test pipes test pipes test pipes

Jordo!

I have seen a few dynos that suggest the ART pipes make a few more (3-4) whp than regular test pipes -- assuming that isn't just measurement variance, it would have to be due to the specific frequency the resonators have; allegedly they were selected to tune the exhaust pulses in order to improve flow.

That is indeed possible to do, and there is some evidence for it.

Not all resonators will have the same frequency, so no, not all resonators will be tuned (i.e., designed) just right to accomplish that.

However, they are very expensive. If you can find a used set, it might be worth trying out, but expect to pay about double what you would for other TP's, even for used ones...

The primary and secondary O2's are monitored (really, clocked) for voltage changes by the ECU.

If a functioning cat is in place (at least one operating within OEM specs), the flow pulses will slow down as it enters the cat, so there will be some delay in voltage change on the sensors between pre-cat (primary) and post-cat (secondary) on each bank.

However, if the cat is gone, the voltages will change at about the same time. This trips a DTC (CEL) and can cause all sorts of issues with how the car runs.

An extender, or series of extenders (try a single + a L shaped one?), will move the 2ndary O2 further downstream to (hopefully) cause enough of a delay in voltage changes between 1 and 2.

Google spark plug de-fouler and you will find images of it. You can find them at any auto shop or even ebay.

It doesn't always work...

Some folks claim adding steel wool in the bung provides enough filtration to slow down the signal changes.

I suppose another option would be some sort of re-wiring on the secondary O2's to alter the rate of voltage change, but I don't know of anyone who has done that on the Z for whatever reason.

Usually, if the mechanical fix (i.e., adding defouler extenders) won't cut it, the only way around is a tune -- that can shut the monitor system off entirely, and, theoretically, with that off, the ECU doesn't then alter its tune (although I've been told even with the CEL off it might, but I have seen no evidence of the tune solution not working).

NOTE: Even using HFC's will not absolutely guarantee that you won't get a CEL. Remember, the ECU is monitoring rate of voltage change -- if a HFC flows well enough it may make the interval too short and therefore trip a CEL.

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