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does removing the catalytic converter add HP? - 6G Celicas Forums

Topic #35476 56 posts Started by nate95
Batman722
#31
ok
first...

most US Celicas have 2 cats (primary and secondary)- 94-95 STs have 2, 96-97 STs have one - the secondary, 94-99 GTs (94-95 cali) have 2, the 94-95 fed (non-cali) have just one, the primary.

removing one or both of your cats will not "add" hp but will "free up" hp from your engine. Removing the secondary cat won't do much but removing the primary cat will give your engine a better (less restrive) air flow - removing both will be less restrictive obviously. How much you ask ? a free flowing exhaust will free up about 5-8 at maximum. That doesn't seem like much but these are economy engines, not performance engines, we are talking about here...

removing these will increse and decrease a few things

increase
flow freeing up some hp with better responce throughout the RPM band
the amount of harmful emissions emitted

decrease
gas mileage

the
my st205 swapandour Beams swap
TheStreetzKing
#32
i punched out my cat when i did my exhaust.. made no difference at all
j0e_p3t
#33
>
QUOTE(Batman722 @ Apr 9, 2006 - 12:21 PM) [snapback]419453[/snapback]
>
ok
first...

most US Celicas have 2 cats (primary and secondary)- 94-95 STs have 2, 96-97 STs have one - the secondary, 94-99 GTs (94-95 cali) have 2, the 94-95 fed (non-cali) have just one, the primary.

removing one or both of your cats will not "add" hp but will "free up" hp from your engine. Removing the secondary cat won't do much but removing the primary cat will give your engine a better (less restrive) air flow - removing both will be less restrictive obviously. How much you ask ? a free flowing exhaust will free up about 5-8 at maximum. That doesn't seem like much but these are economy engines, not performance engines, we are talking about here...

removing these will increse and decrease a few things

increase
flow freeing up some hp with better responce throughout the RPM band
the amount of harmful emissions emitted

decrease
gas mileage

the



so if i do my exhaust... i should remove my primary and keep my secondary? would my car still be legal if i keep at least one of my cats on there?

This post has been edited by j0e_p3t: Apr 9, 2006 - 3:39 PM
ss-iii splitters and 404 skirts areon. which means i need to update my sig.
TheStreetzKing
#34
all i did was punch out my secondary, i mean obviously its more air flow but u wont feel a difference
Batman722
#35
>
QUOTE(j0e_p3t @ Apr 9, 2006 - 4:29 PM) [snapback]419467[/snapback]
>

so if i do my exhaust... i should remove my primary and keep my secondary? would my car still be legal if i keep at least one of my cats on there?

since you live in Cali the emission tests are pretty tough out there so removing your primary would probably make you fail. You might pass if you remove your secondary cat, but I don't know.

IMO If you get an exhaust done, get your car inspected right before, so your sticker would be good for a year and when it is ready to get inspected again, put your old system back on. Then just swap again after.
my st205 swapandour Beams swap
j0e_p3t
#36
>
QUOTE(Batman722 @ Apr 9, 2006 - 4:34 PM) [snapback]419517[/snapback]
>
>
QUOTE(j0e_p3t @ Apr 9, 2006 - 4:29 PM) [snapback]419467[/snapback]
>

so if i do my exhaust... i should remove my primary and keep my secondary? would my car still be legal if i keep at least one of my cats on there?

since you live in Cali the emission tests are pretty tough out there so removing your primary would probably make you fail. You might pass if you remove your secondary cat, but I don't know.

IMO If you get an exhaust done, get your car inspected right before, so your sticker would be good for a year and when it is ready to get inspected again, put your old system back on. Then just swap again after.



tell me about it... my car would have so much more potential if cali laws weren't so anal. plus it requires a lot of money. but other than that, the gains of an exhaust aren't worth the hassle and what-not. the only real reason i want a new exhaust is for the sound. but then again, that might be a lil ricey on my slow car.
ss-iii splitters and 404 skirts areon. which means i need to update my sig.
Batman722
#37
I have a 95 ST just like you, I have a header (corolla one) and my sticker is up at the end of the month. I have my stock manifold and b pipe that I am going to put back on for my inspection, then after it passes, swap the header back on. It really isn't hard to do and the header will make your ST more fun to drive.
my st205 swapandour Beams swap
Bitter
#38
how much of a difference did the header make in terms of performance? do you have a stock exhaust?
2000 Celica GTS 'slowest gts evar'1998 Mazda 626 FS-DE/CD4-E
FAQdaWorld
#39
On a NA 7afe, removing the cat will result in a couple (not 5- 10, more like 2 - 3 ) of gained hp, but will also likely result in a slight loss of torque. Naturally aspirated engines are designed to run with backpressure so removing that backpressure really doesnt help you all that much.
AIM : FAQdaWorld
kenjamatic
#40
little off topic...i just got my headers on last night biggrin.gif ...i don't really feel any difference(except the ricey buzz) at regular(low rpm) driving but when i floor it to mid rpm it seems to not have much torque but there is a pull...then again i won't really know if there's hp's added unless i go the dyno...
Negative
#41
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QUOTE(FAQdaWorld @ Apr 10, 2006 - 7:30 AM) [snapback]419673[/snapback]
>
On a NA 7afe, removing the cat will result in a couple (not 5- 10, more like 2 - 3 ) of gained hp, but will also likely result in a slight loss of torque. Naturally aspirated engines are designed to run with backpressure so removing that backpressure really doesnt help you all that much.


I agree from my experience with actually doing this. No Dyno numbers though.

>
QUOTE(kenjamatic @ Apr 10, 2006 - 7:48 PM) [snapback]419821[/snapback]
>
little off topic...i just got my headers on last night biggrin.gif ...i don't really feel any difference(except the ricey buzz) at regular(low rpm) driving but when i floor it to mid rpm it seems to not have much torque but there is a pull...then again i won't really know if there's hp's added unless i go the dyno...


Wait till you feel the difference at high RPM - the car now will pull through about 6500RPM. I did notice a decrease in low end torque but I was just spinning wheels at WOT anyway so a little low end loss in favor of top end gains was worth it. Lord knows the stock 5s could use some top end LOL.

Man - I can remember when I was the only person I knew with a header on a 5S Celica. Now it seems like everyone has one and my formerly beautiful SS Headers are now a very ugly collection of golds, purples and blues with a little ashy look thrown in for more bad looks. Oh well it's all about to be a moot point when the Turbo goes on this summer anyway.
spke719
#42
just take it all off.....i took off all of that stuff, cat, resignator. and it still passes emmisions.
[font=Comic Sans Ms][size=3]SI VIS PACEM PARA BELLUM (if you wish for peace, prepare for war!)
hitcachi
#43
ummmmmm, 8 months later, ok....
Teh Celica sleeps for Winter '06. Suspension overhaul begins........
spke719
#44
>
QUOTE(hitcachi @ Dec 3, 2006 - 9:55 PM) [snapback]507520[/snapback]
>
ummmmmm, 8 months later, ok....

lol my bad i just read it yesterday. just thought i would put in my input.
[font=Comic Sans Ms][size=3]SI VIS PACEM PARA BELLUM (if you wish for peace, prepare for war!)
n1ckz0r
#45
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QUOTE(bindertch @ Mar 28, 2006 - 8:13 AM) [snapback]414478[/snapback]
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QUOTE(malpaso @ Mar 28, 2006 - 8:59 AM) [snapback]414457[/snapback]
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Fine fellas, I'll try again...

my exhaust has four parts:

IPB Image

first... right names for right parts smile.gif

Is in english right:

1 - horns
2 - calorifier
3 - silencer
4 - muffler

confused.gif confused.gif confused.gif

and second... if I remove part number 2, I will NOT have any HP addition really?


1 - horns - or flex pipe
2 - calorifier - actualy this is the catalitic converter.
3 - silencer
4 - muffler

Actually there is two cats' on the american 7AFE. The first is mounter off of the manifold right below it and the second as malpaos's picture shows is after the flex pipe. I have noticed significant gains from removing both but replacing the second with a hi-flow one and addind a hi-flow muffler, header and CAI.



I did the same thing... I noticed a very nice increase
BonzaiCelica
#46
I've read a straight pipe in place of converter only adds 1whp. But how much louder sites it make it in decibels? Wasn't answered by Google search
Group buy to replicate Narrow E series transaxle partshttp://www.6gc.net/forums/index.php?showto...p;#entry1107514
Box
#47
Holy thread revival Batman!

How much louder depends on a lot of variables, but the smell of raw exhaust is enough for me to leave them in place. Back in the day when they were crudely implemented and they clogged if you looked at them funny yes there were gains to be had, but ever since the late 80's/early 90's or so they really haven't imposed much restriction. Nowadays on a 400+ hp car they might result in a 1 hp loss if that, so why is it people still remove them on a new car is beyond me.
2001 Miata LS 5-speed
BonzaiCelica
#48
Google didn't pull up any other threads. I swear. I don't mind paying 75 extra dollars for one, but the fact that they only last 2-3 years is where I'm like eek. Will have to pay for installation again. But the car is a money pit.
Group buy to replicate Narrow E series transaxle partshttp://www.6gc.net/forums/index.php?showto...p;#entry1107514
Jmk91
#49
Yes it makes your car louder, but not that much louder. Way I look at it... Cats only last 20-50k miles for most of them... If you don't need to pass emissions than bypass it. We bypass almost all of ours whenever they fail in my area. Now some sound raspy without a cat some don't it just depends on current exhaust set up. On most of my cars it was prob as loud as going from a factory manifold to a header in terms of how much louder it was. my mr2 I had no cats with stock piping with eBay header. It sounded kinda mean at 4K Rpms. I liked it.

This post has been edited by Jmk91: Feb 15, 2016 - 1:29 AM
BonzaiCelica
#50
A stainless header added to a beams motor adds 5 decibels. So i assume it'd be same for straight pipe
Group buy to replicate Narrow E series transaxle partshttp://www.6gc.net/forums/index.php?showto...p;#entry1107514
Box
#51
If sound level is the main concern you can put in a straight through muffler in lieu of the cat to tone it down.
2001 Miata LS 5-speed
igpx12
#52
What I'd recommend is mocking up a flanged pipe that will take the place of the cat just in case you maybe want to put a cat back on, then there's no welding involved later on.
1997 ST:Limitedly GreenThis car is not about racing... This car is not about power or performance... It's purely about being cool.
njccmd2002
#53


Removable test pipe
Learned a lot in 10 years...I hardly log in anymore, last loginToday Sept 6 2019, and I was forced just to clarify a post. LOLIf you PM me and I dont respond, dont fret or cry. Im alive, better post your questions in the thread below, maybe I log back in2grfe Swapped...Why I chose the 2GR, before you ask read here...A great civilization is not conquered from without until it has destroyed itself from within.@llamaraxing in Instagram is the best way to find me. I hardly log here anymore.
BonzaiCelica
#54
But what frustrates me is the fact that all these converters no matter the length or diameter are slip fitment. Which means extra piping (more money) because the converters measure 2.5" inner diameter while all 16 gauge piping is 2.5" outer diameter.

Ahh. Are all catalytic converters like this?
Group buy to replicate Narrow E series transaxle partshttp://www.6gc.net/forums/index.php?showto...p;#entry1107514
Box
#55
The direct fit ones are identical to the original in sizing and flanges etc... but you pay for it too. I know MagnaFlow offers some, then I want to say Bosal and Walker might as well.

This post has been edited by Box: Feb 19, 2016 - 2:03 PM
2001 Miata LS 5-speed
BonzaiCelica
#56


What I recently bought. But my question is what type of gaskets do I use? The O type or copper gaskets? The other side test pipe looks the same...

This is what the Y pipe looks liken as you can see the pipe goes past the flange n there is a O type gasket like the ones found at the beginning of the two - one transition section.



This post has been edited by BonzaiCelica: Mar 13, 2016 - 9:21 PM
Group buy to replicate Narrow E series transaxle partshttp://www.6gc.net/forums/index.php?showto...p;#entry1107514
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