Quote:
Originally Posted by SiVX
What is steady state? Remaining at a constant RPM/ lean burn? I also own a VX, bought recently. It has a newish stainless pipe from the cat back. Just measured diameter from outer circumferance. Got a nice 2" pipe.
I'm getting mixed signals about pipe diameter. Not sure if it will throw my O2 readings off, while creating less backpressure...
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Steady state is cruise. Carmakers often have to balance performance (responsiveness) with emissions and fuel economy. Modern control programs are much better than the obsolete stuff like in a VX. With DBW throttle every movement of the gas pedal is smoothed and translated into a torque request. The control routine will then do whatever it deems necessary to deliver the requested torque. Sometimes this means kicking it out of EGR, sometimes adding extra fuel and timing etc.
With a traditional cable driven throttle you would have a very sluggish engine with lots of "hesitation" as it pulls fuel and adds EGR to the mix. At one point I did some mods to my EGR to increase the mixture and you could feel the car when it kicked into EGR mode on the highway.
Unless you have an exhaust leak don't worry about throwing off O2 readings on a VX. Those cars ran an expensive NTK L1H1 (or L2H2) sensor that is quite precise and properly temp compensated. With aftermarket exhausts and increased flow the emissions sometimes go up because the cat won't hold as much heat but a few rolls of fibreglass exhaust wrap can happily fix this.