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!

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

A question we get asked a lot in the Ecoboost community is: Are throttle closures at WOT bad? Well, let’s delve a little deeper and see what throttle closures really mean. We’ll first need to dive into a little bit of background knowledge on how the Ecoboost throttle is controlled.

The first important thing to grasp is the concept of Load. Load as defined by Ford is a representation of how much air is filling the cylinder per intake event compared to an ideal amount of air that would fill it at 100*F air temperature and 200*F engine coolant temperature. A load of 1.0 represents that the cylinder has filled with this ideal amount (or in Ford terms “standard”) of air. A load of 2.0 would thus represent twice that amount of air. Another way to think of load is that it represents engine torque output.

By controlling load, we control the amount of air in the cylinder, which directly controls how much fuel we need (for a set AFR), and ultimately the torque the engine produces.

The ECU takes a torque request from the accelerator pedal, applies torque, fueling, and over-temperature limits to it, and ultimately converts that final torque request into a load. These limits can be vital to engine safety and thus the ECU is keen to sticking to its desired loads. This Desired Load is then further converted into a desired air mass.

This air mass then gets worked backwards through a volumetric efficiency model to FINALLY give us a desired manifold absolute pressure (MAP). This pressure can be below atmospheric (vacuum) or above (boost).

So, we have a desired MAP, but most of us know that Ecoboosts have at least two sensors in the intake tract that measure pressure, one in the manifold (measuring MAP), and one pre-throttle (known as the Throttle Inlet Pressure or TIP sensor).

Theoretically, if the throttle wasn’t a restriction, MAP and TIP should be equal at steady state, but with a throttle in the way, even fully open, there’s a slight pressure drop across the throttle. To solve this issue, Ford actually sets a desired TIP value that is slightly above desired MAP. That way if they try to reach a set TIP pressure, they will simultaneously hit their Desired pressure target.

The throttle plate is opened and closed electronically so that whatever TIP you currently have can be adjusted to your desired MAP. At part throttle, TIP is typically atmospheric since there is no vacuum before the throttle plate, so the throttle remains mostly closed to keep your MAP low. At WOT, you will mainly see a throttle plate that is wide open (about 82% on a COBB AP datalog). The throttle plate moves to make sure we hit our desired pressures and loads/torque as set by the calibration/tune. But wait, there is more!

On turbocharged vehicles under high loads the turbocharger is used to pressurize the intake tract to achieve the desired torque we were shooting for. The turbocharger speed and air delivery is controlled by the wastegate, which also receives its inputs from Desired TIP and Desired Airflow. If the throttle is held wide open, it is only up to the wastegate to control how much pressure and airflow we have under boost.

So why then, would we ever want to see a throttle closure at WOT? Typically if you see throttle plate closures under WOT it means your TIP Actual / Airflow Actual ended up higher than what the ECU is asking for. Thus the ECU has to close the throttle to prevent the manifold from getting too much air. As mentioned previously, we may be limiting this for safety, to make sure we have enough fuel, or maybe we even had a component failure (like a wastegate line popping off!) and need the throttle to shut to save us from a costly mistake.

But, that’s not the only case – there is actually a performance benefit to closing the throttle at times and controlling airflow via BOTH the wastegate and throttle. A turbocharger is a mechanical machine that does NOT have instantaneous response. It has an inertia and it takes time to get it to spin up and start compressing air. One of the big things you see discussed is turbo lag or how long it takes to spool. Because we have both the wastegate AND the throttle controlling airflow, we could theoretically pre-spool the turbo a little more than we need at the moment, and use the throttle as a restriction to hold back that extra pressure from the manifold. This has the effect of moving us straight up on a compressor map. We have higher pressure, but the same airflow. The net result is that when we now request the power, we’ve already built up some turbocharger rotational energy and don’t need to spend time building it up! That means a faster response when stepping and requesting that oh-so-sweet turbo induced torque!

Cut that turbo off! We don’t want more load than we can handle!

This tuning strategy however should not be abused. Keeping the wastegate shut increases pre-turbine pressure, decreases volumetric efficiency, and hurts your fuel economy, so we don’t always want to keep it shut. Like wise, pre-spooling the turbo too much can cause compressor surge. To address this, the ECU controls TIP separate of MAP, which sets a boundary of how much higher we want TIP to be over MAP. As well, the surge line is stored in the ECU and if TIP rises beyond that point, the electronic bypass valve (BPV) can intervene preventing surge. Using this,we can set TIP targets higher in conditions we expect to need acceleration, maximizing performance. This can be a big benefit especially on a road course where you may be part throttle around a sweeper, and once you’re lined up on the straight you can gun it and have a head start on the other cars that take a little longer to spool because they weren’t pre-spooled. However if you see throttle staying consistently at 20-30% for the entire pull, you’re likely dealing with a mechanical or tune issue.

In summary using the throttle smartly when tuning can result in the fastest possible boost response during transient throttle applications while also making sure that boost stays on target. With proper tuning of the system, the wastegate and throttle both allow you to create fast spooling yet smooth and controlled boost. This can be seen on the dyno (or VDyno if you have a clean one without wheelspin!), with nice smooth torque curves lacking any overshoot typical of a poor implementation of mixing throttle and wastegate.

Net result of throttle and wastegate combined: Nice flat torque without overshoot.

So now hopefully it’s clear that having throttle closures isn’t necessarily bad. Quite the opposite – relying on just keeping the throttle open the whole time and using the wastegate only is a step backwards and leaves performance on the table.

Just a little recap on our Fiesta ST. We have tuned it on 91 octane with a COBB intake and no other engine performance modifications. It made very nice power and the little car is just tonnes of fun to drive! Now it was time to see what E85 will do and that meant strapping it on the dyno. 

A little run-down on E85. E85 has a high resistance to knock (high octane) and we love this about it because it allows us to push both boost and timing higher without reaching the dreaded knock threshold and thus make more power with no other hardware changes other than an E85 specific tune. The Fiesta ST uses a high pressure fuel system since it is direct injected and while E85 adds octane, it also takes away fuelling headroom. We were able to watch knock response as well as all fuel pressures using the COBB Accessport.

To run full E85 the fuel system would need to flow 30% more fuel and the high pressure fuel pump would have a hard time keeping up. Because of this we chose to run an E85 blend. That means we mixed 3 gallons of E85 and topped off with 91 octane. The effective mix is around E30 and it adds enough octane such that we can reach MBT (meant best torque) on the stock turbo. What that means is that we were able to advance timing until no additional power was being made and the engine remained knock free.

So this trip to the dyno served several purposes. First, it allowed us to search for and find MBT on the Ecoboost 1.6l in the Fiesta ST. Secondly, it helped verify that the E30 mix offered enough octane to reach MBT on the stock turbo while not depleting the OEM high pressure or low pressure fuel pumps. Finally, it allowed us to build our Stratified E85 Flash Tunes and also verify that by switching to an E30 blend and tune, you will gain approximately 15whp and 15wtq with no other hardware changes. 

On such a light car, those power gains can definitely be felt and add to the enjoyment of an already fun car!

The Fiesta ST (FiST) is an excellent handling car. Not very often do you have front wheel drive (FWD) cars handle as well as the Focus and Fiesta STs. There are several things that make the Fiesta stand out in spite of it having quite a conventional and simple suspension layout (with a solid rear axle!).

One of the advantages the FiST has over the competition is its light weight. There is little that can make as much of a difference as shedding weight. The reason for this is that changes in direction (changes in momentum) require a lot less energy. This in turn translates in less energy lost between the tire contact patch and pavement, less energy lost in compressing the suspension, flexing the chassis, etc. The second great thing about the FiST is the way the suspension was setup from the factory. It is a stiff suspension for a production car; but this is what us enthusiasts crave. Finally, let’s not discount Ford’s torque vectoring. This little trick allows the chassis ECU to independently apply the brakes to any wheel in order to make the car rotate and apply power more effectively in corners. This is something used in the Focus ST and RS as well. All of this adds up to a car that is very happy to handle the turns and that means fast lap times!

Is there a way to improve on this already great recipe? With some careful planning there is! What you want to avoid is to take away some of the rotation happy characteristics of the car. That means that I recommend leaving the sway bars alone initially; especially on a car this light. Instead focus on grip (tires, alignment) damping (shocks) spring rate (springs), and brakes.

Coming to the shocks and springs discussion; I always recommend upgrading to something with the best shocks. Springs are simple compared to the shocks and the ride quality as well as handling bumps and corners almost always comes down to the shocks. A personal favourite is Bilstein for me. They have a reputation for making great shocks and whether you get a B8 shock + spring combo or one of their coilovers you’re in for a treat both on the street and track. We recently installed a set of B14 Coilovers on our 2015 Fiesta ST and they have been great. We have these same coilovers on our 2014 Focus ST as well. Very affordable combined with great performance makes the B14 a go-to option when upgrading the suspension. From our experience – here are a few install tips for the Fiesta ST:

• Purchase the top hats (PN C1BZ3A197D), front strut bearings (PN 8V5Z18198A), and dust boots (PN 8V5Z18A047A) (these act as a spring insulator as well) from the dealer before embarking on the job. You will need two of each. They are affordable, make the assembly of the front suspension a breeze without needing a spring compressor, and they are wear items that should be replaced when upgrading the suspension. 
• When installing the front suspension, push the front strut assembly at the strut tower towards the inside of the car before tightening it down. This will give you the most camber you can get without camber plates. Camber is a good thing.
• When installing the rear shocks, before bolting them to the chassis apply some grease to the top of the bushing (you will reuse the OEM one) and clean the chassis and mounts. If you don’t do this you will hear squeaking from the rear suspension when driving.
• When setting up the ride height, allow the car to have a bit of rake and don’t “slam” it for best performance. You want to look at the front control arms and allow them to be relatively flat with the pavement. 
• Get a professional alignment to set the front toe, make sure the steering wheel is straight so you won’t get poor tire wear. 

After this get out there and enjoy the car. The ride will be a little stiffer but should feel compliant and not jarring. You will notice less brake dive and less body roll. The car should have very good turn in and still be very very happy to rotate. We’ve taken the car to autocross with just this suspension change (and our COBB AP and Tune) and it proved to be one of the fastest cars there … even putting a few expensive German sports car to shame.

It should be mentioned that this Fiesta has a few other modifications installed and these give it more pull out of corners with excellent throttle modulation and control and a nice induction sound.

• COBB Accessport with Stratified Tune
• COBB cold air intake

For tires, there are lots to choose from out there. Because the car is so light you can get away with tires that are a little less extreme than what most use for the same application. The tire wear will also be good, again, because of the light weight. The OEM tires are good and you can work your way up from there. Even for an open track day you can do very well with a set of extreme summer tires such as the Bridgestone RE11/RE71, Dunlop Direzza and others in that category. Those tires would also be great for auto-x as they come up to temperature relatively quickly.

To improve handling further on our particular car, we are looking at tires and brakes next. Engine performance wise, the next steps would be an upgraded intercooler and/or WMI, and some exhaust work. These should maximize the power potential (and sound) of the stock turbo before thinking about upping its size just a bit … Stay Tuned!