Method and system for cylinder compression diagnostics
First Claim
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1. A method for a hybrid vehicle comprising:
- spinning an engine unfueled using motor torque with intake valve timing advanced and an intake throttle open;
based on a change in battery current during the spinning, indicating cylinder compression degradation; and
wherein the spinning is only performed when engine temperature is within a limit and a request has been received by the vehicle for compression testing.
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Abstract
Methods and systems are provided for performing a non-intrusive engine compression test. When compression testing is requested, a hybrid vehicle engine may be spun unfueled using energy from a battery driven electric motor. Changes in battery current over multiple engine cycles is used to infer cylinder compression parameters and assess cylinder compression degradation.
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Citations
16 Claims
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1. A method for a hybrid vehicle comprising:
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spinning an engine unfueled using motor torque with intake valve timing advanced and an intake throttle open; based on a change in battery current during the spinning, indicating cylinder compression degradation; and wherein the spinning is only performed when engine temperature is within a limit and a request has been received by the vehicle for compression testing. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for a hybrid vehicle, comprising,
in response to a request for compression testing, spinning an engine unfueled using torque from a battery-driven motor with an intake valve timing advanced and an intake throttle open; - and
indicating degradation of cylinder compression responsive to variations in cylinder compression pressure inferred from changes in battery current during the spinning; wherein the indicating includes, estimating a compression stroke torque for each engine cylinder based on the changes in battery current including when intake manifold pressure is substantially at or around barometric pressure; inferring a compression pressure for each engine cylinder based on the estimated cylinder compression stroke torque; and indicating compression degradation based on the inferred cylinder compression pressure of a cylinder being lower than an expected cylinder compression pressure for the cylinder. - View Dependent Claims (11, 12, 13, 14, 15)
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16. A hybrid vehicle system, comprising:
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an engine including a cylinder; an electric motor/generator coupled to a battery; an intake cam coupled to an intake valve; an intake throttle coupled to an intake manifold of the engine; and a controller with computer readable instructions for, in response to an operator request for a compression test, spinning the engine unfueled using the electric motor/generator while fully advancing the intake cam and fully opening the intake throttle, wherein spinning the engine includes spinning the engine at an engine speed based on a battery state of charge, the speed increased as the state of charge increases; monitoring a change in battery current during a compression stroke of the cylinder; estimating each of a cylinder compression torque and a cylinder compression pressure based on the monitored change; and indicating cylinder compression degradation based on the estimated cylinder compression pressure deviating from an expected cylinder compression pressure.
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Specification