Exhaust system question...

[Casper]

Guys,

just got the sulfur TSB completed but after taking a look at things im really starting to wonder about the exhaust system on the 4runner.


After looking it seems like there is a main and secondary cat on each bank before the midpipe and then muffler.

Does anyone have CPSI ratings on the cats that are OEM installed on the 4runner? I would love to know about those secondary cats or resonators or what they are.

 

[greasefingers]

Those are resonators which help muffle the sound. They are usually a straight thru design and not baffled. Don

 

[Casper]

hmmm...i think they are about to go bye bye

 

[greasefingers]

It would be very interesting if removing the resonators yielded a nice sounding exhaust note. Cheater than Cat-back systems!

 

[Casper]

well im thinking that by yanking out those secondary cats or resonators or what they are and then creating a less restrictive cross over between the driver side bank and the passanger side bank things could really be livened up a bit...

 

[Presto]

It'll sound good. My buddy did that on his WRX and it sounds tought, and not too loud. (unless you really get on it)

 

[00328]

well im thinking that by yanking out those secondary cats or resonators or what they are and then creating a less restrictive cross over between the driver side bank and the passanger side bank things could really be livened up a bit...

If you wind up actually doing this definitely keep us informed of the process, cost and results.

 

[leesdawgs]

I cut off the final resonator if that is what yall are talking about and it is a noticable difference from the stock option. Of course I also put on a flowmaster muffler too. But I didnt take off the resonator until one month after the flow was put on....

 

[Casper]

Lees

What i am talking about are up prior to the muffler and part of the header system.

there are exhaust manifolds and then they flow into close up catalytic converters (for quick light off and low emissions====not for performance, lord knows that). After that, there are secondary cats or resonators that come after the cats and then they connect into the muffler system.

 

[leesdawgs]

so theoretically taking those off should help out with airflow...

hmmmm....

(wheels turning in head)....

I think Ill look into that, thanks guys.

Lee

 

[Presto]

Yes, improves air flow and voids warranty. Your "check engine" light may also come on afterwards because it will detect something wrong with your cat. converter. My buddy disengaged the sensor on his WRX after doing it. It sounds different at idle and full throttle, so it may raise a red flag at the dealership if it's getting worked on.

 

[OUTRNNR]

Lees

What i am talking about are up prior to the muffler and part of the header system.

there are exhaust manifolds and then they flow into close up catalytic converters (for quick light off and low emissions====not for performance, lord knows that). After that, there are secondary cats or resonators that come after the cats and then they connect into the muffler system.

I'm pretty sure the bulges you are talking about immediately after the cats are resonators. When I was replacing my stock exhaust with the magnaflow my buddy and I fired up the truck with the exhaust off (disconnected at the left bank/right bank intersection under the front passenger seat) and its sounded suprisingly muted. Not much louder than, say, a mustang V8 with a cat-back system.

I bet replacing the resonators would result in better flow and more noise, and I doubt it will effect emissions. The only challenge I see is bending and welding a curved pipe to fit where the resonators are...

 

[leesdawgs]

thanks for the advice. If anyones seen this kind of stuff done could you post back cause Id really like to know the pros and cons from someone who has done a custom exhaust and left these resonators off. My t$r sounds pretty mean already because I cut the tailpipe off 6 inches after the Flowmaster exhaust and put a down tip on it. It really ads rumble and makes you think your moving faster. It is lower but not louder which is what I was goin for...

Lee

 

[Casper]

Before i go ahead and do this i am going to be doing some covert info gathering from the master tech at my dealer.

Once i find out if the 02 sensors are that sensitive to detect a change in pressure and not just 02 levels, and if i can design a better cross over (i think someone already did this---gotta research) I ll do it.

 

[leesdawgs]

keep me updated and if I can help I will, Lee

 

[sharp4runr]

I just found a diagram of the FJ Cruiser and on page 45 it shows a nice diagram of the exhaust system. I do believe from the diagram that the V6 has 4 TWC (Three way Cats). You may want to see if the V8 uses a similar design because you would be eliminating emission control components and could cause you to fail emissions testing (if your State does testing)

FJ Cruiser PDF: http://www.spectervision.com/shared/pdf_docs/FJ_NewFeatures.pdf

 

[leesdawgs]

thanks man Im still looking though...