The factory Scion xB exhaust system on your car is built to evacuate the factory intake calculated amount of air. So if you make Intake modifications you need to release the burnt byproduct just as fast as it came in. Enter xB exhaust. Remember, that an improved flowing intake will create more power with more air. This air does not just disappear, and it must be evacuated.
Now that we are producing more air, we must balance the system. With the Scion xB catalytic converter and factory exhaust muffler in line, you are creating excessive back pressure. If you have not built up your motor internally, and are strictly using bolt on's for power, very little gain will be seen from the rest of the exhaust. But, a gain WILL be seen.
A high flow muffler exhaust has been known to create lots of power on large engines, and none on smaller engines.
- I see it as this, no matter what, from none to some; there is a positive gain with exhaust, not a reduction.
- So, I believe that all set ups benefit from exhaust.
Another step is the exhaust catalytic converter. You may start losing power by replacing or removing your catalytic converter. However, as the compression increases, or boost pressure is used, this becomes another choke point for your exhaust.
There are plenty of high flow catalytic converters out there, that still performs its job as an emissions device, yet creates better flow. There is also the option of installing a test pipe (no cat) or running a straight pipe exhaust (again, no cat). Doing this really only helps those higher powered engines, and is not recommended for street use.
If you do remove your cat on a 1996 or newer xB, you will get a check engine light, for reduced catalyst efficiency. They sell O2 simulators to trick your cars computer into believing the cat is still there and functioning, eliminating the light.
You can install an anti-fouler in line of the rear O2 sensor and trick the sensor into seeing less exhaust, again thinking everything is okay. Any modification to the catalytic system is legal for on road use.
Exhaust pipe size, well there are lots of arguments relating to pipe size, a rule of thumb, match the pipe size to the header outlet size, and all should remain balanced.
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