Summary of Aftermarket ECUs / Controllers

[Nuke]

thanks dude

 

[ryan]

Sticky'd this thread.

 

[Geoff Ang]

wow bro... thanks man... very informative!!!

 

[Whisky_Tango]

Nuke and Geoff

Dun mention, I hope the write out is easy to understand. I have tried my best to make it as simple as possible especially for non-techie.

I also gain some knowledge by doing this and believe me this is only a grain worth of info. There's heaps more which Im still struggling to comprehend.

So I duno if this is a good way to consolidate the info and updating it as time fly by.

Cheers!

 

[Crufty Dusty]

Eric,

Good effort, maybe make some minor amendments:

As a general rule of thumb, it happens at about 20% to 30% and higher of throttle position, which corresponds to about 1.0V from the throttle position sensor (TPS). I have not seen any evidence to show that the ECU looks at any other parameter in determining when to operate at open-loop conditions. If someone knows of any other method, you are most welcome to share the info here.

The ECU also goes into open loop mode when it detects a sensor has become faulty, when the engine is cold etc.

Firstly, for petrol to burn it needs oxygen. For a complete combustion, a ratio of 14.7 parts of air to 1 part fuel should be attained. This air to fuel ratio (AFR) is called stoichiometric or Lambda = 1. This is just a ratio between air and fuel. 14.7:1 AFR is normally considered the best trade off between emissions, fuel economy and power production.

14.7 is lambda 1 for petrol engines only. Other fuels will have different stoichioimetric ratio.

 

[MRacer77]

Isn't the ratio of 14.7:1 a little misleading cause in actuality, the ratio for a NA car is more to be in the 12s and for FI cars in the high 11s?

 

[Crufty Dusty]

Isn't the ratio of 14.7:1 a little misleading cause in actuality, the ratio for a NA car is more to be in the 12s and for FI cars in the high 11s?

No.

Stoichiometric just means that the ratio of air-fuel is chemically ideal, i.e. complete burning of reactants. In this case, for gasoline engines, it is 14.7 parts of air to 1 part of fuel. The stoich point for diesel and alcohol engines are different (can't remember the numbers off-hand).

What you're referring to are some reference points to making best torque, which are not written in stone and may vary greatly depending on load, chamber design (pent roof, wedge etc), NA or FI, compression ratio etc.

 

[MRacer77]

I see. Thanks!

 

[axl]

Wah both Erik and Eric so clever!! I'm so proud to be driving the same car as them!!

Kekek.

 

[Whisky_Tango]

Eric,

Good effort, maybe make some minor amendments:

The ECU also goes into open loop mode when it detects a sensor has become faulty, when the engine is cold etc.

Ok, what kind of sensor? or any sensor tat is within the engine? Please elaborate... Thanks!

14.7 is lambda 1 for petrol engines only. Other fuels will have different stoichioimetric ratio.

Noted, will update in due course.

 

[Crufty Dusty]

Eric,

Good effort, maybe make some minor amendments:

The ECU also goes into open loop mode when it detects a sensor has become faulty, when the engine is cold etc.

Ok, what kind of sensor? or any sensor tat is within the engine? Please elaborate... Thanks!

For example, coolant temp... if the engine is "permanently cold", then the ECU will trigger a MIL and use a default coolant value. In the meantime it "knows" not to make use of the coolant sensor reading, thus it is in open loop. However you can't cheat the ECU and tune that out because the ECU will prevent that (like a "limp home" mode).

 

[The Mixmaster]

Fcuk! There are some serious petrolheads on BMWSG. I am so proud to be associated with these people.

 

[Shaun]

Real nice of you to spend your time creating the table, Eric.

Just to clarify, AFRs are by mass. Sometimes people think volume. Also, I don't think anyone should rely on the Magnuson-Moss warranty act unless they have the money and time to go through a drawn out legal process if the car company decides to be an ass.

 

[Crufty Dusty]

BTW... I have not come across any standalone ECU that has a "throttle map", "load map" etc. Perhaps some explanation is in order.

A map is nothing more than a table of values, kind of like an Excel spreadsheet.

Typically, if there is only 1 row, then it is called a table. If it has multiple rows, it is called a map. For this reason, a map is sometimes referred to as "3D", meaning it has multiple rows and columns. A "2D" table thus only has a single row. This is the basic distinction, although it is common for the terms to be used interchangeably especially in conversation.

Every ECU has at least 2 base maps: fuel and ignition. On each map, there are are rows and columns. The column values are in RPM, and the row values are whatever is determined to be load*. Where the rows and columns intersect, is called a load/RPM site. The ECU simply looks up these values in the fuel and ignition base maps very quickly to determine the proper amount of fuel/ignition timing to give the engine, in real time. Where there is no exact match in terms of load/RPM site, the ECU will use a combination of interpolation, statistics and history to arrive at an appropriate value.

Additionally, there are compensation maps such as coolant temp (cold start), acceleration/deceleration enrichment/enleanment, air temp, fuel temp, gear, so on and so forth.

* Depending on the ECU manufacturer, load can be based on MAF, MAP, MAP/EMAP, MAP/BAP, TPS etc or even a combination of the above.

 

[Crufty Dusty]

Everything else being equal, an ECU that has more load/RPM sites, allows the tuner to have better control over the engine operating parameters. Thus, when selecting an ECU, it is one point of consideration. Too many times enthusiasts have been led down the wrong path by observing what the race teams are using, e.g. "If this 900 bhp drag car is using XYZ ECU, it should work on my 250 bhp daily driver". They fail to understand that a drag car is always at WOT, and thus may not necessarily need high resolution maps.

So does having a 32x32 fuel and ignition map mean everything? Not necessarily. Unless the ECU allows you to customize the map area, it is nothing more than marketing talk. What do I mean? Say the ECU restricts you to 32 RPM sites, at 500 RPM intervals. That means it can control up to 16,000 RPM. Does your engine rev up to 16,000 RPM? It would be better if the ECU allows you to select a shorter interval between RPM points, say 250 RPM intervals. In this manner, you have finer resolution, allowing you greater control.

Another point of consideration is the number of I/O channels an ECU has. Using the earlier example, a drag car has no need for A/C, radiator fan control, idle control etc, so these may be lacking in the ECU as well. Since there is no need for these auxiliary functions, the ECU can omit them in the feature list, thereby reducing the cost.

These are just some basic points to take note of when selecting an aftermarket ECU. Be informed, and choose wisely. Have a clear goal of what you want to achieve with your car, and select an ECU that allows you to get there.

 

[Whisky_Tango]

Eric,

Ok, what kind of sensor? or any sensor tat is within the engine? Please elaborate... Thanks!

For example, coolant temp... if the engine is "permanently cold", then the ECU will trigger a MIL and use a default coolant value. In the meantime it "knows" not to make use of the coolant sensor reading, thus it is in open loop. However you can't cheat the ECU and tune that out because the ECU will prevent that (like a "limp home" mode).

Thanx Erik... I will include this in the "when it goes into open loop" section.

Maybe I will create a new heading for OBD II engine checks(MIL) lights.

 

[Whisky_Tango]

Real nice of you to spend your time creating the table, Eric.

Hey... no prob bro... and also thanx to you and Erik for your feedbacks and comments.

Just to clarify, AFRs are by mass. Sometimes people think volume.

Yes, air and fuel measured in mass. I will highlight this.

Also, I don't think anyone should rely on the Magnuson-Moss warranty act unless they have the money and time to go through a drawn out legal process if the car company decides to be an ass.

Tats true and besides its a foreign company which makes claims usually unsuccessful.
I will take this out.

 

[Whisky_Tango]

BTW... I have not come across any standalone ECU that has a "throttle map", "load map" etc.

Does this means piggyback ECU will not have Maps as well?

A map is nothing more than a table of values, kind of like an Excel spreadsheet.
Typically, if there is only 1 row, then it is called a table. If it has multiple rows, it is called a map. For this reason, a map is sometimes referred to as "3D", meaning it has multiple rows and columns. A "2D" table thus only has a single row. This is the basic distinction, although it is common for the terms to be used interchangeably especially in conversation.

Every ECU has at least 2 base maps: fuel and ignition. On each map, there are are rows and columns. The column values are in RPM, and the row values are whatever is determined to be load*. Where the rows and columns intersect, is called a load/RPM site. The ECU simply looks up these values in the fuel and ignition base maps very quickly to determine the proper amount of fuel/ignition timing to give the engine, in real time. Where there is no exact match in terms of load/RPM site, the ECU will use a combination of interpolation, statistics and history to arrive at an appropriate value.

Additionally, there are compensation maps such as coolant temp (cold start), acceleration/deceleration enrichment/enleanment, air temp, fuel temp, gear, so on and so forth.

* Depending on the ECU manufacturer, load can be based on MAF, MAP, MAP/EMAP, MAP/BAP, TPS etc or even a combination of the above.

Very informative! Will digest this and insert this into a new heading called "ECU Maps"

 

[Whisky_Tango]

Everything else being equal, an ECU that has more load/RPM sites, allows the tuner to have better control over the engine operating parameters. Thus, when selecting an ECU, it is one point of consideration. Too many times enthusiasts have been led down the wrong path by observing what the race teams are using, e.g. "If this 900 bhp drag car is using XYZ ECU, it should work on my 250 bhp daily driver". They fail to understand that a drag car is always at WOT, and thus may not necessarily need high resolution maps.

So does having a 32x32 fuel and ignition map mean everything? Not necessarily. Unless the ECU allows you to customize the map area, it is nothing more than marketing talk. What do I mean? Say the ECU restricts you to 32 RPM sites, at 500 RPM intervals. That means it can control up to 16,000 RPM. Does your engine rev up to 16,000 RPM? It would be better if the ECU allows you to select a shorter interval between RPM points, say 250 RPM intervals. In this manner, you have finer resolution, allowing you greater control.

Another point of consideration is the number of I/O channels an ECU has. Using the earlier example, a drag car has no need for A/C, radiator fan control, idle control etc, so these may be lacking in the ECU as well. Since there is no need for these auxiliary functions, the ECU can omit them in the feature list, thereby reducing the cost.

These are just some basic points to take note of when selecting an aftermarket ECU. Be informed, and choose wisely. Have a clear goal of what you want to achieve with your car, and select an ECU that allows you to get there.

Thanx for more info!

So generally, high resolution maps are for passenger car & race cars (not the hardcore or F1) and low resolution maps are for drag cars.

Any other features or benefits of standalone ECU and hope u can share some of the reliable ones for OBD II system. Thanks

 

[Crufty Dusty]

Does this means piggyback ECU will not have Maps as well?

A piggyback ECU will have its own maps. All it does is intercept the fuel, ignition and airflow sensor readings between the factory ECU and the sensors.

So generally, high resolution maps are for passenger car & race cars (not the hardcore or F1) and low resolution maps are for drag cars.

Low resolution maps are fine so long as you have control over the "problem areas" (i.e. able to specify which load/RPM sites need more resolution). However if you can't modify the map area, then obviously a higher number of load/RPM sites would be better.

Any other features or benefits of standalone ECU and hope u can share some of the reliable ones for OBD II system. Thanks

Standalones are meant to replace the factory ECU so they have no provision nor need to provide OBD data. After all, you can always retrieve the OBD data from the ECU using laptop. Some manufacturers even have hardware that shows engine data on the dash, or even steering wheel!

Having said that, there are some who use standalones as piggybacks i.e. handle only fuel and ignition, leaving all other functions like A/C, idle control, other auxiliary output to the factory ECU. In this manner, OBD data can be retained, but such a standalone is no different from a piggyback in terms of function.