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Link G4 Plus Software Tutorial: Cold Start Tuning

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Cold Start Tuning

05.08

00:00 - When an engine is started from cold, its fuel requirements will be very different from when it is at a normal operating temperture.
00:07 The G4+ includes a number of tables and parameters to let you get an engine to start perfectly regardless of the temperature.
00:15 We're going to discuss how the G4+ handles cold starts and how you can adjust each option.
00:22 If you press the escape key and bring up the ECU settings bar and then click on fuel and cold start, you will see the options we have to adjust.
00:31 These are pre crank prime, crank enrichment, post start enrichment and warm up enrichment.
00:38 Before we go any further it's important to understand how these options relate to what the engine is doing.
00:44 This diagram explains how each option interacts.
00:49 First we have pre crank prime which can be used to add a pulse of fuel from the injectors before the engine is cranked.
00:56 The next option is cranking enrichment which adds an additional amount of fuel while the engine is at cranking speed.
01:03 Once the engine is started, the ECU uses the post start enrichment function before finally reverting to the warmup enrichment table.
01:11 Understanding these different functions is critical if you want to get great cold start performance and make the correct adjustments to your engine.
01:19 A handy tip that will show you which table the ECU is taking enrichment data from at any time, is to press the R key for the run time values screen.
01:27 If you click on the fuel tab, we can see that there are a number of parameters for fuel startup trim.
01:34 This will show you which trim is active during crank, start and warmup period.
01:37 Pre crank prime will deliver additional fuel to the engine before it is cranked.
01:42 This can be particularly beneficial on engines where the injectors are mounted a long way from the intake valve.
01:49 Let's look at the settings available.
01:51 First we have the prime mode which tells the ECU when the fuel should be delivered.
01:55 Options here are off which disables the function, key on which will deliver the fuel as soon as the ECU is powered up and ignition start position.
02:05 This will deliver fuel when the key is turned to the start position.
02:09 This option requires a digital input to be configured as start position.
02:14 Once you've decided when the pre crank prime fuel will be delivered, the injector prime time table can be adjusted to give the required fuel injection relative to engine temperature.
02:24 The pre crank prime function is not required on most engines and is disabled by default.
02:28 The cranking enrichment function provides additional fuel while the engine is cranking prior to it starting.
02:35 Once the engine speed exceeds 400 RPM, the ECU considers the engine to be running and switches to post start enrichment.
02:43 The cranking enrichment function provides three main parameters.
02:46 Firstly we have first crank enrich which offers a percentage increase in fuel enrichment over and above the normal cranking enrichment for the first engine revolution.
02:56 Once the engine is cranking, the ECU will use the crank enrichment table and the crank hold timer to decide how much additional fuel to supply.
03:06 The crank enrichment table is a 2D table of additional fuel enrichment relative to engine temperature while the crank hold time table dictates how long the crank enrichment will remain active after the engine has started and has transitioned into the post start enrichment map.
03:22 Usually the default values that Link supply for the cranking enrichment are very close for most engines and will only need slight manipulation.
03:30 Once the engine is running, the post start enrichment function becomes active.
03:34 This provides additional fuel enrichment defined by three parameters.
03:38 First we have the post start enrichment table which is a 2D table of enrichment versus coolant temperature.
03:46 Next we have the hold time which dictates how long the post start enrichment will be held at a constant level before it begins reducing.
03:54 Lastly we have the post start decay table which defines how quickly the post start enrichment is reduced.
04:00 Again the factory default settings for post start enrichment are normally pretty close.
04:04 One tip is that you can use this table to help stabilise idle on a hot restart when the engine and fuel rails are heat soaked and the engine may tend to run lean immediately after a restart.
04:16 The main warmup enrichment table is a 3D table of coolant temperature versus load.
04:21 This table provides a percentage increase over the numbers in the main fuel table.
04:26 While you can manage with just a 2D table here, including load will let you adjust the enrichment to suit increased airflow at higher loads.
04:34 A tip here is to make sure that you have zero enrichment in the region of the table where you expect the engine to operate normally.
04:41 Perhaps 70-80°C.
04:44 This makes sure your AFR isn't being affected by the warmup enrichment table.
04:49 By default, the load axis is configured as TPS.