Convert Kooks catted x pipe to catless

I didn't think about the drone. I removed the Flowmasters and went with the Roush, because of drone. I can't stand it. Thanks for the info.

Mach2burnout said:

You actually don't "lose" the torque. It just moves in the power band to a higher RPM. And the hollow cats echo and drone and sound terrible.

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So hollowed out cats will sound worse than an off-road pipe? I have Kooks LTs with Kooks high-flow cats but now that my car is boosted, I'm worried about the cats. My tuner gave me a tune to use after I get my new inspection sticker that will apparently help protect me from killing the cats.

I still have my OE cats that I could use if they're better than the Kooks. Using an off-road pipe sounds like an option too. I have Magnapacks installed with Pypebombs too.

Just an FYI. I live in MA, so inspections are tough.

I'm in the Boston area, let me know if you get trouble passing inspection

And yes hollowed out cats will sound much worse. Sounds raspy as hell. Go off road midpipe with the magnapacks or borla stingers which is what I have. If it's too loud, you can add a 12 inch dynomax bullet resonator to each side and you will have no rasp. I've tried almost every exhaust combo out there. I should have my car running in a few weeks, I can meet up or send sound clips if your in the Boston area

I did this a long time ago when I had kooks longtubes, noticed one muffler was cold with almost nothing coming out at idle after driving. So I bought 2 1ft steel straight pipes, cut out the cats and had them welded in. The 2 pipes were like $30 and cost me another $40 to have them welded in. Upon cutting out the cats driver side was completely hollow nothing left and passenger side half the cat material was missing. Got the boroscope and found the driver side over axle pipe was completely clogged. I was na btw and it happened within the first year of having it on the car. Luckily was able to snag a spare over axle pipe from a local guy that day and swap it out.

http://i14.photobucket.com/albums/a341/lightblade543/p_00025-1.jpg

So why is it that the factory blown cars (Roush-Shelby) cats hold up? What is the difference?

06JET said:

So why is it that the factory blown cars (Roush-Shelby) cats hold up? What is the difference?

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Relatively low boost/power levels with a generic conservative calibration using all the factory sensors, limiting rpm, retains rear 02 function for cat cooling, richer fuel stoich, conservative spark, pulls timing based on iat, etc. Which helps keep them cool and lower egt etc. That kind of stuff would have to make a difference on cat life.

Your average guy with an "aftermarket" boosted setup does a lot to the contrary, intake mods, more aggressive cams, more aggressive custom tune(afr and timing) from a wide variety of tuners more boost pulley down, rev higher etc.

06JET said:

OK then, let me ask this---If I have to take the cats off and go with a cat-less pipe will I have to change the tune???? If the cat material starts to break up or fail can I just beat/remove it out and still use the pipe?

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A free flowing exhaust will improve scavenging which means better airflow through the intake/exhaust stream. Depending on the flow difference between the Kooks high flows versus having no cats, you may need a tune update for a richer mixture.

JeremyH said:

Relatively low boost/power levels with a generic conservative calibration using all the factory sensors, limiting rpm, retains rear 02 function for cat cooling, richer fuel stoich, conservative spark, pulls timing based on iat, etc. Which helps keep them cool and lower egt etc. That kind of stuff would have to make a difference on cat life.

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I thought pulling timing will raise EGTs which takes a toll on cats? And a richer mixture means more unburnt fuel through the system which makes matters worse.

I was told that rich cools the cats and lean is hotter = more power (until you melt it down).
So if my rear O2's are working and my tuner said that he was a little fat on the top end then my cats should have a fighting chance......right?

46addict said:

I thought pulling timing will raise EGTs which takes a toll on cats? And a richer mixture means more unburnt fuel through the system which makes matters worse.

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At n/a low load stoich (14:1) retarding timing does raise egt's (which you initial want on start up to heat up the cat) due to some of the burning still taking place past the exhaust valve. Then once car is up to temp and your at low rpm/cruise its common to have a lot of timing advance in the tune, most tunes will run 30 degrees or more, or essentially the most you can get away with under these conditions. Then As load/rpm/cylinder temp/pressure increases there is more air, more fuel and stoich changes and then its beneficial to pull timing to prevent detonation and cool the cylinders which outweighs this effect. Stock tunes add fuel to cool cylinders, egt's, cats. Cats need a certain amount of heat to function and remove hydrocarbons effectively, don't want them too cold or too hot. Heat comes naturally when the car warms up and rear o2's measure how effective the cat is and will add fuel to cool them when needed. This is often bypassed in an aftermarket tune using an open loop commanded afr for maximum power output at the commanded afr and timing level.

06JET said:

I was told that rich cools the cats and lean is hotter = more power (until you melt it down).
So if my rear O2's are working and my tuner said that he was a little fat on the top end then my cats should have a fighting chance......right?

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That is the basic concept. More to prevent detonation but does have that effect.

sman247 said:

And yes hollowed out cats will sound much worse. Sounds raspy as hell.

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I hollowed out the cats on a 92 Mustang LX 5.0 and the damn exhaust rang like a bell on acceleration....sounded HORRIBLE!!

sman247 said:

And yes hollowed out cats will sound much worse. Sounds raspy as hell. Go off road midpipe with the magnapacks or borla stingers which is what I have. If it's too loud, you can add a 12 inch dynomax bullet resonator to each side and you will have no rasp. I've tried almost every exhaust combo out there. I should have my car running in a few weeks, I can meet up or send sound clips if your in the Boston area

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I'll have to look for some Kooks catless downpipes to swap out.

I think Kooks and Pypes are similar in design, no?

Yeah, I live in Raynham and work in Braintree. Do you belong to Mustangs of Mass? Send me a PM.

OK, so the latest is that my cats may already be failing. My car is parked in the garage, and backs up towards a fridge and cabinets. When I got back home last weekend and backed into the garage again, I noticed some "splatter" from both exhaust pipes. It feels like a very fine powder. So, I'm making an assumption, but I'm thinking I may have hollowed out cats before I know it! LOL

I'm looking for options on offroad pipes and using my Kooks cats for inspections to stay street legal.

My setup is a 3V stroker, Kooks LTs, high-flow cats, h-pipe, Magnaflow glass packs and Pypebomb resonated tips. So the current exhaust has some decent low tone.

I would go with the Kooks catless pipes to replace the catted ones you have now. You should be able to get just the 2 short pieces from the headers to the mid pipe and still use the "H" you already have. Then i would look into some mid mufflers like glass packs to go in the two over the axle pipes just before the axle. If not it will be louder with out the cats.

06JET said:

I would go with the Kooks catless pipes to replace the catted ones you have now. You should be able to get just the 2 short pieces from the headers to the mid pipe and still use the "H" you already have. Then i would look into some mid mufflers like glass packs to go in the two over the axle pipes just before the axle. If not it will be louder with out the cats.

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I'm shopping around for options. Seems they're close to $300 shipped. That's why I'm considering the gutted cats. The car as is isn't too bad cruising around with the cats and glasspacks. I doubt removing the cats will be a LOT louder but there's only one way to find out! LOL