Gutting out the stock cats
 

Has anyone gutted out the stock cats?

We used to do this back in the day, and it was always a cheap gain. Admitidly on 10 year old cars with clogged cats.

But, would be interested if someone has tried this. Might get 50% of the gains of a $2000 exhaust system for 1 hours work on a hoist.

I like the idea of it, from a stealth/sleeper point of view.

You'll get better gains from larger diameter piping than from just gutting the cats in the stock header/front pipe. I would bet you get less than 1-2hp from gutting the stock cats but without replacing anything else.

Great idea. You should do it and tell us how that works out.

You will most likely lose or not gain any power. Your better off with a straight through same diameter pipe. The hollow cat will disrupt the exhaust flow and scavaging effect.

I did this to my front pipe. Louder, and engine seems smoother. Especially at higher rpms

Punching out the cat and inserting a pipe the same diameter of the main pipe could probably show a small gain.

Good luck getting a pipe through the cat on either the header or the front pipe, too many bends in there.

you wont see any gains gains going any bigger then 2.5 if you stay NA.

Waste of time and ozone, get high flow cat and larger diameter piping.

Seeing as this will cost nothing, I hardly see how it is a waste of time.

Understand. But, going for sleeper install. Replacing cat with shiny new decat pipe, is a give away. Gutted out stock cat will still look stock.

how many cats do our cars have? 1 header, 1 over pipe, and is there one in the downpipe as well? Ugh i miss only having 1-2 cats being only in the downpipe..

There is one in the header, one in the front pipe. Removing the one in the header causes issues, as there are sensors before and after the cat, that will then think there is an issue and throw a CEL.

There are ways & means around this CEL, but there is mixed reviews on the success of these methods. Of cuorse you could get a flash/tune to solve this.

The one in the front pipe is not measured in this way, and can be removed without issue.

I'm all about keeping my 5 year warranty. Also, we have to get our cars inspected yearly, and they love failing modified cars.

ah okay thanks. I might just gut the overpipe cat then.

Yes, I'm going to do the same.

Taking the cats out stock exhaust gave a fellow 86er great torque gains. In fact I have full 63mm performance pipe with Header and this guy got almost the same gains on a dyno run as I did.

Here is dyno chart of before and after cat removal of stock header and front pipe.

The cat delete pipes are cheap enough... Gutting cats is not worth the time or effort IMHO... You can sell your cats for half the price of a pipe to a scrap yard for the metals alone...

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Finished gutting my header cat when it started to gut itself all on its own with my turbo set up,...so I'm totally catless now. It a little louder now, backfires more frequently as I burn E85 and you definitely can smell the emissions more.

Looks like I will be doing this on my day off. What do you guys use? Just a really long screw driver?

Youll be there forever with a screw driver. Drill with big bit around the outside, then the centre will fall out. Then tidy. Wear breathing protection, who knows what their made out of.

To those commenting about just putting a decat pipe in. Yes this would be easier, but in some places (like Nz) this would fail the warrant of fitness inspection that we have to obtain annually.

2. A vehicle (other than group L vehicle or a class MA or MC motorsport vehicle with a valid motorsport authority card) that was first registered in New Zealand on or after 1 May 2010 and manufactured from 1 January 1990 has a catalytic converter removed where there is evidence that one was originally fitted.

I have a borla cat delete so I will be gutting the stock header.

Why not get the pipes without the cat and just swapping the original ones back in before the inspection? It's a bit of a pita but you'd get better flow then punching out the cats.

Why not just get a proper pipe with a high flow cat??? There are more gains from the larger piping than from punching out the cat in the front pipe.

The stock pipe is like 2 1/8", a 2.5" pipe with high flow cat will make more power across the rev range than the stock pipe with a gutted cat.

'Cause this is free.

It's not free. Since one would be destroying some expensive parts.

The OEM cats are worth a bunch of money. Look up how much they cost new.

If you really want to go catless, keep the OEM stuff in a bin, get a header/test pipe. In a couple years when someone buys a ghetto mod'ed FRS for cheap, they will pay a good price for a set of OEM cats, especially in CA.

Thank god I don't live in CA

I'm just talking economics. The OEM cats a worth a few hundred. It's like throwing money away. The gains will be better with new parts.

^^ This! I bet an OEM front pipe with cat is worth about twice what a catted aftermarket front pipe is.

I know on some VW's the much smaller cat pipe is like $900 from a dealership for a cat with two flanges.

That would mean replacing all the piping, something I don't want to do.

Why not? Replacing the midpipe is dead simple, it's like a 30 minute job working slowly without a hoist. It's only 5 bolts to replace the midpipe, two at each flange and one hanger.

I don't buy into this. There are plenty of people already who have replaced the stock exhaust because they are convinced it is rubbish. You could quite easily pick up a used stock exhaust system from people like this for next to nothing.

Two reasons; one I don't believe the gain/cost is worth it. Two, as I've said numerous times now, I want to keep the car looking unmodifed.

LOL you would be lucky to get $100 for our cats. Who would want to buy our OEM cats for more than $200? Anything higher you can just get a aftermarket mid pipe with a cat. Only people who I see buying them are people who want to revert back to stock. A junk/scrap yard will prob give you $50.

Then don't modify it... gutting cats is IMO a ghetto solution. You're not going to see any useful gains from it.

Junkyards here will pay well over $100 for a rusted out old cat from a 20 year old car, so they'll definitely pay more for an almost brand new one. The metals in them are worth quite a bit for their size/weight.

As posted above, another user has seen gains.

Unless you have your own information contradictory to the above?

If it shows gains, fits in with what I'm trying to achieve, and costs nothing, then I don't see what the issue is.

dam maybe i should drive up to you, over here they wont give me crap for my catted front pipe.

In oregon it's illegal to sell cats that are used..... No one wanted to buy mine anywhere.... So anyone have anymore info about this? My cousin is currently gutting my header cat and replacing my front pipe cat with a pipe.

Wondering how the power will compare to the RevWorks UEL header w/Nameless 2.5 Front Pipe w/High Flow Cat that was just on the car.

When he guts the header cat he is going to shave the inside and polish it... Also going to polish the ports on the head and maybe enlarge them a tad. He is also removing the stock resonator.

I have the 3in nameless mid pipe to dual 2in cat back proto... It was actually quite quiet with the cat less header and high flow cat. So wondering what it will sound like now... If gains are close to the same i'll be surprised. When the 3in pipe splits to the dual 2in there is a resonator in each pipe... Then it runs to two mufflers out the back... So I don't mind running catless... Also around here anyone would sell a stock exhaust for dirt.

Going to be a fun experiment.

My car also has a Innovate charger.... Made 240WHP 200WTQ before.... So will be interesting to see what it after the Gut + pipe replacement. Oh. He is also doing it so all the stock shielding will remain on the pipes.

Also getting a de-fouler for the header. Going to test if it works.

Just to ass to this our cats dont have rare metal in them so they are worth close to nothing.

What do the turbo guys and people who replace header do?

I had the same reason for doing this as well. Overall it works somehow. The gain is there after proving it with a stock 86 on the quarter mile. Beat him by at least 2.5 car lenghts.