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Old 09-14-2011, 04:35 PM   #1
Arsenal11
 
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Help with Hi-flow cats vs No Cats

So I am getting 7/8 LT headers but idk if i should get hi flows or no cats. Whats the difference when it comes to power gains and sound? Will it be so loud without cats that you can't even have a conversation inside the car?
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Old 09-14-2011, 04:37 PM   #2
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Jannetty Racing did a test on this. There are no noticeable performance gains in using off-road pipes (no cats) over high flow cats. If you go with no cats it will sound a bit raspier (my opinion), and your car will smell (fact). The smell is unburnt fuel, oil, etc. Whether it will be too loud inside the cabin or not, that's really dependent on what exhaust you get. The cats don't really have much play in the amount of drone a system has.
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Old 09-14-2011, 04:38 PM   #3
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hey arsenal i am catless...with stock manifolds, and mufflers sounds...perfect...loud but not tacky and old sounding...here my sound clip video.

http://s858.photobucket.com/albums/ab145/angelpapi007/
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Old 09-14-2011, 04:47 PM   #4
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i think its better to go with cats. wont smell, and its gives a cleaner sound.
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Old 09-14-2011, 04:50 PM   #5
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All depends...I'm catless and love the deeper sound better. I'm used to the smell having owned race cars and whatnot previously. It's not bad at all to me FWIW. It's not extremely loud in the car, depends on how you drive it as well. The most annoying thing is the DOD kicking in more than anything.

I've seen similar dyno's showing nominal differences between a hi-flow catted system with longtubes versus a catless longtube system.

If you're talking about STOCK cats, then hell yes there is more power to be had, they are very restrictive.
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Old 09-14-2011, 04:58 PM   #6
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I run catless, with flowmaster outlaws and love the sound. The smell is not all that bad, that being said it will fail any sort of emissions testing.
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Old 09-14-2011, 05:02 PM   #7
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Originally Posted by doomsdayjesus081 View Post
I run catless, with flowmaster outlaws and love the sound. The smell is not all that bad, that being said it will fail any sort of emissions testing.
Definitely something important to consider. Here in TX the OBDII + newer cars only get scanned for codes, no sniffer or physical check.

Of course with a system that allows you to swap off-road pipes and cats you could always swap them out before you get inspected in states that sniff and/or do a physical check.
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Old 09-14-2011, 05:24 PM   #8
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Keep that cats and stay some what legal. There isn't any reason to ditch them unless you're planning to be over 700 horsepower some time soon!
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Old 09-14-2011, 06:22 PM   #9
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haha all the info i needed to know . I was going to go with hi-flows, was just making sure I am not sacrificing any significant power for them. Also the smell does get a bit annoying sometimes. Thanks again for the feedback
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Old 09-14-2011, 07:11 PM   #10
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I have high flow cats my neighbor dont but he has been that way for a year and he is actually going to be putting some on due to the smell. His sounds different than mine but I dont have the smell.
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Old 09-14-2011, 07:32 PM   #11
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Yeah, I'd go with high flow cats. As has been said, we've verified on the dyno, high flow vs no cat has very little change, maybe 3 hp on a good day.

Due to this, emissions, smell, and sound, I recommend getting high flow cats to everyone we sell long tubes to.

The loudness of no cats is kinda cool at idle and light throttle, but at heavy throttle and WOT, its too loud and raspy IMO.
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Old 09-14-2011, 07:48 PM   #12
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Originally Posted by Arsenal11 View Post
So I am getting 7/8 LT headers but idk if i should get hi flows or no cats. Whats the difference when it comes to power gains and sound? Will it be so loud without cats that you can't even have a conversation inside the car?
We only see a couple rwhp difference between good high flow cats like the ones we use and no cats. I personally run cats on my cars.
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Old 09-14-2011, 08:20 PM   #13
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I don't run cats, it was more money I could put towards something else.
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Old 09-14-2011, 08:25 PM   #14
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Originally Posted by stieger View Post
Jannetty Racing did a test on this. There are no noticeable performance gains in using off-road pipes (no cats) over high flow cats. If you go with no cats it will sound a bit raspier (my opinion), and your car will smell (fact). The smell is unburnt fuel, oil, etc. Whether it will be too loud inside the cabin or not, that's really dependent on what exhaust you get. The cats don't really have much play in the amount of drone a system has.
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i think its better to go with cats. wont smell, and its gives a cleaner sound.
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Old 09-14-2011, 08:26 PM   #15
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Obviously its up to u. The 2 reasons I upgraded my exhaust were that I wanted my car louder and to make more power. No cats u get a few more ponies and a lil more noise. It was a no brainer for me. NO CATS. I have had more than one first gen carbed camaros, so a lil smell of good ol petrol smells good to me!!
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Old 10-25-2011, 10:53 PM   #16
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We only see a couple rwhp difference between good high flow cats like the ones we use and no cats. I personally run cats on my cars.
I have approx, 680-700 rwhp with your complete system w/2" primaries. Will the hi flow cat's live at this level? Is there a HP level where you would not recommend cat's? (performance or realiability reasons)
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Old 10-26-2011, 01:14 AM   #17
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I agree with keeping the cats, but it comes down to what power level and power adder you will be running, NA at 450 to 500 rwhp it may only make 3-5 rwhp less with them on, but for boosted or nitrous I would say to take them off since the richer mixtures along with less timing will raise your exhaust temps and probably melt the cats if raced on a regular basis.

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Old 10-26-2011, 01:19 AM   #18
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I have approx, 680-700 rwhp with your complete system w/2" primaries. Will the hi flow cat's live at this level? Is there a HP level where you would not recommend cat's? (performance or realiability reasons)
In your case I would take them off, unless you mostly cruise the car but with 700 RWHP you probably dont.
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