29 August 2018 : HIOKI Memory HiCorder MR8880-20 For Engine Cranking Test

HIOKI Memory HiCorder MR8880-20 For Engine Cranking Test

Engine Cranking Role And Importance

Engine cranking or engine starting is an engine rotation initiation process for its operational cycle [1]. In short, an engine cannot start without first going through engine cranking. Engine cranking requires an exterior force such as a starter (electric, pneumatic or hydraulic). Gasoline and small diesel engines typically use battery energized electric starter [2]. Figure 1.0 shows the parts of an electric starter.


Figure 1.0 : Parts of An Electric Starter

An energized starter provides torque to the engine flywheel through the drive pinion of the turning armature [3]. The rotating flywheel drives the crankshaft rotation of the engine. Piston movement for combustion process starts when the crankshaft rotation hits a certain threshold. The engine cranking process completes after the engine starts running sustainably with stabilized voltage.
A slow piston movement (slow cranking) results in compression leak by piston rings; leading to insufficient compression pressure and heat for proper fuel ignition. Improper fuel ignition causes engine start failure or starts with incomplete combustion which equals to excessive emission.

Hioki HiCorder MR8880-20 for Engine Cranking Test

Engine cranking time is useful for predicting potential engine issues. Hioki HiCorder MR8880-20, a high-speed waveform monitoring and recording device, records the battery voltage response with time during engine cranking.

The real-time recording interval range of 100µs to 500µs and pre-trigger point recording enables highly detailed engine cranking test time recording since this process happens quickly. Figure 2.0 shows the battery voltage response with time during different stages of engine cranking measured using MR8880-20.

Figure 2.0 : Battery Voltage Response With Time During Engine Cranking[4]

The engine cranking current trend can also be monitored and recorded concurrently with voltage using a current sensor. Figure 3.0 is a screenshot of these 2 parameters measurement using MR8880-20 coupled with the CT7742 current sensor and CM7291 display unit combo*. Voltage dip with current inrush is observed during the start of the engine cranking process.

*Note: CT7000 series sensor needs to pair with display unit CM7290, CM7291 to connect with Memory HiCorders.

Figure 3.0 : Battery Voltage and Current Response With Time During Engine Cranking

Engine cranking test requires slightly extended period of monitoring to establish any potential problems with the engine. The signal tapping is done in engine compartment which is subjected to substantial temperature fluctuations due to heat from the engine and surrounding temperature. Current drift due to temperature fluctuations is a common phenomenon associated with long-term DC signal measurement. The CT7742 current sensor is capable of operating at wide temperature fluctuations and with auto-zero adjustment to minimize the drift. Measurement range is up to 2000 A.

The engine cranking test time during different period and situation enables prediction of potential engine issues before it takes place. Prolonged engine cranking process drains the battery, overheats and shortens the lifespan of the starter. This test serves as preventive maintenance to prolong the engine cranking system lifespan, troubleshoot potential engine problems and prevent unnecessary hassle due to unprepared downtime.

HIOKI Memory HiCorder MR8880-20 Catalogue