engineandecu101
Differences
This shows you the differences between two versions of the page.
| Both sides previous revision Previous revision Next revision | Previous revision Next revision Both sides next revision | ||
|
engineandecu101 [2009/02/26 11:56] twdorris |
engineandecu101 [2009/02/26 12:02] twdorris |
||
|---|---|---|---|
| Line 1: | Line 1: | ||
| - | ===== Engine operation and ECU tuning concepts ===== | + | ====== Engine operation and ECU tuning concepts ====== |
| It's simply impossible to give a full account of engine operation and ECU tuning concepts in a couple paragraphs. So please don't take the following as a complete summary of everything involved. It's not. This section is simply intended to orient the reader's mindset in the right direction with some high level concepts. | It's simply impossible to give a full account of engine operation and ECU tuning concepts in a couple paragraphs. So please don't take the following as a complete summary of everything involved. It's not. This section is simply intended to orient the reader's mindset in the right direction with some high level concepts. | ||
| Line 8: | Line 9: | ||
| - | ==== Air flow ==== | + | ===== Air flow ===== |
| The amount of air going into an engine is a critical piece of information the ECU needs to know **very** accurately so that it can accurately calculate how much fuel to inject. If the real airflow going into the engine is different from the amount the ECU thinks is going into the engine, the ECU will schedule an inappropriate amount of fuel and the engine's operation will suffer as a result. So accurate airflow metering is really important. | The amount of air going into an engine is a critical piece of information the ECU needs to know **very** accurately so that it can accurately calculate how much fuel to inject. If the real airflow going into the engine is different from the amount the ECU thinks is going into the engine, the ECU will schedule an inappropriate amount of fuel and the engine's operation will suffer as a result. So accurate airflow metering is really important. | ||
| Line 18: | Line 19: | ||
| - | ==== Fuel flow ==== | + | ===== Fuel flow ===== |
| From the amount of air the ECU is told is going into the engine, the ECU calculates an amount of fuel required to maintain a 14.7:1 A/F ratio using stock injectors at stock fuel pressure. This is where things can get a little tricky to keep straight in your head. The ECU is coded from the factory to account for the configuration the engine came with from the factory. That is, stock injectors and stock fuel pressure. On a stock 2G DSM, that's 450 cc/min injectors at 43.5psi base fuel pressure. On a stock 1G manual DSM, that's 450 cc/min injectors at 37psi. Stock 1G automatics came with 390s at 43.5psi. This determines the flow rate of fuel into the engine. From that flow rate assumption, the ECU can calculate how long to hold the injectors open to get a specific flow rate required for the air it believes is coming into the engine. | From the amount of air the ECU is told is going into the engine, the ECU calculates an amount of fuel required to maintain a 14.7:1 A/F ratio using stock injectors at stock fuel pressure. This is where things can get a little tricky to keep straight in your head. The ECU is coded from the factory to account for the configuration the engine came with from the factory. That is, stock injectors and stock fuel pressure. On a stock 2G DSM, that's 450 cc/min injectors at 43.5psi base fuel pressure. On a stock 1G manual DSM, that's 450 cc/min injectors at 37psi. Stock 1G automatics came with 390s at 43.5psi. This determines the flow rate of fuel into the engine. From that flow rate assumption, the ECU can calculate how long to hold the injectors open to get a specific flow rate required for the air it believes is coming into the engine. | ||
| Line 24: | Line 25: | ||
| + | ==== Closed loop ==== | ||
| + | |||
| + | ==== Open loop ==== | ||
| + | |||
| + | {{ http://www.ecmtuning.com/images/forums/ecmlink101/2gdsmafr3d.gif }} | ||
| - | ==== Timing (ignition advance) ==== | + | ===== Timing (ignition advance) ===== |
| 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. | ||
engineandecu101.txt · 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
