Can't do a Car-Show burnout due to heat soak causing slow spoolup?!

[Syclone0044]

Hey guys I figured you would have some experience with this same problem. Happens on my 91 GMC Syclone with CK Stage 2 700R4 trans, and a fairly tight 2700 RPM Yank nitrous/blower converter. Normally my truck spools up great with upgraded heads/cam and a small PT51 turbo @ 20 PSI w/SMC Alky. I can fry the tires with a strong boost launch, etc.

Here's the scenario, I'm driving around (car spools up great) and pull into a car show or a parking lot, shut the engine off. Talk with the guys for 10-30 minutes (engine is heat-soaking in the meantime) and they want to see the truck do what it does. So I get in and pull out (engine has only been running for 1-2 minutes) and try to impress everyone and the damn thing can barely build boost against the footbrake and when I go WOT its WAY more doggy than normal!!! So my truck doesn't even come close to spinning the tires and full boost doesnt come till 2nd gear, and everyone thinks my truck is slow off the line. (Normally its a Monster off the line!)

If I drive around the block (get some cool airflow over the radiator and stock Air-to-Water Intercooler) then it will be back to normal.

So what can possibly affect the spoolup like this? It almost feels like something in the engine/transmission? I don't recall my datalogs showing an unusually rich AFR or anything that sticks out to me..

Does this have to do with the trans oil getting hot or draining to the bottom of the pan when the engine gets freshly shut off? It just feels like the converter gets really tight when I let it heat-soak.

 

[boostingbuick]

Was it building boost the same way it always does? It sounds like the wastegate stuck open. I assume this was the only time it happened.

 

[Syclone0044]

No - This problem happens consistently every single time. It's not the wastegate sticking because if I go WOT, eventually (2nd gear) it reaches normal controlled full boost.

Nobody else has this problem??

 

[Turbo6Smackdown]

Whats the cruising water temperature on the scan tool? Does this happen in both hot and cold ambient air temps?

 

[Chuck Leeper]

A low volume of H2O in that W2A i/c is likely the problem.
Aren't there upgrades for the rad on the I/C, and a big, external tank?
Want to verify?
Add a couple thermocouples. Read the I/C air out, and the H2O temp at the I/C, when truck operates "normally". Compare those #'s w/ those that show when the truck lays down.
If burnouts are your "thing", maybe drive around the block B4 you do 1???