The FC3S turbo uses two stock catalytic convertors. The first,
"pre-cat" is used purely for cold-start emissions; once the engine
(and exhaust/main cat) is warmed up to normal operating temperatures, the
pre-cat does little to aid emission other than ending up as an exhaust
A popular upgrade for the exhaust
is to replace this pre-cat with a downpipe. With this downpipe, you keep
your main catalytic convertor intact and thus the majority of emissions still
In fact, we recommend replacing the pre-cat with a downpipe,
especially if you have very high mileage pushing 100,000 miles on the
odometer. The stock pre-cat has a notorious reputation of failing; once
the pre-cat fails, this normally plugs and kills the main cat at the same
time. Again, replacing your pre-cat with a downpipe will have no bearing
on emissions once everything is warmed up; you'll pass any emissions test, short
of a visual test, with no problem.
Popular 2.5" downpipes which are
drop-in replacements for the stock pre-cat are made by Racing Beat and
MindTrain. HKS offers a 3" downpipe that replaces the stock pre-cat.
Racing Beat also offers a 3" downpipe, but it does not fit with the stock main
Downpipes can gain you up to 2psi of boost.
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