Boost Reduction with AC on? Options

[Geddes]

It was a fairly hot day today (over 30 degrees celcius) and I was cruising down the highway with the ac on which I don't normally have on.. and noticed that the car was not boosting as per normal..

I know the TSVS setup will reduce boost levels if it thinks its seeing knock, so with the very hot air im assuming it was pulling a bit of boost for that reason, but having the ac system turned on drops the boost even more (I have no actual numbers to give you as I dont have my boost guage hooked up yet), but for comparison, the car with the ac off will peg the boost needle near the top (on a colder day it will hit the plus sign above the top of the guage) but when i turn the ac on, it only makes it to about bar 4 of 6 on the guage..

TLDR version: any one else with a GT-4 with no boost controller installed notice a reduction in boost with the ac on? or is mine just doing something odd..?

for reference, I checked between ac on and off in 3rd gear every time.

[celica74]

With any car, the ac functions because of the compressor, which is belt driven off the crank. With the ac turned off, the clutch on it is disengaged and there is no load from it. when the ac is turned on the clutch on the compressor kicks in and you get the rpm drop because of this. This is caused by the load from the size of the pulley and the amount of torque required to turn the compressor so your ac works. If youve ever done an underdrive pulley set up, this principle comes into play. Underdrive pulleys are just smaller pulley on the alternater, powersteering, and even the waterpump in some cases. By having smaller pulleys you have less force to turn them, and you unleash 10-20hp depending on how small you go. The engine isnt gaining any power, its just allowing the engine to put more of it to the ground instead of your alternator and so on.
Anyways, like i was saying all cars have the problem. When boost is in play, the turbo gets its power for the amount of exhaust gases from the engine. You add more resistence to the motor(not motor under load. but more forces for the motor to deal with) you get less exhaust, and thats why you arent able to get full boost. Same thing applys to superchargers aswell.