The Godfather

Ok so I took out my resonator a while back and the sound well...sounds pretty much the same. It is a bit deeper but not that much. I got an xpipe made to replace the resonator.

I'm thinkinga bout removing the two little secondary cats. Questions are:

a) Will it affect performance, due to backpressure changes
b) Will I still pass smog
c) wtf are they there for in the first place anyway?

Thanks. xoxo.

Qmax03

Coming from a couple Boosted cars, if your looking for TOP-END power, the less restrictions on the exhaust side the better... but if your looking for LOW-END power.. this isnt the Mod for you.

My buddy Gained 13WHP by deleting all his Resonators and Cats on a Boosted M3.... Many Evo/Sti guys gains 10+hp from removing cats/resonators ....


You Might not pass smog... If you remove all of them.

Cats are put in from the dealership becasue cataylst converts the nitrogen oxide into harmless emmissions... basically it takes away harmful fumes to the enviorment..

Vic55

Get rid of the post cats but keep the resonators to retain some back pressure needed with the supercharged engine.

ECBAOBAO

If I remove the resonator and take out the muffler fillings that should not affect any power different, correct?

Thanks

Qmax03

The best option is to delete the cats. Leave the muffler and resonators alone.

Timeless

When you delete the cats, do you run straight pipes? And what size pipe (2.75" or 2.5") and what type (stainless or basic aluminum)? Does this also add some growl to the exhaust or does the resonator still quiet it down?

Qmax03

I can only tell you about what i done on my other cars, since it hasnt been done on the E55 yet...

i usually run 3" SS straight pipes only because the the size of the enitre exhaust from the cat on .

It does change the sound of the exhaust by a little.... im makes it sound a bit more "grunty" ... If your looking to make it sound louder or anythgin to that effect... cut out the resonators as well... i was more into making power then noise, so i just took out the cats.... and put took out the muffler and put a resonated type muffler with OEM Exhaust tips.

ECBAOBAO

Why?

I still need to pass smog tho

prodigymb

take em off

Qmax03

Im alot more perfomance oriented, If your looking for SOUND then go ahead and delete the resonators and gut the mufflers... but if your looking for some extra hp cut the cats off.

With no res and guted muffler youll pass smog and it wont hurt/effect the performance.. ( well the gutted muffler might since its taking away some restriction from the exhaust) ... well you know what im trying to say.

jangy

I had mine removed at VRP. I am going 3" tubes from the primary cats to the X-pipe and then from x-pipe to mufflers tomorrow. I dunno what the pressure difference will be.

Qmax03

Keep us updates please... id like to hear about the results.

Thanks, -Q

slavik

so best way to gain some hp from exhaust is to take off 2ndary cats? adding an x pipe would help?

Hammer Down

Can you replace the resonator with an X-Pipe or with that cause you to loose some back pressure?

MJ50

my current setup is just like it...
2nd cat delete
resonator delete
3" piping with x-pipe

Hammer Down

How does it sound and are you running stock mufflers?

MJ50

it's tad louder than b4...
i'm running magnaflow mufflers...

Hammer Down

Sound clip?

MJ50

nope...
someday i will have sound/video clip...

RonnieRenaldi

Will removing the resonator with two straight pipes affect performance? (all cats still in place)

MJ50

no, but might as well go all out at once then deleting resonator first and then end up doing more deletes later...

RonnieRenaldi

Do you know how much the typical cost to replace the resonator with straight pipes (parts + labor)?

MJ50

resonator delete is normally under 100...

jangy

Yes you can.

jangy

Not at all.