Anyone ever used an OEM cat after a LT header? - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

cc-rider · 01-03-2016, 01:13 PM

I've read a million posts and threads on cats lately because I plan to now add some headers to my supercharged LS3. After all the reading, it's impossible to reach any conclusion other than the aftermarket cats are low quality garbage when it comes to holding up to forced induction.

So here's my question...

Has anyone ever cut out the large front cats from the OEM set up and welded them into an off-road connection pipe that comes with any given LT header?

The theory would be:
- The OEM cat is much higher quality and there seems to be some consensus that they hold up to more abuse than any other aftermarket cat (that's not to say they are indestructible...just much more robust than aftermarket)
- The large front cat from the OEM set up looks to be as large or larger than any of the aftermarket options
- The cell count is higher which intuitively would mean less flow, but I can ZERO flow bench cfm data to support that the OEM cat is indeed less flow than an aftermarket cat
- Perhaps just the front OEM cat flows decently well (rather than the daisy chained 2 cat set up)?
- This would cost less. You have the stock cats there and available. Why not use them.

Entertain me with this theory? Any thoughts? Anyone tried this?

1KillerSS · 01-03-2016, 02:07 PM

Why reinvent the wheel? Why not just go high flow or cat less? C5 is littered with threads of FI people who have had to replace or remove cats. Doesn't seem worth the trouble to me. Could it work? yea, why not? But is is worth it? Doubt it.

Unreal · 01-03-2016, 02:11 PM

Factory cats are not any higher quality than aftermarket ones. They will fail just as fast.

cc-rider · 01-03-2016, 03:57 PM

Quote:

Originally Posted by 1KillerSS

Why reinvent the wheel? Why not just go high flow or cat less? C5 is littered with threads of FI people who have had to replace or remove cats. Doesn't seem worth the trouble to me. Could it work? yea, why not? But is is worth it? Doubt it.

Because the high flow cats available have all proven to be garbage for forced induction. The only exception might be the new Dynatech Supercats. Not too many out there yet. But good reports thus far it seems. And they are $550...and only work with Dynatech headers.

Going catless is not for me. Every car I've been in that's catless stinks like hell and I hate it.

But all you have to do is do a bit of searching and reading here to see that aftermarket high flow cats are relatively poor quality.

cc-rider · 01-03-2016, 04:01 PM

Quote:

Originally Posted by Unreal

Factory cats are not any higher quality than aftermarket ones. They will fail just as fast.

Not from what I've read. There are literally hundreds of failed aftermarket cats posted on this site. And multiple people attesting for the stock cats durability (Jannetty one of them)....albeit there is less flow. Perhaps I missed it...but there aren't many posts of stock cats failing.

But another great mystery is just how much more flow does an aftermarket cat than a stock cat (especially just the front OEM larger cat)???? There is ZERO flow bench cfm data to show flow comparisons. Now I do believe they flow more. But how much is the question?

Unreal · 01-03-2016, 04:08 PM

I've seen numerous stock cats fail. They are ok at low power levels, but anything 550+ will take them out quickly. If you just have a 500rwhp setup then they should last awhile.

cc-rider · 01-03-2016, 04:29 PM

I may just try this and test the theory out. Take the stock cats and some aftermarket cats (if I can get my hands on some) to a shop with a flow bench and get some actual data. Flow the entire OEM pipe, and then flow both the front and rear cats independently.

It might be fun to do....and may provide some actual data to the unsubstantiated claims of "high flow" cats.

01-03-2016, 01:13 PM	#1
cc-rider Drives: 2010 Camaro SS Join Date: Dec 2006 Location: MN Posts: 1,172	Anyone ever used an OEM cat after a LT header? I've read a million posts and threads on cats lately because I plan to now add some headers to my supercharged LS3. After all the reading, it's impossible to reach any conclusion other than the aftermarket cats are low quality garbage when it comes to holding up to forced induction. So here's my question... Has anyone ever cut out the large front cats from the OEM set up and welded them into an off-road connection pipe that comes with any given LT header? The theory would be: - The OEM cat is much higher quality and there seems to be some consensus that they hold up to more abuse than any other aftermarket cat (that's not to say they are indestructible...just much more robust than aftermarket) - The large front cat from the OEM set up looks to be as large or larger than any of the aftermarket options - The cell count is higher which intuitively would mean less flow, but I can ZERO flow bench cfm data to support that the OEM cat is indeed less flow than an aftermarket cat - Perhaps just the front OEM cat flows decently well (rather than the daisy chained 2 cat set up)? - This would cost less. You have the stock cats there and available. Why not use them. Entertain me with this theory? Any thoughts? Anyone tried this?

01-03-2016, 02:07 PM	#2
1KillerSS Too much is never enough! Drives: AGP TT SS [COTW] 4/20/15 Join Date: Feb 2014 Location: Toledo,OH Posts: 4,149 View My Garage	Why reinvent the wheel? Why not just go high flow or cat less? C5 is littered with threads of FI people who have had to replace or remove cats. Doesn't seem worth the trouble to me. Could it work? yea, why not? But is is worth it? Doubt it. __________________ AGP TT kit, 54/57 Forged rotating assembly, Custom grind cam... Dual nozzle meth, ID850's, Livernois dual fuel pumps, ECS BAP, 25% UDP, 3 inch Magnaflow catback with X pipe, Mantic 9000 clutch, DSS 1000hp axles, DSS aluminum driveshaft, ZL1 rear end, solid subframe bushings, HE differential offset bushings, BMR Trailing arm, BMR toe rods, Lingenfelter LNC-2000,SJM Line Lock. 747 whp 714wtq *Build thread* http://www.camaro5.com/forums/showth...55#post8107855

01-03-2016, 02:11 PM	#3
Unreal Drives: 2006 Z06 Join Date: Oct 2010 Location: Gilbert, AZ Posts: 5,712	Factory cats are not any higher quality than aftermarket ones. They will fail just as fast. __________________ Nick Corvette Z06 -1200ish rwhp

01-03-2016, 04:08 PM	#6
Unreal Drives: 2006 Z06 Join Date: Oct 2010 Location: Gilbert, AZ Posts: 5,712	I've seen numerous stock cats fail. They are ok at low power levels, but anything 550+ will take them out quickly. If you just have a 500rwhp setup then they should last awhile. __________________ Nick Corvette Z06 -1200ish rwhp

01-03-2016, 04:29 PM	#7
cc-rider Drives: 2010 Camaro SS Join Date: Dec 2006 Location: MN Posts: 1,172	I may just try this and test the theory out. Take the stock cats and some aftermarket cats (if I can get my hands on some) to a shop with a flow bench and get some actual data. Flow the entire OEM pipe, and then flow both the front and rear cats independently. It might be fun to do....and may provide some actual data to the unsubstantiated claims of "high flow" cats.