fusion13
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Ok don’t worry about it saying focus st as the ecoboost motors specifically the 2.0l and the 2.3l are very very similar to each other. I think this article from Stratified Automotive does a great job of explaining knock and ignition correction in the ecoboost motor.
http://stratifiedauto.com/blog/understanding-knock-and-ignition-corrections-in-your-high-performance-ecoboost-engine/
Understanding knock and ignition corrections in your Ecoboost powered Ford
All engines knock! Ok, now that that’s out of the way
. Knock or detonation is a phenomenon where the combustion process does not start at the spark plug and propagate completely smoothly pushing the piston down. Instead, there are several small flame fronts that usually appear at the edges of the main flame front during the power stroke. These smaller uncontrolled explosions cause pressure spikes in the combustion chamber. High enough pressure spikes for a long duration can cause damage so naturally we want to avoid high intensity knock in our Ecoboost cars … but not completely eliminate knock … Let me explain why.
Modern cars such as the one above have well tuned “microphones” called knock sensors that pick up on these sounds and react very quickly to stop detonation when it starts. The 4 cylinder Ecoboost in the Focus ST has two of these little guys:
When the ECU detects knock it reduces ignition timing advance. Back in the day when the knock sensor technology was not advanced engines knocked all day long without immediately blowing up. You could hear them pinging going up hills. These days, we push small engines to make a lot more power and we realize that maximum power is made right at the knock threshold. Another way to say it is that we want to keep the engine RIGHT at the edge of knock and the modern ECU in the Ecoboost does exactly this through some smart programming.
The ECU always listens to the knock sensors and knows which cylinder is knocking while it keeps adding timing. Once it starts to hear knock it reduces ignition timing on a cylinder by cylinder basis and eventually it learns an ignition trim that scales the entire ignition table up or down depending on how much knock it picks up. This trim is called the OAR – the Octane Adjust Ratio. Over time, the closer this value is to -1, the more timing the ECU is adding without hearing knock meaning you have high octane and there is power left on the table. The closer it is to +1, the more knock the ECU is picking up meaning either the octane you are using is poor or the tune is too aggressive or both. So having a peek at your OAR using a logging tool such as the COBB AccessPort ever so often will give you an idea of the fuel quality and how the tune is behaving. ***Keep in mind that the tuner has the ability to adjust how the OAR parameter learns so in some cars OAR will sit at one value and in others it will move around more. If you have concerns, bring it to their attention.***
Using a logging tool such as the COBB AccessPort during a wide open throttle (WOT) run can give you further insight. After datalogging such a run you can look at two parameters to get a good idea of how the tune and fuel are performing. These parameters are knock count for each cylinder (how many times the particular cylinder knocked) and knock intensity for each cylinder (how much timing was pulled during each count – called Ign Corr.) When ignition correction is adding timing, that means no knock is heard by the ECU. When it is pulling it back, it has done so because it heard knock in that one cylinder.
Keep in mind that the way the ECU reacts to knock is tunable. So some tuners will have the ECU pull a good amount of timing when the severity is higher while others are more aggressive. This is something to discuss with your tuner. Once you get familiar with what you’re seeing in datalogs you will know what is and isn’t normal. It is also important to choose a tuner that is experienced with the ECU and how it adjusts timing to get the most from this feature without risking the safety of the motor.
In terms of knock counts – remember that when it’s not knocking the ECU is adding timing until it knocks until it reaches the tuner-set ceiling for amount of timing added. Because of this, you are likely to get some knock counts during a pull if the tune is built to maximize performance.
The idea is for the tune to be setup such that knock event intensity is low and that the tune adds timing in a way that doesn’t cause a lot of sudden knock. It’s normal to see the ECU add a little timing and taking some away. What you don’t want to see is very large and continuous negative ignition corrections.
Let me give you an example. Below are the knock counts on a 4th gear pull for cylinders 1-4. This tells you that some knock has happened during the pull but it doesn’t tell you anything about how severe/intense it was. This is incomplete information.
To complete the information here are the cylinder ignition corrections for the same pull. As you can see, the most severe correction was around 1* on cylinder 1 and right away that cylinder added more timing and didn’t knock again. You can also see that each cylinder walks ignition up a little, then steps down when it reaches knock. Finally, you can see all the cylinders are well balanced – there isn’t one cylinder that is significantly better or worse than another one. This big turbo Focus ST is running well and it is fine tuned for its modifications and fuel.
Also note that there will be differences from pull to pull and this is again normal. Always take a couple of pulls to make sure the data is consistent.
Here is a tune that needs attention or the car is using poor quality fuel. You can see that all the cylinders move into the negative ignition correction zone and some with larger steps meaning that the ECU is picking up knock and lowering timing. You can also see that they are not recovering like the graph above. This car does not instantly blow up. Far from it. However if you see consistent data that looks like this, either higher octane fuel is needed or the tune should be adjusted.
Happy Tuning,
The Stratified Team
http://stratifiedauto.com/blog/understanding-knock-and-ignition-corrections-in-your-high-performance-ecoboost-engine/
Understanding knock and ignition corrections in your Ecoboost powered Ford
All engines knock! Ok, now that that’s out of the way
Modern cars such as the one above have well tuned “microphones” called knock sensors that pick up on these sounds and react very quickly to stop detonation when it starts. The 4 cylinder Ecoboost in the Focus ST has two of these little guys:
The ECU always listens to the knock sensors and knows which cylinder is knocking while it keeps adding timing. Once it starts to hear knock it reduces ignition timing on a cylinder by cylinder basis and eventually it learns an ignition trim that scales the entire ignition table up or down depending on how much knock it picks up. This trim is called the OAR – the Octane Adjust Ratio. Over time, the closer this value is to -1, the more timing the ECU is adding without hearing knock meaning you have high octane and there is power left on the table. The closer it is to +1, the more knock the ECU is picking up meaning either the octane you are using is poor or the tune is too aggressive or both. So having a peek at your OAR using a logging tool such as the COBB AccessPort ever so often will give you an idea of the fuel quality and how the tune is behaving. ***Keep in mind that the tuner has the ability to adjust how the OAR parameter learns so in some cars OAR will sit at one value and in others it will move around more. If you have concerns, bring it to their attention.***
Using a logging tool such as the COBB AccessPort during a wide open throttle (WOT) run can give you further insight. After datalogging such a run you can look at two parameters to get a good idea of how the tune and fuel are performing. These parameters are knock count for each cylinder (how many times the particular cylinder knocked) and knock intensity for each cylinder (how much timing was pulled during each count – called Ign Corr.) When ignition correction is adding timing, that means no knock is heard by the ECU. When it is pulling it back, it has done so because it heard knock in that one cylinder.
Keep in mind that the way the ECU reacts to knock is tunable. So some tuners will have the ECU pull a good amount of timing when the severity is higher while others are more aggressive. This is something to discuss with your tuner. Once you get familiar with what you’re seeing in datalogs you will know what is and isn’t normal. It is also important to choose a tuner that is experienced with the ECU and how it adjusts timing to get the most from this feature without risking the safety of the motor.
In terms of knock counts – remember that when it’s not knocking the ECU is adding timing until it knocks until it reaches the tuner-set ceiling for amount of timing added. Because of this, you are likely to get some knock counts during a pull if the tune is built to maximize performance.
The idea is for the tune to be setup such that knock event intensity is low and that the tune adds timing in a way that doesn’t cause a lot of sudden knock. It’s normal to see the ECU add a little timing and taking some away. What you don’t want to see is very large and continuous negative ignition corrections.
Let me give you an example. Below are the knock counts on a 4th gear pull for cylinders 1-4. This tells you that some knock has happened during the pull but it doesn’t tell you anything about how severe/intense it was. This is incomplete information.
To complete the information here are the cylinder ignition corrections for the same pull. As you can see, the most severe correction was around 1* on cylinder 1 and right away that cylinder added more timing and didn’t knock again. You can also see that each cylinder walks ignition up a little, then steps down when it reaches knock. Finally, you can see all the cylinders are well balanced – there isn’t one cylinder that is significantly better or worse than another one. This big turbo Focus ST is running well and it is fine tuned for its modifications and fuel.
Also note that there will be differences from pull to pull and this is again normal. Always take a couple of pulls to make sure the data is consistent.
Here is a tune that needs attention or the car is using poor quality fuel. You can see that all the cylinders move into the negative ignition correction zone and some with larger steps meaning that the ECU is picking up knock and lowering timing. You can also see that they are not recovering like the graph above. This car does not instantly blow up. Far from it. However if you see consistent data that looks like this, either higher octane fuel is needed or the tune should be adjusted.
Happy Tuning,
The Stratified Team
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