Engine cold testing, what is engine cold test
Engine cold testing system overview
Engine manufacturers need the reliable and cost-effective engine end-of-line testing to capture any leakage during engine assembly stage. The cycle time for engine hot test is long with required special resources and expensive facilities.
EOLexpertise engine cold testing bench provides economical and flexible alternative to engine hot test. In engine cold test, electric motor is used to rotate the crankshaft of the engine. The engine actually is not running so there is no gasoline or special ventilation is required.
The process signature software records and analyzes from different sensors including torque, crankshaft angle and pressure. By comparing the waveforms with good engine, their common characteristics can be identified to reject those abnormal or faulty engines.
How engine cold testing works?
EOLexpertise engine cold testing can find out problems during engine final assembly stage. The major engine cold test includes high speed test, low speed test and static test for operation checking. Typical defects of engine can be discovered as below.
- Incorrelate cam and crank timing
- Excessive engine vibration
- Wrong exhaust valve open and close timing
- Ignition coil failure
- Intake manifold leakage
- Wrong intake valve open and close timing
- Leaky head gasket
- Leaky intake and exhaust valves
- Missing cam and crank bearings
- Missing piston rings
- Sticking oil pump relief valve
- Improper gap setting of spark plug
- Sticking variable valve timing camshaft actuators
Major tests of engine cold testing
At the fixed crankshaft rotation speed, the process signatures of crankshaft torque, intake vacuum and exhaust pulse are collected and analyzed. The mechanical defects like low intake vacuum, lost or damaged gasket, valve defect can be inspected.
2. Oil system
Oil system can be tested during the crankshaft rotation by electric motor. The signatures of oil pressure against angle, time domain and frequency domain analysis (FFT) are inspected. Loss or damaged gasket and oil pump not to conform to specification can be determined during oil system test.
3. Fuel system
The standard fuel rail leakage test, no matter it is due to pressure drop or flow drop, is performed when the engine is rotated by electric motor. The electronic engine control (EEC) injector pulses are examined. Fuel rail and injector pressure signatures are extracted to identify faulty components, leaks and wiring defects.
4. Ignition system
Engine is rotated for ignition system testing. The inductive sensors on clamps are compared with primary sensor readings. The system analyzes the ignition pulses with the signatures of crank angle, spark height (in volt) and spark width (in time). The ignition problem like shorted spark plug, swapped ignition wires and faulty spark plugs which are not firing can be found.
5. EGR valve
When the engine is rotated, the engine sensors are tested for ERG valve system testing. The intake vacuum signature is analyzed with ERG valve cycle to find out the malfunction or misconnection of EGR valve, the missing or damaged gaskets.
The signatures of voltage, current and resistance of engine sensor, electrical component and the wiring harness are used for sensor test verification. The defects of vacuum, coolant temperature, oil pressure, oil temperature, crank position sensor (CPS), manifold absolute pressure (MAP), cylinder identification (CID) and wiring harness can be found.
The electric motor rotates crankshaft at a fixed speed. The signatures based on accelerometer values and FFT (Fast Fourier Transformation) analyses are examined. The defects leading vibration like balance issue, compression problem, gear or timing chain issue, missing bearing and reversed sprockets can be identified.
Features of engine cold testing
1. High accuracy
The encoder is highly accurate. The encoder output signal is used as reference for all analog signals. Therefore the encoder is designed as low noise. On the other hand, reducer is excluded in the whole test bench in order to achieve high torque and high speed rotation.
2. Strict requirement on main shaft balance
Comparing with crankshaft balance, main shaft balance requirement is even tighter. After mounting the rotating head, the main shaft is ensured to be perfectly balanced.
3. Highly rigid and vibration-free foundation
Even the engine is in high speed rotation, the engine is not resonated with foundation due to special foundation design and low center of gravity.
4. Accurate air intake and exhaust pressure
Our special piping design ensures the realistic and accurate air intake and exhaust testing pressure.
5. Noise control with air intake design
The air intake whistling sound is reduced by adopting big cross-section air intake design. The correct NVH can also be achieved.
6. Noise control with exhaust hose
The exhaust continuous bounding sound is reduced by implementing big cross-section rigid exhaust hose with low volumetric changes.
7. Noise control with reinforced plastic plate
The noise generated by high speed rotation can be reduced by transparent Lexan cover.
8. Cabling noise reduction
The cable duct structure can well separate noise from any analog signals, especially from power cable.
9. Test mode selection by specific pallet ID
The rotation speed, crank halting angle and test mode can be controlled through Profibus communication with specific pallet ID.
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