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Camaro V8 LS3 / L99 Engine, Exhaust, and Bolt-Ons Bolt-Ons | Intakes | Exhaust

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Old 06-21-2013, 05:09 PM   #1
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HP Gains From Getting Rid of Cats on N/A Motor?

Been awhile since I posted on here last, but title pretty much says it all. I live somewhere where there are effectively no emissions laws and was wondering what HP gains can reasonably be expected with removing my cats on a car that already has intake and exhaust. (ECU tuning is out of the question for now) Thanks!
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Old 06-21-2013, 05:23 PM   #2
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If you won't be tuning the car do not remove them.
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Old 06-21-2013, 05:33 PM   #3
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if you pull them I dont think you will see any gains, also, if you pull them and dont tune the ecu to delete the rear o2 sensors your check engine light will light up.
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Old 06-21-2013, 05:34 PM   #4
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Swap them for Hi-Flows 10-20whp'ish... and if you decide to go with nocats at all, yea youll gain a little, it will be bit more raspy and you will probably smell fuel out the backside...You will need a tune to get rid of the CEL though.
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Old 06-21-2013, 06:11 PM   #5
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as brim said. there is a gain from stock cats to no cats or hfc. and a good gain at that
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Old 06-21-2013, 07:54 PM   #6
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If tuning is out of the question then you will need the Solo high flow cats. Those do give a good gain and don't throw a CEL or require a tune. I think I read that there is a way to use the JBA high flow cats to where you don't have to tune and wont get a CEL but someone else will have to chime in on that one as I don't know for sure.
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Old 06-21-2013, 11:08 PM   #7
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So would about 20 hp be expected as a reasonable gain? With a few little things to deal with of course, thanks for the tips guys.
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Old 06-22-2013, 08:26 AM   #8
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So would about 20 hp be expected as a reasonable gain? With a few little things to deal with of course, thanks for the tips guys.
20 is way high. At most you'll get 10 hp. The factory cats are restrictive but not that restrictive. As already stated, unless you get a tune, don't bother doing it.
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Old 06-22-2013, 10:30 AM   #9
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Oh alright, probably won't bother unless I go for tune, thanks.
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Old 06-22-2013, 02:31 PM   #10
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20 is way high. At most you'll get 10 hp. The factory cats are restrictive but not that restrictive. As already stated, unless you get a tune, don't bother doing it.
I respectfully disagree. 20 is attainable, 10-15 is avg.
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Old 06-22-2013, 04:18 PM   #11
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I respectfully disagree. 20 is attainable, 10-15 is avg.
I agree as well and if you do the Solo high flow cats you wont need a tune. No cats would be out of the question with out a tune.
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Old 06-22-2013, 04:38 PM   #12
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I respectfully disagree. 20 is attainable, 10-15 is avg.
1000% 10 is very low. those cats from factory suck for hp.
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Old 06-22-2013, 04:49 PM   #13
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Well then lets just agree to disagree but I've seen a car dynoed, get hi-flos and a cat back installed, then redynoed and gain just a little over 10 hp with no tune.
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Old 06-22-2013, 04:59 PM   #14
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Well then lets just agree to disagree but I've seen a car dynoed, get hi-flos and a cat back installed, then redynoed and gain just a little over 10 hp with no tune.
First, anytime there is a change you should allow for a re-learn period......Second, every dyno is different as is every car and the conditions in which they are dyno'd. And third, I have seen 3 cars personally in my club (TBC) who have put on HFC's who have made over 15whp. 10 is on the lowside. But as you said...agree to disagree.
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Old 06-23-2013, 08:33 AM   #15
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Interesting
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Old 06-23-2013, 10:32 AM   #16
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Yeah love hp speculations and if cars and dynos reacted all the same to a given part it sure would be easier to know for sure what all these parts made hp wise.
I just did JBA shortys, the hiflow cats and a tune and got 32hp on a 85 degree day that is back to back repeatable even after a brief cooldown.A freind got about the same with the same setup and another freind did 5 better with a auto car. On mine 12 was from the tune and 20 from the shortys and hiflows.How much from each combined I dont know but from what most see, and JDP said the same, is probably 10-12 with the hiflows and 8-10 with the shortys? The shorty's being helped with the better cats. Now by themselves I would think the hiflows could be 15-20 as people have seen, the shortys 0-5
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Old 06-23-2013, 11:08 AM   #17
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Our stock manifolds flow about as efficiently as the "Shorty" headers, the only real gain from them is appearance for the most part.

Nice #s
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Old 06-23-2013, 11:24 AM   #18
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^^yes
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Old 06-23-2013, 11:29 AM   #19
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i think Jannetty did some dyno run with and without. If memory serves me it like 1 or 2 hp.
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Old 06-23-2013, 11:48 AM   #20
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nope...get a shop to get on the level with you and they will tell you that you can get half the hp as a set of longtubes with a set of cat deletes (not high flows, I said deletes)...N/A. Now, make this motor a forced induction (blower) application and you can get almost the same hp...you leave maybe 10whp on the table with a set of longtubes on just a supercharged car. Forced induction likes to have something to push against to put it in simple terms. You are trying to build positive pressure.
NOW...2 disclaimers to my above comments.
1. you add a cam or cam/heads, you totally could see gains on a 2" primary header.
2. Pfadt's new tri-Y is yet to be tested on a forced induction application. I'm curious on these. Even if they made the same horsepower as a set of cat deletes, they may gain substantial torque down low...don't know yet. I've pm'd them. Trust me.
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Old 06-23-2013, 12:13 PM   #21
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nope...get a shop to get on the level with you and they will tell you that you can get half the hp as a set of longtubes with a set of cat deletes (not high flows, I said deletes)...N/A. Now, make this motor a forced induction (blower) application and you can get almost the same hp...you leave maybe 10whp on the table with a set of longtubes on just a supercharged car. Forced induction likes to have something to push against to put it in simple terms. You are trying to build positive pressure.
NOW...2 disclaimers to my above comments.
1. you add a cam or cam/heads, you totally could see gains on a 2" primary header.
2. Pfadt's new tri-Y is yet to be tested on a forced induction application. I'm curious on these. Even if they made the same horsepower as a set of cat deletes, they may gain substantial torque down low...don't know yet. I've pm'd them. Trust me.
I'm going to somewhat disagree. FI responds very well to long tubes and allows you to add a Lil more boost. But that's not the topic here. The op is NA and deleting the cats will give you 10-15 hp.
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Old 06-23-2013, 01:16 PM   #22
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^^this
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Old 06-23-2013, 01:47 PM   #23
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i think Jannetty did some dyno run with and without. If memory serves me it like 1 or 2 hp.
Jannetty Racing did a test using HF cats vs. no cats during the header primary size tests. They did not try stock cats vs no cats. The only way to even do that test would be with stock manifolds or shorty headers.

A big reason that you pick up 30 - 35 HP with LT headers is the deletion of the stock cats.
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Old 06-23-2013, 05:09 PM   #24
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i think Jannetty did some dyno run with and without. If memory serves me it like 1 or 2 hp.
Added Edelbrock shorties on my 98 and got maybe 5.Those and the cat back made it run lean. Richened it up, took out some timing and got 10 total, so yeah probably most from the tune
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Old 06-23-2013, 05:12 PM   #25
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Our stock manifolds flow about as efficiently as the "Shorty" headers, the only real gain from them is appearance for the most part.

Nice #s
Yeah and thanks! I think shorties, like mufflers from the few dynos I've even seen dont get much peak hp but you do get and notice more tq down low and in the mid range. Probably want folks say they "feel"
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