[KingLT1]

Long story short, I was going to do secondary cat delete, but after checking with several shops and custom exhaust builders, nobody will do the job around here. I know sounds dumb...I agree. Lots of folks have had this done, not sure what the deal is. I could probably keep making calls until I found a place but I am over it.

Anyway, After reading up a bit, it appears the primary cats are the biggest restriction and the secondary do not really do much. So I decided to buy the Bullet performance bolt-in delete pipes and I will use the rear o2 adapters from Big Daddies garage that pull the rear o2's away from the exhaust stream which keeps the PCM from throwing a cell. So I should not need to hook up my HP tuners and void the warranty by turning the codes off.

Anybody else done this?

[Techn9cian805]

Originally Posted by KingLT1

Long story short, I was going to do secondary cat delete, but after checking with several shops and custom exhaust builders, nobody will do the job around here. I know sounds dumb...I agree. Lots of folks have had this done, not sure what the deal is. I could probably keep making calls until I found a place but I am over it.

Anyway, After reading up a bit, it appears the primary cats are the biggest restriction and the secondary do not really do much. So I decided to buy the CA performance bolt-in delete pipes and I will use the rear o2 adapters from Big Daddies garage that pull the rear o2's away from the exhaust stream which keeps the PCM from throwing a cell. So I should not need to hook up my HP tuners and void the warranty by turning the codes off.

Anybody else done this?

A tune is still strongly recommended to make sure the car is running right with the right A/F ratio.

[marknagy13]

I'm curious to know this as well

[KingLT1]

Originally Posted by Techn9cian805

A tune is still strongly recommended to make sure the car is running right with the right A/F ratio.

I will verify how its running by data logging with hp tuners. I have never heard of needing a tune for cat deletes in the 20yrs I have been modding cars. The "tune" is just to address the CEL from removing the cats which can also be addressed by using the adapters that I mentioned. My brother is running cat deletes with no tune on his 2016 Scat Pack and it runs great.

[TEEZYSS]

I did see where someone installed cat deletes and the ecm started picking up false knock that had to be corrected by the tune.

[Ian SS]

You'll never get anyone to agree to cut out 2nd cats over the phone...it is a federal offense....shops get audited for that stuff. Go talk to them in person.

[ninetres]

And remember.....They are "resonators"....not secondary cats

[KingLT1]

Originally Posted by Ian SS

You'll never get anyone to agree to cut out 2nd cats over the phone...it is a federal offense....shops get audited for that stuff. Go talk to them in person.

I took the car to a guy that builds custom exhaust. We drove it on the lift Saturday and he looked at it and said "I am going to decline this job". Had nothing to do with removing cats. He just said that he would not be able to tig weld the pipes and get it to seal correctly without completely removing it. So I called the next place and they were booked till November. I have another option that is about 45 minutes away, but I decided to say screw it and remove the primary and keep the secondary for now. it's a bolt-in deal and no hacking up the factory NPP.

Originally Posted by TEEZYSS

I did see where someone installed cat deletes and the ecm started picking up false knock that had to be corrected by the tune.

How would removing primary cats cause false knock?

[Teem0s42]

I deleted my rear cats and have had no issues... you do not need a tune.

[KingLT1]

Ok I found some good info. When you remove the front (primary) cats, the delete pipes are thinner and let more engine noise pass thru. Since the knock sensors are located on the sides of the block, they can pick up the increased exhaust noise. This is the primary reason for needing a tune for headers and cat delete pipes. The tuning is to reduce knock sensor sensitivity and remove the CEL codes that are triggered.

I am going to buy some header wrap and wrap them before installing. If I run into issues, I will pull them off until I am ready to delete the warranty and tune it.

[TEEZYSS]

Originally Posted by KingLT1

How would removing primary cats cause false knock?

I'm trying to remember what the thread said and trying to find it on here. Op had installed the CA primary cat deletes which caused I believe a drone in the exhaust or something along those lines. He didn't see any gains and when he checked the HPTUNERS he saw that after he installed the deletes it was detected more knock and pulling more timing.

[KingLT1]

This thread has some good info.

http://www.camaro6.com/forums/showth...=448702&page=2

[TEEZYSS]

Originally Posted by KingLT1

This thread has some good info.

http://www.camaro6.com/forums/showth...=448702&page=2

I have owned a set of CA deletes for about 5 months now. Did all the research before buying them because some say they saw no gains. In my research on here I came across the thread talking about the false knock. This is a good thread but you may look for more. If I have time today I'll see if I can find it as well

[KingLT1]

I read about the false knock and I commented on it in my previous post. However it seems to be hit or miss. The factory cat pipes are thicker and do not amplify engine noises like headers and cat delete pipes do. That is why I mentioned wrapping them.

On a side note, I'm going with Bullets instead of CA. I found the Bullets on Vengeance racing ebay page for a better price. Plus they have the hanger brackets.

http://www.bulletperf.com/chevrolet/...at-delete.html