Megasquirt MS3 Output Testing

Megasquirt 3 - Output testing

Injectors and coils testing - Idle valve testing

The test modes allow you to confirm operation of some system components independant of the normal ECU operation. This is highly recommended before first starting the engine.

Injectors and coils

The test mode allows direct control of the coils and injectors. Used by accident this could cause flooding of the engine and potential damage. Therefore a special initialisation method is required to enable it. Test mode should NOT be used on a running engine.

First you must enter 12345 in the top box, TAB out, wait a couple of seconds and then click Burn. (Note, if this box already contains 12345, first enter 0, TAB out, then start again.) This sequence then enables the test mode. Do NOT click Burn again at any point during testing.

First check that the mode is on, but turning the fuel pump on/off.
You will notice that "Ready" lights up on the TunerStudio dash when the fuel pump is enabled. If you get no activity, try starting again. However, if Ready lights up but the pump doesn't run, you need to check you fuel pump relay and pump wiring.

Coils

The coil test mode is useful to confirm you have the coils wired correctly and to check dwell settings.
(Do be careful as ignition coils put out a potential lethal voltage. Typically 30,000V or more.)

To enable coil testing
- select coils in the Test mode drop down.
- choose your dwell time in milliseconds. Start low. e.g. 2.0ms.
- choose which coil to test
- set Coil testing mode to One
- if your coils are powered via the fuel pump relay as is recommended, set the fuel pump to On.

The Coil testing mode called Sequence runs the coils in sequence up to the chosen coil. So if you have four coils and selected Coil D and Sequence then the test mode will repeatedly fire Coil A, then Coil B, then Coil C, then Coil D in turn.

The Output Interval specifies how often to fire the coils. For example a 4 cylinder wasted spark engine at 6000rpm will fire the a coil every 5ms, so each coil is fired every 10ms. Note that the test mode does not allow dwell periods to overlap in the sequence mode, unlike normal operation where the dwell periods overlap as required. (This is why traditional V8 distributor spark was weak at high revs - there was not enough time to charge the single coil between sparks.)

Injectors

The coil test mode is useful to confirm you have the injectors wired correctly and to experiment with opening times, PWM settings or to measure flow rate if you have an injector test bench setup.
(Using flammable liquids while testing is hazardous and can lead to serious fires. Non-flammable injector test liquid is available.)

If your injectors are fitted to the engine you MUST NOT run the test mode with fuel pressure or you will fill your engine with fuel! Remove the fuse from your fuel pump and de-pressurise the line first.

To enable injector testing:

- select Injectors in the Test mode drop down.
- choose your pulsewidth time in milliseconds.
- choose which injector to test
- set Injector testing mode to One
- if your injectors are powered via the fuel pump relay as is recommended, set the fuel pump to On.
- for functional testing, set the total number of injections to 65535 (the maximum) or for flow tesing use your chosen number.
(When performing repeated tests at the same number, you need to enter 0, TAB out, then enter the number you want and TAB out again.)

The injectors may be sequenced like the coil test mode.

The PWM settings section allows you to test different PWM settings for the injectors while in test mode.

When you have finished using the test mode, close the test mode window and power off the Megasquirt. If you disconnected you fuel pump, reconnect it now.

Demonstration video

Here is a video demonstrating the test mode on the bench http://www.youtube.com/watch?v=gkhqwSD86No

More information about using test mode to flow test injectors is available here.

Idle Valves

The idle valve test mode can be used with the engine running or stationary. Note that with a PWM idle valve you may need to run a temporary fused 12V supply to the valve if you normally take power from the fuel pump relay and are testing with the engine off.

The top selection may be used at any time and enables or disables the test mode, be sure you do not have the test mode enabled by accident!

Stepper Idle valves (e.g. 4 wire)
The next box is Run/Home. This allows you to reset a stepper idle valve through the homing routine and can be used to confirm the "home steps" setting in the idle control settings. Due to the way the tuning software works, select run, then select home. The valve will close by the "home steps" number of steps and should bottom out. It will then open to the "iac steps" value.
The "iac steps" box allows entry of 0-255 steps. Zero means fully closed, the fully open value will depend on your valve and how it is installed.

You are unlikely to need one of these, but this is a fixture used to measure stepper operation on the bench

PWM Idle valves (e.g. 2 or 3 wire)
PWM valves do not need a homing routine as the PWM output directly controls their position. As noted above, be sure your valve has power when testing.
The "iac steps" box allows entry of 0-100% duty output. This could be used to confirm operation of the valve and learn what duty you require for hot idle for example.

If you have a question, comment, or suggestion for this FAQ please post it on the forum.