Could any of you recommend a non-OEM catalytic converter for a 2001 Carrera 4S?
Mine were shot so I had the inside removed from both. There is no emission control in my country. However, now I have too much noise and my engine runs uneven. I would like to get back the former sound and feel without spending the $$$ on OEM cats.
Thanks!

 

there are many aftermarket exhaust systems and most use a 200 cell cat. most are under $1000 per pair. try maxspeed or ztech or look on ebay

 

Thank you okbarnett! Tell me. . . do you know if just leaving the "gutted" cats there is ok or if I should replace the entire pipe and empty cats with a by-pass pipe set?

 

I cant say except that if you have no cat cleaning the gases you are going to get a constant 02 sensor fault. if the cat is working it will make a normal 02 reading

 

The exhaust system needs to be functional to the point the DME using (mainly) the O2 sensor readings detects nothing amiss.

If it does, if the sensors after the converters signal improper converter function the DME will attempt to modify the engine's fueling to try to bring the O2 sensor readings after the converters into line.

Otherwise, not only will the check engine light be on almost all the time the engine's fueling will be subpar and the engine's performance will likely be subpar as well. Performance, fuel economy and perhaps even engine longevity will be negatively affected.

Not only does the car become a gross polluter chances are it will run worse than it would have with the stock system left intact and properly functioning.

Sincerely,

Macster.

 

Unless the Porsche is completely different then the downstream 02 sensors can not affect fuel trim. Only the pre cat 02's can do that. The only purpose of the downstream 02's are to monitor the cats for emissions purposes only. 3 of my 6 vehicle do not have cats and the fuel trim is the same as when they had cats on them.

 

the 2 sensors compare the pre cat amount and the after cat amount

 

I understand exactly what they do but only the ones in front of the cat adjust the fuel trim. The second one is purely an emissions piece of garbage that monitors the efficiency of the cat and trips the light if it's not up to par.

 

The #1 sensors do not adjust the fuel trims. They reflect the fuel trim adjustment the DME constantly does. The DME constantly (at idle every second and at higher rpms more often than every second) varies the injector pulse widths to inject a bit less fuel then a bit more fuel than the target ratio.

By monitoring the #1 O2 sensor voltage outputs, the levels but also the timing, the knows it has the necessary control of the fueling.

The #2 sensors monitor the abilty of the converters to store oxygen obtained when the DME moves to a slightly leaner air:fuel mixture. The converters store oxygen at this time and release it when the DME moves to a slightly richer mixture.

If the #2 sensors do not report the right voltages at the right times the DME will attempt to change the air fuel mixture to bring the #2 sensor readings into the acceptable range. If (when) the DME has gone as far as it can go and not met with success it will turn on the CEL.

At this point, and in fact during the time the DME is attempting to adapt to what the #2 sensors are reporting, the engine's fueling is not optimium.

Sincerely,

Macster.

 

Fabspeed?

FM

 

Thanks for the clarification Macster. Apparently these cars are a little different from others I have tuned.

 

So a gutted cat would not affect performance? Would the only effect be making the car noisier? I am experiencing a slow reaction to my stepping on the gas pedal in the morning and this began after I stripped the cats.