While idling at a stop light with A/C on I noticed my boost gauge was at -8psi. Normally while idling i am at-10psi or lower because needle is maxed low. Milage decreased to 22.8 mpg vs the 26-30 i usually get. Never thought about it but it seems even idling with A/C on cause the eaton to spool. I suspect it caused an increase in my driving boost level across whole RPM range. If I nail the gas I know it still maxes out at +8Psi just thought it odd the extra drag from A/C to increase the work on engine enough for S/C to spool at idle.

 

Is this a question or an observation?

 

8" of vacuum seems a little weak. I would guess that you have a vacuum leak somewhere. Mine runs, at idle, at -30. I am not sure what is considered normal for a SC 3800 though. Good luck!

 

Observation. never thought A/C would cause enough drag to make engine rpm go high enough to cause boost at idle. Never used A/C but it was 98* and in a black car that is like 100 million*. I actually usually take the A/C out of my cars lumina had a good old bypass pully. Intimidator gets hot enough inside to melt plastic so keeping A/C in this one.

 

There is a good amount of drag on our cars when the AC is being used. If you think it is too much, maybe the pulley is having some resistance?

 

Thats alot of drag. It all looks good makes no noise. Basically looks all brand new. Blows Ice out the vents. But it must take an extra 40 horse just to run A/C. Thats nuts.