Diesel Tuner's Blog

Ford EcoBoost Thermal Limits

Posted by Nick Priegnitz on Mar 20, 2020 11:01:43 AM



If you've tuned your Ford Ecoboost with us you're well aware of how much more power and torque is available by simply re-flashing the ECU.  Maybe you've caught the horsepower bug and are curious what else you can do.  In this blog we'll walk through the platform and offer suggestions on future modifications.  The Ecoboost is a very smart platform.  It's well equipped with sensors and built with significant mechanical overhead to hedge long term reliability while towing.   Our performance tunes are geared at taking advantage of that built in overhead so long as the truck is able to stay cool. In other words, as long as you're not pushing the truck hard enough to hit its thermal limits you'll never notice that they exist.  

InkedF150 EcoBoost 2019 on Dyno (1)_LI-1

Thermal limits?  Let me explain why they exist and how they might influence your next round of modifications.  In their essence thermal limits protect the engine from damage caused by excessive heat.  This heat can come in a few ways, which are listed below. There are different vehicle usage scenarios that compromise these systems, your particular operating conditions and environment will determine which you want to address with your next round of mods. 

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  1. Engine Coolant temperature (ECT): Coolant temp is the most traditional means of measuring engine temp.  Coolant temp is usually the last temp threshold to come up as a limit because the cooling system is large and can absorb a lot of energy before entering the danger zone.  This usually only happens on extended pulls, up a grade, towing heavy, in hot environments (worse at altitude with A/C on).  We rarely recommend upgrading the cooling system of the truck. 
  2. Manifold Charge temperature (MCT): Manifold charge temperature is measured in the intake manifold of the EcoBoost.  It's the temperature of the air as it enters the engine.  MCT can have a large effect on the engine's ability to make power.  When the air temperature in the manifold exceeds 100*F the ECU begins to limit the engines ability to make power and by 180*F this limit is significant. The ECU imposes these limits by trimming the throttle body closed.  The reason for this intrusion by the ECU to protect the engine from pre-ignition, which can cause major engine damage.  The ECU refers to the engines tendency toward pre-ignition as combustion stability.  The problem with hot air in the intake is that it cannot be counted on to combust with fuel in a smooth and predictable way which can lead to piston and ring failure among other things (all ugly).  Raptor Snoball-1

The best way to lower MCT aside from only driving the truck in the winter is to upgrade the inter-cooler to a larger unit with more capacity/surface area.  Furthermore the turbochargers can be upgraded if the airflow target (HP target) is above the stock units' ability to deliver air efficiently.  Our suggestion for the inter-cooler upgrade is the AMS kit which includes a large core aluminum front mounted inter-cooler and all needed mounting hardware.  This upgrade will allow the truck to maintain high output on longer pulls without pushing MCT into the danger zone.  It's especially useful in hot environments and on trucks operating at higher altitudes. 

  1. Compressor outlet temperature (COT): This is the measured temperature of the charge air as it leaves the turbocharger but before the inter-cooler.  High compressor outlet temperatures indicate that the turbocharger is operating at high speeds and is likely out of its efficiency range. Compressor efficiency is impacted by the ambient air temperature, negative pressure or vacuum in the intake pipe, and pressure in the discharge pipe (boost pressure).  If the COT exceeds 350*F the ECU will start to attempt to protect the turbocharger by limiting power. It does this by opening the waste-gates and closing the throttle. COT temperature spikes are usually only seen at high load and high RPM but can come on quickly.  

The best way to keep these temperatures in check is to take steps to keep the turbocharger operating efficiently.  Removing intake restrictions by upgrading the intake tubes to higher flowing units such as those from AMS.   

  1. Exhaust gas temperature (EGT): Exhaust gas temperature is defined as the gas temperature in the manifold pre-turbocharger.  Because the ECU knows exhaust gas mass, turbine efficiency, lambda, and ignition timing it's able to use a predictive model to calculate EGT.  This temperature is important because excessive EGT can cause accelerated degradation of exhaust components such as the exhaust turbine, flange hardware, and O2 sensors. Of even higher concern is the impact that high EGT has on the exhaust valve itself.  When the exhaust valve becomes super heated the ECU loses control of combustion stability. This happens when the fuel air charge can be lit off by the exhaust valve instead of the spark plug.  The end result in these circumstances is an engine that's susceptible to pre-ignition.  When these circumstances are detected the ECU will quickly take steps to lower the EGT by closing the throttle and enriching the mixture. 

    Raptor Dirt Drags

The best way to avoid high EGT situations is to use high octane fuel, this allows the ECU to run higher timing numbers which keeps the energy in the combustion chamber and out of the exhaust gas. Ethanol fuel such as E85 is the ideal here, allowing timing numbers closest to optimal.  For this reason we offer tunes designed for trucks using higher ethanol blends (E30-E45%) and even higher (E85) with sufficient fuel system upgrades such as the Deatschwerks pumps, XDI pumps and/or high flow injectors

  1. Catalyst temperature: The catalytic converter on the Ecoboost is designed to work in a temperature window.  When the cat is below temp it cannot effectively do its job and if it's over temperature it can be damaged.  For this reason the ECU jump in after sustained high load scenarios to richen up the mixture or even limit power to protect the catalyst from exceeding its allowed ceiling.  In this instance the prescribed upgrade would the high flow catalyst. 
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The high flow cats do a better job of managing temperatures at high engine loads especially during longer pulls and will keep your available engine power up without the threat of ECU limitation. 


What’s next?

The Ford EcoBoost is great platform to build a high performance truck that can still maintain a high level of reliability.  The key is understanding the basic functions of how the system works and where you can capitalize on upgrading the right parts.  While each build is somewhat unique, knowing the principles of Thermal Limits will help you decide the best course to upgrade your Ford EcoBoost.

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Topics: Ford, SMART, EcoBoost, 3.5L EcoBoost, Raptor