So I have a 2007 350z the only changes I have made to the intake and exhaust system before today was a cold air intake, K&N typhoon I believe was the name of it. Today I installed ART motordyne resonated test pipes and I now have a bit of a rasp at lower to mid range rpms when accelerating at a normal speed.

now during the install the bolts from header to cat were almost impossible to get off and both ended up breaking so had to heat and chizzle it out then the passenger side o2 sensor on the cat wouldn't come off so heated that and cut it out and placed in test pipe. The CEL is on for that o2 sensor because it was heated to high and now went read anything so I have a replacement on the way.

my question is why the rasp? I got resonated pipes to avoid this. Is it possible the 02 sensor is deformed in some way after heating that there is a leak? Will update once I get and install the new one. But is there any other reason it's a bit raspy? Is there really a break in period for test pipes, what can I do please help I hate the rasp

 

oem exhaust still? with any test pipe there will be some rasp, although resonated ones do cut it down. once the insides of the pipe get coated with carbon it will change the sound of it some

 

Rasp blows. If you're fine with the smell, ditch the t.p.'s and get some ppe longs.

 

Smell is minimal, and he wont spend money on the ppe's

 

As travlee said, any test pipes will give you some level of rasp, but from what I have heard, on the ART pipes it is minimal.

My AAM test pipes were raspy as hell. Fixed it with the resonated XYZ

 

Did you install non-fouler plugs when you reinstalled your O2 sensors?

If not, this would account for the code throw. The delta between pre- and post-cats (upstream and downstream) is NOT where it should be so the ECM is reading this delta as a non-func catalyst, lighting up the dash like a Christmas tree.

Remedy, re-install the sensors with the non-fouler caps (all four sensors but emphasis on the downstream units), clear the DTCs, you should be good.

As for rasp, that's already been adequately explained; however, should be noted that if you don't want to go to the expense of the resonated Y-pipe, you can tame (not eliminate, TAME) the rasp by adding a low restriction resonator aft of or replacing the OEM mid-pipe resonator. Like a Vibrant to fit your mid-pipe. That's the budget approach.

Personally, I'd just go with a MD XYZ (with its adequately sized resonator that takes out most of the resonance that the test pipe's Heimholtz chambers cannot handle) or better yet, the complete TDX2 which includes the XYZ Y-pipe, large diameter STRAIGHT piping but with another pair of Heimholtz' at the tailpipe.

 

Non-foulers are not required on the 2 front (primary) sensors. Only on the back (secondary).

The purpose of the primary sensors are to adjust A/F ratio, while secondary are to check cat efficiency.

I would think putting non-foulers on the primary would be counterproductive as the sensors would not be getting accurate readings for the A/F.

 

Hence my comment "(all four sensors but emphasis on the downstream units)"..... but you're absolutely right, downstream only needed but I'd be curious now to see how non-foulers on the upstream units would affect overall performance. Seems that A/F would still be metered - but yes, probably not accurately - but CEL would still trigger since the delta between up/down sensors would be nil.

But what do I know, I don't do that stuff.... too much hassle to swap cats back in every two years for smog checks.

 

Damn California. And I though NY was bad

 

So I have an '04 DE running test pipes that was registered in FL for a very long time(no inspection) and I now live in NJ which doesn't do SMOG or check for cats, only OBD2 monitor readiness to pass inspection, would I be best served to non-fouler all four o2 sensors, or could I get away with just the two post cat without tripping CEL? Sorry for replying to such an old thread but your response is preemptively appreciated and awaited!

 

You could always get HFC the difference if performance is minimal and the smell way better lol. The 04s from what I've heard are a mixed bag when it comes to CELs from cats or lack there of, from a mechanical standpoint you want the primary O2s to read so you have proper AFR.

 

It's production date was March of '04 if that helps at all. I'm considering it, the smell doesn't really bother me to be honest, it's literally just to pass inspection in my new state, but since I'm about $7k deep into a rebuild with it currently I was trying to save money wherever I could, but I've also heard of some HFC's still throwing codes. Looking into ISR or Berk if non-foulers don't remedy the CEL. Any guidance would be certainly helpful given my situation

 

FWIW I've had both Berk and Z1 HFC and no CEL, but then again (mixed bag) some cars will get CEL others won't.

 

I guess all that's left to it is to do it. Going to go the cheapest route first in o2 sensor non-foulers, if that doesn't fix it I'll either just go straight to HFC's with and without non-foulers and pray, my only option after that would probably be to just get it tuned out?

 

If you’re really stuck you can build an RC (resistor-capacitor) network to compress and smooth the transience of the signal from the narrow band secondary O2 sensors. That often can settle down any “catalyst below efficiency”-type code. There’s plenty of info out there on how to do that, often from the Honda gang. Helped me get my R53 Mini through IL emissions when it had a Milltek header with HFC and exhaust.

+1 to what Dark said about HFCs. I have Z1s and the car doesn’t throw codes.

 

Thanks Sundown, I did see the old posts about building that circuit, I'm just a little afraid of playing around with the ECU at all, definitely going to go less invasive routes first and see where I end up, going to double up on non-foulers on the post cat o2 and try the brillo stuffing method if she still throws a code without brillo. I do want to get a tune regardless, do you know if the monitors will still set with everything tuned out with Osiris?

 

I built the network right on the O2 sensor lead, no cutting of anything on the car side. I’ve never done the Brillo method, but I’ve used 90-degree foulers with some success over the years.

I’m not sure what “tuned out” would be, but the firmware is usually looking for the delta between the upstream and downstream. If you solve it before you tune it’s one less thing for your tuner to deal with during an expensive dyno session.

Good luck.

 

Oh that's much simpler than I originally thought, I was under the impression I'd be coming off the ECU for the RC circuit, I'll try to dig up more information on that method and see where it takes me. Do you have a guide you used/recommend before I go digging, Sundown? I'll take your word for it and try a 90 degree bung over a double stacked straight one, there's plenty of room with these pipes. I've got the shop to myself all weekend and found one of the resonator housings inside of my pipes has detached slightly so it'll definitely make that annoying resonator rattle, so just going to throw HFC's at it at this point.

 

Oh, also, what year is your Z, Sundown? I know with '03s they virtually never throw codes when running non-foulers but '04 is where they start to be a mixed bag

 

Non-foulers in the front will hurt performance and fuel economy, they are only required in the rear 02 positions because those are used to monitor catalyst efficiency, so by using n/foulers, you’re slowing their response time and tricking the ecm to think the cats are present still.
FYI there is (or used to be at least) such a thing as “mil elims”, which are patch sections that go between your 02 sensor wire and vehicle harness similar to what Sundown is telling you to do. Either method will be a hit/miss proposition, but combined I’m sure will pretty much guarantee a solution.