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.


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.


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.



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.



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.


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):


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.


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


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.



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


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.
Feel free to contact us with any questions, and enjoy data analysis and making sure your tune is on point!

The Stratified Team

Focus RS Turboback Exhaust Results

With turbocharged cars, there are a few proven recipes to making power. One such recipe is to free up the exhaust. This does 2 things: It reduces pumping losses from the engine and it reduces the post-turbo exhaust pressure. This improves the turbine efficiency giving it the ability to spin the turbo faster and make more boost, faster. That means more power and a faster spool.

Back in the day, the engine controls and ECU were not fast or advanced enough to adapt to hardware changes made to the engine such as upgrading the exhaust. This combined with very restrictive emissions components (catalytic converters) and small diameter piping meant that throwing on a turboback exhaust resulted in big changes in boost pressures as well as power levels. Often, the turbos experienced boost creep and uncontrollable boost that led to cars running lean and damaging motors.

With modern cars things have changed quite a bit. First of all, the engine controls are a lot more sophisticated and faster acting. Boost and torque levels as well as fueling are monitored and targeted very closely by the ECU and tune. The exhaust systems are much better these days as well. Ford was able to extract 350hp from a 2.3 litre engine in factory trim and that means the exhaust system is a far cry from what was found on the turbo cars of the 1990s.

In order to extract performance from a modern turbo car you absolutely have to address the tune first and foremost. Without adjusting the ECU tune to enable the higher performance, adding flow hardware will have minimal effects on performance. Once the tune is on point, in a relentless pursuit for more horsepower we looked to the aftermarket to see what can be done with the exhaust system on the car.

The Focus RS has a single catalytic converter in the downpipe right after the turbo followed by a catback exhaust that is free flowing enough to add a nice burble with pops and bangs for good measure. The stock system diameter is 2.75″ which is an adequate diameter for stock power levels. 
focus-rs-exhaust-oemWe started with a car that is bone stock and developed a Stratified tune built for 93 octane fuel. The tune maximizes what can be done on the stock hardware with the local 93 fuel. The vehicle was loaded on the dyno by our friends at Custom Performance Engineering with just the tune for a baseline. Below are the results on a Mustang dynamometer comparing stock (red), COBB OTS tune (green), and the Stratified custom tune (blue). It should be noted that this dyno is setup to mimic the acceleration of the car on the actual road very well. The airflow over the charge air cooler is not quite what we would see on the street but the car is loaded correctly to mimic a 4th gear run on the road. Because of this we were able to use data collected via the COBB Accessport very accurately.


Once the baseline was established, the first part added to the car is a beautifully built full 3″ exhaust system made by the good people at Custom Performance Engineering. The car was loaded on the dyno for another set of runs. We used data from the Accessport collected on the dyno and the Virtual Dyno software for the next comparison.


In this case, while maintaining the same torque targets in the tune the car made an additional ~20whp, ~18wtq. Analyzing the acceleration data further, you can see how with a catback exhaust the car gets to redline around 0.6 seconds quicker.


The torque targets, timing, charge air temperatures, and fueling were the same between these runs. However fuel trims tell us a little bit more about what is going on. They indicated that the ECU had to add 1-2% more fuel to achieve the same air fuel ratios with the catback versus the bone stock car. This means the catback actually improved the volumetric efficiency of the engine. This means more air was entering the cylinders and producing more power. This, along with a drop in pumping losses accounts for the performance gains. We were pleasantly surprised to see this much of a difference from the catback exhaust but it was consistent across multiple runs.

The next part installed was an off-road catless downpipe replacing the OEM catalytic converter and downpipe. Again, keeping the same tune, multiple runs were made with the car and we found negligible differences in performance versus the stock downpipe with the aftermarket catback.


In this case from the exhaust standpoint we seemed to have reached the point of diminishing returns from a flow and pumping loss standpoint. Good job Ford on a well flowing downpipe! But wait … there is more to this. On closer analysis of the data, it’s evident that the wastegate is telling us of some gains achieved from the downpipe. The average wastegate duty cycle after the downpipe install during the entire run was 10% lower than with just a catback. You can visually see this difference especially near the end of the run.focus-rs-turboback-exhaust-wastegate-and-boost-stratified

This means that there is a larger pressure differential across the turbine. This in turn means that should we want to, we CAN run more boost, especially in the top end and make more power. The ECU is controlling the wastegate very precisely to hit the targets in the tune, but we can then adjust the tune for more boost.

So why didn’t we? The reason is because we are at the knock limit of this fuel especially given the OEM intercooler still being installed. Running more boost would only result in knock, an unhappy engine, and no power gained. We will be back for more with a larger intercooler and higher octane fuel.

So what have we learned here? We’ve seen that a catback exhaust results in a power gain from a volumetric efficiency and pumping loss decrease standpoint. We’ve also seen that while a downpipe did not result in more power, it does enable us to run more boost if the charge air cooling and fuel octane support it. In other words it enables more power with more supporting modifications.

Finally, we learned how precisely the ECU controls the engine in this vehicle and how important it is to have the tune on point in order to extract additional performance from your RS.

Thank you to the team at Custom Performance Engineering for the excellent data collection and quality parts!

Detecting WMI failure using fuel trims

Turbochargers like high octane and a cold intake charge. Using a water-methanol injection system (WMI) to fulfill that need is effective in terms of results as well as costs (especially if high octane fuel like E85 is not readily available). These injection systems were used in aircraft before World War II and more recently even BMW implemented a system in their M4 GTS. The results speak for themselves – more reliable power!

A Virtual Dyno comparison before and after the WMI system was installed.


The issue with these systems (and any system) is that they can fail, leak, or get clogged. To maintain reliability we need to be able to detect this. There are several ways to go about failure detection. One is to purchase a system with a failsafe while another is to look at temperature differences in the charge air. However some cars (such as the Ecoboost engines) have the charge air temperature sensor BEFORE the injection nozzle (at the intercooler outlet). Unfortunately due to this sensor placement, it will not pick up the difference in temperatures brought on by the WMI spray.

For these vehicles we have another indicator as to whether or not WMI is indeed working. Methanol is combustible. This means that if you inject it, it will affect total fueling entering the engine. The Ecoboost has a sensitive wideband oxygen sensor and it adjusts fueling in real time under wide open throttle (when WMI is also spraying).

This means that you can datalog or monitor your short term fuel trims (STFT) to see if WMI is injecting when it’s supposed to under boost. First you must establish a baseline and check that the system works. Before you turn your WMI system on, take a WOT datalog and make note of your STFTs under boost with WMI off.


In the graph above you will see that the STFT settles between positive +5 to +10%. This means the ECU is detecting that it should inject 5-10% extra fuel to meet the fuel targets in the tune. In similar temperatures and without adjusting boost, turn the WMI system on and take another datalog.


You can see that now at the same boost pressure and with WMI injecting the STFT reading has dropped to -5%. This means that WMI is contributing to around 10-15% of the total fueling on this particular car and setup and the ECU is now taking away 5% of the fuel instead of adding 5-10%. Excellent, now you have verified that the WMI system works and have seen its effects on fuel trims. This is your new baseline for fuel trims with the WMI system working.

If the system were to fail, you will see not just additional knock, but also a shift of the STFTs towards positive territory as that extra fuel is no longer supplied.

Keep in mind that engine part changes, WMI nozzle changes, different temperatures, changes in boost pressure, and fueling system changes overall (including the fuel used) will affect the fuel trims in varying degrees. However if you often monitor your car you will have a good idea where the STFT trims sit under WOT with WMI working. If you see a sudden positive shift in those trims accompanied by knock under steady wide open throttle and boost, you should inspect that your water-methanol system is leak free and still delivering the liquid to the engine.

Keeping things fueled and cool,

The Stratified Team