM for a warranteeable period of 7-8 years. Most aftermarket cats are not. Stock cats have more precious catalyst metals than aftermarket cats do, which is 1 of the factors of them being 2-3 times the cost of aftermarket cats.
I like the smell of racefuel, I can still smell it through cats. Race fuel wont harm the cats so long as its unleaded. I hate the dirty uncatted smell. But I also hated the older rotten egg sulphur smell that eminated from the early cat designs.
peace
Hog
The rear O2 sensors are used for small 1-2% fueling corrections.
The rear fuel trim corrections are learned in KAM (Keep Alive Memory).
Internally this system is known as Fore Aft Oxygen Sensor Control (FAOSC). Note that FAOSC learns and reacts very slowly because the catalyst, with its large/slow oxygen storage and release characteristic, is part of the control loop.
Rear O2s if you will are a fine tune of the commanded fuel flow but are very much part of the model used in the PCM's math to correct AFR for closed loop.
In the trucks after 1996 the cats flow quite well.
If I were looking for a long lasting high flowing cat, I would look to the 2500HD dual 3" cats. these cats are designed by GM for a warranteeable period of 7-8 years. Most aftermarket cats are not. Stock cats have more precious catalyst metals than aftermarket cats do, which is 1 of the factors of them being 2-3 times the cost of aftermarket cats.
I like the smell of racefuel, I can still smell it through cats. Race fuel wont harm the cats so long as its unleaded. I hate the dirty uncatted smell. But I also hated the older rotten egg sulphur smell that eminated from the early cat designs.
peace
Hog