[Aragorn]

Does anyone know the pros and cons of this procedure? Performance, cel, sound and legal issues...
Thank you.

[Clos.95]

Originally Posted by Aragorn

Does anyone know the pros and cons of this procedure? Performance, cel, sound and legal issues...
Thank you.

I had it done 1 month after I got mine, been two years now no issues
No real performance gain nor positive or negative
No CEL if done by a competent shop
Sound is a nice 10-15% sound increase, if you run 91 or 93 it adds more pops
Unless you live in California no legal issues what’s so ever and remember they’re just “resonators”

[Aragorn]

Originally Posted by Clos.95

I had it done 1 month after I got mine, been two years now no issues
No real performance gain nor positive or negative
No CEL if done by a competent shop
Sound is a nice 10-15% sound increase, if you run 91 or 93 it adds more pops
Unless you live in California no legal issues what’s so ever and remember they’re just “resonators”

Interesting, what do you replace them with? Any drone inside the cab? Thank you

[Clos.95]

Originally Posted by Aragorn

Interesting, what do you replace them with? Any drone inside the cab? Thank you

Just standard exhaust piping that most shops carry
They cut it out and weld a pipe make sure to match the pipe to the factory 2.75’ exhaust.
Drone depends what muffler you’re running if you on Stock muffler either NPP or non NPP no drone

[TJay74]

Removing the secondary cats are worth around 5hp, as long as the state you live in doesnt use the C.A.R.B. system you will be fine.

[oldman]

Originally Posted by TJay74

Removing the secondary cats are worth around 5hp, as long as the state you live in doesnt use the C.A.R.B. system you will be fine.

don't think so, the primary cats maybe, but the secondary probably so little as to be untestable at 455 to 550 HP levels.

[TJay74]

Originally Posted by oldman

don't think so, the primary cats maybe, but the secondary probably so little as to be untestable at 455 to 550 HP levels.

For years in the early stages of going from 49 state vehicles to 50 state vehicles when GM was having to deal with the C.A.R.B. stuff, GM noted that the secondary cats only came with a 5hp penalty at the engine. In the early years of this process GM notated it, once the 50 state assembly line became the norm they no longer mentioned the loss of power from having to run the secondary cats.

On my SS 1LE I noticed the power pick up when I deleted them, it was enough that in my testing area the RPM and speed at which the rear tires would break loose was lower. That along with the increase in sound was worth it to me.

[BlackbeastSS2]

You get rid of any resistance via full cat delete, just secondary cat delete, muffler delete, straight pipes or just a better flowing muffler you will definitely see an increase in power. How much is the question? Lowering back pressure and increase air flow via air intake system is the key with any engine.

[Mike Aruba]

How much have you guys been paying for the secondary cat deletes? A buddy of mine was charged $140 at a local shop for both primary and secondary deletes.

[68Vette]

Originally Posted by Mike Aruba

How much have you guys been paying for the secondary cat deletes? A buddy of mine was charged $140 at a local shop for both primary and secondary deletes.

The shop I went to did it for $100.00 and they used 3.00 inch pipe, so $140.00 sounds reasonable.

[Aragorn]

My bumper to bumper is expired but I still have one year left on Powertrain. Any risk to that? Thank You

[oldman]

Originally Posted by TJay74

For years in the early stages of going from 49 state vehicles to 50 state vehicles when GM was having to deal with the C.A.R.B. stuff, GM noted that the secondary cats only came with a 5hp penalty at the engine. In the early years of this process GM notated it, once the 50 state assembly line became the norm they no longer mentioned the loss of power from having to run the secondary cats.

On my SS 1LE I noticed the power pick up when I deleted them, it was enough that in my testing area the RPM and speed at which the rear tires would break loose was lower. That along with the increase in sound was worth it to me.

The stock front Cat is like 1.7 ID and it is a flat smash with an 02 sensor stuck in there and a bend, the second cat is 2.20 ID nice straight shot. It has been show on a dyno and on GTECH that the front cat delete is worth about 6 HP. So how is deleting a Cat that flows maybe 60% better and it a straight shot and is cooler to much cooler going to give 5 HP?

Here is my cat AFTER I cut it open and widen it. Have not ground away the 02 bung and I space the 02 pretty far out of the stream.

[oldman]

from 4 years ago, and no I have not seen any data for the secondary cat deletes. if you can post GTECH or dyno.

Originally Posted by EFI Tuning

I have the CA deletes on my vehicle. I installed them more for easy wideband access more than anything. There is a little bit of power to be gained at the top end but nothing earth shattering. From 6000-6500 RPM there was a 5-7 RWHP gain (stock tune). The car does get louder without the primaries. The secondary cats may be holding things back a bit. If I wasn't going to install headers soon I would test it out.

The knock sensors absolutely needed attention on my vehicle. A resonance gets created in certain RPM spots on certain cylinders that excite the knock sensors significantly. It is completely addressable.

If you are interested I can supply a completed tune for E85/CA delete and the E85 kit itself.

Please let me know if you have any questions!
Tim

Originally Posted by TSloper

Red - stock cats/stock tuning
Blue - pipe delete/stock tuning
Orange - pipe delete/my tuning

The delete pipes show that the factory cats aren't a huge restriction on a stock engine. There is some to be gained past 6K with the reduced backpressure but nothing earth shattering. For $300 is beats a ported TB.

Tuning is really needed to maximize the bolt on path. These are all with the stock intake manifold and no other mods.

Attachment 790246

[oldman]

How good is the stock exhaust?

It is the same exhaust on the ZL1 (slight difference in the driver's side cat, it is not as dented).

Lingenfelter 720 HP uses the stock exhaust all 4 cats
Ligenfelter 1000 HP has LT cats and stock after 2nd cat deleted back
Hennessy 1000 HP see above
Hennessy 1200 HP has LT cats and midpipe, stock muffler

This is my opinion and it is SOTP but I do have a GTECH.
FBO, there is little be gained past front cat delete on the exhaust.

FBO with LT (with or without aftermarket cats made for the LT) will add 12 or so HP above front cat deletes. There is little to be gained from the rest of exhaust.

Supercharged, upto 750 engine HP, I like Lingenfelter feel money should be spent elsewhere, but the first mod would be front cat deletes (mainly I feel they have a potential to melt down).

LT (with or without aftermarket cats) will add 15 to 30 HP, 3" exhaust probably 5 to 10 HP.

Nutshell even wild, CA front deletes + 1.5 to 2 lbs of boost (small pulley change) = LT, high flow cats and 3" back (about $2000 to $3000 depending on what you want).

And yes above 750 engine I would only go 2" LT, metal cats and 3" after.