Glossary of terms used in tuning

Anything technical worth keeping around related to EEC Tuning or just general engine tech info.

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Glossary of terms used in tuning

Post by cgrey8 » Sat Aug 02, 2008 5:28 pm

Most people are at least somewhat familiar with the abbreviations used for the various parts on a car like the ACT, ECT, EGR, and MAF. However there are some abbreviations and terms that are specific to tuning that you'll see used heavily throughout the site's threads but are not commonly used or even known about outside of the tuning world. This thread is meant to introduce you to those terms and important info about them. It certainly isn't everything that can be known. But it should get you started. Keep in mind, many of these terms are related to each other so some explanations may use a word that isn't explained until later or is assumed already known prior to reading this. For those that may not be familiar with all the parts of a typical Ford Injected Engine, I've included them as well.

ACT Sensor (aka IAT)
This is the Air Charge Temp sensor or also called the Intake Air Temp sensor. This tells the computer what the temperature of the intake air is. Depending on where the ACT is located will determine how useful this sensor input is. On most 89-93 Mustangs, this sensor is in the #5 runner of the lower intake. It migrated to the upper intake on a few vehicles and then was moved to the rubber intake tube between the airbox and the Throttle Body. On naturally aspirated engines, the ACT is not an extremely useful sensor and in many cases can be easily tuned out and eliminated from the tune. However in boosted applications, the ACT becomes a very important sensor. As boost increases, so does the boosted air temp. The hotter the intake charge into the engine, the more likely the air/fuel mix will be to predetonate. Most people have heard of predetonation referred to as valve knock even though the audible noise associated with predetonation has little to do with valves. Predetonation can most often be controlled via spark advance. Excessive spark advance can cause predetonation. And in a clean engine, retarding the spark will reduce or eliminate predetonation. In carbureted engines, it was also quite common to have heavy carbon buildup in the combustion chambers that would also create predetonation. The sharp edges of the carbon would heat up during the combustion process and stay glowing-hot after the exhaust left and the intake of air and fuel was brought in. When fuel would come in contact with the glowing carbon...predetonation would occur and would do so despite the spark advance.

Adaptive Learning (aka Adaptive Control)
Adaptive Learning is enabled when ACT and ECT are in a certain range (definable in tune). Also Adaptive Learning can only learn when CL is active. But the interesting part about Adaptive Learning is the values learned can be used while in OL. The result of Adaptive Learning is in the KAMRFs and is discussed in more detail in KAMRFs.

Air Fuel Ratio (aka AFR)
Air Fuel Ratio is important to know and maintain in an engine. Different running conditions require different AFRs to run the engine correctly. For 100% gasoline, perfect AFR is 14.64. However while driving at WOT conditions, a much richer (lower value) mix is needed to get max torque and a safely cool burn. Naturally aspirated engines tend to hit max torque around ~12.4 AFR...some higher some lower. However boosted engines generally will get more enrichment, not so much to get additional torque, but to cool the engine's burn. When you shove more air into a cylinder, you increase the heat produced by the subsequent combustion. To keep those combustion temps at manageable levels, additional fuel is added to the mix. AFR can be measured using a Wideband O2 sensor often called a Wideband Lambda sensor. It's also worth noting that the AFR an engine should run at is specific to the fuel it is burning. If you change fuels to E10, E85, Propane, or some other alternative, the AFR the engine will need to run at will be different. You'll sometimes read about AFRs being derived from a Lambda measurement. More on Lambda later...

This refers to a group of components that work together and independently of any other bank of grouped components. In the case of dual exhaust setups, you'll generally have 2 HEGOs, 1 per bank. Most 4 cylinder EEC strategies control the engine with only have 1 bank. V6 and V8 strategies can run as 1 or 2 banks. Most Speed Density applications will only have 1 bank. Most V6 & V8 MAF-based strategies will have 2 banks, but are not required to have 2. In certain instances, they can be configured for only 1 bank, but usually that's a custom configuration, not a factory setup. Generally Bank1 refers to the values controlling on the injectors and monitoring the HEGO for side of the engine that Cylinder 1 is on. For 302/351 Windsors, Bank1 is the passenger side. Bank2 the driver's side.

In the tuning software, you'll notice other terms that also reference the bank number within their name such as LAMBSEs, KAMRFs, Injector Pulse-Width, and HEGOs. Thus LAMBSE1, KAMRF1, InjPW1, and HEGO1 are all associated with Bank 1. Generally a bank will always have these 4 components. If for instance your application only uses 1 HEGO sensor, your strategy should run the engine with only 1 Bank.

BAP Sensor(aka BARO)
Barometric Absolute Pressure sensor. In Fords, this device was often the same exact physical device as a MAP sensor, but is used on MAF-based injection systems. They are the same shape, same electronics, same harness connector. The only difference is BAPs usually have a rubber piece that covers the vacuum nipple to prevent someone from trying to wrongfully put a vacuum hose on it. And for that, the BAPs often sell for way more than MAPs do.

Short for BinaryEditor. A tune editor and datalogging software written by Clint Garrity (86GT) and available for purchase from

Canister Purge
This is purely an emissions device. It serves no performance purpose. All it does is contain charcoal that the gas tank vents to. As the outside temp increases, the air in the gas tank will expand. The expansion flows into the canister so the unburned fuel fumes can be collected in the charcoal vs. being released into the atmosphere. When the engine runs, the canister purge solenoid allows the engine to draw in small amounts of air from the canister and thus free the unburned fuel in the charcoal into the air to be burned by the engine. The EEC controls the purge solenoid. That's about all there is to say about this device.

Catalytic Converter (aka CAT)
Catalytic converters are emissions devices that sift through the engine exhaust and attempt to continue to combust fuel particles that didn't quite get completely burned in the engine's combustion chamber. Most CATs today have 3 active catalysts to burn the 3 main emissions an engine produces, Hydrocarbons (HC), Carbon Monoxide (CO), and Nitrogen Oxides (NOx). CATs require the ability to store oxygen so they have a ready supply of oxygen to burn the HC and CO emissions with. Older CATs had a very limited ability to store oxygen and required the assistance of smog pumps to supply the oxygen. Newer CATs however have vastly improved their oxygen storing capacity and can draw unburned oxygen out of the exhaust for use when it is needed. However to do this effectively requires an EEC that can maintain the engine's AFR very close to stoic (perfect AFR for the fuel you are using).

Closed Loop (CL) not to be confused with Adaptive Learning or Adaptive Control
Closed Loop is used once the engine has made it through the Startup scenario and is in normal running conditions. Closed Loop is only meant to operate at light to moderate loads. Once the engine gets into a heavy load condition, Open Loop should be forced to enrich the mix and thus cool the burn and keep the AFRs from ever bouncing the slightest bit lean as they tend to do in Closed Loop. Closed Loop works by adding and removing fuel to keep the HEGOs switching about a switch-point voltage, usually around .423v for most EECs. As long as the EEC can readily keep the HEGOs moving about the switch-point voltage, the EEC knows it has the engine burning is near stoic (aka Lambda = 1). This is important to the Environmental Protection Agency (EPA) because CATs work best when the engine produces a burn with a Lambda measurement very close to 1. More on this later when HEGOs are further explained.

Definition File
A file that describes various offsets into a tune. A tune file is nothing more than binary values strung together in a way that the EEC can execute them to control the motor. But there’s no human-readable info in the tune file. And unless you are really good with Assembly Language, there’s no obvious logic to the file either. However there is order to the madness. And for those skilled individuals that can decipher a tune-file, they can associate what they find in human discernable forms by converting the tune values into values that make sense to us as well as giving the value a name, possibly even units (i.e. RPM, °F, etc), and even a detailed description. This information is associated with the value in the tune in the definition file. Definition files often have a 1-to-1 relationship with the strategy they define. Read more about this on Strategy below.

Definition files are opened using a tune editor such as BinaryEditor, TunerPro, or CalEdit.

CalEdit uses a proprietary format and only supports that format. Likewise no other editor uses CalEdit’s def files.

TunerPro uses *.xdf files as definition files. The format is proprietary, but editable within TunerPro. It’s generally not recommended to edit *.xdf files manually. Any mod you might need to make can be done within the TunerPro user interface.

BinaryEditor (or BE) can import TunerPro’s *.xdf files, however it natively uses *.xls files or Excel spreadsheet files. This allows BE defs to be easily edited using Excel. BE also has a proprietary def file format called *.cry files. These files are encrypted and are generally purchasable. Some developers of def files consider their info proprietary and don’t want their efforts being used by other tune companies or they wish to sell the skill since decoding a BIN is an enormously tedious job that requires a good bit of skill as well as familiarity with Ford’s encoding methods to do correctly and accurately. Therefore they encrypt the def file so it can’t be altered, edited, or plundered of the offset info. However BE can display the CRY file’s info and allow a validly licensed CRY definition file to be used to edit tunes that fit the strategy the CRY was meant to decipher.

ECT Sensor
The Engine Coolant Temperature sensor. This sensor is used extensively in all tuning applications. The EEC uses this sensor to determine how to enrich the fuel during startup and transient conditions. During startup, the EEC must emulate the action of a carb's choke by supplying a fairly rich AFR to the engine. The amount of enrichment required depends on the temperature of the engine. Colder engines need a heavier concentration of fuel (lower AFR)for a bit longer than a warmer engine. The computer decides how much enrichment to give on startup based on the ECT.

Transient conditions are times of instability right when a change was made in the running condition of the engine. The main source of "change" comes from the throttle body. When a driver moves the throttle plate to let in more air, the vacuum in the intake changes. When that happens, more air is allowed to flow into the engine. But the time between when the cylinders receive this extra air and when the registers this increase can throw the AFR out of whack. As much as we'd like to pretend that things happen instantaneously in a engine, they don't. There's also just a need for a slightly richer mix during moments increased engine load that are just generic to most engines. Carburetors made up for this using an accelerator pump that literally squirted fuel directly into the intake when the throttle was increased. The EEC has a similar function...Acceleration Fuel Enrichment. The amount of enrichment needed is related to the temp of the engine. Accel enrichment is ONLY applied during detected throttle movements.

There is also a wall-wetting phenomenon that happens on accel and decel. This is where the walls of the intake soak with fuel. The amount they soak is relative to the amount of fuel being sprayed and the temperature of the wall. The cooler the wall, the more fuel will stick to the wall instead of evaporating off into the air. So if fuel is sticking to the intake walls and not getting into the cylinders during an increase in engine load, the computer will need to compensate for this until the wall is saturated. Likewise, as less fuel is sprayed, the wet walls will evaporate giving the next few air charges more fuel than was delivered by the computer. So the cylinder could get a momentary rich deceleration condition due to the wall evaporation. The computer compensates for this as well by momentarily pulling fuel on decel. This enrichment/de-enrichment action is called Transient Fuel Enrichment. Transient Enrichment is only added during changes in engine load and a few moments after. Generally Transient Enrichment continues for about 1/8 to 1 second after a change in throttle position. How long it lasts and how much it gives or pulls depends on the change in load. But Accel and Transient Enrichment are VERY related to ECT.

EDISx Module
Electronic Distributorless Ignition System module. Ford made 3 different flavors. The EDIS4, EDIS6 and EDIS8 for the 4, 6, and 8 cylinder EEV-IV EDIS-equipped engines. However there are only 2 main types of coil packs, 2-coil and 3-coil packs. Six Cylinder engines use the 3-coil packs. And 4 cylinders and V8s use the 2-coil packs. Obviously V8s will require two 2-coil packs.

The EDIS module is similar to the TFI. It monitors the engine RPM via an exciter ring and sensor. The ring is usually on the harmonic balancer. Based on that wheel, the module determines which coil in the EDIS coil pack(s) that needs to fire. As with the TFI, the EDIS module gets info from the EEC as to how much spark advance to apply and sends a PIP signal back up to the EEC for calculating RPMs with.

Often people want to know how to convert their distributor-based TFI system to EDIS. First and foremost, it requires an EDIS module and coil packs as well as some tune-adjustments in the EEC to communicate the right signals to the EDIS module. Evidently the signal being sent to an EDIS module and TFI module are different enough that the EEC needs to know which ignition type is being used. Although I think general consensus is that with the exception of the TFI module's tendency to burn out due to being mounted directly to the distributor, the TFI-based system isn't that inferior and can handle most any street application and most moderately built strip applications with the right ignition upgrades (i.e. ignition box and dizzy replacement).

Notice, EDIS only has 1/2 the total number of coils as the engine has spark plugs. This means the EDIS system will fire 2 spark plugs at once unlike normal distributor based ignition systems. This creates a rather unique spark plug need. In a normal distributor system, the positive high-voltage side of the coil goes into the spark plugs from the tip, jumps the plug gap, hits the "hook" which is welded to the plug case. And of course the case of the plug is threaded into the head which is bolted to the block. From the block the voltage returns to the coil through ground lines.

EDIS doesn't work this way. The positive charge will go through the tip of one plug, jump that plug's gap to the "hook", to the engine, to the hook of the corresponding plug, jumps the gap of the 2nd plug, up through the tip and back into the coil. This means 1/2 the plugs in an EDIS system actually have the electricity to flow through the plug "backwards". The significance of this is that the electrical polarity that the electricity flows through the plug dictates which electrode erodes quicker. Generally, it's the tip that erodes faster and thus why generic Platinum plugs have the platinum on the tip. However in EDIS systems, the eroding tip is actually the hook thus putting the platinum on the tip wouldn't be helping anything. This is why if you ever noticed, Ford often built EDIS engines with 2 different spark with a platinum disc on the tip and the other with the platinum disc on the hook. The aftermarket doesn't sell the oddball plug with the platinum disc only on the hook with the possible exception of through the dealer. What they do sell is Double Platinum Plugs which has Platinum discs on both tip and hook so you can't install them wrong.

It's also worth note that it is possible that a heavy overlap cam that would allow air and fuel to scavenge to the exhaust during the overlap period could detonate the unburned air and fuel since there is a spark being produced in that cylinder at that time. I don't know that this has ever been recognized as a problem on EDIS systems running heavy overlap cams, but it is interesting to think about.

Another interesting fun fact about EDIS systems is the voltage always goes to the cylinder that's on the compression stroke. This isn't intuitive to most people since you'd think the voltage would be split between the two plugs since the plugs are electrically in series with each other. However what's changing between the two plugs is the resistance between the gaps. The plug on the compression stroke has far more air and fuel molecules filling the gap due to the compression which gives that gap more resistance than the other plug that would be on the exhaust stroke. So the voltage goes to the plug that needs it just the same as if you had a 10 ohm and 1000 ohm resistors in series. The 1000 ohm resistor would have more voltage across it than the 10 ohm resistor would. This doesn't really mean much in the tuning world, but it is interesting to think about and be aware of.

Short for EEC Analyzer. EA is a tuning tool used to analyze datalogs from softwares such as BinaryEditor, CalCon (TwEECer), and others. It includes a number of calculators and datalog visualization tools to help you make use of the mass amount of data in datalogs. It is written by Clint Garrity (86GT) and available for purchase from

EEC (aka ECM, PCM, MCU, the computer, black box)
This is the computer processor that interprets the various sensor readings on a fuel injected engine and controls the various outputs.

EGR Valve
Exhaust Gas Return valve. In the early days of engine management, it was recognized that NOx emissions are created when combustion temps rise above a certain amount. Under normal driving conditions, exhaust temps spike high in temp when the AFR goes lean, even a little. And as was mentioned, the mix needs to go just a tad lean to get some unburned oxygen to the CATs to do their job. So to do this and control combustion temps, Exhaust gas is circulated back to the intake to act as an inert agent to slow down the combustion and ultimately cool it. There is a point of diminishing return and if exceeded, there's actually a negative return. That happens when too much exhaust is in the intake putting too much space between the fuel molecules and oxygen molecules and so a larger number of them can't burn which creates a high oxygen & HC content even if the mix is a little lean. However when EGR is accurately controlled, there's an emissions & potentially a fuel economy benefit. Most people are quick to delete the EGR, but EGR when setup on EFI systems isn't necessarily a bad thing.

EVP Sensor
EGR Valve Position Sensor. On the older EGR systems, the EGR valve's position is monitored via a position sensor. Given certain RPM/Loads/Position, the computer can estimate the EGR flow and match the intake of air with a certain amount of flow. With the newer systems, differential pressure is used to actually measure the amount of exhaust gas flowing independent of actual valve position.

When people delete their EGR, it leaves this input available on the EEC. So many people will hijack that input and use it for their Wideband. Then datalog the EVP along with their other TwEECer payload to get their WB feedback...very convenient. And a compelling reason to unfortunately delete the EGR if you don't care.

Fuel Management Unit (FMU)
A Fuel Management Unit replaces the FPR, however the intention of an FMU is to change the differential pressure across injectors as pressure in the intake manifold increases above a certain point. The purpose of an FMU is to make stock or undersized injectors act larger than they really are. They are common in boosted applications where the owner doesn't want to retune the vehicle and thus wants to keep the existing injectors. But nothing comes for free. The catch is running an FMU runs line pressure WAY above where it would be with an FPR and correctly sized injectors. For instance, an FPR is usually designed to maintain 39PSI on fuel rails at atmospheric pressure. If a supercharger boosts an engine by 10PSI, then that's 10PSI above 39 that the rails should be running at that time...hence 49PSI. That's not terribly difficult for most fuel pumps to deliver, even stock ones. However with an FMU, it may need to increase the differential pressure across the injectors well above 39PSI at boost. So perhaps it needs a differential pressure of say 55PSI to make 19lb injectors act like 36lb injectors. Now take that 55PSI and add the 10PSI that boost will apply, and now line pressure is in the 65PSI range. This is getting into the area where fuel pumps quit supplying their rated fuel delivery. Not to mention the added stress of 65PSI on a fuel system. As boost grows above 10PSI to say 15PSI, then you could easily run 70+PSI in the rails.

Add to this, it's nearly impossible to tune an application with FMUs involved. Even in untuned applications, it's a sloppy and very unpredictable way to get added enrichment on a boosted application and thus it usually leaves a lot of HP on the table since most FMUs are oversized and thus will run the engine WAY too rich just to be on the safe side. The EEC expects a constant, predictable behavior from the injectors. And that can only happen with a well maintained differential pressure across the injectors using an FPR. So, the correct answer is DO NOT USE FMUs WHEN TUNING A VEHICLE. Instead, install the correctly sized injectors and run a normal FPR dialed in to 39PSI. If you slightly undersized the injectors, you can adjust the fuel pressure up to say 45PSI and be assured that your fuel line pressures are still in a very safe range even at 15PSI of boost.

Fuel Pressure Regulator (FPR)
An intake doesn't have a constant pressure. At light loads and decel, there is a substantial vacuum in an intake manifold. In the case of boosted applications, there are pressures above atmosphere in the intake. However, the flow of fuel through an injector requires that the differential pressure above and below the injector be the same at all times. If the differential pressure across the injector increases, more fuel will flow than is expected. Same with decreases in differential pressure...less fuel would flow. So to maintain a constant differential pressure across the injectors, a device is needed that will increase and decrease the fuel line pressure by the same amount that the intake pressure is changing by. The FPR is the device that does this.

Heated Exhaust Gas Oxygen Sensor (aka HEGO)
A HEGO is similar to a normal oxygen sensor with the addition of a heater to help the sensor element get up to temp quicker and thus allow the EEC to go Closed Loop sooner. Oxygen sensors, often called narrow band lambda sensors, are used to communicate the status of an engine's exhaust burn. Narrow bands are only useful when the exhaust lambda is very near 1 or near stoic. For gas engines, stoic is attained with a 14.64 AFR. That's 14.64 parts air to 1 part fuel. The voltage on the O2 sensors is not a very accurate feedback of AFR, so only a switch-point is monitored. If the voltage is above .423v, the mix is assumed to be rich. If the voltage is below .423v, the mix is assumed to be lean. When in Closed Loop mode, the EEC uses that info to determine whether to add or pull fuel. While in Closed Loop, the EEC never homes in on a specific AFR and stays there. It is constantly adding and pulling fuel to keep the HEGO voltage going above and below the switch point. A transition across this switch-point is called a HEGO switch. HEGOs, like KAMRFs & LAMBSEs are associated with a specific bank. For more on Banks, refer to "Banks" above.

There is an emissions benefit in letting the mix go a tad lean and a tad rich at a high frequency. The way the CATs work is they convert rich-gas emissions like HC (hydrocarbons) and CO (carbon monoxide) to H2O (water) and CO2 (carbon dioxide) using O2 (oxygen). Likewise they also convert lean-burn emission gas like NOx (nitrous oxides of varying types) to N2 (nitrogen) and O2. CATs are fairly useless at excessively rich and lean mixes. So, the HEGOs attempt to not only keep the engine in a good burning AFR, but also in an AFR range that works best for the CATs. Since the CATs need a small amount of oxygen to do what they do, the EEC must allow the AFR to go a tad lean from time to time so the CATs can scavenge the oxygen they need for when the burn goes a tad rich. Pre-OBD-II systems used Thermactors (smog pumps) to give CATs extra oxygen to do an even better job at converting rich mix emissions. However the newer OBD-II complaint CATs are capable of stock-piling 10x the amount of oxygen the older OBD-I complaint CATs could and thus don't need smog pumps as long as the EEC is controlling the AFR to the HEGOs.

IAC Valve(aka ISC)
Idle Air Control or Idle Speed Control Valve. This is a valve that mounts up near the throttle body to control the amount of air that is bypassed around the throttle body to maintain engine idle. On cold mornings, the EEC often wants to rev the engine a bit higher to help get the engine up to a safe running temp before it is put in gear and loaded. It also helps to get the CATs up to temp so they do their civil duties quicker.

Injector Breakpoint(BP)
The breakpoint describes at what amount of fuel the EEC quits using the low slope and begins using the high slope for Injector PW calculations. This gets to be a very complicated subject and there are other threads that cover this topic in much more detail. In short, here's the flow of how the calculation goes. If the calculated amount of fuel is less than the breakpoint amount of fuel, only the low slope is used to calculate the PW. However if the amount of fuel is greater than the breakpoint amount of fuel, then the quantity of fuel above-n-beyond the breakpoint quantity uses the high slope. The PW calculations from the low slope and high slope calculations are added together to make the total used. Here's the calculation in formula form:

If fuel needed < BP then PW = Fuel Needed / Low Slope
If fuel needed > BP then PW = (BP / Low Slope) + [(Fuel Needed - BP) / High Slope]

Note the closer high slope and low slope are, the less affect the BP has on fuel delivery. This is why if injector slopes are equal, the breakpoint value has no affect.

Injector Offset
This is an Injector PW adder function. The result of this function is in terms of Injector PWs and is added to the result of the Slope/BP calculations described above. Since Injectors require DC voltage to open, it's no surprise that the rate at which they open could be affected by voltage. When the electrical system is strained with lots of electrical loads (i.e. head lights, stereo, dash blower engine, etc), the voltage supplied to the injectors drops. Even with the alternator running, the voltage could potentially get into the 12s if the electrical load is high. With a bad or undersized alternator, the voltage could easily get into the 10s. However when the engine is running with a good alternator and minimal electrical loads, the voltage could be in the 14v range. If voltage affects the opening rate, this affects the amount of fuel that gets delivered. So the EEC must account for voltage fluctuation in its calculation of Injector PW. This change in behavior is communicated to the EEC via the Injector Offset function. When you swap out stock injectors for larger injectors, this function must be updated along with the Slope/BP calculations above to communicate the new injector behavior.

On a side note, I've found that often this function can be responsible for the need to run an excessively high low-slope value. Reducing each point on the offset curve should allow you to run a lower low-slope.

Injector Slope
Slopes describe the injector behavior to the EEC. When the EEC gets a measure of air from the MAF or MAP, and it has an AFR target, it now knows how much fuel is required to accompany that air. However fuel delivery is done in terms of injector pulse-width. Longer PWs will release more fuel. However the EEC needs a baseline so it knows what length PW to command to get the correct amount of fuel. The only way it can know that is to somehow have a description of how much fuel the injectors can flow with a 100% pulse-width assuming a constant differential pressure across the injectors (thanks to the FPR). From that, it can estimate how much fuel smaller PWs will deliver. Some EEC strategies will have a single injector slope. But most have 2. The high slope is the one that best reflects the advertized injector size. However at lower PWs, the injector may behave like a larger injector than it really is. To make up for this, some strats have an Injector Low slope value. This is usually a value higher than the rated injector value so the EEC knows that when the Injector 1st opens and closes, there's more than the rated amount of fuel for the PW being released.

These are often called the Long Term Fuel Trims. KAMRFs are always in the fuel delivery equation similar to the LAMBSEs and are associated with a specific bank. For more on Banks, refer to "Banks" above. While in Closed Loop, LAMBSEs are adjusted up and down to get the HEGOs to switch. However the switch-point may not result in a LAMBSE value of 14.64 or anywhere near 14.64 in some RPM/Loads. When Adaptive Learning is enabled, the EEC will adjust the KAMRFs up or down to add and remove fuel in an effort to get the LAMBSEs to be 14.64. The value the KAMRFs adjust to is saved in Keep Alive Memory (KAM) and reused next time the engine is in the same RPM/Load. The theory is that the same adjustment that brings the LAMBSEs to 14.64 once will do it again...or at least get the LAMBSEs closer to 14.64 than they would without the KAMRF adjustment. KAMRFs start off as values of 1.0. A value lower than 1 pulls fuel. A value above 1 adds fuel.

Now not all RPM/Loads will learn by default. Which RPM/Loads learn is defined in the Adaptive Update table. In this table are positive and negative values. Positive values indicate cells that are allowed to learn. The number's significance is how long the EEC must remain in a stable driving condition before the KAMRFs will adjust when Adaptive Learning is enabled/allowed. The negative values are cells that do not learn. The significance of the value is a reference to another RPM/Load to reference. So for instance, a value of -57 would reference the cell in row 5, column 7. Also keep in mind the rows and columns are numbered starting at 0. So row 5 is the 6th row. In most stock tunes, this is the 50% row. Likewise column 7 is the 8th column and commonly is the column for 2500 RPMs. In GUFx tunes, the 2nd-to-top row is mostly references to -57. This means at WOT conditions, the KAMRF value that was learned for 2500RPM/50% load is used. Therefore even though the EEC is in OL during WOT conditions and cannot glean any info about how close it is meeting its target, it uses info it learned while in CL conditions as an adjustment for OL-WOT. This is the factory's method of adjusting for engineering differences in MAFs and other engineering tolerances. Evidently they found that whatever adjustment is needed around the 2500RPM/50%Load area is also what's required to bring the WOT AFRs closer to target when using a 100% stock tune on a stock motor and all stock equipment. However I'm not convinced this should stay this way when a tuner has access to a WB and can manipulate the tune to adjust for those same engineering differences. So replacing all the -57 entries with 10s will result in KAMRFs always being 1 during WOT so you can adjust the tune without the KAMRFs getting in the way.

Also note, the very top row. Only the first 4 cells of the top row are used. They represent "special idle" conditions. The ISFLAG value indicates which cell is used during idle.

ISFLAG = Flag that indicates the degree of loading on the engine at Idle.
0 = Drive
1 = Drive + A/C (WAC Relay De-Energized)
2 = Neutral
3 = Neutral + A/C (WAC Relay De-Energized)

Note that only tunes setup for automatics make use of the 1st two cells.

Lambda (aka λ)
This is a measure of an engine's exhaust that describes how close to a stoic the exhaust burn is. Lambda is measured using a Wideband O2 sensor also known as Wideband Lambda sensors. Lambda is a fuel-independent term. All fuels have a stoiciometrically perfect AFR. Gasoline happens to be 14.64. E85 is around 9.76. What the Lambda measurement does is feedback how close to a stoic burn the exhaust was. At Closed Loop conditions, the EEC strives for a stoichiometrically perfect burn where Lambda is held as close to 1 as possible. However at WOT conditions, the EEC will command very rich mixes. In the case of naturally aspirated gasoline engines, the EEC usually will target a .85 Lambda burn. To determine what .85 is in terms of gasoline AFRs, you multiply the perfect AFR of gasoline by the lambda value. In this case it would be
14.64 x .85 = 12.44 AFR for gasoline

But note a .85 lambda burn with E85 would yield a different AFR:
9.76 x .85 = 8.3 AFR for E85

Therefore when using a Wideband O2 sensor, you are really measuring the exhaust's Lambda rating. The WB controller is ASSUMING a particular fuel in order to deliver an AFR to the user in the form of a gauge or datalog.

Often called Short Term Fuel Trims. In short, LAMBSEs are the AFR the EEC believes should be resulting from whatever fuel it is delivering. That description is accurate for LAMBSE at any mode. Keep in mind, this is not the actual AFR. That can only be measured with a Wideband O2 sensor. As it relates to tuning, there are 2 ways to interpret and deal with LAMBSE depending on whether the LAMBSE is at OL or CL. LAMBSEs, like KAMRFs & HEGOs are associated with a specific bank. For more on Banks, refer to "Banks" above.

In OL, the LAMBSE value should reflect the AFR going out the tail pipe. If it doesn't, then MAF/Injector values will need to be altered to get the AFR and LAMBSE closer together.

In CL, the LAMBSEs are what the EEC adjusts to get the HEGOs to switch. So if the mix is keeping a HEGO rich (above .423v), then the LAMBSEs will rise to lean the mixture. If the mix goes lean keeping a HEGO below .423v, then the LAMBSE value is lowered. Under normal CL conditions, the EEC should be constantly adjusting the LAMBSE value(s) up and down to keep the HEGOs just barely above and below their switch voltage. And by just barely, the voltage will often go as high as .5-.6v and as low as 0-.1v. Any higher than about .65v, and the change in voltage is not accurate enough to associate to a specific AFR. The .6v range seems to be 14.5 AFR and 0v seems to be around 15.0 AFR. That may be slightly different from setup-to-setup and WB to WB. But that's in the neighborhood of expected behavior.

Another note about LAMBSEs. The name is a derivative from Lambdas. When talking about exhaust mix, you measure the exhaust in terms of Lambdas. Since Wideband O2 sensors (WBs) are used to measure exhaust mix, they are often called Lambda sensors. A Lambda of 1 indicates the mix burned at perfect stoichiometric mix. You get LAMBSE from Lambda by multiplying the Lambda by the AFR to give you perfect mix. In the case of gasoline, it's 14.64. However if you were dealing with Propane or E85, the multiplier to get LAMBSE would be different. In the event you happen to want to use a Mustang EEC to control an engine burning E85, the most effective way to do this is to keep the EEC believing it is burning gasoline and adjust the Injector settings. This is a topic all into itself and discussed a few different times on the forum. Just search for E85.

This is the instantaneous volumetric efficiency. Volumetric efficiency is a rating of how much air the engine is aspirating vs. what the max possible is with atmospheric pressure. For every 2 revolutions of the crank, the theoretical max aspirated air is the CID of the engine. Using that as a baseline (a value entered in the tune), the EEC can calculate how much of that max is actually making it into the engine at any moment. A stock engine will usually max out in the 70-80% range. A modified engine will be in the high 80s to mid 90s. A boosted engine will be well above 100% since the booster uses pressures higher than atmospheric to get the air into the engine. A modified engine running 10PSI can be as high as 160-170% Load.

This is an instantaneous measure of the engine's max possible capacity. The intention is for Load% to indicate ~100% when at WOT for any RPM. Any mods to an engine that increases the engine's output will increase the Load and thus Load% will increase and will need to be rescaled down to keep Load% in the 95-105% range.

Load Scaling
When a stock tune is modified to accommodate a modified engine, all the tables need to be rescaled to accommodate higher Load potentials. This is not so much a problem for naturally aspirated engines, but boosted engines that go well above 100% need the Spark tables rescaled to allow Spark to be adjusted up to the 120-130% range. Most all tables have their column and rows rescaled using Scaling Functions. The important thing to keep in mind when rescaling is often multiple tables will use the same scaling functions. So after you make mods in a Scaling function, you'll need to find all tables that were affected, and adjust the values in those tables to accommodate for the change.

LTFT(aka Long Term Fuel Trim)
Long Term Fuel Trim is a learned value over time. This is exactly the same as KAMRF but presented in a percentage rather than a multiplier. This value changes gradually in response to conditions, fuel mixture, engine wear, air leaks, variation in fuel pressure and so on. Long Term Fuel Trim is stored in a nonvolatile memory called RAM and is not erased when the engine is shut down. This information is used during all operational conditions such as WOT, Startup, Part Throttle and so on.

Mass Air Flow sensor. This is a device that measures the amount of air being aspirated into the engine. However the amount of air is not being measured in CFMs or any other volume-based unit. It's being measured in the name suggests. The MAF sensor converts airflow to a voltage. Ford made many different MAFs, each with different flow characteristics. And the aftermarket has numerous different offerings as well. All the MAF does is measure the amount of air flowing through it and convert that flow to a voltage. But as stated, each MAF has different flow characteristics, so each MAF design will translate the same flow to different voltages. Thus when you swap a MAF for a higher flowing MAF, its important to inform the computer of the change so the computer is aware that there is a different association of flow and voltage. This association is called the MAF curve.

Most people are likely also familiar with calibrated MAFs. Often you'll see MAFs calibrated for 24lb injectors or 42lb injectors and claim they don't require a tune. What these MAFs are doing is ASSUMING the computer still believes it is controlling a stock computer with stock injectors and is sensing a stock MAF. When a calibrated MAF is installed along with its matching injectors, the MAF basically lies to the EEC and gives the EEC a voltage that will correspond to the right pulse-width of fuel on the injectors to deliver about the right amount of fuel. It's a very inaccurate way of doing things and as you increase the injector size, it has a very bad side-effect. The side-effect is that the computer calculates engine load to be much lower than it really is. If you've sized the injectors to the engine's capacity correctly, the effects will not be nearly as detrimental as if you grossly oversize the injectors for the engine. If all-out racing is the only purpose for such an application, then perhaps you can get away with doing this. However if you are looking for good drivability, you are not likely to get this by lying to the computer about the injector size and MAF that's actually installed. You are far better to communicate the actual MAF curve and injector size to the computer so it knows what's going on and can control things accordingly.

Manifold Absolute Pressure sensor. It's also been called Manifold Air Pressure sensor. Either are acceptable since they reuse the same letters. MAPs are generally only associated with Speed Density computers. In these older systems, the RPM, Air temp, Engine Temp, and MAP were all used to determine the amount of air actually being aspirated into the engine so a comparable amount of fuel could be injected. These systems were surpassed by MAF-based systems. However you may frequently read about people using GM 3-bar MAPs in their tuning setup. These are high pressure MAPs that people with boosted applications will use to electronically determine the boost pressure. Obviously, you don't need one of these sensors to run a gauge on the dash. But you do need one if you want to datalog the boost pressure along with other data such as datalog info coming in from a TwEECer or a Wideband sensor.

Open Loop (OL)
An EEC is given a certain number of criteria about a engine that lets it make assumptions about the engine's possible behavior, in specific about how much fuel will deliver what AFR. Through the use of sensors, the EEC can estimate the amount of air being brought into the engine, and knowing about the injector size, can calculate a comparable amount of fuel to deliver the target AFR. During OL, the EEC doesn't have the benefit of feedback to know how accurate it's calculations are. It's the tuner's job to verify what the computer thinks it is delivering to what actually gets delivered and make adjustments when the tune is way off base. The MAF curve and Injector settings are the common place to start in making such adjustments. OL is used during the first minute or so after crank (Startup Mode) and during heavy load conditions like WOT or when OL is forced due to high-load for an extended period of time.

Short for Quarterhorse. The Quarterhorse is electronic hardware used as a tuner/datalogger and is manufactured and sold by Craig Moates for use on Ford EEC-IV and EEC-V engine management computers equipped with a J3 interface port. The Quarterhorse can be purchased from

STFT(aka Short Term Fuel Trim)
Short Term Trim is an instantaneous fuel correction value and is derived based on feedback from the HEGO Sensor(s) during CL operation. This is the same thing as LAMBSE but represented as a percentage from stoichiometric AF mix. Under normal CL conditions, the HEGO cycles plus or minus a predefined amount around 0.423v. When Short Term trim exceeds plus or minus 10 percent for too long, the Long Term trim (LTFT/KAMRF) begins changing to bring the Short term trim back within range. Short term trim can vary as much as plus or minus 25%. The above correction logic works to keep STFT within plus or minus a predetermined percentage. If the target is 14.64 and the STFT is 4.5 then this means the EEC is commanding a 4.5% richer mixture than what is required to keep the HEGO(s) switching about the switch point. The math looks something like this:

100 - 4.5 = 95.5% or .955 (had the correction been in the lean direction, 4.5 would be added to 100)

14.64 * .955 = 13.98 LAMBSE

A strategy describes the memory alignment of a tune. A tune is nothing more than data and executable instructions for the EEC’s processor. The organization of the instructions and data are referred to as the strategy. Tunes that share the same organization are said to be from the same strategy. A definition file is usually used to associate human readable information to the cryptic data contained within the tune. There’s usually a 1-to-1 relationship between strategies and definitions. Although there are some strategies that are so similar that the majority of the useful data that tuners care about is all in the same places and thus tunes from these similar strats can reuse the same definition file. This is the exception, not the norm however.

Common strategies are GUF1, GUFA, GUFB, GURE, CBAZA, CDAN4, CRAI8, and CRAJ0. There are hundreds of different known strategies, but only a very few are well reverse-engineered enough to be usable. If at all possible, use an EEC that is well supported with the software and hardware you plan to tune with. For instance, if you have a mid 80s 5.0L Crown Vic, you might seriously want to consider doing a MAF conversion to it and controlling it with one of the 89-95 Mustang (GUFx or CBAZA) processors. This doesn't mean other processors don't have some support. It just means to get the most out of your tuning experience, it puts you far ahead of the tuning game to have a well-supported EEC right from the get-go. Read more on this topic in the thread Things to know BEFORE buying a TwEECer

TFI Module
Thick Film Ignition device. This is a device that mounts to the distributor or in some cases was remotely mounted. The EEC is not nearly fast enough to maintain spark timing. So the duties of spark timing are handled exclusively by the TFI. The TFI monitors the distributor and controls the tach & coil, as well as informs the EEC when it performs a spark so the EEC can accurately calculate RPMs via a PIP (Profile Ignition Pickup) signal. The EEC does maintain and calculate spark advance, and thus communicates that down to the TFI to apply using a high speed pulse-width signal where the pulse frequency and duty cycle tell the TFI module the spark advance and the spark time duration to apply. The details of this interaction between the EEC and TFI are rarely ever important to a tuner. What's important to understand in the EEC does not decide when the spark happens. That's the TFI's job. The EEC decides the advance that's placed on the spark.

This is the name for the air pump system used to pump air into the CATs. It's purely an emissions thing and has no performance benefit.

Throttle Position Sensor. This tells the computer what the position of the throttle plate is, when it moves, what direction it moves, and how fast it is moving. Each of these details are used to make decisions, usually about fuel delivery. As discussed above, TPS change triggers Accel Enrichment. The EEC often breaks TPS position into 3 positions...Closed Throttle (CT), Part Throttle (PT), and Wide Open Throttle (WOT) and from this it can determine what "mode" it needs to be in. When at CT and at low RPMs, it knows it is in Idle mode and thus follows the Idle Functions to control the IAC and Spark. When the TPS is cracked open, it transitions to PT and begins using normal Spark tables for spark and may preposition the IAC in preparation for a de-clutch or decel. At higher TPS positions, the EEC can force Open Loop or enter WOT-mode if your EEC has a WOT-mode. And if configured in your EEC, CT while cruising in gear can shut off injectors for Decel-Fuel-Shutoff (DFSO) mode. DFSO is supported by most EECs from 1989-up, but is not active on most stock tunes. As stated above, TPS is also one of the major players in Accel Enrichment calculations. And since Throttle Position changes usually result in load changes, throttle position is also indirectly related to Transient Enrichment too.

Also, it seems to be something of a myth that you must "set" the TPS so that CT always gives a voltage between .94-.98 or some range like that. Looking through the execution code of the most common EECs, this appears to be unnecessary. As long as the voltage is below 1.25v and above about .6v, there should be no reason to worry about making such a tedious effort. Most TPS/TB combinations will result in a CT voltage in the .85 to 1v range.

TPS Ratchet
At Closed Throttle (CT), there's no telling what the TPS voltage is. This is based on engineering tolerances of the TPS sensor, the TB it is mounted to, the idle set screw adjustment, amount of wear on the sensor and possibly even the amount of buildup on the TB's butterfly which could be keeping the throttle position just off of the idle set screw. So there's no way the computer can reliably associate specific TPS positions to certain modes without a common reference. This common reference is the Closed Throttle voltage. All other TPS breakpoint voltages will be based off of this voltage. So for instance, lets say a tune has a TPS Breakpoint voltage to enter WOT set at 2.7v (assuming the tune's strategy has a WOT-mode). In order for this breakpoint to actually be exceeded, the TPS voltage must exceed 2.7v plus the TPS Ratchet voltage. Thus if the TPS Ratchet voltage was latched in at 1v and the breakpoint is 2.7v in the tune, then the actual TPS voltage would need to exceed 3.7v to transition to WOT-mode.

This voltage is called a ratchet voltage because the EEC ratchets in the lowest TPS voltage it sees from the time the ignition is turned on. For example, if you turn the ignition on and the TPS voltage is .96v. The EEC locks in .96v as the TPS ratchet voltage. Then after you open the TB to take off, say to pull out of your garage then return the throttle to CT, the plate may close a tad further than it was when the engine was cranked. So the voltage at this point may be .95v. At this point, the EEC will latch in .95v as the TPS ratchet voltage. Lets say at some other point during the drive, the CT voltage drops to .94v. The EEC will latch in .94v as the ratchet voltage. I think you get the idea. The TPS ratchet voltage is reset each time the ignition is turned off.

Tune File (aka *.BIN File)
This is a file-representation of the instructions and data used by the EEC’s processor. In file form, a PC-based application and analyze it and even made edits to the file. And using hardware such as a Moates chip or a TwEECer, that file can be flashed to these devices' memory so the EEC runs the altered file instead of the stock tune permanently burned into the EEC’s ROM. Tune files are opened using a tune editor such a BinaryEditor (my favorite), TunerPro, or CalEdit (POS). Note that CalEdit can open *.BIN files, but any modifications made to the tune within CalEdit can only be saved in CalEdit’s proprietary tune format.

When dealing with embedded devices such as chips and dataloggers, conceptually, think of your PC/laptop as more capable/superior compared to the embedded device (chip/datalogger), thus the PC is "above" the chip. That's exactly opposite of the IT world where you think of your PC (client) as "below" a server. Thus when you write a tune to a chip (sending info from your PC to the connected device), you are downloading the chip. And when you read a tune from the chip (receiving info from the connected device), you are uploading the chip. This difference from the Internet-centric way of thinking explains why read buttons in BinaryEditor have an UP arrow from the chip and the write buttons have a DOWN arrow to the chip. The embedded industry's use of the terms upload & download are old and predate the IT world's use of those same words. But in all fairness, the IT industry didn't get it completely wrong. IT administrators think of servers as being more capable/superior to a client accessing that server which is why they conceptually put their servers "above" client PCs.

Wideband O2 Sensor (aka WB but more correctly named Wideband Lambda Sensor)
A sensor used to measure the resulting exhaust Lambda an engine is producing from the current amount of air and fuel it is burning. Wideband O2 sensors go into an exhaust system similar to a HEGO, but that’s where their similarities end. WBs require a controller for 2 reasons. First, WBs need to be heated to an extremely high temperature which requires a WB controller to regulate. You cannot simply slap 12v to the sensor and have it work like you can with HEGOs. A WB controller also interprets the feedback coming from the WB sensor. Again unlike normal HEGOs, a WB does not output a simple voltage. It requires a constant amp flow be given to it. That doesn’t sound complicated at first. But in reality, the resistance the WB puts up is constantly changing as the exhaust conditions change. So to maintain a constant amp flow requires the WB controller constantly increase and decrease the supply voltage going to the sensor in an effort to keep the amp flow as constant as possible. The feedback from the WB sensor is also amp related. The WB controller must monitor what the amp flow is on the sensor return line. The interesting thing is the return can have a positive or negative amp flow based on the exhaust’s lambda condition. When the WB is measuring a Lambda of 1, the sensor return line has an amp flow of 0. However as the Lambda increases or decreases from 1, the amp flow increases towards or away from the controller. The controller has to be able to measure this and convert that to a Lambda value. In software, that Lambda feedback value is usually multiplied by the stoic AFR of the fuel being burned to display an AFR value to the user. For more details on how WBs work, visit these sites:

There are plenty of others that could be listed here especially from the OBD-II world. But these are the main ones that directly relate to engine tuning and controlling. So now, onto the tuning-specific terms that may not be as familiar outside of the EEC tuning world.
...Always Somethin'

89 Ranger Supercab, 331 w/GT40p heads, ported Explorer lower, Crane Powermax 2020 cam, 1.6RRs, FMS Explorer (GT40p) headers, Slot Style MAF, aftermarket T5 'Z-Spec', 8.8" rear w/3.27s, Powertrax Locker, Innovate LC-1, GUFB, Moates QuarterHorse tuned using BE&EA



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