I would like to learn what exactly 3D engine maps are, and in what ways are they related with traction control. I know this has been discussed a lot of times before, but I think it is worth discussing it again now, especially after Frentzen's accusations and the GP os Malaysia.
3D engine maps
Started by
Hellenic tifosi
, Mar 18 2001 18:33
2 replies to this topic
#3
Engineguy
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- 989 posts
- Joined: February 01
Member
Posted 18 March 2001 - 20:07
A 2D map is like a simple graph you can plot on paper. For example, put RPM along the horizontal (X) axis, and injector open time along the vertical (Y) axis. In an ECU this would be stored as a "look-up table" in memory. The ECU says, "let's see... my count from the crank sensor indicates we're turning 13,300 RPM, so, looking that up in my table, I need to hold the injector open .013 ms on the next injection event."
A 3D map adds a third axis to the plot. For example, put RPM along the horizontal (X) axis, and intake vacuum along the vertical (Y) axis. Injector open time is now plotted as an elevation (Z axis). When these are graphically depicted they look like a hilly terrain (i.e. If I go 13 miles west and 7 miles north, what is the elevation above sea level at that spot?). In an ECU this would be stored in an array in memory. The ECU says, "let's see... my count from the crank sensor indicates we're turning 13,300 RPM, AND the intake port vacuum is 0.1 bar, so, looking that up in my memory array, I need to hold the injector open .016 ms on the next injection event."
In reality most ECU's operate more like 6D because they get a base value for the injector open time from a 2D or 3D map and then start applying several modifiers from independent maps. "Based on what the coolant temp is, I see I need to mutiply the open time by 0.933." "Based on how far the thottle rotated in the past ms, I see I need to multiply the open time by 1.333" (this is the electronic equivelent of the accelerator pump in a carb).
What does mapping have to do with traction control? Rather than simply dropping random cylinders (cut off fuel or ignition) like a "crude" rev limiter, pit speed limiter, or traction control sysem, which causes that ugly and obvious misfiring sound, simply add another "D" or modifier to your open time calculation. Have a map where you look up the multiplier for the current "RATE of RPM INCREASE" and apply it (see my post under the "Legal TC" thread). Much harder to detect from sound or tire markings on the grid, because it is a smooth (map curve) transition of the power level of all the cylinders rather than an on/off switch like completely dropping cylinders.
A 3D map adds a third axis to the plot. For example, put RPM along the horizontal (X) axis, and intake vacuum along the vertical (Y) axis. Injector open time is now plotted as an elevation (Z axis). When these are graphically depicted they look like a hilly terrain (i.e. If I go 13 miles west and 7 miles north, what is the elevation above sea level at that spot?). In an ECU this would be stored in an array in memory. The ECU says, "let's see... my count from the crank sensor indicates we're turning 13,300 RPM, AND the intake port vacuum is 0.1 bar, so, looking that up in my memory array, I need to hold the injector open .016 ms on the next injection event."
In reality most ECU's operate more like 6D because they get a base value for the injector open time from a 2D or 3D map and then start applying several modifiers from independent maps. "Based on what the coolant temp is, I see I need to mutiply the open time by 0.933." "Based on how far the thottle rotated in the past ms, I see I need to multiply the open time by 1.333" (this is the electronic equivelent of the accelerator pump in a carb).
What does mapping have to do with traction control? Rather than simply dropping random cylinders (cut off fuel or ignition) like a "crude" rev limiter, pit speed limiter, or traction control sysem, which causes that ugly and obvious misfiring sound, simply add another "D" or modifier to your open time calculation. Have a map where you look up the multiplier for the current "RATE of RPM INCREASE" and apply it (see my post under the "Legal TC" thread). Much harder to detect from sound or tire markings on the grid, because it is a smooth (map curve) transition of the power level of all the cylinders rather than an on/off switch like completely dropping cylinders.
