does removing the catalytic converter add HP? Options

[Negative]

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.

little off topic...i just got my headers on last night ...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]

just take it all off.....i took off all of that stuff, cat, resignator. and it still passes emmisions.

[hitcachi]

ummmmmm, 8 months later, ok....

[spke719]

ummmmmm, 8 months later, ok....

lol my bad i just read it yesterday. just thought i would put in my input.

[n1ckz0r]

Fine fellas, I'll try again...

my exhaust has four parts:



first... right names for right parts

Is in english right:

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



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]

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

[Box]

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.

[BonzaiCelica]

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.

[Jmk91]

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]

A stainless header added to a beams motor adds 5 decibels. So i assume it'd be same for straight pipe

[Box]

If sound level is the main concern you can put in a straight through muffler in lieu of the cat to tone it down.

[igpx12]

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.

[njccmd2002]

Removable test pipe

[BonzaiCelica]

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?

[Box]

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

[BonzaiCelica]

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