timing ratard for nitrous (IAT)
The IAT rewire is easy and works well. You should use relays to alter the sensor path. Here is the resistance data for the IAT sensor. Then you just alter the desired row in the IAT-Timing table. Just be sure to wire it such that the sensor itself is totally out of the circuit when you want to pull timing, otherwise your resistance will vary with temp both ways.
9420 ohms = 32 *F - 0 *C
7280 ohms = 41 *F - 5 *C
5670 ohms = 50 *F - 10 *C
4450 ohms = 59 *F - 15 *C
3520 ohms = 68 *F - 20 *C
2796 ohms = 77 *F - 25 *C
2238 ohms = 86 *F - 30 *C
1802 ohms = 95 *F - 35 *C
1459 ohms = 104 *F - 40 *C
1188 ohms = 113 *F - 45 *C
973 ohms = 122 *F - 50 *C
667 ohms = 140 *F - 60 *C
467 ohms = 158 *F - 70 *C
332 ohms = 176 *F - 80 *C
241 ohms = 194 *F - 90 *C
177 ohms = 212 *F - 100 *C
132 ohms = 230 *F - 110 *C
100 ohms = 248 *F - 120 *C
77 ohms = 266 *F - 130 *C
60 ohms = 284 *F - 140 *C
47 ohms = 302 *F - 150 *
9420 ohms = 32 *F - 0 *C
7280 ohms = 41 *F - 5 *C
5670 ohms = 50 *F - 10 *C
4450 ohms = 59 *F - 15 *C
3520 ohms = 68 *F - 20 *C
2796 ohms = 77 *F - 25 *C
2238 ohms = 86 *F - 30 *C
1802 ohms = 95 *F - 35 *C
1459 ohms = 104 *F - 40 *C
1188 ohms = 113 *F - 45 *C
973 ohms = 122 *F - 50 *C
667 ohms = 140 *F - 60 *C
467 ohms = 158 *F - 70 *C
332 ohms = 176 *F - 80 *C
241 ohms = 194 *F - 90 *C
177 ohms = 212 *F - 100 *C
132 ohms = 230 *F - 110 *C
100 ohms = 248 *F - 120 *C
77 ohms = 266 *F - 130 *C
60 ohms = 284 *F - 140 *C
47 ohms = 302 *F - 150 *
Digging up an old post to add more info since I was poking around. Click on the thumbnail to bring up a picture of a table with a few examples of full IATS resistance values pulled from stock HPT tunefiles. These figures go below a temp reference of freezing. Allot of the IAT spark tables I have seen for GM go down to -40*F which is a much less likely temperature to encounter in natural driving situations then 32*F.
