Replace the catalytic converter.
Thread Starter
New Member
Joined: Mar 2000
Posts: 125
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Replace the catalytic converter.
Does anyone take off their Catalytic Converter and put a bypass pipe or a fake cat in the A4 before? Can anyone give me advise on this? Because I want to take off the cat to increase the flow of my exhaust.
Thanks.
Thanks.
Thread Starter
New Member
Joined: Mar 2000
Posts: 125
Likes: 0
Re: Replace the catalytic converter.
Yes, I know is illegal, but I usually use the car for track. The check engine light will go on and will that affect the performance on the car?
Also, if I put the cat back on for smog, will the check engine light go out?
Also, if I put the cat back on for smog, will the check engine light go out?
AudiWorld Senior Member
Joined: Jun 2000
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Not worth the effort, will throw DTCs
The HP gain is minimal (if you can feel 3 hp, then by all means do it, because your butt dyno is much better calibrated than mine) its illegal, and your OBD][ compliant engine computer will throw DTCs because the post cat oxygen sensor will read the same as the pre cat one.
Generally its a bad idea.
Generally its a bad idea.
AudiWorld Super User
Joined: Nov 2000
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This looks like a lot more than 3 hp.......
As posted on <a href="http://18turbo.com">http://18turbo.com</a>
You've got torque 300 RPM sooner, and it's more all accross the board, and a huge difference on the top end.
<img src="http://18turbo.com/dyno-giac-apr3inch-dp.jpg">
FWIW, I just put a Random Technology cat on my car, and it pulls much harder on the top end then it did before. Before, in 3rd gear, the car would pull to about 80, and start to die off, now it pulls to 100 mph no problem (redline in 3rd is about 105)
You've got torque 300 RPM sooner, and it's more all accross the board, and a huge difference on the top end.
<img src="http://18turbo.com/dyno-giac-apr3inch-dp.jpg">
FWIW, I just put a Random Technology cat on my car, and it pulls much harder on the top end then it did before. Before, in 3rd gear, the car would pull to about 80, and start to die off, now it pulls to 100 mph no problem (redline in 3rd is about 105)
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AudiWorld Super User
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Can't really justify that. The cat on the A4 1.8T is essentially part of the down pipe.
what I'd be curious to see is a result of that downpipe (3") hooked up to a high flow catalytic converter further down stream like typical cars. Still illegal but green when warm plus may have added performance while keeping the NOx down 
