To anyone that has installed their catless downpipes, have you had a code pop for not having a catalytic converter? Did you get a o2 defouler or can the code be tuned out? I haven't seen a wiring diagram for the o2 sensors so I'm not sure which one is actually used by the car to correct AFR. Pros/ cons of a defouler?
Catless downpipes, CEL's, defoulers and tuning
BE3RS
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Go back to post #15 above and click my install page link that I posted.
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on my focus RS i ran a catless downpipe for white a while with no tune and no defouler.
same thing happened on my focus ST. i ran a catless downpipe before i tuned it, didn't cause any damage but did throw the code.
- yes it throws a P420 code immediately.
- yes, you can drive the car without a tune. it does not effect the fuelling of the car
- the upstream o2 sensor is what calculates the AFR of the vehicle (which is unaffected by the downpipe) and the downstream o2 sensor is to read the effectiveness of the catalytic converter (will throw the p420 code because there is no cat, or its not sufficient)
- email or message alex @ stratified tuning, he can explain how the cobb accessport gets around the code being thrown, and why it will not pass emissions.
- emissions testing is different everywhere, but if you plug the obd2 tester in, it will know the system is running in this non-oem setup (open loop or closed loop or something, i can't remember, see the above point) and you will fail the test.
same thing happened on my focus ST. i ran a catless downpipe before i tuned it, didn't cause any damage but did throw the code.
Autolite are damn good plugs, I can't understand why folks rush out to replace them.
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Thanks this is what I'm looking for and nice write-up as usual, but I'm not seeing it on Vibrant's site. I guess I'll be giving them a call tomorrow.
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Due to the recent "issues" with the EPA, you may have to purchase the Vibrant item from Amazon, Summit, or someone else. Good luck.
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was able to order one off ebay.. yay.. lol
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Re-Tune
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You can’t use a tune anymore to turn off the CEL. It will always stay illuminated.
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A defouler seems to prevent the cel light. Not really my concern more worried about it performance wise. Would it be safe to run catless even though I’m currently tuned for mountune catted downpipe? I assume it wouldn’t make that much of a difference. Thanks for the help!
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A cat less DP Won’t need a tune. There are gains to be had by tuning it because you can remove the catalyst over temp protections which will allow the EGTs to go higher.
But that CEL will always remain. A defouler doesn’t always work.
But that CEL will always remain. A defouler doesn’t always work.
If you don't need a re-tune and the performance isn't different... then I can't see a reason to make the change from catted to catless.
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Because RaceCur!
Also fireball come out!
In seriousness, for track and if I am not in SoCal I would love to go catless.
Yeah fair. The "I can't have it so I want it" is strong. I've run them in the past and it's cool, but the smell really gets old. I couldn't go anywhere without smelling like I just mowed the lawn. I like the high flow cat route.
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Not on an e30 tune......the smell of e85 is awesome!
I am not blessed with the high octane goodness
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Shame, I have 2 choices each within 15 mins of my house.....little bit spoilt!I am not blessed with the high octane goodness
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161 Posts
Just did catless today I love it. Previous mountune catted downpipe made the nx2 turbo feel very restricted. Went with whoosh catless DP paired with mountune v2x exhaust sounds great. This setup only gets loud when go about 50% wot & even then it’s not that loud just sounds how a sports car should imo.
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