the_mork
15+ Year Contributor
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- 26
- Mar 10, 2008
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Eau Claire,
Wisconsin
It is long past time to start splitting the evo8 ecu thread into relevant smaller discussions so here is the first fork. This is a topic that has relevance to a large section of the community including everyone that runs a flashable ecu be it an evo8 ecu or the H8 based 98/99 ecus as well as any EMS that uses an electronic boost controller. This post will be updated as we explore the topic with graphics, better information, and error corrections.
What is ecu based boost control and why do I want it?
Ecu based boost control has been popular for a long time in many communities including the Evo and Subaru worlds but has been unrealistic for DSMs because our ecus were so limited (until recently). The introduction of the Evo8 ecu mod and the Openport 2.0 cable have opened an opportunity for us to join the party. Being able to change the settings for boost control within the computer allows us to change our previously useless BCSs into a potent and free boost controller with a versatile array of options.
Traditionally we have used manual boost controllers to manage boost which limits us in a few ways. The first is that we are forced to tune for boost using a fairly meaningless and potentially dangerous measure of how much air a turbo is pushing (PSI). Since PSI is a relative measure of airflow and doesn't take into account volumetric efficiency or atmospheric conditions it isn't a measure that is portable from car to car or even day to day which makes for an excessive amount of confusion for new members and the potential for damage in cars that are being pushed to the ragged edge (coincidentally also most common with new members). The second way is that boost has a tendency to be all or nothing with a manual boost controller which makes for a nice and snappy DD but also limits the accelerator to being very similar to an on/off switch past about 35%tps on a fast spooling car.
BCS controlled boost solves both of these problems by controlling boost either directly to a certain pressure which in this case is a pressure above absolute vacuum as opposed to pressure above ambient conditions like a manual boost controller or by having a targeted load which is the ECUs internal unit for airflow which can be converted either to lbs/min or g/s which is really the preferable direction for tuning because it makes for a consistent car which rarely deviates from a very particular load range at WOT meaning that a car with a narrowly modified map will rarely fall off of the "tuned" section as well as having instant and predictable adjustments for changes in atmospheric conditions which helps to keep cars reliable, consistent, and fast. The computer also allows you to control boost with your foot in an even more direct way than we are used to managing it. The base wastegate duty cycle for the BCS is modified by multiplying it against TPS% which means a light throttle correction may only target a load or PSI range that is half of your normal WOT boost but you still retain the on/off switch effect of boost under all WOT and near WOT conditions.
Gear based boost control is the final and in my opinion most amazing option with ECU based boost control. This is a new and very exciting feature which I personally use in order to give my poor FWD car a fighting chance at maintaining traction while still making power. Not only can you run a different boost level for every gear but you but also for every RPM step for each gear in 500 RPM increments that should be rescalable if for some reason you need more resolution than that.
How much boost does it handle?
The simple answer is I don't think anyone has the answer for sure when it comes to a stock DSM BCS because no one has used one with an adjustable load target as far as I know but if someone with an evo8 ecu could test this it would be nice to add the results. What we do know is that on an evo the BCS cannot control boost to a level any higher than stock without a simple but effective modification called a pill. A pill is simply a piece of aluminum dowel with a hole of varying size drilled in it. A pill allows a stock evo BCS to hold boost past 25 psi (if someone could confirm the accepted maximum I'll edit this part). Pills cause a small problem though since they reduce the response and correction speed of the BCS.
What if I want to handle more boost?
This is very simple. The traditional answer from and Evo or Subaru guy is to buy a GM 3-port BCS off of a Grand National or turbo Trans Am. These BCSs handle more boost and have a better response time than their Mitsubishi counterparts and are easy to install simply by splicing it into the current BCS wiring with a resistor (polarity doesn't matter).
Well and good but those things used to be $15 and now they're over $50! No problem, Mitsubishi was very kind to us and provided us with a functional 3-port BCS just a few feet away that serves very little purpose so it can be removed without adversely affecting driveability. It's simple, just hack off your fuel pressure regulator solenoid and solder it in in place of your BCS. Doing this will cause a check engine light but anyone who does this already has a flashable ecu so just flip a periphery bit and it'll be gone (FAA bit5?)
Okay you've convinced me, now how do I get it?
You'll need an Evo8 ECU in order to do anything significant for the moment but the boost control tables should all exist in the H8 computer as well so someone just needs to find the definitions for them, you can probably ask Ceddy politely to look into it or start learning the disassembly on your own.
For evo8 ecu cars please read these threads for implementation. I'll go through and add instructions directly here at some point but I'll be out of town for the next week but I wanted to get the ball rolling on this discussion. For gear based boost control you'll need to run a v7 Tephra rom. When I get the opportunity I plan to start a thread like this on tuning flashable computers which I hope to write the first draft for tomorrow night although if someone beats me to it that's fine too.
ECU boost control mods - evolutionm.net
how-to: ECU-based direct boost control - evolutionm.net
HOW TO - Control boost using ECUFLash and the stock boost solenoid - evolutionm.net
HOW TO - Control boost using ECUFLash and 3 port GM boost solenoid - evolutionm.net
TephraMOD V6 - testing! - evolutionm.net v6 becomes v7 later in the thread.
What is ecu based boost control and why do I want it?
Ecu based boost control has been popular for a long time in many communities including the Evo and Subaru worlds but has been unrealistic for DSMs because our ecus were so limited (until recently). The introduction of the Evo8 ecu mod and the Openport 2.0 cable have opened an opportunity for us to join the party. Being able to change the settings for boost control within the computer allows us to change our previously useless BCSs into a potent and free boost controller with a versatile array of options.
Traditionally we have used manual boost controllers to manage boost which limits us in a few ways. The first is that we are forced to tune for boost using a fairly meaningless and potentially dangerous measure of how much air a turbo is pushing (PSI). Since PSI is a relative measure of airflow and doesn't take into account volumetric efficiency or atmospheric conditions it isn't a measure that is portable from car to car or even day to day which makes for an excessive amount of confusion for new members and the potential for damage in cars that are being pushed to the ragged edge (coincidentally also most common with new members). The second way is that boost has a tendency to be all or nothing with a manual boost controller which makes for a nice and snappy DD but also limits the accelerator to being very similar to an on/off switch past about 35%tps on a fast spooling car.
BCS controlled boost solves both of these problems by controlling boost either directly to a certain pressure which in this case is a pressure above absolute vacuum as opposed to pressure above ambient conditions like a manual boost controller or by having a targeted load which is the ECUs internal unit for airflow which can be converted either to lbs/min or g/s which is really the preferable direction for tuning because it makes for a consistent car which rarely deviates from a very particular load range at WOT meaning that a car with a narrowly modified map will rarely fall off of the "tuned" section as well as having instant and predictable adjustments for changes in atmospheric conditions which helps to keep cars reliable, consistent, and fast. The computer also allows you to control boost with your foot in an even more direct way than we are used to managing it. The base wastegate duty cycle for the BCS is modified by multiplying it against TPS% which means a light throttle correction may only target a load or PSI range that is half of your normal WOT boost but you still retain the on/off switch effect of boost under all WOT and near WOT conditions.
Gear based boost control is the final and in my opinion most amazing option with ECU based boost control. This is a new and very exciting feature which I personally use in order to give my poor FWD car a fighting chance at maintaining traction while still making power. Not only can you run a different boost level for every gear but you but also for every RPM step for each gear in 500 RPM increments that should be rescalable if for some reason you need more resolution than that.
How much boost does it handle?
The simple answer is I don't think anyone has the answer for sure when it comes to a stock DSM BCS because no one has used one with an adjustable load target as far as I know but if someone with an evo8 ecu could test this it would be nice to add the results. What we do know is that on an evo the BCS cannot control boost to a level any higher than stock without a simple but effective modification called a pill. A pill is simply a piece of aluminum dowel with a hole of varying size drilled in it. A pill allows a stock evo BCS to hold boost past 25 psi (if someone could confirm the accepted maximum I'll edit this part). Pills cause a small problem though since they reduce the response and correction speed of the BCS.
What if I want to handle more boost?
This is very simple. The traditional answer from and Evo or Subaru guy is to buy a GM 3-port BCS off of a Grand National or turbo Trans Am. These BCSs handle more boost and have a better response time than their Mitsubishi counterparts and are easy to install simply by splicing it into the current BCS wiring with a resistor (polarity doesn't matter).
Well and good but those things used to be $15 and now they're over $50! No problem, Mitsubishi was very kind to us and provided us with a functional 3-port BCS just a few feet away that serves very little purpose so it can be removed without adversely affecting driveability. It's simple, just hack off your fuel pressure regulator solenoid and solder it in in place of your BCS. Doing this will cause a check engine light but anyone who does this already has a flashable ecu so just flip a periphery bit and it'll be gone (FAA bit5?)
Okay you've convinced me, now how do I get it?
You'll need an Evo8 ECU in order to do anything significant for the moment but the boost control tables should all exist in the H8 computer as well so someone just needs to find the definitions for them, you can probably ask Ceddy politely to look into it or start learning the disassembly on your own.
For evo8 ecu cars please read these threads for implementation. I'll go through and add instructions directly here at some point but I'll be out of town for the next week but I wanted to get the ball rolling on this discussion. For gear based boost control you'll need to run a v7 Tephra rom. When I get the opportunity I plan to start a thread like this on tuning flashable computers which I hope to write the first draft for tomorrow night although if someone beats me to it that's fine too.
ECU boost control mods - evolutionm.net
how-to: ECU-based direct boost control - evolutionm.net
HOW TO - Control boost using ECUFLash and the stock boost solenoid - evolutionm.net
HOW TO - Control boost using ECUFLash and 3 port GM boost solenoid - evolutionm.net
TephraMOD V6 - testing! - evolutionm.net v6 becomes v7 later in the thread.
