Practical Standalone Tuning: Idle Ignition Timing
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Idle Ignition Timing
02.20
| 00:00 | Before we go too far, we need to understand how the engine will respond to ignition timing or idle, and what sort of numbers it may want to see. |
| 00:08 | The effective ignition timing at idle is no different than it is under load. |
| 00:12 | As we advance the ignition towards MBT timing the engine will produce more torque, and this will tend to make the idle speed increase. |
| 00:19 | If we retard the timing, conversely the idle speed will drop due to the reduction in torque. |
| 00:25 | The first point here is to make sure that the ignition timing numbers in your idle area are smooth and consistent. |
| 00:31 | Erratic changes in the timing numbers will make it hard to hold a stable idle. |
| 00:36 | Secondly, we need to choose the idle ignition timing, and there's no set-in-stone rule for what this must be. |
| 00:43 | After tuning thousands of different engines, I find that most will idle nicely with ignition advance in the 15 to 20 degree vicinity. |
| 00:50 | So this is where I would suggest starting out. |
| 00:53 | 15 degrees is almost certainly going to be less than the MBT timing, but there are some advantages in doing this. |
| 01:00 | Many ECUs now give you the option of using an overlay table to alter the ignition timing in relation to the area between actual idle speed and target idle speed. |
| 01:11 | This works on the principle that advancing the timing towards MBT increases idle speed while retarding will reduce it. |
| 01:18 | For this to be effective though, we need to have the base ignition advance set below MBT so there is some scope to move the timing both ways. |
| 01:27 | You can see how the engine responds to timing at idle by increasing it a couple of degrees at a time. |
| 01:33 | You will notice the idle speed increases slightly. |
| 01:36 | When you get to the point that there is no increase, this is going to be pretty close to MBT. |
| 01:42 | If you want to make use of ignition idle control, I recommend retarding the base idle ignition by six to eight degrees from this point. |
| 01:50 | If you have an engine that is heavily modified, and particularly one with a large cam that provides a lot of overlap you'll usually see more stable idle speed control with a slightly more retarded ignition timing. |
| 02:03 | I find that 12 to 15 degrees usually works well, but you will need to adjust the timing and see how the engine responds. |
| 02:10 | This slightly retarded idle ignition timing reduces torque and makes the idle life of a large cam less pronounced. |
