A bypass HC—NO x system includes a NO x conversion control module that generates a signal indicating whether a close coupled catalyst is active. The system further includes a bypass valve control module that, in response to the signal, opens a bypass valve located in an active HC—NO x adsorber assembly to purge hydrocarbons from an HC adsorber, wherein the bypass valve is located upstream from the HC adsorber and a NO x adsorber. The bypass valve control module also determines a temperature of a three way catalyst and closes the bypass valve to purge nitrogen dioxide from the NO x adsorber if the temperature of the three way catalyst is greater than a predetermined temperature threshold.
1. A system comprising:
a NO x conversion control module that generates a signal indicating whether a close coupled catalyst is active; and
a bypass valve control module that:
in response to the signal, opens a bypass valve located in an active HC—NO x adsorber assembly to purge hydrocarbons from an HC adsorber, wherein the bypass valve is located upstream from the HC adsorber and a NO x adsorber, and wherein the HC adsorber is located downstream of the NO x adsorber;
determines a temperature of a three-way catalyst; and
closes the bypass valve to purge nitrogen dioxide from the NO x adsorber if the temperature of the three-way catalyst is greater than a predetermined temperature threshold.
2. The system of claim 1 , wherein nitrogen dioxide accumulates in the NO x adsorber and hydrocarbons accumulate in the HC adsorber.
3. The system of claim 1 , wherein the bypass valve control module purges the HC adsorber if the close coupled catalyst is active.
4. The system of claim 1 , wherein the bypass valve control module purges the NO x adsorber if a post catalyst oxygen sensor reading is greater than a predetermined threshold.
5. The system of claim 1 , further comprising a venturi tube that directs exhaust gas to the HC adsorber if the bypass valve is open.
6. The system of claim 1 , wherein exhaust gas is forced through the NO x adsorber and the HC adsorber if the bypass valve is closed.
7. The system of claim 1 , wherein the bypass valve control module opens the bypass valve if the purge of the NO x adsorber is complete, wherein the purge is complete if an amount of nitrogen dioxide in the NO x adsorber is below a predetermined nitrogen dioxide threshold.
8. The system of claim 1 , further comprising a catalyst light off control module that initializes a catalyst warm up strategy if an engine is in a catalyst light off mode.
9. The system of claim 8 , wherein the catalyst light off control module activates an air pump if the engine is in the catalyst light off mode.
10. A method comprising:
opening a bypass valve located in an active HC—NO x adsorber assembly to purge hydrocarbons out of an HC adsorber, wherein the bypass valve is located upstream from the HC adsorber and a NO x adsorber, and wherein the HC adsorber is located downstream of the NO x adsorber;
determining a temperature of a three-way catalyst; and
closing the bypass valve to purge nitrogen dioxide out of the NO x adsorber if the temperature of the three-way catalyst is greater than a predetermined temperature threshold.
11. The method of claim 10 , wherein nitrogen dioxide accumulates in the NO x adsorber and hydrocarbons accumulate in the HC adsorber.
12. The method of claim 10 , wherein the HC adsorber is purged if a close coupled catalyst is active.
13. The method of claim 10 , wherein the NO x adsorber is purged if a post catalyst oxygen sensor reading is greater than a predetermined threshold.
14. The method of claim 10 , further comprising directing exhaust gas to the HC adsorber using a venturi tube if the bypass valve is open.
15. The method of claim 10 , further comprising forcing exhaust gas through the NO x adsorber and the HC adsorber if the bypass valve is closed.
16. The method of claim 10 , further comprising opening a bypass valve if the purge of the NO x adsorber is complete, wherein the purge is complete if an amount of nitrogen dioxide in the NO x adsorber is below a predetermined nitrogen dioxide threshold.
17. The method of claim 10 , further comprising initializing a catalyst warm up strategy if an engine is in a catalyst light off mode.
18. The method of claim 17 , further comprising activating an air pump if the engine is in the catalyst light off mode.