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EVERYONE PLEASE DO NOT POST QUESTIONS OR COMMENTS IN THIS THREAD. ALL QUESTIONS SHOULD BE POSTED IN THE PRO-M SECTION BELOW.
I was bored so I asked John Janek to assist me in answering some Frequently Asked Questions on the Pro-M Engine Management System (EMS). We had a good time putting this together and we hope it helps.
Q. Why is the Pro-M EMS so expensive?
A. Good things aren’t cheap. The quality of manufacturing and components that go into the Pro-M EMS cost money.
The processor is manufactured by the Visteon Corporation. Visteon is a Fortune 500 company spun from the Ford Motor Company in 2000. Visteon designs and manufactures many of the factory electronic parts in your Mustang.
The software developers who code the Pro-M EMS strategies are actual Ford Engineers who are constantly updating the software to make the system better (more on this later). They get paid very well.
The Ford connectors, wiring, terminals, wire loom, and harness wrap are top-notch quality pieces and are specifically designed for automotive engine bays. The system doesn’t utilize cheap, generalized wire that can be purchased at Home Depot or hobby kit connectors from a place like your local electronic store. Lay a competitor's wiring harness next to a Pro-M wiring harness and the differences are immediately clear. Their harnesses contain a bare minimum of circuits. You get only what is needed to run the engine. One competitor claims to have a “Fox Body Mustang Specific” harness. That claim could not be more untrue. The Pro-M harness literally has three times the wiring theirs does, contains all the original circuits used in the original harnesses and uses all the original connectors. The competition claims that their “Fox Body Specific” harness fits all model years. Pro-M makes TEN DIFFERENT HARNESSES FOR THE FOX BODY alone. Not to mention the six other harnesses they make for the other Mustangs from 96 through 2004. Why? Because the original harnesses differ from year to year and that is what is necessary to make a true vehicle specific harness.
Add-on features like traction control, launch assist, progressive Nitrous and Water/Methanol Control are included in the price at no additional cost. Want to add traction control to the other guy's system? Be prepared to spend $600 to $1000 for an add on box that works as well as the Pro-M does. It’s not an apple to apple comparison when people try to compare low dollar EMS’s against a Pro-M EMS because of the quality and features built into every Pro-M system. Compare the initial cost of the Pro-M EMS to any other EMS with comparable features (Holley Dominator) out there and you'll see the cost is about the same.
Q. What makes the Pro-M processor unique?
A. Self-protecting, self-diagnosing and production quality processor
Self-protecting processor: If the Pro-M EMS processor detects a short circuit, it will shut down the affected ECM driver. Of course, it will also turn on the check engine light and store a code to direct you to the problem.
Self-diagnosing processor: The Pro-M EMS processor continuously checks itself for faults. No more guessing whether or not the processor is the source of trouble. These processors are extremely robust and have already been through the most rigorous testing in the industry long before going on the shelf, so the chance of ever having trouble with one is slim to none. But when doing diagnostics, wouldn't it be nice to know whether or not the processor could be at fault? No testing needed. If there is trouble, it will let you know.
Production quality processor: As noted above, the Pro-M EMS processor is made by Visteon, the same manufacturer who makes the processors for Ford (how nice). This is something you simply will NOT find anywhere else. The competition uses low production modules that cannot compare to the quality of the Pro-M EMS processor and do not go through the rigorous testing that the Pro-M EMS processors do. The Pro-M EMS processors must meet the same quality standards as the Ford factory processors. They are built in the same plant, side by side with the Ford factory processors. Furthermore, the strategies loaded into the processors are written by Ford contractors. Quite honestly, everyone involved in this project is absolutely the finest in their field.
Q. Just how quickly does the Pro-M EMS react to sensor input and control my engine?
A. Let’s use an example. If MAF voltage were sampled at an anemically slow 1MHz (in reality, the system samples faster than this), that would be 1 million samples per second. For an engine that idles at 1000rpm, the engine revolves approximately 16 times per second. Given that there are 4 cylinder events per revolution, that means there are 64 cylinder events per second and 1/64 of a second between cylinder events. In the time between cylinder events, the processor will have analyzed 15,625 data points and will use them to decide what to do for the next event. That’s a lot of data. Let’s take it to 6000rpm. It’s still 2,604 data points between cylinder events.
Q. What strategy does the Pro-M EMS use?
A. There has been some misinformation posted online that the Pro-M strategy is likely the same one that was used by Ford in 1986. That is wrong. In 2013, the first Pro-M EMS version released was 3.60, and that wasn’t even close to what was used in 1986. Currently today, Pro-M is at version 7.23 and it might even be higher than that by the time we finish writing this. All numbers to the left of the decimal signify major changes to the strategy and all numbers to the right of the decimal point denote minor changes to the strategy. To think that a strategy for fuel, spark or nitrous oxide from 1986 is the same or close to the same strategy as that employed by Pro-M today is ridiculous. (There would be no need to be paying Ford engineers to write code for the Pro-M EMS now if that were true.) To help illustrate the point, the Pro-M EMS uses adaptive strategies for idle and fuel, and those concepts never even existed back in 1986, never mind Progressive Water/Methanol Injection, Progressive Nitrous Control, Traction Control, and Launch Assist, etc. The best comparison we can give is the iPhone. Let’s compare the first-generation iPhone to the current iPhone 11. Both iPhones can make phone calls and surf the internet, but the latest generation does it better and faster with more capabilities than the first-generation iPhone. As far as providing any technical specifications documenting exactly how the Pro-M EMS is coded, that’s PROPRIETARY information.
Q. How come no one else builds a Mass Air based EMS?
A. For the same reason, no one else uses production quality processors and no one else makes high-quality direct fit wire harnesses with all the correct connectors…..it’s MONEY. It costs more money to produce a Mass Air based EMS and less money to produce a Speed Density system.
Q. What are the four things you must-have for an engine to run?
A. Air, Fuel, Compression, and Spark.
1) Air – Airflow at any given time is a function of the combination of the engine parts and how much air is permitted to enter the engine via the throttle blade.
2) Fuel – The proper amount of fuel is added to that air via the fuel injectors.
3) Compression – The air-fuel mixture must be compressed in order to create the powerful expansion necessary to make power once the compressed air/fuel mixture is ignited.
4) Spark – Spark must occur to ignite the air/fuel mixture and it must happen at the proper time. The time at which this occurs is known as spark advance.
Only two of these things are engine management related. Those things are “Fuel” and “Spark.” The other two (Air and Compression) are strictly mechanical and are not controlled by the engine management system. The exception to that rule is electronic throttle control, but that topic is not relevant here.
In a net shell, basic engine management is a matter of providing the proper amount of fuel and providing a spark at the proper time. In order to determine the proper amount of fuel to inject and when to ignite it, you need to know the airflow. The BEST way to determine airflow is to monitor it directly with a Mass Airflow Sensor. Once you understand that, it becomes clear why the Pro-M EMS is unique.
Q. What is Mass Air Engine Management?
A. It's important to understand that the mass of the air being ingested by the engine is the single most important value necessary to determine how much fuel to supply to the engine and to determine what the spark advance should be. A Mass Air engine management system uses a Mass Air Meter to directly measure the mass of the air being ingested by the engine at any given time. You should also understand that the combination of engine parts is irrelevant when using Mass Air engine management. That combination will result in some amount of air mass. Since that air mass is directly measured, the combination of engine parts that resulted in that air mass simply does not matter. And for this reason, you can change that combination of engine parts as often as you'd like. You can even add a supercharger or a turbocharger and this rule still applies. I made an additional 90 rwhp at the wheels by simply removing an air filter off the inlet of my supercharger with NO TUNING, and the car was safe.
The air mass value is used to calculate a value for “Load”. Load is defined as “Ingested Air Mass divided by Potential Air Mass.” It sounds complicated but it isn't. The ingested air mass is simply the reading taken by the mass air meter. The potential air mass is a calculation done by the PCM that uses the engine's cubic inch displacement and RPM. When you have “Load”, you have everything you need to know. Load will determine what your air/fuel ratio should be. It will also determine what your spark advance should be.
Q. What is Speed Density and how it is used in OEM applications?
A. Speed Density systems use a method where the manifold vacuum and engine RPM are used to calculate the volume of air being ingested by the engine when using a fixed combination of parts. That estimated volume of air is then corrected for temperature and pressure. There is much more to it than this, but for the purpose of this writeup, this explanation will suffice. There are several articles on the web that explain this in greater detail if you care to gain a deeper understanding of speed density.
So why do so many auto manufacturers use Speed Density? In the auto industry where cost is a major factor, there are obvious cost benefits to not having to install a Mass Air Meter in every vehicle. For that reason, and that reason alone, some OEMs will use Speed Density engine management. In an OEM application, speed density makes a lot of sense. Think about how much money they can save by not having to buy millions of mass air meters!
The method the OEM manufacturers use to do this is very time consuming and very expensive, but worth it since they can amortize this time over hundreds of thousands of vehicles that are all using the same engine.
That last sentence is very important. They will have an entire team of calibrators spend about six months mapping out a specific combination of engine parts in a controlled environment on an engine dyno. They will hold that engine at every possible combination of RPM, throttle position, temperature, and atmospheric pressure and use a Mass Air meter to record the air mass at each operating point. This data is used to calculate the Load values for the calibration or tune that will be used for that engine. It is important to understand that the Speed Density systems used in the OEM still use load for their fueling and spark advance calculations. They call this Speed Density, but a Mass Air meter was used to generate the data needed.
This method works quite well for cars running out of the showroom with identical combinations. But let’s look at why we were/are in the market for an EMS in the first place. We have modified things in the effort to gain performance, and now we need something to control this very different combination. Every engine is different. Plummer’s isn’t even remotely close to John’s. Different displacement, different heads, different intakes, different cam profiles, different number of cams, different compression… we could go on endlessly. You can't justify the time, even if you had access to the necessary equipment, to set up a proper speed density tune for each of these different combos. For this reason, this version of speed density is not applicable to the aftermarket but is important to understand how this is done.
Q. So how is Speed Density used in the Aftermarket?
A. Today, Speed Density systems are almost always “Self-Learning” systems.
The process... Tell the ECU what air/fuel ratio you want under the varying operating conditions. The “Self-Learning” systems will use feedback from a wideband oxygen sensor to achieve those values. Here is the problem… Where do you come up with those values? The answer? You guess until it runs.
While much better than the old methods, due to the significant savings in the amount of time spent tuning these, the simple truth is that it is just a faster method to get to the same old incorrect result.
The problem… You simply do not have the information you need to create a proper tune, because you have no method to measure air mass, and therefore no way to calculate “Load”.
Idle is simple. An air/fuel ratio of 14.7:1 will work. Experiment from there. Wide-open throttle is a bit more involved but still simple. You experiment with values on the dyno until it makes max power. Not complicated but time-consuming and expensive. The rest, which is everything in between, is just a bunch of guesswork until you get it to run reasonably well. Understand that there are too many possible scenarios to ever get this anywhere near as good as it would be using a mass air engine management system. Outside of drag racing, the fact is the area between idle and wide-open throttle is where you spend 99.9% of your time driving your vehicle, and it's also where speed density in the aftermarket gives you the worst results.
Don't confuse “Self-Learning” with “Self-Tuning”, which is what many aftermarket manufacturers call it. There is no such thing as self-tuning. The tuner still must dictate to the ECU what the air/fuel ratios will be, and without a value for load, it’s all just guesswork.
How about spark advance? Speed Density offers you nothing to use to come up with proper spark advance values. Understand that spark advance is half the battle, and all you can do is take a guess.
You should also know that speed density systems work poorly with aggressive camshafts. Speed density systems rely heavily on the reading from the Manifold Absolute Pressure (MAP) sensor. Aggressive cams produce a little vacuum and therefore little for the MAP sensor to work with.
Additionally, Speed Density systems need to be re-tuned every time you make a change to the engine. Even a small change. That’s great for the tuning shop. Not so great for you. Remember Plummer’s car picking up 90 HP to the wheels when he removed his filter and did nothing else? Try that with Speed Density. (No, don’t try it. It’s not safe.)
There are two reasons why an aftermarket EFI manufacturer wants to sell you a Speed Density system. Neither of them benefits the customer. First, they are less expensive to manufacture. Second, they put the burden of getting your engine to run properly on the end-user.
Q. Can you run the Pro-M EMS as a Speed Density system?
A. Have you been reading? The answer is actually… Yes, but it doesn’t make sense to do so in all but the rarest cases. The Pro-M EMS is designed as a MAF based EMS because MAF is easier to tune and use. Speed Density can be enabled with the addition of the optional MAP sensor for those that are intent on making things difficult.
Q. Why would someone want to buy the Pro-M EMS?
A. There are people who want a processor that was developed with a budget far exceeding the budget of every one of these other systems combined, with software and strategies developed by the same people who developed the strategies for the vehicles that have to meet all the federal safety regulations and minimize warranty claims, and with hardware that has a real measured mean time between failure under every possible operating condition.
In addition, they want these systems to run their car without having to spend lots of time tuning. Simply remove the factory processor and harness, and plug the new harness in. No wiring. No real knowledge required. The dashboard works, the fans work, A/C control works, everything. And without making the argument again, MAF is easier to tune, period. In most cases, the default base fuel and spark maps (and all the modifier tables to them) that come with this system will work right out of the box.
In all fairness, each style system (MAF and Speed Density) will make the same power and have the same drivability when tuned properly. The Pro-M EMS tune is already at the OEM level right out of the box for Mass Airflow engine management. Airflow is directly measured, and everything stems from that. The chances of tuning Speed Density properly at an OEM level are slim. We believe MAF will adapt better than Speed Density or Alpha/N, but they all work. It just depends on what your objective is and how much time you want to spend. As was mentioned earlier, if you’re dead set of making things difficult, you can run the Pro-M EMS as Speed Density.
Q. Why does the Pro-M Engine Management System use two (2) widebands instead of one?
A. In a perfect world, there would be no reason to, but things aren’t perfect. The reality is most intake manifolds don’t distribute airflow exactly evenly between banks. As a result, one bank may run slightly richer than the other. This can be witnessed by looking at the readout of each bank’s wideband with the system’s fuel control set in open loop. They likely won’t be the same. For example, bank 1 might be running 14.0 while bank 2 is running 15.5. Utilizing two widebands allows the system to correct the a/f in each bank independently. Again, this can be witnessed by looking at the readout for each bank, but this time with the system in closed loop. Corrected independently, both banks should now be at 14.7. This would be impossible with only one wideband. In fact, using the above example, closed loop with only one wideband will make the situation in one of the two banks even worse. If the sensor were placed in bank 1, the system would assume that the entire engine is running rich at 14.0. It will pull fuel from BOTH banks until bank 1 gets to 14.7. But, therefore, bank 2 went from an already lean 15.5 to somewhere around 16.0-16.2. If a lone wideband were to be placed in bank 2 instead, the same problem exists, just in the opposite direction. As you can see, one wideband is poor. It costs more to run two widebands, and you get what you pay for.
Q. Is the Pro-M EMS truly a “Plug & Play” Engine Management System?
A. Honest answer… neither of us likes this term. Do you literally plug it in and drive away? No. You absolutely MUST set up your calibration properly with GOOD injector data, GOOD MAF data, and proper bore, stroke, and the number of cylinders. If you’re not comfortable with that, Chris Richards will do it for you for a small fee. Your engine MUST be in proper operating condition. And you MUST properly follow the directions with setting up base idle. If you don’t follow these directions, plug in the system, and just expect the car to drive away perfectly, then you will be disappointed. However, if you are methodical and follow the instructions, then it’s about as “plug & play” as possible.
Q. Can the same Pro-M Engine Management System for my 96 Mustang GT be used on other model-year Mustangs?
A: Yes and No. The processor itself is the same. That is 100% transferrable. In fact, Plummer’s processor that he uses in his 94 Mustang was once put into another of our friend’s 98 Cobra to prove that a problem he had was NOT the processor. (His cams were degreed wrong.) It took us all of 2 minutes to make the swap. Flash the proper calibration file into the processor and plug it into the harness in the car. The harnesses themselves are different as they contain wiring and connectors specific to the engine/sensors/ignition system in the car. If you have a complete system for a 96 and want to put it into a 94-pushrod car, you’ll need the 94-95 harness. The calibration files themselves have different settings selected, but technically it is all the same software. When initially purchased, Chris puts all the proper settings in the calibration for you based on the year vehicle you have. Swapping to another year is just a matter of changing the appropriate settings.
Thanks
Michael Plummer and John Janek
I was bored so I asked John Janek to assist me in answering some Frequently Asked Questions on the Pro-M Engine Management System (EMS). We had a good time putting this together and we hope it helps.
Q. Why is the Pro-M EMS so expensive?
A. Good things aren’t cheap. The quality of manufacturing and components that go into the Pro-M EMS cost money.
The processor is manufactured by the Visteon Corporation. Visteon is a Fortune 500 company spun from the Ford Motor Company in 2000. Visteon designs and manufactures many of the factory electronic parts in your Mustang.
The software developers who code the Pro-M EMS strategies are actual Ford Engineers who are constantly updating the software to make the system better (more on this later). They get paid very well.
The Ford connectors, wiring, terminals, wire loom, and harness wrap are top-notch quality pieces and are specifically designed for automotive engine bays. The system doesn’t utilize cheap, generalized wire that can be purchased at Home Depot or hobby kit connectors from a place like your local electronic store. Lay a competitor's wiring harness next to a Pro-M wiring harness and the differences are immediately clear. Their harnesses contain a bare minimum of circuits. You get only what is needed to run the engine. One competitor claims to have a “Fox Body Mustang Specific” harness. That claim could not be more untrue. The Pro-M harness literally has three times the wiring theirs does, contains all the original circuits used in the original harnesses and uses all the original connectors. The competition claims that their “Fox Body Specific” harness fits all model years. Pro-M makes TEN DIFFERENT HARNESSES FOR THE FOX BODY alone. Not to mention the six other harnesses they make for the other Mustangs from 96 through 2004. Why? Because the original harnesses differ from year to year and that is what is necessary to make a true vehicle specific harness.
Add-on features like traction control, launch assist, progressive Nitrous and Water/Methanol Control are included in the price at no additional cost. Want to add traction control to the other guy's system? Be prepared to spend $600 to $1000 for an add on box that works as well as the Pro-M does. It’s not an apple to apple comparison when people try to compare low dollar EMS’s against a Pro-M EMS because of the quality and features built into every Pro-M system. Compare the initial cost of the Pro-M EMS to any other EMS with comparable features (Holley Dominator) out there and you'll see the cost is about the same.
Q. What makes the Pro-M processor unique?
A. Self-protecting, self-diagnosing and production quality processor
Self-protecting processor: If the Pro-M EMS processor detects a short circuit, it will shut down the affected ECM driver. Of course, it will also turn on the check engine light and store a code to direct you to the problem.
Self-diagnosing processor: The Pro-M EMS processor continuously checks itself for faults. No more guessing whether or not the processor is the source of trouble. These processors are extremely robust and have already been through the most rigorous testing in the industry long before going on the shelf, so the chance of ever having trouble with one is slim to none. But when doing diagnostics, wouldn't it be nice to know whether or not the processor could be at fault? No testing needed. If there is trouble, it will let you know.
Production quality processor: As noted above, the Pro-M EMS processor is made by Visteon, the same manufacturer who makes the processors for Ford (how nice). This is something you simply will NOT find anywhere else. The competition uses low production modules that cannot compare to the quality of the Pro-M EMS processor and do not go through the rigorous testing that the Pro-M EMS processors do. The Pro-M EMS processors must meet the same quality standards as the Ford factory processors. They are built in the same plant, side by side with the Ford factory processors. Furthermore, the strategies loaded into the processors are written by Ford contractors. Quite honestly, everyone involved in this project is absolutely the finest in their field.
Q. Just how quickly does the Pro-M EMS react to sensor input and control my engine?
A. Let’s use an example. If MAF voltage were sampled at an anemically slow 1MHz (in reality, the system samples faster than this), that would be 1 million samples per second. For an engine that idles at 1000rpm, the engine revolves approximately 16 times per second. Given that there are 4 cylinder events per revolution, that means there are 64 cylinder events per second and 1/64 of a second between cylinder events. In the time between cylinder events, the processor will have analyzed 15,625 data points and will use them to decide what to do for the next event. That’s a lot of data. Let’s take it to 6000rpm. It’s still 2,604 data points between cylinder events.
Q. What strategy does the Pro-M EMS use?
A. There has been some misinformation posted online that the Pro-M strategy is likely the same one that was used by Ford in 1986. That is wrong. In 2013, the first Pro-M EMS version released was 3.60, and that wasn’t even close to what was used in 1986. Currently today, Pro-M is at version 7.23 and it might even be higher than that by the time we finish writing this. All numbers to the left of the decimal signify major changes to the strategy and all numbers to the right of the decimal point denote minor changes to the strategy. To think that a strategy for fuel, spark or nitrous oxide from 1986 is the same or close to the same strategy as that employed by Pro-M today is ridiculous. (There would be no need to be paying Ford engineers to write code for the Pro-M EMS now if that were true.) To help illustrate the point, the Pro-M EMS uses adaptive strategies for idle and fuel, and those concepts never even existed back in 1986, never mind Progressive Water/Methanol Injection, Progressive Nitrous Control, Traction Control, and Launch Assist, etc. The best comparison we can give is the iPhone. Let’s compare the first-generation iPhone to the current iPhone 11. Both iPhones can make phone calls and surf the internet, but the latest generation does it better and faster with more capabilities than the first-generation iPhone. As far as providing any technical specifications documenting exactly how the Pro-M EMS is coded, that’s PROPRIETARY information.
Q. How come no one else builds a Mass Air based EMS?
A. For the same reason, no one else uses production quality processors and no one else makes high-quality direct fit wire harnesses with all the correct connectors…..it’s MONEY. It costs more money to produce a Mass Air based EMS and less money to produce a Speed Density system.
Q. What are the four things you must-have for an engine to run?
A. Air, Fuel, Compression, and Spark.
1) Air – Airflow at any given time is a function of the combination of the engine parts and how much air is permitted to enter the engine via the throttle blade.
2) Fuel – The proper amount of fuel is added to that air via the fuel injectors.
3) Compression – The air-fuel mixture must be compressed in order to create the powerful expansion necessary to make power once the compressed air/fuel mixture is ignited.
4) Spark – Spark must occur to ignite the air/fuel mixture and it must happen at the proper time. The time at which this occurs is known as spark advance.
Only two of these things are engine management related. Those things are “Fuel” and “Spark.” The other two (Air and Compression) are strictly mechanical and are not controlled by the engine management system. The exception to that rule is electronic throttle control, but that topic is not relevant here.
In a net shell, basic engine management is a matter of providing the proper amount of fuel and providing a spark at the proper time. In order to determine the proper amount of fuel to inject and when to ignite it, you need to know the airflow. The BEST way to determine airflow is to monitor it directly with a Mass Airflow Sensor. Once you understand that, it becomes clear why the Pro-M EMS is unique.
Q. What is Mass Air Engine Management?
A. It's important to understand that the mass of the air being ingested by the engine is the single most important value necessary to determine how much fuel to supply to the engine and to determine what the spark advance should be. A Mass Air engine management system uses a Mass Air Meter to directly measure the mass of the air being ingested by the engine at any given time. You should also understand that the combination of engine parts is irrelevant when using Mass Air engine management. That combination will result in some amount of air mass. Since that air mass is directly measured, the combination of engine parts that resulted in that air mass simply does not matter. And for this reason, you can change that combination of engine parts as often as you'd like. You can even add a supercharger or a turbocharger and this rule still applies. I made an additional 90 rwhp at the wheels by simply removing an air filter off the inlet of my supercharger with NO TUNING, and the car was safe.
The air mass value is used to calculate a value for “Load”. Load is defined as “Ingested Air Mass divided by Potential Air Mass.” It sounds complicated but it isn't. The ingested air mass is simply the reading taken by the mass air meter. The potential air mass is a calculation done by the PCM that uses the engine's cubic inch displacement and RPM. When you have “Load”, you have everything you need to know. Load will determine what your air/fuel ratio should be. It will also determine what your spark advance should be.
Q. What is Speed Density and how it is used in OEM applications?
A. Speed Density systems use a method where the manifold vacuum and engine RPM are used to calculate the volume of air being ingested by the engine when using a fixed combination of parts. That estimated volume of air is then corrected for temperature and pressure. There is much more to it than this, but for the purpose of this writeup, this explanation will suffice. There are several articles on the web that explain this in greater detail if you care to gain a deeper understanding of speed density.
So why do so many auto manufacturers use Speed Density? In the auto industry where cost is a major factor, there are obvious cost benefits to not having to install a Mass Air Meter in every vehicle. For that reason, and that reason alone, some OEMs will use Speed Density engine management. In an OEM application, speed density makes a lot of sense. Think about how much money they can save by not having to buy millions of mass air meters!
The method the OEM manufacturers use to do this is very time consuming and very expensive, but worth it since they can amortize this time over hundreds of thousands of vehicles that are all using the same engine.
That last sentence is very important. They will have an entire team of calibrators spend about six months mapping out a specific combination of engine parts in a controlled environment on an engine dyno. They will hold that engine at every possible combination of RPM, throttle position, temperature, and atmospheric pressure and use a Mass Air meter to record the air mass at each operating point. This data is used to calculate the Load values for the calibration or tune that will be used for that engine. It is important to understand that the Speed Density systems used in the OEM still use load for their fueling and spark advance calculations. They call this Speed Density, but a Mass Air meter was used to generate the data needed.
This method works quite well for cars running out of the showroom with identical combinations. But let’s look at why we were/are in the market for an EMS in the first place. We have modified things in the effort to gain performance, and now we need something to control this very different combination. Every engine is different. Plummer’s isn’t even remotely close to John’s. Different displacement, different heads, different intakes, different cam profiles, different number of cams, different compression… we could go on endlessly. You can't justify the time, even if you had access to the necessary equipment, to set up a proper speed density tune for each of these different combos. For this reason, this version of speed density is not applicable to the aftermarket but is important to understand how this is done.
Q. So how is Speed Density used in the Aftermarket?
A. Today, Speed Density systems are almost always “Self-Learning” systems.
The process... Tell the ECU what air/fuel ratio you want under the varying operating conditions. The “Self-Learning” systems will use feedback from a wideband oxygen sensor to achieve those values. Here is the problem… Where do you come up with those values? The answer? You guess until it runs.
While much better than the old methods, due to the significant savings in the amount of time spent tuning these, the simple truth is that it is just a faster method to get to the same old incorrect result.
The problem… You simply do not have the information you need to create a proper tune, because you have no method to measure air mass, and therefore no way to calculate “Load”.
Idle is simple. An air/fuel ratio of 14.7:1 will work. Experiment from there. Wide-open throttle is a bit more involved but still simple. You experiment with values on the dyno until it makes max power. Not complicated but time-consuming and expensive. The rest, which is everything in between, is just a bunch of guesswork until you get it to run reasonably well. Understand that there are too many possible scenarios to ever get this anywhere near as good as it would be using a mass air engine management system. Outside of drag racing, the fact is the area between idle and wide-open throttle is where you spend 99.9% of your time driving your vehicle, and it's also where speed density in the aftermarket gives you the worst results.
Don't confuse “Self-Learning” with “Self-Tuning”, which is what many aftermarket manufacturers call it. There is no such thing as self-tuning. The tuner still must dictate to the ECU what the air/fuel ratios will be, and without a value for load, it’s all just guesswork.
How about spark advance? Speed Density offers you nothing to use to come up with proper spark advance values. Understand that spark advance is half the battle, and all you can do is take a guess.
You should also know that speed density systems work poorly with aggressive camshafts. Speed density systems rely heavily on the reading from the Manifold Absolute Pressure (MAP) sensor. Aggressive cams produce a little vacuum and therefore little for the MAP sensor to work with.
Additionally, Speed Density systems need to be re-tuned every time you make a change to the engine. Even a small change. That’s great for the tuning shop. Not so great for you. Remember Plummer’s car picking up 90 HP to the wheels when he removed his filter and did nothing else? Try that with Speed Density. (No, don’t try it. It’s not safe.)
There are two reasons why an aftermarket EFI manufacturer wants to sell you a Speed Density system. Neither of them benefits the customer. First, they are less expensive to manufacture. Second, they put the burden of getting your engine to run properly on the end-user.
Q. Can you run the Pro-M EMS as a Speed Density system?
A. Have you been reading? The answer is actually… Yes, but it doesn’t make sense to do so in all but the rarest cases. The Pro-M EMS is designed as a MAF based EMS because MAF is easier to tune and use. Speed Density can be enabled with the addition of the optional MAP sensor for those that are intent on making things difficult.
Q. Why would someone want to buy the Pro-M EMS?
A. There are people who want a processor that was developed with a budget far exceeding the budget of every one of these other systems combined, with software and strategies developed by the same people who developed the strategies for the vehicles that have to meet all the federal safety regulations and minimize warranty claims, and with hardware that has a real measured mean time between failure under every possible operating condition.
In addition, they want these systems to run their car without having to spend lots of time tuning. Simply remove the factory processor and harness, and plug the new harness in. No wiring. No real knowledge required. The dashboard works, the fans work, A/C control works, everything. And without making the argument again, MAF is easier to tune, period. In most cases, the default base fuel and spark maps (and all the modifier tables to them) that come with this system will work right out of the box.
In all fairness, each style system (MAF and Speed Density) will make the same power and have the same drivability when tuned properly. The Pro-M EMS tune is already at the OEM level right out of the box for Mass Airflow engine management. Airflow is directly measured, and everything stems from that. The chances of tuning Speed Density properly at an OEM level are slim. We believe MAF will adapt better than Speed Density or Alpha/N, but they all work. It just depends on what your objective is and how much time you want to spend. As was mentioned earlier, if you’re dead set of making things difficult, you can run the Pro-M EMS as Speed Density.
Q. Why does the Pro-M Engine Management System use two (2) widebands instead of one?
A. In a perfect world, there would be no reason to, but things aren’t perfect. The reality is most intake manifolds don’t distribute airflow exactly evenly between banks. As a result, one bank may run slightly richer than the other. This can be witnessed by looking at the readout of each bank’s wideband with the system’s fuel control set in open loop. They likely won’t be the same. For example, bank 1 might be running 14.0 while bank 2 is running 15.5. Utilizing two widebands allows the system to correct the a/f in each bank independently. Again, this can be witnessed by looking at the readout for each bank, but this time with the system in closed loop. Corrected independently, both banks should now be at 14.7. This would be impossible with only one wideband. In fact, using the above example, closed loop with only one wideband will make the situation in one of the two banks even worse. If the sensor were placed in bank 1, the system would assume that the entire engine is running rich at 14.0. It will pull fuel from BOTH banks until bank 1 gets to 14.7. But, therefore, bank 2 went from an already lean 15.5 to somewhere around 16.0-16.2. If a lone wideband were to be placed in bank 2 instead, the same problem exists, just in the opposite direction. As you can see, one wideband is poor. It costs more to run two widebands, and you get what you pay for.
Q. Is the Pro-M EMS truly a “Plug & Play” Engine Management System?
A. Honest answer… neither of us likes this term. Do you literally plug it in and drive away? No. You absolutely MUST set up your calibration properly with GOOD injector data, GOOD MAF data, and proper bore, stroke, and the number of cylinders. If you’re not comfortable with that, Chris Richards will do it for you for a small fee. Your engine MUST be in proper operating condition. And you MUST properly follow the directions with setting up base idle. If you don’t follow these directions, plug in the system, and just expect the car to drive away perfectly, then you will be disappointed. However, if you are methodical and follow the instructions, then it’s about as “plug & play” as possible.
Q. Can the same Pro-M Engine Management System for my 96 Mustang GT be used on other model-year Mustangs?
A: Yes and No. The processor itself is the same. That is 100% transferrable. In fact, Plummer’s processor that he uses in his 94 Mustang was once put into another of our friend’s 98 Cobra to prove that a problem he had was NOT the processor. (His cams were degreed wrong.) It took us all of 2 minutes to make the swap. Flash the proper calibration file into the processor and plug it into the harness in the car. The harnesses themselves are different as they contain wiring and connectors specific to the engine/sensors/ignition system in the car. If you have a complete system for a 96 and want to put it into a 94-pushrod car, you’ll need the 94-95 harness. The calibration files themselves have different settings selected, but technically it is all the same software. When initially purchased, Chris puts all the proper settings in the calibration for you based on the year vehicle you have. Swapping to another year is just a matter of changing the appropriate settings.
Thanks
Michael Plummer and John Janek
