# cat delete? Is this a problem causer?



## mr.boh (Dec 17, 2011)

I'm thinking of deleting my catalytic converter. If I do will this cause problems. I'm getting ready to do exhaust work, while I'm at it I was going to yank the cat out. If it will be a problem I'll just leave it. But I would like to open the exhaust and let the motor breath. There is a ram air pipe in mind as well. As far as I know no one makes a cold air intake for a mk1. Will I be running into problems with any of these plans? Any info will help. Thanks.


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## Seax_Smith (Jun 1, 2007)

Legalities aside, hollow cats and "test pipes" are far from uncommon. "Bad" emission will increase if you have a green side.

Cold air intakes ... just be sure you are not setting yourself up to suck a puddle up into your intake.


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## DuncanDonutz (Nov 17, 2009)

Your car will literally produce dozens or even hundreds times more harmful emissions (particularly those that contribute to acid rain) without a catalytic converter. Im no tree hugger but Ive never understood why someone would do this.


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## cuppie (May 4, 2005)

+1

And, there's a reason that no one makes a "cold air intake" for a Mk1:
It's CIS. You _have_ to run an airbox - that's what the airflow meter (and, with it, the fuel distributor) are mounted to.

Oh, and: unless someone removed the intake hose from the airbox, it already has a cold-air intake. VW engineers aren't stupid - the box, from the factory, already draws air from the front of the car (as opposed to the engine bay.)  
Want a bigger hole to breathe thru? Get thyself a Scirocco 16v airbox. The inlet tube is, ah, quite large.


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## mr.boh (Dec 17, 2011)

cuppie said:


> +1
> 
> And, there's a reason that no one makes a "cold air intake" for a Mk1:
> It's CIS. You _have_ to run an airbox - that's what the airflow meter (and, with it, the fuel distributor) are mounted to.
> ...


Well let me rephrase my quote. The air inlet tube is gone from the 16v scirroco air box. And right now its just sucking in hot engine bay air. My question is with the air inlet pipe back in place, if I remove the cat will this cause back pressure problems. I understand what a catalytic converter does. But with this removed it makes it possible for optimum air flow. But will this create back pressure problems.


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## DuncanDonutz (Nov 17, 2009)

Like cuppie said, VW engineers knew what they were doing when they designed the exhaust system. Unless your catcon is broken or plugged up it shouldnt be restricting your airflow to any significant degree.


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## cuppie (May 4, 2005)

mr. boh? The only "backpressure problem" on an engine is _excessive_ backpressure.

The "engines need some backpressure" myth is based (falsely) in people (stupidly) putting a too-large exhaust system on an engine, and seeing a power loss from doing so. An example would be putting a 3" exhaust on your 1.6. It's simply too large - you'd end up with crap for exhaust velocity, to the point that the flow can actually stall in the pipe. 

That said... unless it's clogged and/or breaking up, deleting your cat won't improve power. It won't hurt power, either. All you'll get is dirtier exhaust.


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## Glegor (Mar 31, 2008)

cuppie said:


> mr. boh? The only "backpressure problem" on an engine is _excessive_ backpressure.
> 
> The "engines need some backpressure" myth is based (falsely) in people (stupidly) putting a too-large exhaust system on an engine, and seeing a power loss from doing so. An example would be putting a 3" exhaust on your 1.6. It's simply too large - you'd end up with crap for exhaust velocity, to the point that the flow can actually stall in the pipe.
> 
> *That said... unless it's clogged and/or breaking up, deleting your cat won't improve power. It won't hurt power, either. All you'll get is dirtier exhaust.*



tis the truth..

ive not ran one VW with a cat for a long period of time.. ive NEVER noticed power gains, except for when my muffler was plugged up with cat matrix.. it USUALLY increases your fuel economy by 1-2mpg tho, for me atleast.. but i always end up cutting off plugged up, 3/4 dead cats..

the only big gain you get, is the MUCH NICER exhaust note..

im a firm supporter of deleting cats..


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## WaterWheels (Aug 14, 2005)

You don't really get cleaner exhaust but rather treated exhaust which is cleaner or shall we say better for everyone living on this earth and their children. The exhaust is just as dirty before the CAT as it would be at the tailpipe without having a CAT. The CAT just does a chemical cleaning of sorts before it exits the tailpipe. Really just playing with the wording used and I am not faulting anyone for what they said. Just having some fun 

On a serious note though, a CAT does not restrict your exhaust (not now days anyway). This myth, it was true at one time, comes from before most people here were born or old enough to leave the house unsupervised. The EPA forced the auto makers to reduce the emissions and the first attempts were fiascos. "Lean burn" was a real brainer as was the air injection (still used some places) and EGR (also still in use). The converters came into being at this time also and were very restrictive back then. It was common for people to install "test pipes" and pick up some noticable power. Now days they are larger and flow much better. Even European cars have them, they were not required until around mid 90's, and produce great power wile reducing emissions.

Although I'm no real Green Guy most times, there really is no logical or justifiable reason for deleting it from your exhaust now days. Cheap does not count, wait a little longer, more power is not true and if you are worried it will start a fire when parked on the dry grass install the heat shield or park on the street.


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## mr.boh (Dec 17, 2011)

Thanks to everyone for their responses, it is much appreciated.


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## fwdvw (May 12, 2000)

WaterWheels said:


> ........ there really is no logical or justifiable reason for deleting it from your exhaust now days......


 Not going to argue with this statement, but will add, in California we have to buy California specific Cat's. 49 State verses California Cats are respectively $150 verses $249. I would like to suggest that there is a very good reason to take one out to limit the wear on the CAT. We test every 2 years, and it might be cost effective to shelve the CAT and reserve it for the test times. I am not doing this but it would be an economic benefit. 

I usually have to get a CAT every 3 to 5 years. I am not suggesting that anyone do this, its just incentive for folks to dirty the air with legislation.


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## SteveFrench (Oct 29, 2012)

I know this is a million year old thread but it has peaked my interest because I'm about to purchase a mk1 1.6 8v scirocco. I'm considering a K407 carb kit for it. The fuel injection system is all gummed up from the years of unuse. I'll probably grab this kit because it's simple and brand new. Out with the old and in with the new! Based on how tune-able the carbs are would I get some noticeable horsepower using techtonics tuning headers and exhaust system without the cat? Can the stock FI system adapt to these mods like carbs can? Yes I am aware of the emissions. Thanks for your thoughts on the matter.


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## SteveFrench (Oct 29, 2012)

This is the kit I'm thinking of

http://www.carburetion.com/Products/ProductDetails.aspx?part=K407


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## Butcher (Jan 31, 2001)

I had 40 DCOE carbs in the past but I went from a single carb to the Weber's. I would never go from fuel injection to carbs. There are way too much running issues with carburetors than fuel injection. I certainly would not have a cat converter unless I had a good working Lambda control system which would not be possible with that set up.

It's cool to look at under the hood and to brag to your friends about, but it gets old when the driveability is not perfect.


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## SteveFrench (Oct 29, 2012)

Thanks very much. You have changed my mind.


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## scotttu (Jul 20, 2008)

Here is my experience. 

I Put a 1991 Jetta digifant engien in my MK1 Scirocco and deleted the CAT due to it busting up years before.

Ran FAST, man it had power and got ungodly gas mileage but when downshifting coming to a light it was always POP POP POP Bang....and it's annoying.

So I called TT and got a hi-flow CAT, solved that problem, dropped from 55mpg to 48mpg (Yes I measured it, hwy only without lead foot). But the engine ran SMOOTH.

Put a hi-flow cat in and get the best of both worlds, the engine wants a bit of back pressure.


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