Units of Measure
There isn't much to learn here, but it helps to get used to thinking of engine load in terms of kPa instead of inches of mercury (or inches of vacuum) and temperature in terms of degrees Celsius.
kPa: The PCM measures intake manifold pressure in kiloPascals, abbreviated kPa. It's essentially the same thing as what your vacuum gauge displays, but converted to metric units. What makes it a little confusing is that the numbers are "backwards" compared to vacuum. Unless you have a blower or turbo, your vacuum gauge reading at full throttle is probably near zero, and if you wind the engine out in first, then sharply let off the gas while leaving the engine in gear, you probably see something around 25 inches of mercury (Hg). Small numbers (near zero) correspond to serious acceleration and big numbers correspond to engine braking.
But full throttle in metric-land results in a reading somewhere around 95-100 kPa, and high vacuum conditions (engine braking) produce a manifold pressure in the 20's or 30's. So small numbers correspond to engine braking and big numbers correspond to acceleration. Print out a conversion table to keep near the PC you use to modify your PCM files. Eventually you'll get used to thinking in kPa. Maybe.
Here is a conversion table:
kPa |
20 |
25 |
30 |
35 |
40 |
45 |
50 |
55 |
60 |
65 |
70 |
75 |
80 |
85 |
90 |
95 |
100 |
in Hg |
24.0 |
22.5 |
21.1 |
19.6 |
18.1 |
16.6 |
15.2 |
13.7 |
12.2 |
10.7 |
9.3 |
7.8 |
6.3 |
4.8 |
3.3 |
1.9 |
0.4 |
mV: milliVolts is the unit used for the oxygen sensor output. One mV is 1/1000 of a Volt, so a mV is pretty little.
degrees C: degrees centigrade or Celsius. Another unit from metric-land. Here's a conversion to good ol' degrees Fahrenheit:
deg C |
-40 |
-28 |
-16 |
-4 |
8 |
20 |
32 |
44 |
56 |
68 |
80 |
92 |
104 |
116 |
128 |
deg F |
-40 |
-18 |
3 |
25 |
46 |
68 |
90 |
111 |
133 |
154 |
176 |
198 |
219 |
241 |
262 |