Car ECU tuning software

In the hex dump window you see a series of highlighted bytes, 43 7A 00 00, and in the Inspector window you see "Float 250".

This is showing a map or constant value, in 32 bit floating point format, of 250.

The next series of 4 bytes, 43 FA 00 00, is a value of 500.

A value of 00 00 00 00 is a zero value.

Notice there are lots of 32 bit floats in the area of memory. This is part of a table.

The 20 values shown are:

250, 500, 0, 0, 9, 800, 1200, 1600, 2000, 2400, 2800, 3200, 3600, 4000, 4400, 4800, 5200, 5600, 6000 and 6400.

The values 200 and 500 are not RPM based on the magnitudes (RPM would not normally be lower than 650), the values 800 thru 6400 are most likely RPM values used in a lookup table or map.

What is a Map? Look at the array below...

The numbers in red represent RPM values, the green numbers represent Mass Air Flow and the numbers in the yellow matrix represent fuel injector pulse width.

The longer the injector pulse the more fuel gets injected into the rotor.

To find this table you would look for ascending RPM values, ascending MAP values and many fuel injector pulse values, RPM X MAP numbers, in this case 13X9. This is a purely hypothetical MAP for illustration only.

Going back to the ECU hex dump, the ascending RPM numbers could be the start of a fuel map, or it could be a timing map, or possibly a map to control oil injection, at this time we don't know the definition of that map.

To find a Constant, you need to know what to look for.

An RPM limit would be a 32bit float at 9000 for a standard transmission car or 7500 for a automatic.

You would do a search for "46 0C A0 00" to find all values of 9000.

Pick one and change to 8000 and see if you hit the RPM limit.

Not all values are stored as floats, there are also single byte values of 0-255, unknown if 16 bit integers are used.

Once you take a look at the MAP area in memory, you will see it's nearly all floats or byte values.

On the last note...

Even though chip tuning is possible with any ordinary HEX editor (as described above) — the fact is it can be very time consuming, tedious and error-prone.