Exhaust heat recovery for engine heating and exhaust cooling

1. A heating method for a vehicle engine, comprising:

heating intake air via a gas-to-gas heat exchanger in communication with exhaust gases;

heating a fluid flowing through the engine with the intake air via a gas-to-liquid heat exchanger, the engine having a turbocharger and the gas-to-gas heat exchanger positioned upstream of an exhaust catalyst; and

cooling the exhaust catalyst when the turbocharger is in operation and boost is greater than a threshold value.

2. The method of claim 1 , wherein the fluid is at least one of engine oil, engine coolant, or transmission oil.

3. The method of claim 1 , wherein an amount of heated intake air is adjusted via an air bypass valve.

4. The method of claim 1 , further comprising heating the intake air and the fluid during a cold engine start.

5. The method of claim 1 , further comprising heating the intake air during warmed-up operation.

6. A method for a turbocharged engine in a vehicle, the engine having an exhaust catalyst, comprising:

heating intake air via a gas-to-gas heat exchanger, the gas-to-gas heat exchanger in communication with exhaust gases and positioned upstream of an exhaust catalyst;

passing the heated intake air through a gas-to-liquid heat exchanger to heat a fluid that flows through the engine and to reduce a temperature of the heated intake air;

delivering the heated intake air to a cylinder of the engine via an air bypass valve; and

cooling at least one of engine oil and the exhaust catalyst when the turbocharger is in operation and boost is greater than a threshold value.

7. The method of claim 6 , wherein the fluid is at least one of engine oil, engine coolant, or transmission oil.

8. The method of claim 6 , wherein the method is carried out under cold start conditions when the turbocharger is not in operation.

9. The method of claim 6 , wherein an amount of heated intake air delivered to the engine is adjusted via the air bypass valve.

10. A heating system for an engine, comprising:

a throttle in an intake passage of the engine;

an air bypass valve;

a turbocharger;

an exhaust catalyst;

a gas-to-gas heat exchanger in communication with exhaust gases and intake air;

a gas-to-liquid heat exchanger in communication with intake air and a fluid circulating through the engine; and

a control system comprising a non-transitory computer readable storage medium, the storage medium comprising instructions for:

during a first operating condition, adjusting openings of the throttle and air bypass valve such that intake air flows in a first direction through the gas-to-gas heat exchanger and then the gas-to-liquid heat exchanger and heated air enters a cylinder of the engine;

during a second operating condition, adjusting the openings of the throttle and air bypass valve such that intake air flows in a second direction through the air bypass valve, the second direction being the reverse of that during the first operating condition, and the exhaust catalyst is cooled; and

during a third operating condition, closing the air bypass valve.

11. The heating system of claim 10 , wherein the first operating condition includes cold engine start while the turbocharger is not in operation.

12. The heating system of claim 10 , wherein the exhaust catalyst is positioned upstream of the gas-to-gas heat exchanger, and the second operating condition includes boost greater than a threshold value when the turbocharger is in operation.

13. The heating system of claim 10 , wherein the third operating condition includes fluid temperature greater than a threshold temperature.

14. The heating system of claim 10 , wherein the third operating condition includes fluid temperature less than a threshold temperature when the engine is boosted.

15. The heating system of claim 10 , wherein the third operating condition includes time since start.

16. The heating system of claim 10 , further comprising instructions for adjusting air-fuel control based on an operating condition of the engine.