MFD clarification

[cowboy_dan]

First off, I don't have Minotaur, but am considering it. In the mean time, I'm trying to learn.

I understand the basic fuel rate unit is known as MFD.
And, the graph:

http://i641.photobucket.com/albums/u...TowingMFD2.jpg

indicates to me that this is not an actual number, but rather a percentage.

Now, for the fun part: What is it a percentage of? A fixed value, a value that changes with RPM only, a value that changes with RPM and MAP?

Like I said, I don't know nuthin', so I'm just learning.

[soutthpaw]

MFD is in Milligrams per stroke.. its not a percentage. but it is a Desired which means it not always what you are really getting as several factors affect the actual fuel delivered.
The Map itself in using Accelerator pedal position 0-1024 A/D counts and engine RPM to the the MG/Stroke value...

You will find that there are many values that cannot be set directly because there are many other maps and parameters that alter the individual map..
Start of Injection (SOI) is probably the best example of that.... just cuz u set a SOI at a specific point, you will rarely actually get that SOI

[cowboy_dan]

Ok, so that value that corresponds to a pedal position of 100% is a fixed value, which can be modified (I assume) in the Minotaur.

[Pocket]

Originally Posted by cowboy_dan

Ok, so that value that corresponds to a pedal position of 100% is a fixed value, which can be modified (I assume) in the Minotaur.

If you mean the fixed position of 1023 A/D counts, yes that's 100% pedal position. The resolution of the pedal position in A/D counts can be changed. That image is exactly that, a table that Cody modified to have more resolution for pedal input.

After he shared that tidbit in the other thread, I tried it out on my truck. The result of it was a much smoother pedal that wasn't super touchy. I really like the MFD map like this much more than stock.

[cleatus12r]

Just for your information:

A/D counts are a more precise way of measuring the 0-5 volt input to the PCM from the Accelerator Pedal Position (APP) sensor. There are 204 A/D counts per volt of input.

Keep in mind that the APP sensor DOES NOT put out 0 volts, nor does it go all the way to 5 volts. This means that you will never get 0 A/D counts or a full 1023 A/D counts. More like 100 to 918 A/D counts.

For those of you who have this "updated" MFD scale, you might want to take this into account on your MFD map.

[cowboy_dan]

Originally Posted by Pocket

If you mean the fixed position of 1023 A/D counts, yes that's 100% pedal position. The resolution of the pedal position in A/D counts can be changed. That image is exactly that, a table that Cody modified to have more resolution for pedal input.

After he shared that tidbit in the other thread, I tried it out on my truck. The result of it was a much smoother pedal that wasn't super touchy. I really like the MFD map like this much more than stock.

Actually, what I said was

that value that corresponds to a pedal position of 100% is a fixed value

and what I meant was

that MFD value (in mg/stroke) that corresponds to a pedal position of 100% is a fixed value

In other words, the number (in mg/stroke) that is multiplied by the pedal % is a fixed number for a given calibration/tune. The number does not change with rpm, load, boost, or any other variable.

[cowboy_dan]

Originally Posted by cleatus12r

Just for your information:

A/D counts are a more precise way of measuring the 0-5 volt input to the PCM from the Accelerator Pedal Position (APP) sensor. There are 204 A/D counts per volt of input.

Keep in mind that the APP sensor DOES NOT put out 0 volts, nor does it go all the way to 5 volts. This means that you will never get 0 A/D counts or a full 1023 A/D counts. More like 100 to 918 A/D counts.

For those of you who have this "updated" MFD scale, you might want to take this into account on your MFD map.

Yup. Keeping the operating range from swinging to either of the voltage rails also allows for diagnostic capabilities. 5v systems are usually 0.5-4.5v operating range. Any signal voltage less than 0.5v is considered shorted to low source (ground), and anything over 4.5 volts is considered shorted to high source (5v or 12v).
Another benefit is that the A/D is usually most accurate in the middle of the range. So by taking either end of the range out of the usable system, the overall accuracy of the operating range is increased slightly.