engineandecu101
Differences
This shows you the differences between two versions of the page.
| Both sides previous revision Previous revision | Next revision Both sides next revision | ||
|
engineandecu101 [2009/02/26 12:29] twdorris |
engineandecu101 [2009/02/26 12:30] twdorris |
||
|---|---|---|---|
| Line 47: | Line 47: | ||
| At some point, air and fuel is going into the engine and getting all mixed up and pressurized by the piston going up on the compression stroke. The ECU then schedules the ignition of that mixture. The precise point at which the ignition takes places is very critical. Firing too early (advanced too far) can cause very bad things to happen as cylinder pressures increase dramatically beyond design limitations and stuff starts to break. Firing too late (too retarded) generally just causes poor performance. So the trick is finding the happy middle ground. | At some point, air and fuel is going into the engine and getting all mixed up and pressurized by the piston going up on the compression stroke. The ECU then schedules the ignition of that mixture. The precise point at which the ignition takes places is very critical. Firing too early (advanced too far) can cause very bad things to happen as cylinder pressures increase dramatically beyond design limitations and stuff starts to break. Firing too late (too retarded) generally just causes poor performance. So the trick is finding the happy middle ground. | ||
| - | The ECU from the factory has a couple big tables it uses to look up basic ignition advance values. Those values, just like the A/F ratio values for fuel, are tweaked a bit based on operating conditions. But the bulk of ignition advance figures comes straight from the ECU's timing tables. As engine speed (RPM) increases, timing needs to increase as well. "Why" is a long story, but take it for granted that it does. As engine load (cylinder pressure) increases, timing needs to decrease. So these ignition tables are laid out with RPM on one axis and engine load on the other. The result looks something like the following. | + | The ECU from the factory has a couple big tables it uses to look up basic ignition advance values. Those values, just like the A/F ratio values for fuel, are tweaked a bit based on operating conditions. But the bulk of ignition advance figures comes straight from the ECU's timing tables. As engine speed (RPM) increases, timing needs to increase as well. "Why" is a long story, but take it for granted that it does. As engine load (cylinder pressure) increases, timing needs to decrease. So these ignition tables are laid out with RPM on one axis and engine load on the other. The result looks something like the following. You can see that as load increases, timing decreases and as engine speed (RPM) increases, timing increases. |
| {{ http://www.ecmtuning.com/images/forums/ecmlink101/2gdsmtmng3d.gif }} | {{ http://www.ecmtuning.com/images/forums/ecmlink101/2gdsmtmng3d.gif }} | ||
engineandecu101.txt ยท Last modified: 2024/03/15 11:16 (external edit)
Page Tools
Except where otherwise noted, content on this wiki is licensed under the following license: CC Attribution-Share Alike 4.0 International
