Well, just did a little R&D out in the driveway/roadway. It's amazing what that GM-6 turbo will do on a hot day... I wasn't even wanting (or even attainted) 12 psi boost for long periods of time... but I was cookin' just the same.

Steady accelleration without peggin' out the boost gauge, and IAT temps climb and climb.

I have another thread started from last week about sudden loss of power, and had wondered about IAT temps getting too high.

So today, with temps in the 90°'s, thought would be a good time to see what's up. Took my Cooper thermometer (NIST calibration mind ya) and see what this baby's cookin' up to.

Without even getting close to the max limit for boost, I was running around 200° for IAT. At best 7 psi boost... not 12, but 7. I barely even kissed 219° for not even a split second, and power was gone. Then I could run it to the floor, and had nothing much left. Boost was maxed out, never really got past 9 with WOT, but the IAT's kept up. At one point, after the power loss, my IAT (I was pushing it to see what it would do) was climbing to over 230°!!!! Waahhooo!

So the moral of the story, boost ain't the end of it, you need the rest of the story there Paul Harvey.

This was a "temporary" setup until I could dive in the vacuum system, and get it back to stock (where I like to keep it at). Currently I'm running with wastegate tied shut... something I don't endorse being done, because of the danger that lurks from doing crazy things like that and shortening engine life. But, if I had the vacuum system set up, the boost would have been dumping before just going into limp mode to help keep IAT's in check.

On a side note, I'm going to find the IAT resistance values to given temps to see if the IAT sensor is out of range/spec...

thought I'd let you in a some of the data collected and lessons learned... like maybe gettin' an intercooled CDR or something... some of you ole timers may remember that from years ago....

Good post, knk - informative, illuminating, and educational on the practical level.

Like jimmy swaggert allus said - ya cain't preach it till ya've lived it!

And how would I know? - been there, done that with a 100-300deg Isspro electric oil temp gage, sensor installed in the intake plenum back when I was doing the R&D around the turn of the century - a Tech2 showed the Isspro gage to be very accurate

It is possible your IAT sensor is off, as the ~220deg over-temp condition must be met for ~20secs to go limp.

These are codes for Boost pressure and temperature -

DTC47\P0112* - IAT low ohms or shorted to ground
DTC48\P0113* - IAT hi ohms or open
DTC61\P0238* - MAP hi, open circuit or shorted to +5v
DTC62\P0237* - MAP low or shorted to ground
DTC78\P1656 - over-Boost

*also tested during WTS

DTC78\P1656 is for over-Boost - over-temp at hi-Boost has no dtc but PCM goes limp, reduces fuel - power-cycle off-on to reset

These resistance values are for all 6.5 PCM temp sensors - IAT, ECT, IP fuel =

*F......Ohms
-40 = 100700
-22 = 52700
-04 = 28680
+05 = 21450
+14 = 16180
+23 = 12300
+32 = 9420
+41 = 7280
+50 = 5670
+59 = 4450
+68 = 3520
+77 = 2796
+86 = 2238
+95 = 1802
104 = 1459
113 = 1188
122 = 973
140 = 667
158 = 467
176 = 332
194 = 241
212 = 177

Now you know why you need an intercooler with higher boost level.

More boost = Higher temps = Less power per PSI

Just a thought, but dosn't the ecm also limit fuel because of hi IAT's? if so that would explain the fact you could not get over 9psi, thats what mine would do when it defueled,(no codes were triggered as well) at WOT boost IIRC was under 10psi and EGT's limited to 600F, a good test would be to fool IAT's to see if the ECM still limits boost and fuel.
which actually limits boost? as both go hand in hand. high boost causes hi IAT,
Does anyone know which one triggers the ECM to defuel?

Wow GM & DP are quick on the keyboard!