I heard that a turbo will increase exhaust temps higher than stock so that it will degrade the catalysts faster...so would it be a good idea to get a new performance cat so as to make an air inspection a breeze.
most people will have the wastegate gases recirculated back to the downpipe for a closed loop system.. but having the wastegate gases dumped to the atmopshere does give you a slight performance bump.. but having a wastegate dump is
1) HELLLLLLA LOUD..
2) will no way in hell pass smog and visual..
how will you explain to them wtf is that pipe just pointing to the ground..
oh and how loud is it? here is a little sample.. this is on a dsm http://sddsm.org/pages/movies/o2dump.mpeg
not exactly a wastegate dump.. but similar.. he is running an internally gated turbo with the dump on the o2 housing..
my explanation isnt that great.. so i'll let the more technical people help you on that..
hmmm.... I have custom downpipe leading to custom straight pipe to custom exhaust.... If you want a Cat might want to think about metal substrate cat, it allows more air flow than normal honeycomb filter in normal cat. If your turbo is not CARB approved no point adding a cat, but if everything on the car is CARB approved definately get a metal substrate cat to pass smog
like i said.. thats why you get a TEST PIPE! and when smog time comes around.. just replace that test pipe with ur hf cat.. simple solution for having both max performance and being able to pass smog.. just an easy swap of that test pipe section with cat.. though those of you who are running external wastegate dumped to atmosphere. it wouldnt matter.. cause that alone wont pass visual..