x-pipe and not cat's
Melting Slicks
Joined: May 2000
Posts: 2,974
Likes: 5
From: CenTex Texas
Re: x-pipe and not cat's (MC TORCH RED)
10-12rwhp:confused: Yeah right....Maybe on a stroker motor.
Here's a few threads regarding the issue:
http://forums.corvetteforum.com/zerothread?id=639556 http://forums.corvetteforum.com/zerothread?id=638722 http://forums.corvetteforum.com/zerothread?id=610442
Here's a few threads regarding the issue:
http://forums.corvetteforum.com/zerothread?id=639556 http://forums.corvetteforum.com/zerothread?id=638722 http://forums.corvetteforum.com/zerothread?id=610442
Racer
Joined: Mar 2002
Posts: 488
Likes: 0
Re: x-pipe and not cat's (97C5ENVY)
I gained 3+mph from off-road X-pipe and Z06 mufflers.
Tell me this, how would someone dyno 5rwhp lower when putting on hi-flo cats from no cats, yet not lose ANY HP if they had stayed with stock cats? Doesn't make any sense does it?
You non-believers kill me LOL
Anyway, like somene stated above, works for some people, apparently doesnt work for others. It worked for me even if it is a bit stinky at times. ;)
Tell me this, how would someone dyno 5rwhp lower when putting on hi-flo cats from no cats, yet not lose ANY HP if they had stayed with stock cats? Doesn't make any sense does it?
You non-believers kill me LOL
Anyway, like somene stated above, works for some people, apparently doesnt work for others. It worked for me even if it is a bit stinky at times. ;)
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Former Vendor
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From: DFW, TX www.vettestripes.com
St. Jude Donor '03-'04-'05-'06-'07-'08
Re: x-pipe and not cat's (LittleBoyBlu99)
About 12-15rwhp and a headache :smash: :cheers: .
Melting Slicks
Joined: May 2000
Posts: 2,974
Likes: 5
From: CenTex Texas
Re: x-pipe and not cat's (F8LPONY)
Tell me this, how would someone dyno 5rwhp lower when putting on hi-flo cats from no cats, yet not lose ANY HP if they had stayed with stock cats? Doesn't make any sense does it?
As far as being a non believer my dyno chart proves my point......wheres yours?
Racer
Joined: Mar 2002
Posts: 488
Likes: 0
Re: x-pipe and not cat's (97C5ENVY)
So you are telling me that you can run no cats and have 300rwhp (example), put hi-flow cats on and lose 5rwhp to make it 295rwhp, then put stock cats back on and you will gain your 5rwhp back or even more? That's some funky logic.
I can't get the dyno sheet to go large enough to read the #s but when you removed your cats did the tune the AFR back up since removing cats generally makes you run richer? Did the disable COT? Just curious as to why I have seen gains on 2 of my cars yet some of you don't. Hell i never even did tuning on either one when i did this. Maybe those of us that dose see gains have partially clogged cats (failry common on F-bods).
Either way, glad to saee someone finally posting documentation instead of just regurgitating what they read somewhere. As for mine I have to find someone to scan my timeslips before and after and I can calculate the DA for each day.
I can't get the dyno sheet to go large enough to read the #s but when you removed your cats did the tune the AFR back up since removing cats generally makes you run richer? Did the disable COT? Just curious as to why I have seen gains on 2 of my cars yet some of you don't. Hell i never even did tuning on either one when i did this. Maybe those of us that dose see gains have partially clogged cats (failry common on F-bods).
Either way, glad to saee someone finally posting documentation instead of just regurgitating what they read somewhere. As for mine I have to find someone to scan my timeslips before and after and I can calculate the DA for each day.
Melting Slicks
Joined: May 2000
Posts: 2,974
Likes: 5
From: CenTex Texas
Re: x-pipe and not cat's (F8LPONY)
So you are telling me that you can run no cats and have 300rwhp (example), put hi-flow cats on and lose 5rwhp to make it 295rwhp, then put stock cats back on and you will gain your 5rwhp back or even more? That's some funky logic.
I have never seen anyone post a dyno graph of a stock cubed motor that ditched their cats and GAINED hp/tq. I'm not saying it ain't possible, but rather they would be the exception rather then the rule.
As far as tuning goes.......what is there to tune? I mean how would removing the cats cause the car to run rich? After all it's the front O2's that determine the fuel trims not the rear.
Racer
Joined: Mar 2002
Posts: 488
Likes: 0
Re: x-pipe and not cat's (97C5ENVY)
I will admit I have not seen anyone dyno with cats then remove them and dyno again but I go off track results with DA measurements. So now the question would be is it common to see gains or not. I did , you didn't so we know it must not work in every case :(
As for tunning generallly speaking when you remove your cats and don't turn COT off the PCM is dumping extra fuel into the motor to help cool the cats (Cat Over Temperature). When your turn COT off you stop this and most people on LS1Tech were getting a 10rwhp gain simply by turning this feature off on LS1 Edit. This would be in addition to any gains from a free flow exhaust. I still have plenty of back pressure through my Z06 mufflers which can be heard/seen just from reving with the mufflers on vs. disconnected so I doubt it is too free flowing.
As for tunning generallly speaking when you remove your cats and don't turn COT off the PCM is dumping extra fuel into the motor to help cool the cats (Cat Over Temperature). When your turn COT off you stop this and most people on LS1Tech were getting a 10rwhp gain simply by turning this feature off on LS1 Edit. This would be in addition to any gains from a free flow exhaust. I still have plenty of back pressure through my Z06 mufflers which can be heard/seen just from reving with the mufflers on vs. disconnected so I doubt it is too free flowing.
Racer
Joined: Mar 2002
Posts: 488
Likes: 0
Re: x-pipe and not cat's (MC TORCH RED)
Oops, forgot to mention I have seen people with FLPs dyno, then take off the off-road pipe and put the hi-flows on and and lose power. I myself lost 5rwhp by doing this (on my heads/cam/nitroused T/A). Just wish I would have dyno'd the Vette for modding :(
Melting Slicks
Joined: May 2000
Posts: 2,974
Likes: 5
From: CenTex Texas
Re: x-pipe and not cat's (F8LPONY)
COT's?:confused: That's a new one for me.
Let me ask you this, why would removing the cats cause this COT thing to occur? Is it because the PCM is now getting bad readings from the rear O2's?.........(which would be the only way anything on the car would ever know that cats are gone). If so, then yes i can see a need to turn off this COT thing. But for us LS1Edit-less folks that's why O2 SIMULATORS were made.:yesnod: Which BTW I am running. :cheers:
[EDIT] One more thing just for clearity purposes, on my before/after dyno the AFTER dyno was with an MTI Off-Road X-Pipe in place of the cats......in other words directly connected to the collectors (supposedly the optimal location for an X-Pipe).
[Modified by 97C5ENVY, 3:23 PM 9/30/2003]
Let me ask you this, why would removing the cats cause this COT thing to occur? Is it because the PCM is now getting bad readings from the rear O2's?.........(which would be the only way anything on the car would ever know that cats are gone). If so, then yes i can see a need to turn off this COT thing. But for us LS1Edit-less folks that's why O2 SIMULATORS were made.:yesnod: Which BTW I am running. :cheers:
[EDIT] One more thing just for clearity purposes, on my before/after dyno the AFTER dyno was with an MTI Off-Road X-Pipe in place of the cats......in other words directly connected to the collectors (supposedly the optimal location for an X-Pipe).
[Modified by 97C5ENVY, 3:23 PM 9/30/2003]
Thread Starter
Le Mans Master
Joined: Jan 2003
Posts: 6,427
Likes: 0
From: houston texas
Re: x-pipe and not cat's (97C5ENVY)
well guy's they just came off, and if i don't gain any hp/tq thats cool too because it sounds like a man now. wot sounds mean a hell now. thanks for all input. while up in the air i had it dropped 1 inch all way round. looks and sounds meaner.... :yesnod:
[Modified by MC TORCH RED, 9:11 PM 9/30/2003]
[Modified by MC TORCH RED, 9:11 PM 9/30/2003]
Melting Slicks
Joined: May 2000
Posts: 2,974
Likes: 5
From: CenTex Texas
Re: x-pipe and not cat's (MC TORCH RED)
...... because it sounds like a man now. wot sounds mean a hell now.
[Modified by 97C5ENVY, 4:21 PM 9/30/2003]