Gutted cat flow ~= SLP Loudmouth Resonator? Flow cant be hurt I dont think..

[08Anamoly]

SoI have been reading a lot about how gutting out a stock 2nd cat is bad and will cause horrible flow characteristics. I can see that being possibly true for an "old school" huge brick and mortar cat, but given the shape of our stock 2nd cat, I doubt its the same. The inlets taper in and out and the center section is just larger.

SLP Performance sells "Loudmouth" resonators that look nearly identical, nothing inside, the flow goes from inlet size to 4" back to the original inlet size with no internal packing or anything. I'm wondering why they would sell these if they destroyed flow balancing or caused a power loss.

I can maybe see the downpipe being a different story considering the dead elephant baby shape, etc.

Thoughts?

I know a few have done this and have not reported any issues with performance, but wanted to get some other thoughts.


"SLP Loudmouth I Resonator"


"SLP Loudmouth I Resonator Inside view"


"Stock Speed3 2nd Cat Shape (assume empty)"

[wankular]

"I'm wondering why they would sell these if they destroyed flow balancing or caused a power loss."

Companies will sell anything, regardless if it will help or harm the car's performance. A quick search on ebay will turn up $25 "performance chips", $40 electric superchargers and those tornado things that go in your intake and supposedly increase mileage.
I don't think those SLP pipes will rob power but it doesn't seem like it would increase it either.

[08Anamoly]

SLP is a pretty reputable company, and they dont sell their's to increase power, but as an option to drop the noise on an exhaust system. I was stating that I dont think they would use this type of noise control shape if it hurt power too.

The only gain in the speed3 situation would be that the cat no longer had internals, and again the dispute being whether the power gains would be lost to poor flow after their removal.

[SRTie4k]

Head over to the dynos section and check out bioevolve's build. He gutted the stock downpipe and gained 20HP or so.

Now I can see an aftermarket downpipe as having a "smoother" flow than stock, so it will probably make more power, but even the stocker will gain some power without the catalyst in the way. That's just fluid dynamics.

[08Anamoly]

Definately agree regarding the power and have seen those posts, was just wondering regarding the stock 2nd cat only, and also how it would affect exhaust resonance, throttle input, etc.

[MSMS3]

Given that a race/test pipe is pretty cheap and only gains maybe 5 whp, (as previously noted, it's the dp where the serious restriction is located). I'm wondering whether it's worth the effort to gut that cat. Just a cost-benefit question. Free is always better, if you are sure you might not need to go back to stock for any reason.

You could just about as cheaply cut out that cat and weld in a straight pipe between the flanges and not worry about the change in internal contours and what that might do to exhaust turbulence and flow characteristics. Just a thought.

I welded in a 3 inch Vibrant reso (straight through design) in my 3 inch rp to tame droning and did not see any loss in power, but it is absolutely a 3 inch straight tube with a shell around the center core. The shell is filled with solid sound absorbing material, so there is no change in internal contour.

[spnkr21]

I would replace the 2nd cat with a straight pipe and sell the cat for 50 bucks or so. They will only pay if the cats intact not if it's gutted. I ended up gutting my CPE cat because I wanted it to look like I still had one. Those are much smaller than stock though.


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