i finally gutted out the rear cats near the muffler! sounds great. i don't have a aftermarket exhaust yet but it shows good pick up and a nice little tone. i think its going to sound great with the mopar exhaust!

 

...you can also gut the mini cats (fronts) and keep the ECU from setting a fault code by soldering in a MIL eliminator. I did this on my previous ride, and it worked out beautifully. You may know this, but the front O2 sensor before the cats actually measures and adjusts A/F. The downstream O2 sensor is just for OBD purposes (i.e. making sure the catalytic converters are converting unburned hydrocarbons and CO to CO2). Therefore, if you modify the output of the rear O2 and make it "lie" to the ECU, then there is no negative impact on engine performance and no check engine light. If interested, let me know. I can point you in the right direction if you want more information. Oh, and BTW - it did make a nice difference in my Mazda!

 

C'mon Kids! You know that isn't legal.

 

yeah we had to do that with my friends test pipes on his 350z, i think we used capers 02 sims, i think i'm going to keep the 02's in for now until i get the borla and see what the sound is like, i don't want a too raspy sound.

 

It is legal just not for highway use like many performance parts. He is only running his crossfire on private land...so there is no problem. lol.

Keep us informed of your progress.

 

...um, my car (without the emissions controls) was driven daily. Half of the mods that are done for "off public road use" find their way on to the street. With a gutted cat and MIL eliminator, any cop who pulls you over is not going to know what you've done. The casing is still there, and it looks like a catalytic converter. I would only worry about it if I lived in a state that requires annual emissions checks (like California). It would take an actual sniffer to know that the cats are hollowed out. Or, someone who understands automotive electronics well enough to know that the O2 harness has been spliced into.

Disabling emissions controls can be argued on a moral basis as well, but I expect few people on this forum to take the other side of the argument. After all, a car that gets 17 city / 25 highway is inherently environmentally unfriendly. Even if all the emissions are just CO2, that's a greenhouse gas as well!

Hollow out your cats. Go fast. And, know that you are polluting less than the hippie in the VW bus with the Earth Day bumper sticker on the rear of it.

 

I am not a fan of gutted cats. Nor should anyone who breathes be. High flow cats will provide all the flow of a test pipe while keeping the exhaust clean.

 

Not true about the high flow cats but it will be close. Besides with most N/A engines you want some back pressure or you will lose low end TQ.

 

Gutted cats are cheap to do (costs only about $15 for each MIL eliminator, substantially less if you take a trip to Radioshack and make your own). Thus, gutted cats will run $30. High flow cats will set you back a couple of hundred bucks.

Personally, I am going to be very pragmatic with any mods that I do to my car. My previous ride had a ton of aftermarket stuff on it, and as a result, it was stiff riding, loud, buzzy, and a lot more difficult to live with. Though not as much as speed, refinement is addictive in its own right. And, refinement is one of the things that the Crossfire does exceptionally well (for a sports car).

 

our cars with the gutted cats probably pollute less than, large suv with cats mustangs, camaros, ect... and its not like every car on the road has gutted cats! them damn cows pollute more than our cars damn greenhouse effect!

 

Are you going to put them back when it comes time for emissions inspection? I guess you must live in a state that doesn't require them.
As far as pollution is concerned, it's more about smog and poor local air quality from exhaust impurities.

 

I have owned 3 SUV's and all of them are very close across the board and better in some area's than the SRT6 from the factory.

 

yeah our state now doesn't require you to run through inspection with new cars! you have 5 years then they send you a new tag for your license that's about it. older cars have to run though.

 

Gut the cats and let the smog grow uncontrolled, automatic population control and more HP, where's the downside!!!

 

where do I get the MIL sims at??

 

Regarding back pressure, you probably get enough from the bends in the manifold and exhaust system.

If you require extra back pressure with gutted/removed cats you can do the following:-
Install a 'thumb screw' (one of those with a football shaped head) on the inside of the exhaust.
This can then be turned to cross the stream, or be with the stream of exhaust gases.
By doing this you can fine tune the amount of back pressure.

If this doesn't create enough back pressure, then weld a regular flat washer onto a screw/bolt
and install it into the exhaust system as above.

If you don't understand these ramblings, let me know and I'll make a quick sketch and try and upload it.

I've done this on a motorcycle exhaust system, and it does work.

 

I hope you sleeved the cats, otherwise your screwing up airflow, thus creating an expansion area. Usually this causes slower revs, hesitation and bogging. Your better off with the cats on.

 

actually dynamics i have no idea were you have received your info from, but i myself have removed the rear two cats, and installed straight pipes and installed a flowmaster. and the car does gain i would estimate approx 5 rwhp. i was very impressed. i've never heard anyone claim to lose hp from taking off cats, especially when their were 4 to begin with.

 

Actually you didn't read my post correctly, straight pipes will not cause airflow problems, I said if you gut the cat without sleaving them you will be creating an expansion area, which can cause bogging...

 

Isn't that messy gutting out the rear of a cat??? That's just not right?