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Best High-Flowing Cats

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Old 07-25-2005, 05:08 PM
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Default Best High-Flowing Cats

Anyone know what the best aftermarker high flowing cat convert. is? Also is it even really worth it to be changing the stock cats. If so which one would you guys recommend and $$$ is not an issue.
Old 07-25-2005, 07:43 PM
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I would have to say an empty one but if you wanted a full one i would say dynateches are pretty good and about 140 a peice i think.
Old 07-25-2005, 09:16 PM
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just dont go with carsound. mine blew out on me 2 weeks after install
Old 07-26-2005, 01:13 AM
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does anyone know if you can pass smog with a cleaned out cat. convert. in cali?
Old 07-26-2005, 01:48 AM
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I think Random tech makes the best cats. I only saw about a 5 horse drop with mine. You won't pass Cali smog with hollowed out cats. The purpose of the cat is to create a chemicle reaction to reduce Hydrocarbons I think. Basicly get the car to burn cleaner. With out them you will run richer out of the tail pipe.
Old 07-26-2005, 09:53 AM
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Random metalics or dynomax powercat,also metalic constuction, nothing else close.
Old 07-26-2005, 05:37 PM
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For the price, Magnaflow makes some good high-flow cats. You can get them on eBay for around $55.
Old 07-26-2005, 07:15 PM
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magnaflow aka carsound cats aren't that great....they are what come on QTP y-pipes, they are huge 9.5 long and 7.5 wide and they only flow 440 cfm..... i would spend the money like i did to fix my QTP y and get the randomtech cats.....9.5 long and 4 round = a lot smaller and they flow 598 cfm......just my .02
Old 07-26-2005, 07:54 PM
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yup random tech cats are the best
Old 07-26-2005, 08:14 PM
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someone bench flow tested a bunch of a cats a while back, and FLP cats flowed the most CFM.
Old 07-26-2005, 11:43 PM
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thinking i'm gona go wit da random tech. ones, wtf is FLP cats?
Old 07-27-2005, 06:58 AM
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wtf is FLP cats?
FLP, "finish line performance". make an awsome header-oryp-hf cat, package....

i think there called dyna tech now? not sure.... MTI sells them.

but yeah, there cats flow the most CFM on the market! ill try to find that page....
i think car sounds were last....
Old 07-27-2005, 07:06 AM
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Catalytic Converters
Ready, set, flow!



Cats, not the furry four legged meow gremlins that that make you sneeze and place foot prints all over your freshly Zaino’d car. I am talking about the tree hugger’s solution to pollution and the horsepower-robbing enemy underneath your car. Every new car is shipped with catalytic converters in order to clean the exhaust emissions from your car to keep the air clean.



Unfortunately for us drag racer’s, the time is coming (and already arrived for some cities) for emission’s test for everyone in the United States. That means we have to find the highest flowing catalytic converters we can so we can pass emissions test and minimize horsepower loss.



Why use a flow bench


How do you go about finding out which catalytic converter will sacrifice the least amount of horsepower? You can track/dyno test each cat or flow them on a flow bench. Seeing how the later choice is the cheapest, and easiest, we ended up at White Performance in Kingsport, TN. Flowing pieces on a flow bench will allow you chose pieces that minimize flow restrictions and maximize horsepower.



First you have to find a flow bench to use. White Performance had a Super Flow 600 flow bench and was the site where our test took place. They manufactured an adapter to connect the catalytic converters to the flow bench prior to our visit.



All units were flowed at a 20.4” of H2O pressure drop and converted to 28” of H2O. Both results are given in Table 1. Why such an odd number? David Vizard’s exhaust flow research is the precise reason we flow exhaust pieces at 20.4”. Pieces can be flowed at 28” or 1” and converted to 20.4” in just a few seconds with simple math. In this case we wanted the actual reading at 20.4” of H2O for accuracy since the research references a specific pressure drop.



David Vizard’s flow research shows the required air flow a muffler needs to attain, in order to keep horsepower loss due to back pressure to a minimum, is 2.2 cfm for every one horsepower. This general rule set by David Vizard keeps horsepower losses under one percent.1



The 2.2cfm per one horsepower represents a free flow condition and may be more or less depending on your car. We use that standard as a basic guideline with our test results. If the muffler has to follow this rule, then so should the rest of your exhaust system, including your catalytic converters.



Flow test and results


Five catalytic converters were chosen for the flow test. The passenger and driver’s side converters off of a 99 LS1 F-Body, TTS Bullet, FLP, and Carsound converters. The factory catalytic converters were modified from stock. Each was opened up to have a 2.5 inch entrance and exit to match those of the competitors. Of these, the passenger side converter has been regarded as the lowest flowing one for reasons expressed later in this article. Enough rambling, let’s get to the flow test.



Table 1


Inlet Diameter (in.)
Outlet Diameter (in.)
CFM @ 20.4” H2O
CFM @ 28” H2O









Passenger Side Catalytic Converter
2.5
2.5
299.5
350.9

Driver's Side Catalytic Converter
2.5
2.5
268.3
314.4

TTS Bullet Catalytic Converter
2.5
2.5
277.1
324.6

Carsound Catalytic Converter
2.5
2.5
372.7
436.7

FLP Catalytic Converter
2.5
2.5
376.0
440.5




Results discussion


On a stock LS1 F-Body, the driver’s side catalytic converter has been praised as the higher flow converter of the two that are on the car. A few reasons for this assumption have been: The driver’s side converter can be found on past Corvettes. The fact that the F-Body has a converter off of a Corvette surrounds the converter with an aura of performance history. Also, the converter is smaller and sleeker appearing than the passenger side converter and that gets the mindset that it has to be better.



The theory that the driver’s side catalytic converter is the “high flow” converter of the two found on LS1 F-Body, ranks up there with high performance muffler bearings. The data above shows that the passenger side catalytic converter flows more than 35 cubic feet per minute (cfm) more than the driver’s side cat. That is a significant difference.



The real shocker of our flow test involves the TTS Bullet catalytic converters. The total combined flow of two TTS catalytic converters would be 554.2 cfm. Compare that to the modified factory catalytic converters of 567.8 cfm. Something is definitely wrong with this comparison. The TTS cats are not even close to delivering the flow of either FLP or Carsound. Installing a set of TTS Bullet cats on your car would be taking steps backwards compared to the stock units found on LS1 F-Body’s. How TTS can sell these catalytic converters with their excellent long tube headers is beyond anything imaginable. TTS does have a new oval catalytic converter that should outperform their current catalytic converter. The new oval unit is currently being tested for OBD II compliance.



The FLP and Carsound converters strutted their stuff on the flow bench. Both sets flowed over 190 cfm per pair more than TTS converters. These test results were what we expected to find with every set of aftermarket high flow catalytic converters. No one should hesitate to place these to converters on their car.



Mathematical Models


Each pair of catalytic converters restrict about eight (8) rear wheel horsepower on stock LS1’s. David Vizard’s research shows that 2.2 cfm of flow at 20.4” of H2O will support 1 horsepower. 2.2 cfm is the optimum flow through the exhaust system and reflects open pipe flow. Removing the stock catalytic converters on the LS1 usually results in a gain of 8 rear wheel horsepower. Assuming that the average LS1 puts 300 horse power to the ground, that is a 2.67% increase in power.




Stock catalytic converters:





Final thoughts


Adding a cat back to your exhaust system helps, but by no means makes it more free flowing than replacing the stock exhaust manifolds on back to your muffler tips with headers, larger diameter pipe and high flow mufflers. Replacing just your catalytic converters with high flow pieces may not necessarily help flow if you have a factory muffler on your car. The same could be said if you have a high flow muffler or run an exhaust cutout, but have factory cats installed. So be smart and plan your exhaust system out and realize that replacing just one piece of the exhaust system isn’t the end of the job.






--------------------------------------------------------------------------------





1. Vizard, David. How to Build Horsepower. Volume 3. Page
Old 07-27-2005, 07:07 AM
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ok, sar sounds wer 2nd.

this test is a few years old. so there may be better flowing cats on the market now, but if you can get there flow numbers you can compare them to these.

hope this helped!
Old 07-27-2005, 07:11 AM
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Final thoughts


Adding a cat back to your exhaust system helps, but by no means makes it more free flowing than replacing the stock exhaust manifolds on back to your muffler tips with headers, larger diameter pipe and high flow mufflers. Replacing just your catalytic converters with high flow pieces may not necessarily help flow if you have a factory muffler on your car. The same could be said if you have a high flow muffler or run an exhaust cutout, but have factory cats installed. So be smart and plan your exhaust system out and realize that replacing just one piece of the exhaust system isn’t the end of the job.
thats my favorite part! "hey i just put on a flowmaster, my exhaust is done!"
haha.
Old 07-27-2005, 07:28 AM
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Originally Posted by M6HuggerSS
Catalytic Converters
Ready, set, flow!



Cats, not the furry four legged meow gremlins that that make you sneeze and place foot prints all over your freshly Zaino’d car. I am talking about the tree hugger’s solution to pollution and the horsepower-robbing enemy underneath your car. Every new car is shipped with catalytic converters in order to clean the exhaust emissions from your car to keep the air clean.



Unfortunately for us drag racer’s, the time is coming (and already arrived for some cities) for emission’s test for everyone in the United States. That means we have to find the highest flowing catalytic converters we can so we can pass emissions test and minimize horsepower loss.



Why use a flow bench


How do you go about finding out which catalytic converter will sacrifice the least amount of horsepower? You can track/dyno test each cat or flow them on a flow bench. Seeing how the later choice is the cheapest, and easiest, we ended up at White Performance in Kingsport, TN. Flowing pieces on a flow bench will allow you chose pieces that minimize flow restrictions and maximize horsepower.



First you have to find a flow bench to use. White Performance had a Super Flow 600 flow bench and was the site where our test took place. They manufactured an adapter to connect the catalytic converters to the flow bench prior to our visit.



All units were flowed at a 20.4” of H2O pressure drop and converted to 28” of H2O. Both results are given in Table 1. Why such an odd number? David Vizard’s exhaust flow research is the precise reason we flow exhaust pieces at 20.4”. Pieces can be flowed at 28” or 1” and converted to 20.4” in just a few seconds with simple math. In this case we wanted the actual reading at 20.4” of H2O for accuracy since the research references a specific pressure drop.



David Vizard’s flow research shows the required air flow a muffler needs to attain, in order to keep horsepower loss due to back pressure to a minimum, is 2.2 cfm for every one horsepower. This general rule set by David Vizard keeps horsepower losses under one percent.1



The 2.2cfm per one horsepower represents a free flow condition and may be more or less depending on your car. We use that standard as a basic guideline with our test results. If the muffler has to follow this rule, then so should the rest of your exhaust system, including your catalytic converters.



Flow test and results


Five catalytic converters were chosen for the flow test. The passenger and driver’s side converters off of a 99 LS1 F-Body, TTS Bullet, FLP, and Carsound converters. The factory catalytic converters were modified from stock. Each was opened up to have a 2.5 inch entrance and exit to match those of the competitors. Of these, the passenger side converter has been regarded as the lowest flowing one for reasons expressed later in this article. Enough rambling, let’s get to the flow test.



Table 1


Inlet Diameter (in.)
Outlet Diameter (in.)
CFM @ 20.4” H2O
CFM @ 28” H2O









Passenger Side Catalytic Converter
2.5
2.5
299.5
350.9

Driver's Side Catalytic Converter
2.5
2.5
268.3
314.4

TTS Bullet Catalytic Converter
2.5
2.5
277.1
324.6

Carsound Catalytic Converter
2.5
2.5
372.7
436.7

FLP Catalytic Converter
2.5
2.5
376.0
440.5




Results discussion


On a stock LS1 F-Body, the driver’s side catalytic converter has been praised as the higher flow converter of the two that are on the car. A few reasons for this assumption have been: The driver’s side converter can be found on past Corvettes. The fact that the F-Body has a converter off of a Corvette surrounds the converter with an aura of performance history. Also, the converter is smaller and sleeker appearing than the passenger side converter and that gets the mindset that it has to be better.



The theory that the driver’s side catalytic converter is the “high flow” converter of the two found on LS1 F-Body, ranks up there with high performance muffler bearings. The data above shows that the passenger side catalytic converter flows more than 35 cubic feet per minute (cfm) more than the driver’s side cat. That is a significant difference.



The real shocker of our flow test involves the TTS Bullet catalytic converters. The total combined flow of two TTS catalytic converters would be 554.2 cfm. Compare that to the modified factory catalytic converters of 567.8 cfm. Something is definitely wrong with this comparison. The TTS cats are not even close to delivering the flow of either FLP or Carsound. Installing a set of TTS Bullet cats on your car would be taking steps backwards compared to the stock units found on LS1 F-Body’s. How TTS can sell these catalytic converters with their excellent long tube headers is beyond anything imaginable. TTS does have a new oval catalytic converter that should outperform their current catalytic converter. The new oval unit is currently being tested for OBD II compliance.



The FLP and Carsound converters strutted their stuff on the flow bench. Both sets flowed over 190 cfm per pair more than TTS converters. These test results were what we expected to find with every set of aftermarket high flow catalytic converters. No one should hesitate to place these to converters on their car.



Mathematical Models


Each pair of catalytic converters restrict about eight (8) rear wheel horsepower on stock LS1’s. David Vizard’s research shows that 2.2 cfm of flow at 20.4” of H2O will support 1 horsepower. 2.2 cfm is the optimum flow through the exhaust system and reflects open pipe flow. Removing the stock catalytic converters on the LS1 usually results in a gain of 8 rear wheel horsepower. Assuming that the average LS1 puts 300 horse power to the ground, that is a 2.67% increase in power.




Stock catalytic converters:





Final thoughts


Adding a cat back to your exhaust system helps, but by no means makes it more free flowing than replacing the stock exhaust manifolds on back to your muffler tips with headers, larger diameter pipe and high flow mufflers. Replacing just your catalytic converters with high flow pieces may not necessarily help flow if you have a factory muffler on your car. The same could be said if you have a high flow muffler or run an exhaust cutout, but have factory cats installed. So be smart and plan your exhaust system out and realize that replacing just one piece of the exhaust system isn’t the end of the job.






--------------------------------------------------------------------------------





1. Vizard, David. How to Build Horsepower. Volume 3. Page


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