How to perform a relative compression test in practice?
I-TESTER RELATIVE COMPRESSION TEST SYNC - PRACTICAL EXAMPLES
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Inductive pick-up clamp
- Connected to In2 or In15 to get current signal from the injector;
- Connected to In2 or In15 to get current signal from the primary ignition;
- Connected to In15 to get signal from classic secondary ignition system.
Note: Inductive pick-up clamp has an arrow marked which should match the current direction! Incorrect connection will cause a lack of synchronization signal!
If you don’t know the current direction, you may have to experiment with the inductive pick-up clamp orientation until you get a sync signal!
- Connected to In2 to get current signal from the injector;
- Connected to In2 to get current signal from the primary ignition.
Note: Current clamps have an arrow and “+” marked which should match the current direction! Incorrect connection will cause a lack of synchronization signal!
If you don’t know the current direction, you may have to experiment with the current clamps orientation until you get a sync signal!
- Connected to In15 to get voltage signal from the injector;
- Connected to In15 to get voltage signal from the primary ignition (with 10:1 attenuator).
Cylinder identified as a synchronization cylinder is always A and it’s marked with "*". By knowing the injection sequence/firing order of the engine and the cylinder number used for synchronization, you can identify the cylinder numbers and their percentages.
Important note: Before performing the relative compression test, you must disable the fuel system to prevent the engine from starting. This can be done by removing the fuel pump fuse, relay or disconnecting the fuel pump itself.
Example:
If cylinder 3 is used for synchronization, according to the injection sequence/firing order (1-3-4-2), cylinders on the above screen are:
A*-3: 98%
B - 4: 92%
C - 2: 100%
D - 1: 96%
Note: You may receive errors/warnings during the test! See their description in the user manual!
Note: Only the “DC Voltage” relative compression measurement method has been demonstrated in this file! “DC Current” method is identical and it is not covered in this guide! Using the main signal cable with 20:1 attenuator to sync from the primary ignition coil is NOT recommended!
3. Relative compression synchronization tests on real cars
Car 1: Toyota Auris 1.4 VVTI (engine code: 4ZZ-FE) petrol 2009
|
Test method |
Sync input |
Sync probes |
Sync from |
Notes |
|
DC Voltage |
In15, In2 |
Inductive pick-up |
Primary ignition (current) |
Clamp only 1 of the coil’s wires! Clamps must match the current direction! Using In15 or In2 depends on the signal strength from the inductive pick-up! |
|
In2 |
10/20A High sensitive, high frequency current clamp |
Primary ignition (current) |
Clamp only 1 of the coil’s wires! Clamps must match the current direction! |
|
|
In15 |
Main signal cable and a voltage attenuator 20:1 |
Primary ignition (voltage) |
HIGH VOLTAGE!!! YOU MUST USE THE 20:1 ATTENUATOR!!! |
|
|
In15 |
Main signal cable |
Injector (voltage) |
Back probe both injector pins until you get a sync! |
|
|
In2 |
10/20A High sensitive, high frequency current clamp |
Injector (current) |
Clamp only 1 of the injector’s wires! Clamps must match the current direction! |
|
|
In2 |
Inductive pick-up |
Injector (current) |
Clamp only 1 of the injector’s wires! Clamps must match the current direction! |
Sync input In2 or In15 depends on the primary ignition coil current and you may have to experiment changing inputs until you get synchronization!
You must clamp only one of the injector wires!
If you don’t get a sync signal, rotate the current clamps or clamp the other coil wire!
Please see the technical documentation for the current car or use an oscilloscope first to identify the system!
Connecting an ignition coil with a 400V control voltage directly to i-Tester without using 20:1 attenuator, will damage the device!!!
Test 6: Using an inductive pick-up connected to In2 to sync from injector:
|
Test method |
Sync input |
Sync probes |
Sync from |
Notes |
|
DC Voltage |
In15 |
Inductive pick-up |
Classic secondary ignition system |
Clamps must match the current direction! |
|
In15, In2 |
Inductive pick-up |
Primary ignition (current) |
Clamp only 1 of the coil’s wires! Clamps must match the current direction! Using In15 or In2 depends on the signal strength from the inductive pick-up! |
|
|
In2 |
10/20A High sensitive, high frequency current clamp |
Primary ignition (current) |
Clamp only 1 of the coil’s wires! Clamps must match the current direction! |
|
|
In15 |
Main signal cable and a voltage attenuator 20:1 |
Primary ignition (voltage) |
HIGH VOLTAGE!!! YOU MUST USE THE 20:1 ATTENUATOR!!! |
|
|
In15 |
Main signal cable |
Injector (voltage) |
Back probe both injector pins until you get a sync! |
|
|
In2 |
10/20A High sensitive, high frequency current clamp |
Injector (current) |
Clamp only 1 of the injector’s wires! Clamps must match the current direction!
|
|
|
In2 |
Inductive pick-up |
Injector (current) |
Clamp only 1 of the injector’s wires! Clamps must match the current direction! |
Sync input In2 or In15 depends on the primary ignition coil current and you may have to experiment changing inputs until you get synchronization!
Note: Some ignition coils have the ignition controller integrated inside them. In the current case the ECU controls the circuit with low voltage and thus we can use it directly or with 10:1 attenuator.
See the technical documentation for the current car or use an oscilloscope first to identify the system!
Connecting an ignition coil with a 400V control voltage directly to i-Tester without using 20:1 attenuator, will damage the device!!!
|
Test method |
Sync input |
Sync probes |
Sync from |
Notes |
|
DC Voltage |
In15 |
Inductive pick-up |
Injector (current) |
Clamp only 1 of the injector’s wires! Clamps must match the current direction! Not performed in this test! See description below! |
|
In2 |
10/20A High sensitive, high frequency current clamp |
Injector (current) |
Clamp only 1 of the injector’s wires! Clamps must match the current direction! Not performed in this test! See description below! |
|
|
In15 |
Main signal cable |
Injector (voltage) |
Back probe both injector pins until you get a sync! |
|
Test method |
Sync input |
Sync probes |
Sync from |
Notes |
|
DC Voltage |
In15 |
Inductive pick-up |
Injector (current) |
Clamp only 1 of the injector’s wires! Clamps must match the current direction! |
|
In2 |
10/20A High sensitive, high frequency current clamp |
Injector (current) |
Clamp only 1 of the injector’s wires! Clamps must match the current direction! |
|
|
In15 |
Main signal cable with 10:1 attenuator |
Piezo injector (voltage) |
PIEZO INJECTORS HAVE CONTROL VOLTAGES UP TO 140V!!! Using the 10:1 attenuator is mandatory!!! Back probe both injector pins until you get a sync! |
|
Test method |
Sync input |
Sync probes |
Sync from |
Notes |
|
DC Voltage |
In15 |
Inductive pick-up |
Classic secondary ignition system |
Clamps must match the current direction!
|
|
In15, In2 |
Inductive pick-up |
Primary ignition (current) |
Clamp only 1 of the coil’s wires! Clamps must match the current direction! Using In15 or In2 depends on the primary ignition coil current!
|
|
|
In2 |
10/20A High sensitive, high frequency current clamp |
Primary ignition (current) |
Clamp only 1 of the coil’s wires! Clamps must match the current direction!
|
|
|
In15 |
Main signal cable and a voltage attenuator 20:1 |
Primary ignition (voltage) |
HIGH VOLTAGE!!! YOU MUST USE THE 20:1 ATTENUATOR!!! |
