How the Knock Detection System Works in the Ecoboost

The Ford Ecoboost knock detection system is one of the more complex systems out there. A lot of the vehicles using the Ecoboost engine are rated to use fuel that ranges in octane from 87 to 93 octane. Because of this, Ford built a system that is very powerful and adaptive. It actually learns your fuel quality while you drive. All the EB engines we work with use this adaptive timing system. This is great for us calibrators as we can build failsafes and adaptability into the tunes – but it has to be setup correctly.

The knock detection system starts with the sensors (microphones) that pick up engine noise and are mounted to the engine block. If the engine noise falls within the correct frequency and window of operation (around the time the spark plug fires), the ECU registers this as knock. When knock is registered, the ECU looks at the Knock Response table pictured below. Based on the intensity of the knock it subtracts timing advance from the Ign. Corr. Cyl X Parameter (which you can view and datalog) on a per cylinder basis. On each knock events it also increments the Knock Count Cyl X parameter which can also be viewed. Both of these parameters are reset to 0 once you let off the throttle, shift gears, or experience a throttle closure.

Keep in mind that the following ECU tables shown have OEM values. We adjust these to better suit our performance criteria, but the principles remain the same.

ignition-reduction-table

The amount of timing being pulled for each knock intensity and engine speed is completely under the control of the tuner who builds the tune. You want to make sure that you pull enough timing per knock event to maintain engine safety and stop the knocking. Here’s how this looks in a graphed datalog of a single cylinder during a pull.

ecoboost-knock-count-and-ignition-correction

These negative ignition values are always subtracted from the current Ign Corr. Cyl X variable for each cylinder. This is important to understand because the Ign Corr. Cyl X variable also ADDS timing when the system does not “hear” any knock and you are on the throttle.

The rate at which timing is added and how much total timing is being added is also adjustable in the tune. Ideally the tune should walk timing up at a reasonable rate that is not so fast such that knock is induced and not too slow such that performance is left on the table.

One thing that has to be understood is that all engines will knock at some point regardless of tune and fuel used. The combustion process is a chaotic process and sometimes you get some irregularities. This is inevitable. You want to tune out heavy and sustained knocking, but completely eliminating all knock is not something that is realistic – especially in a street engine. Handling knock correctly is the key. Light knock will NOT damage an engine especially if timing is reduced via a reduction in Ignition Corrections when it happens. LSPI (Super Knock) and bouncing off a Rev Limiter have a MUCH more damaging effect on the pistons and rods.

The beauty behind this knock control system that both adds and subtracts timing is that it also LEARNS the quality of your fuel over time. The learning variable is called OAR (Octane Adjust Ratio). This variable is like a fuel trim but used for ignition and load/boost targets. It can range from -1 to 1. Below is the table that allows the ECU to learn and adjust OAR. You can see from this table that in order for this system to work, ignition timing and the Knock Response table must be set such that the ECU can ADD and SUBTRACT enough timing to make the Ign. Corr. Cyl X parameters positive as well as negative during a pull. With an adaptable tune you are likely to see Ign. Correction numbers that are both positive and negative at times.

how-oar-learning-works-ecoboost

Finally, this OAR number is not just another pretty face. It affects the timing AND load/boost tables the car will be targeting. An OAR that is closer to 1 will remove both timing and boost reducing future knocking. An OAR closer to -1 will add timing and boost due to good quality fuel and increase performance. It is normal for OAR to fluctuate slightly depending on your fuel quality and driving conditions (5th gear pulls are more likely to knock compared to 3rd gear pulls and OAR will adjust to reflect this). Below is the timing table that is multiplied by OAR in the OEM calibration and added to the overall ignition timing the ECU runs. In this case an OAR of -1 will add 4* timing and an OAR of 1 will remove 4* of timing near redline. OAR dependent boost/load limits are setup via a blend of several tables not shown here.

oar-multiplication-table-ford-ecoboost

It should be clear now that NEVER seeing any negative corrections is an indication of a tune not setup to use this learning system to its full potential. This is not ideal on a street driven car as it means that it will not adapt to keep the engine safe when fuel quality or driving conditions change nor will it extract more performance when the situation allows. 

Keep in mind that these knock detection systems are extremely fast to react. If knock is detected, if setup correctly, the system will very quickly pull timing to stop the knocking during that pull and adjust the tune for future pulls. Excessive repeatable knock or only positive ignition corrections are something that should be addressed in the tune – and can only be done by the person that has set the tune up. More on knock in this article. 

Now let’s have a look at a set of logs see this in action across four cylinders.

Here’s a normal 3rd gear pull with all 4 cylinder Ign Corrections and Knock Counts graphed. As you can see, ignition timing walks up when there is no knock in a step-wise fashion. When there is knock it drops down stopping further knock. If the knock events happened earlier in the pull or were of a higher intensity, Ign Correction could have become negative.

ecoboost-knock-count-and-ignition-correction-2

Here is how we can setup the same knock detection system in a less ideal manner. At first glance, it looks like this engine is basically not knocking at all. However if you look carefully, you can see that there were 4 knock events. The amount of timing pulled for each event is very little. This does two things. One, not enough timing is being pulled to stop the occurrence of further knock. Secondly, pulling so little timing will mean Ign Correction values will not be negative even though the engine could be knocking heavily and continuously. This in turn will mean the OAR will not adjust and the tune will not adapt to the fuel quality used.

ecoboost-poor-knock-handling

For this reason, watching Min/Max Ign Correction on the AP can be very misleading. Not only does it not show you how many times the engine knocked, it also doesn’t show you how intense the knock was. To determine the performance of the tune, a full datalog is always necessary or at least a good understanding of HOW the tune handles knock events. 

Happy Tuning,

The Stratified Team

Misfires and the Ecoboost, when should you worry?

I’ve seen a number of recent inquiries regarding the misfire count on Ford Ecoboost cars and I wanted to explain a little bit more about what it means, how the ECU determines when the car misfires, and when you should worry about it.

What are Misfire Counts?

First of all, the Misfire Count as a live parameter or datalogged represents the number of misfires detected by the ECU since the last engine start. ecoboost-misfire-count

In the case shown above, the COBB Accessport monitor shows that there have been a total of 8 misfires since the engine has been running WITH THE COBB AP turned on.

 What is a Misfire?

Combustion is a complex process. The power generated by an engine comes from the “power” stroke of the 4 stroke cycle. The power stroke is where the spark plug lights the air-fuel mixture inside the cylinder and you get a propagating flame front that evenly pushes the piston down. This is of course the ideal scenario. However sometimes, for a variety of reasons discussed below, the spark plug does not effectively ignite the mixture inside the cylinder. This causes what is known as a misfire. For that one cylinder, power is either low or not made at all during that one cycle and you will feel it as a short hiccup in what is otherwise smooth engine running and power delivery.

How is a Misfire Detected by the ECU?

Modern cars have a high resolution crank position sensor and multi toothed wheels. This is attached to the crank where the accessory pulley is and looks like this.

ecoboost-crank-wheel

The ECU knows when the spark plug fires for each cylinder with respect to the position of the crank wheel and expects the engine to be accelerated during the power stroke. If the crank teeth are not accelerated during the power stroke (you can also feel this sitting in the car) it will determine that the particular cylinder has misfired.

Why does a Misfire Happen?

The engine needs a few elements for good combustion. These are air, the correct amount of fuel, effective mixing between the air and the fuel in the combustion chamber, a strong enough spark, and good compression.

During NORMAL and HEALTHY engine operation misfires do happen but they are random and intermittent. For example, the Ecoboost engine tends to misfires at idle. This is because sometimes the air and fuel do not effectively mix and light off. This is a common issue with direct injection engines where the fuel and air are injected directly in the cylinder with poorer mixing characteristics. Engine designers and engineers get around this in multiple ways – sometimes with tumble flaps that increase air velocity (which the Ford does not have) – and through extensive internal combustion chamber and injection designs. These random idle misfires are undesirable for smooth running and emissions; however they do still happen even in healthy engines. The Misfire Count will pick these up and increment but a Check Engine Light (CEL) will not necessarily be triggered.

Another common reason for misfire is spark plug gap. This happens at high load under wide open throttle operation. A gap that is too large may prevent the plug from lighting when there is a dense mixture in the chamber under boost. We recommend a 0.026 inch spark plug gap to avoid these. You can feel these as small intermittent losses of power at wide open throttle but they are a simple fix.Spark Plug Gap

Other failures of the ignition, injection, or air induction system can cause misfires (including carbon buildup) but the above two causes are the most common in healthy engines.

If there is internal damage to the engine such as a damaged ringland and associated loss of compression this can trigger a continuous misfire for that cylinder. The misfire count will increment much faster and eventually it will trigger a check engine light. This constant misfire is something you will FEEL and HEAR with the car at idle and it will be outside of the norm. A quick compression test will verify the internal health of the engine so there is no guesswork in this diagnosis.

Ecoboost Compression Test

When are the Misfires Codes (P0300, P030X for each cylinder) Triggered

The OEM ECU has a complex mechanism for determining when a misfire is part of normal operation, or when it means there is something that needs to be addressed. When it determines that something needs to be addressed; it will illuminate the Check Engine Light (CEL) and usually indicate which cylinder the issue occurred in (P0301 indicates cylinder 1, P0302 indicates cylinder 2, and so on).

There are two programs built into the ECU for determining two different types of failures. We will call these Type A and Type B.

Type A detects a failure that has recently happened or is sudden in nature (failed coil pack for example). This detects failures over a period of 200 revolutions. If the engine misfires in excess of 23% of the time (46 misfires per 200 engine revolutions) at low RPM or in excess of 5% at high RPM it will trigger the fault code under this condition.

Type B detects a condition that is progressing over time. This has a detection period of 1000 engine revolutions. For example in the Focus RS it triggers if 1.2% of revolutions  result in misfires (12 misfires per 1000 engine revolutions). This is designed to catch progressing conditions such as worn spark plugs.

For the sake of simplicity, assume that your car is idling at 1000RPM. This means that for you to have enough misfires to indicate an out of tolerance condition, you will need to have at least 12 misfires during 1 minute of running at idle.

When should you worry and what should you do?

check-engine-light-ecoboost

Because the ECU is keeping track of the misfires, you don’t need to! When a fault code is triggered for a misfire, this is when you want to investigate and look for an issue. Otherwise, keep spark plugs fresh and gapped correctly and keep in mind that misfires can and do happen on perfectly healthy engines!

The Stratified Team

So you got a bad tank of gas … now what?

It happens. You are travelling, you don’t use your regular gas station, they change the fuel quality in your area. So now you are stuck with a bad tank of gas (and what I mean by this is fuel with lower actual octane than what you usually use) in your pride and joy and your heart sinks at the thought. Here’s what that looks like, means, and how to address it.

First of all, keep in mind that your car has modern reactive knock sensors and these will pick up the knock from the poorer gas and pull back timing to keep the engine safe. This applies to all modern vehicle platforms. On an Ecoboost for example, the car will LEARN the fuel octane you are using. The OAR (octane adjust ratio) parameter is used to do this. It will adjust closer to positive 1 and timing will be pulled preemptively from the tune to prevent the knock from occurring.

The engine won’t all of a sudden explode because of knock from a bad tank of gas if the tune is setup to make use of these safety features. It is not ideal, and if the fuel quality in your area has permanently changed you should have the tune adjusted. However, this NON-LSPI poor fuel quality knock can be handled quite well by the knock sensors to ensure engine safety.

Keeping an eye on your datalogs and live monitors will tell you if something is out of the norm. Here’s how our 3rd gear pull corrections look like with a bad tank of gas.

focus-rs-bad-gas-knockYou can see that the timing additions in this 3rd gear pull stop after adding about 1.5* and then drop due to knock ending up in the -2.5* region.

Here’s how our usual “good gas” behaves. These pulls are taken on the same road, same modifications, and same temperatures but with better fuel.

focus-rs-bad-good-gas-no-knock

Notice that there are much fewer “drops” as the ECU is adding timing during the pull. Most cylinders are adding 1.5-2* near the end of the pull instead of pulling -2.5*.

Aside from the engine safety concern, this loss of timing advance does hurt performance. How much? In the case of our Focus RS the timing difference is worth a solid 16whp and 10 ftlb of torque. A ballpark figure is that 1* of timing accounts for around 3whp on the Ecoboost 2.0 and 2.3 engines.

focus-rs-gas-quality-comparison-pull-stratified

So what can be done if you run into bad gas? Here are some tips:

  • Wait it out if you know it’s a poor tank. Unless the gas is VERY bad the car will rely on its sensors to adjust timing dynamically. If you are seeing consistent corrections take it a bit easier until the tank runs out.
  • Run a low boost map – we include this with all of our tunes.
  • Add some octane booster to the tank. A bottle of the over the counter stuff will make a 2-4* timing advance difference. More expensive Race Gas or Boostane brands will have a bigger impact but they can’t be found everywhere.
  • Add 1-2 gallons of E85 to the tank and top up with premium. Adding a splash of E85 increase the octane enough to ride a bad tank out and does not require a tune change.
  • If you are consistently seeing “bad gas” in your area, consider having the tune adjusted.

Understanding your PCV system, upgrades, and catch cans

Upgrading the PCV system on turbocharged cars is common among the enthusiast community. This has historical roots with older vehicles that had sub-par PCV systems and looser piston sealing tolerances that NEEDED modification to vent effectively. Modern cars have much better designed systems that actually include catch cans (catch and release actually) right from the factory. More on this later.

First of all we have to know what we’re working with. This means delving into what the PCV system is and what it does. The PCV system serves 2 purposes:

1. It maintains a low crankcase pressure. Every piston engine will have some level of blowby which is caused by combustion gasses that move past the piston rings during the power stroke due to the high in-cylinder pressure. The looser the tolerances on the motor, the more of these gases will escape below the pistons. If you don’t vent them from the crankcase they can cause issues such as a decrease in power and will push oil out of the crankcase. This can mean dipsticks popping out, seals leaking oil, and turbos smoking from the oil drain being backed up and not draining. We often seen turbo seals misdiagnosed due to the poor crankcase ventilation.

2. Excessive crankcase pressure used to be vented directly to the atmosphere. However this does pollute and now it is being recirculated back into the intake tract. While this does bring some oil into the intake tract, pulling it back in HELPS in reducing crankcase pressure which is a good thing for performance.

On turbocharged cars you need to vent crankcase pressure under 2 distinct conditions: boost as well as under vacuum. This is why you will see 2 PCV pathways on modern turbo cars.

1.The vent under vacuum. The image below shows what it looks like on an Ecoboost or Mazda DISI engine but all manufacturers have a similar version of this idea. It is made of an air to oil separator (an OEM catch can), a valve that closes under boost, and a hose directly to the manifold. This side of the PCV system pulls crankcase pressure out when there is vacuum in the intake manifold such as at idle and during cruising. It separates the oil film and gases through the OEM separator, returns the oil to the crankcase and pulls the gases through the manifold. Under boost the PCV valve closes and prevents boost pressure from entering the crankcase so this side of the system does not flow at all under boost.

pcv-crankcase-vent-ecoboost-stratified

ecoboost-oem-air-to-oil-separator

2. The vent under boost. When the PCV valve is closed and the car is under boost as well as to a lesser extent under vacuum when it works together with the first system, this is where crankcase pressure is pulled from. The intake before the turbo has a vacuum effect from the turbo pulling in air through the intake tube and gases are PULLED from the top of the valve cover. The valve cover itself acts as an air to oil separator (a second OEM catch can which is also baffled) and returns the separated oil to the crankcase where it belongs.

pcv-crankcase-vent-under-boost-ecoboost-stratified

pcv-crankcase-vent-valve-cover-ecoboost-stratified

Now, let’s talk about improvements to these systems. Most people try to improve a few things:

1. The PCV system flow. If you have a motor that is pretty loose (a more race oriented built engine with forged internals) you will need to pull more crankcase gases because the engine does not seal as well especially when cold. Combine that with very high boost and you may need to vent more. The RS motor for example has larger PCV openings versus the ST motor in the Fords. In order to improve flow, you need to add more passages or enlarge air passages. However keep in mind that the OEM PCV system is well designed for the OEM motor. If you are getting a lot of blowby with the OEM motor, you probably need to address why there is so much blowby from the pistons rather than a better flowing PCV system. Also keep in mind that any obstruction you add to the PCV system (ie extra catch cans) can impede flow and therefore can cause issues such as higher oil consumption, leaking, and smoking turbos.

2. Keeping oil out of the manifold/engine. This is a big one for DI (direct injection) cars and turbo cars in general as oil coats the intake valves and can cause knock if a lot of it enters the air stream. This is the intent when installing ADDITIONAL oil to air separators such as catch cans. The additional catch can DOES help in the separation BUT the effectiveness is difficult to measure. It can look like they are doing a lot when emptied but the fluid pulled out is in large part condensation that is a normal occurrence as motors come up to temperature after a cold start. Below are some of our observations regarding installing additional air to oil separators on top of the OEM ones already there.

catch-cans

A. They do not stop carbon buildup on the back of valves in DI (direct injected cars). We have seen this time and time again and this is because some oil film still makes its way past the catch cans just like it does past the OEM catch cans. Further, flow reversion during engine operation still brings in oil over the valves. The most effective methods at preventing carbon buildup are: 1. Using high quality oils (some are being designed for DI operation specifically), 2. changing the oil often, 3. driving the cars hard to maintain high valve temperatures (yes having fun!) 4. and if possible running secondary injection across the intake valves which washes them clean and which more and more OEMs are starting to use.

B. They can cause PCV flow issues and should be monitored. If they overflow or freeze during the winter (which they do; remember the content of these is mostly water) they can block the system altogether. Similar issue if the fittings leak.

C. The most common location people install them is on the manifold to crankcase connection. This connection is not flowing any gases while the car is under boost. Remember there are 2 PCV systems.

D. They will not solve mechanical issues such as smoking turbos, excessive oil consumption, etc.; they can exacerbate these issues. Make sure you fully investigate the root causes of such issues.

The options to eliminate oil completely from the intake have their caveats. One is to vent the gases to the atmosphere which we don’t recommend. This is not as effective flow wise because there is no vacuum draw from the turbo or manifold and to top it off these gases smell and get pulled into the cabin air vents. Another option is to use the exhaust system to pull gases out using a venturi. This does require a good amount of customization to the exhaust system. Finally, you can have a separate pump to pull crankcase pressure out which is a bit extreme for a street driven vehicle.

Overall, it is important to understand that the flow of the OEM PCV system in a modern car is well matched to the OEM motor. Excessive crankcase pressure means something is mechanically wrong – either a blocked PCV system or excessive cylinder leakage that should be addressed. On a looser race built engine, increasing that flow means adding additional pathways for crankcase venting as well as different air to oil separators to match the new system. This means an overhaul of the OEM system altogether with bigger or multiple tubes and new separators/catch cans. 

Hope this sheds some light on the the PCV system in your car. Happy Tuning!

The Stratified Team

Is your Ecoboost Tune on point? Here’s what to look for

We’ve had the opportunity to tune thousands of Ecoboost vehicles over the years and have developed a thorough understanding of the ECU and how it controls the engine. We also analyze A LOT of data from cars all over the world in all kinds of different configurations. Data analysis is a very important part of tuning the vehicle and making sure it is behaving and driving optimally.

As we refine and dial in the tunes, there are some key characteristics in the collected datalogs that indicate that the tune is well adjusted to the vehicle. In this article we go over tuning parameters you can check yourself by analyzing the logs from your own car.

The example vehicle used in this case is a Focus RS with an upgraded FMIC and catback and running 93 octane fuel. These key elements discussed in this article however apply to any Ecoboost powered car.

First things first – you have to valid data. Here are the parameters that we recommend datalogging for this exercise using your COBB Accessport (and here is how you set these up):

focus-rs-st-datalog-parameters-cobb-accessport

After you’ve setup your Accessport to datalog the correct parameters, it’s time to take some datalogs. There are two types of logs that we like to see because they highlight different aspects of how the engine is responding.

The first is a single, full gear pull. This can be done in 3rd or 4th gear. 4th gear will load the engine more and we prefer seeing this data ONLY if safe or possible. Press the logging button on the AP and wait for the numbers to start updating again on the screen. After this punch the throttle to the floor at 2500RPM and hold it there until the tach needle reaches the indicated redline.

The second type of pull is a multi gear pull. This is a demanding pull and it stress tests the tune and how it responds to fast changes. Good tunes behave predictably as you go through the gears. Here you start in 2nd and finish in 3rd (or 4th if safe). You once again punch the throttle and quick shift into the next gear near redline. No need to FFS, a fast shift is enough.

After the data is collected using a graphic software of your choice (Excel, Open Office, etc) to visually represent the data. Let’s start with the single gear pull.

FUEL  

Correct fueling is essential for performance and reliability. These cars come with full time closed loop wideband control. That means that the ECU will try and achieve the fuel targets in the tune at all times using the OEM wideband sensor.

How much fuel to inject is primarily calculated based on the manifold pressure sensor (MAP) as there is no MAF sensor on these vehicles. Deviations from safe fuel targets means that either the tune is not dialed in, fuel system can’t supply the needed fuel, or the wideband sensor is not working properly. The charts below show you what to look for in a single gear pull datalog.focus-rs-st-fuel-pressuresfocus-rs-st-air-fuel-ratios

BOOST CONTROL

A turbocharged car with poor boost control is both unpleasant and unpredictable to drive as well as unsafe for the engine. The Ecoboost controls torque and boost control via the wastegate and throttle. The wastegate is used to spool the turbo and adjust the turbo speed and boost level in the charge air system. The throttle is used to finely adjust and trim boost without having to slow down the turbo. This makes for a very responsive system when dialed in correctly.

focus-rs-st-boost-control

KNOCK CONTROL

The Ecoboost has a very responsive knock control system. It listens for knock at all times and reduces timing when it picks up knock-like noise. At WOT, it will add timing until it reaches the knock limit and also LEARN the octane quality via the OAR parameter. This is a very powerful system and if tuned well can exploit the full performance of the vehicle on the fuel it is using while keeping the engine safe from excessive knock. More about knock here.focus-rs-st-knock-control

PUTTING IT ALL TOGETHER – THE MULTI GEAR PULL

Stress testing a tune is very important. This will tell you whether the tune is setup to take on daily driving tasks as well as track conditions. We don’t drive our cars in steady state WOT, we drive them in transient conditions (coming on and off the throttle at different RPMs all the time). Single gear pulls/sweeps don’t expose these areas and they are easy to miss especially if the tune is only done on a dyno.

If there are weaknesses in the tune you are likely to find them in a multi gear pull. Here’s what to look for in a multi gear pull above and beyond the single gear behavior found above.
focus-rs-st-multi-gear-pull
Feel free to contact us with any questions, and enjoy data analysis and making sure your tune is on point!

The Stratified Team