Exhaust help:Shorties w/HF cats or LT w/HF Cats

[WspoonSS]

Good evening everyone! I’m the owner of a new to me 2010 Camaro 2SS LS3 and I am looking at exhaust mods. I bought the car used from a dealer and it already has what looks to be an SLP X pipe crossover kit on it. I would like to get some LT headers and HF cats to cut down on noise, but I live in CA so I’ll need to remove them come smog time. My only other option is Shorties W/HF cats. My question is, will both of these options mount up at roughly the same spot and connect to the SLP crossover pipe. I have stock manifolds and cats right now, so I’d need a totally reversible setup that bolts right back up to what I am currently using. Having shorties and just swapping back in the stock cats is much easier than swapping the whole header especially since it won’t cause any problems when popping the hood for any cops. Any help will be greatly appreciated.

This is the x-pipe/catback system I believe I have:

https://www.phastekperformance.com/2...pipe-30223.htm

[CamaroCracka]

If I used a shorty header, I would not bother with a hi-flow cat. Stock cats are not that restrictive to notice a power difference if you are only using shorty headers. I'm not even sure how much they help on a LTs. I think they are more for appearance and passing inspections in states less strict than CA that still require an inspection. Living in Florida, none of this is a problem. I sold my cats to the recycler for $80.

Shorties would be maintenance free as long as they are CARB approved and you could plan on a few hours a year swapping the LTs and cats (or catless tubes), plus $20 in gaskets and you might booger up an O2 sensor here or there. However, the power gain is significantly better with long tubes.

As to the idea of cutting down on noise, LTs are louder, not quieter.

[VR Baron]

Originally Posted by CamaroCracka

If I used a shorty header, I would not bother with a hi-flow cat. Stock cats are not that restrictive to notice a power difference if you are only using shorty headers. I'm not even sure how much they help on a LTs. I think they are more for appearance and passing inspections in states less strict than CA that still require an inspection. Living in Florida, none of this is a problem. I sold my cats to the recycler for $80.

Shorties would be maintenance free as long as they are CARB approved and you could plan on a few hours a year swapping the LTs and cats (or catless tubes), plus $20 in gaskets and you might booger up an O2 sensor here or there. However, the power gain is significantly better with long tubes.

As to the idea of cutting down on noise, LTs are louder, not quieter.

Agreed. I have shortys. Get jba or other brand that are smog compliant and come
With a carb sticker. Hiflow cats aren’t going to pass Kali smog checks and will have to be swapped out to stock. As to fitting to the slp part I don’t know. Shortys and hiflows will fit to aftermarket catback or stock exhuast. The combo will definitely be more quiet then LTs. As to power, I noticed a slight drop when I put back the stock cats. JDP tested my hiflows to se what they got on there own.
They made 10 lb ft of tq from 2200 rpm through 4800. Peak hp was 15 at 5600, but dropped from there, making about 6 hp at 6200. At stock 5900 rpm peak they made 11-12. So they do make power. The shortys at peak make 8-9.
With LTs without a tune make around 28-30, so difference is only about 10 hp and tq . Note if you go hiflow you can and probably will get a cel light. I read that getting a o2straight extenders, and a angled o2 simulator coneected together will keep that from happening.

[pyroguy]

Originally Posted by CamaroCracka

If I used a shorty header, I would not bother with a hi-flow cat. Stock cats are not that restrictive to notice a power difference if you are only using shorty headers.

I think you reversed the recommendation. The factory high flow cats are the biggest restrictive piece in the entire factory exhaust system.

OP, welcome to the forums and congrats on your new to you ride. Unfortunately for modifying your new ride you are in the most restrictive state in the union. Unless you're buying long tube headers second hand you won't get a manufacturer to send them to you, from what I understand. Many have tried, but they are illegal in CA. If you can get away with high flow cats in CA I'd do them first or at all over shorty headers. If you can't get away with them then shorty headers are said to have some gains, but it's very marginal. They get maybe as much gain as a cold air intake, if that.

As for cutting down noise, put the factory cats back in with stock manifolds or shorty headers and that should get you legal or close to legal. Long tube headers with or without high flow cats and high flow cats by themselves will make the car louder than factory. Shorty headers might add some volume, but not a crazy amount when paired with factory cats.

As others have said, make sure you get CARB compliant shortys if you get them and whatever you do, if it's not 100% CA compliant, plan on a day/afternoon to swap them over and another day/afternoon to swap them back.

[WspoonSS]

When I said to cut down noise, I meant compared to the off road pipe option. I should have worded that better. My plan is to either get LT w/HF Cats and swap out both come smog time, or get shorties wHF Cats and swap out the cats during smog time. Most cops will overlook the cats, but not the LTs. I just want to be to be able to swap back to my factory/SLP exhaust come smog time. The SLP x pipe system looks to be a catback/x pipe combo that mounts at the same spot as the factory catback, but this is my first Camaro

[VR Baron]

Originally Posted by WspoonSS

When I said to cut down noise, I meant compared to the off road pipe option. I should have worded that better. My plan is to either get LT w/HF Cats and swap out both come smog time, or get shorties wHF Cats and swap out the cats during smog time. Most cops will overlook the cats, but not the LTs. I just want to be to be able to swap back to my factory/SLP exhaust come smog time. The SLP x pipe system looks to be a catback/x pipe combo that mounts at the same spot as the factory catback, but this is my first Camaro

I was pulled over in PV once. Looked at the shortys, tried to look down at the hiflows, and saw them and the carb sticker I pointed out for the shortys.Didn’t say anything. Did mention the cai that wasn’t legal. I was lucky or was no big deal. To him anyway. Now a off-road pipe no way

[pyroguy]

High flow cats will cut out some rasp in the exhaust compared to catless pipes, but it will still be loud or louder than stock.

[JRBumfuddle]

I have JBA shorties with a CARB sticker. Definitely felt more torque compared to stock manifolds. Then added JBA HF cats, and noticed another bump in torque, and louder exhaust. I had RDP tunes for both stages. Have to smog this summer, so will change cats back to stock, which is easy.

[WspoonSS]

Originally Posted by JRBumfuddle

I have JBA shorties with a CARB sticker. Definitely felt more torque compared to stock manifolds. Then added JBA HF cats, and noticed another bump in torque, and louder exhaust. I had RDP tunes for both stages. Have to smog this summer, so will change cats back to stock, which is easy.

Perfect. I think I’ll go the same route to save me a few headaches. Thank you!

[Avenging Orange]

I'd make it the least amount of trouble. Proper shorties and cats. But if the majority says hi flow will not pass....how about "gutted" stock cats? Still would not be much louder than stock. Get a proper dyno tune and have fun.

[JRBumfuddle]

you're welcome sir

[WspoonSS]

Originally Posted by Avenging Orange

I'd make it the least amount of trouble. Proper shorties and cats. But if the majority says hi flow will not pass....how about "gutted" stock cats? Still would not be much louder than stock. Get a proper dyno tune and have fun.

The cats are so easy to replace on this that it won’t take much time at all to swap come smog time. Full headers would take a considerable amount of time in comparison. I can keep the shorties on for the smog

[BLU DUCE]

Now this is just me. I wouldn't put all this money,time,work just to have to worry and change every year and worry about the cops giving me a ticket.
I know this is not everyone but I would just but a ZL1 and not have to worry about the friggin CA. law.

[Livernois Motorsports]

Shorty headers are not really worth anything for power just a sound increase definitely go with longtubes for sure if you are looking for both and the HF cats dont really change much either but if you plan on making alot of power down the line they can overheat and cause issues depending on the end power goal of the car