Downstream CAT question on 4.0

TooMuchControl · Postby **TooMuchControl** » Fri Oct 23, 2020 6:01 am

Are the downstream CATs, actually CATs?

I took it to the dealer and the lead mechanic stated they are not CATs, but resonators?
Is this true?

Just trying to isolate some noise in the exhaust and wondering if these are resonators that anyone has replaced or investigated for noises / failures.

Thank you for any / all feedback.

silverarrow27 · Postby **silverarrow27** » Fri Oct 23, 2020 10:00 am

According to nissanpartsdeal.com, no secondary cats.

TooMuchControl · Postby **TooMuchControl** » Fri Oct 23, 2020 1:54 pm

I browsed there, and saw the same...exhaust tube....

Resonator at the back, tail of muffler...you look up RockAuto...they are under Catalytics...

Went to the Walker website...
direct fit catalytic...16400...16399....
O2 sensor installation is pre catalytic...converter quantity 1.

Very expensive for just a pipe/resonator? I'm going to have to drop one out and have a look at it.

Postby **smj999smj** » Sat Oct 24, 2020 1:33 am

They are rear catalytic converters, but they are not monitored for efficiency like the upstream converters.

silverarrow27 · Postby **silverarrow27** » Sun Oct 25, 2020 2:16 am

That sucks if they're catalystic converters. I wonder if you just hollowed out the secondary cats, it would pop a CEL?

Postby **smj999smj** » Sun Oct 25, 2020 6:25 am

As I just mentioned, they are NOT monitored by the ECM, so, "no," they will not trigger the check engine light if you hollow them out. I replaced mine with DT mid-pipes and no issues.

silverarrow27 · Postby **silverarrow27** » Sun Oct 25, 2020 12:03 pm

Thanks for the confirmation. It'll be a cheap "fix" and/or upgrade.

TooMuchControl · Postby **TooMuchControl** » Sun Oct 25, 2020 9:00 pm

smj999smj wrote: ↑
Sun Oct 25, 2020 6:25 am
As I just mentioned, they are NOT monitored by the ECM, so, "no," they will not trigger the check engine light if you hollow them out. I replaced mine with DT mid-pipes and no issues.

DT mid pipes...what is das?

Postby **smj999smj** » Mon Oct 26, 2020 3:17 am

They are straight pipe replacements for the secondary converters made by Doug Thorley:

http://www.dougthorleyheaders.com/83206 ... ipes_15714

TooMuchControl · Postby **TooMuchControl** » Mon Oct 26, 2020 2:53 pm

Awesome! Thanks for the link.

Postby **smj999smj** » Tue Oct 27, 2020 4:32 am

A good, custom exhaust shop could take your existing post cats and turn them into something similar for a lot cheaper, I would think. Cut the cat off, weld on a new section of pipe and a flange...it shouldn't be that hard. If you live in a state that has strict emissions inspections, they will fail it if the secondary cats are not in place. DT lists them for "off road use."

Downstream CAT question on 4.0

Downstream CAT question on 4.0

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