Hey guys,

I have the oppertunity to run an ECU Program that allows for No Emissions warning if i choose to run cat-less in my 2.8L. I may have to get some exhaust work done soon anyway so i was wondering what the direct benifits of running with no cats would be? Can it do nothing but help or is there a downside? Where will my power band get stronger, where will it suffer, or is it all gravy? Can anyone who runs no cats on either their 1.8T or 2.8L tell me what it has done for your A4?

Thanks alot guys n gal

 

you will get slightly more power by letting the exhaust flow a little bit better, little bit better throttle response, your not going to get huge power from it, but it will be a little boost.

if you need to pass emissions in your state you wont be able to. if you dont have to then it should be fine to get rid of the cats. the "no emissions warning" just makes it so having no cats doesnt trigger a CEL. the emissions people will still know about it and will fail your car.

 

yea, im pretty sure they actually look for the cat.

 

Hmmm, maby i will go with a gutted or dummy cat. Would there be any loss of tq? Because i understand that when an exhaust is opened up for more flow that there might be problems with loosing tq at the lower rmp. is this true with the no cat?

 

idk.. if you want it for the sound get a cut out.. im putting that on my car when i get my exhaust done

 

your talking about loosing back pressure which would only apply to a turbo'd car. on a NA engine you want as little restriction as possible to help the air move thru.

if you have to go thru emissions there is no way around your cat. they test the exhaust gas coming from the tail pipe, if you dont have a cat, or have a gutted or dummy cat that doesnt actualy burn the exhaust gasses, you will fail. it doesnt just have to look like you have a cat, you actualy need to have one and theres no way around it.

 

ghost, i dont meen to question your experience, but then why do people, use dummy cats? or gut them instead of just running straight pipe?

Ok, so now i know that with my NA engine, this will be fine. But what about a supercharged application? I am planning on it within the next year or so. It is said that the Supercharged 2.8L benifits greatly from a high flow exhaust but do you think i will have any problem?...my guess would be no, because the supercharger does not run off of exhaust pressure like a turbo, am i correct?

 

if you use a test pipe, there is no heatshield around it and it radiates alot of heat into your engine bay, dummy cats have a shield around them like the stock cat does. people use gutted cats because they are too cheap to spend $100 on a test pipe. dummy cats might fool the police if they ever decide to open your hood and see if you are legal. they would never do this unless you give them a good reason to (if they catch you street racing, or if something else on your car is clearly illegal).

these reasons have nothing to do with emissions, you cant hide whats in your exhaust gasses. if they are full of hydrocarbons they will catch you. only way to get away with it would be to make sure your engine is burning every last drop of gas and is super clean. on a 10 year old car thats very hard.

correct.