Ok, i think i have decided to go test pipes, seems most natural imo, a straight pipe, no bs!

I have HFCs, mainly because my buddy with a 350Z had test pipes and I felt like I was getting high on fumes when I drove his car. My other reason is that, last time I took my 350Z in for emissions, they did the sniffer test (I live in Washington State). Anybody successfully passed a sniffer test with test pipes on a VQ engine? Is it even possible?

I'm in Florida, no sniff tests, but I'm counting on the Smell being sweet aroma as I'm mashing the throttle!

Btw, swinging through a new Tuner shop in Oldsmar to check out the turn around time on the

I've got the Stillen HFC's and im throwin a CEL light. Clears itself away randomly but comes back eventually. Going to try to get o2 bung extenders to see if i can stop it from throwing the CEL so I'll chime back in later. Anyone know the thread on the o2 sensors? 18X1.5mm i assume? that way i can i get the correct size.

Well, work kept me from getting to the shop so hoping I can get some mods before the Nopi run so i'm not feeling so Stock and caught with my pants :icon23:

I know this is an older thread, but seems like some disinformation.

1) CEL thrown due to a change in CAT will be because the ECU has found the amount of pollutants is out of param and cannot correct the A/F ratio enough to bring it back in line. The easiest solution and recommended is to tune the vehicle. Simply deleting the sensor will likely leave the ECU in the last known state of the A/F ratio.

2) Test pipes will throw a CEL on a stock ECU. Your choice is to live with it, periodically reset it or delete the sensor through a program like Uprev.

3) HFC due to their construction will be more expensive and theoretically will pass emissions testing and not throw a CEL. In practice YMMV.

4) Free flowing exhaust will produce more HP on the top and mid range. Some engines may see a decrease in low end torque. IMO I would rather have the free flowing exhaust and take the increase in HP.

5) Changes in the exhaust system will result in sound changes. Some good, some bad depending upon your taste. Personally I can live with a little more sound outside the vehicle, but would not want increase in drone. Would also want to carry on a normal conversation inside the vehicle. My goal is increased HP with moderate increase in sound.

I always wondered where tuners take the AFRs readings from, a sniffer on the tail pipe or from the O2 sensors on the vehicle.

I'd imagine that if you had a j-shaped O2 bung it would read slightly leaner than if the bung where right inside the test pipe. Therefore you would tune with a bit more richer AFR to offset that.

I'm pretty sure people using J-shaped O2 bungs on there test pipes are leaving power on the table because the O2 sensor is getting an in accurate AFR. Correct me if I am wrong here.

The second O2 sensor is on the test pipe / HFC, the first one is on the header (right?). AFR readings are only taken from the first sensor, the second sensor is merely a check to see if the cat is doing its job.

whats the best test pipe to get? when i was getting my intake installed, a guy was on the dyno and they were saying cause that art test pipes were restricting the flow and he wasn't getting as much hp as he should.

That doesn't sound right. Test pipes are the least restrictive unless he managed to get test pipes with the wrong I.D. for his application.

I loved my MXP test pipe and didn't throw a check engine light.

That could be a possibility.