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arkansasfiddler
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need a difinitive ans: on a turbocharged/superch. engine, all things being unchanged, will hot, wet air sustain less boost than cool/dry air? in other words will my boost (87 gn) be somewhat less in summer (95 deg.), than in fall (50 deg.) i am showing about 19# even after shortening my waste gate rod. ------------have alch. inj. knock will eat me up if is not used. i know that the alch. spray cools the egt. and a little boost will be lost but i would like to be able to run about 20/21# if possible. any help....appreciated
 

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hot wet air is less dense than cold dry...therefore, you will have to run the turbo harder to achieve the same number of air molecules in the cylinder on a hot day.

You should be able to run more boost than that in the summer with alky injection, however. IF everything is working right in the combination.

All injectors spraying the same, coolant temp in the 170s-180, clean intercooler, and so on.
 

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An engine running when the ambient temp is high usually can't use as much boost as one running in cool weather. But if you didn't change anything, the boost shouldn't change from one day to the next. The waste gate actuator is working off the differential pressure between the atmosphere and the turbo discharge. That means the waste gate will open, lowering boost, without much change, if any, due to temp. The knock sensor and the ECM may be shutting off the wastegate solenoid, though, and decreasing boost. Some of the chip gurus will have to answer that- I can't remember is there's a temperature input to the tables that control the wastegate solenoid. If you run "tuner style", and take the waste gate solenoid out of the picture, then boost should stay about the same, regardless of ambient temp. Or that's what I think, anyway. :D
 

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arkansasfiddler said:
need a difinitive ans: on a turbocharged/superch. engine, all things being unchanged, will hot, wet air sustain less boost than cool/dry air? in other words will my boost (87 gn) be somewhat less in summer (95 deg.), than in fall (50 deg.) i am showing about 19# even after shortening my waste gate rod. ------------have alch. inj. knock will eat me up if is not used. i know that the alch. spray cools the egt. and a little boost will be lost but i would like to be able to run about 20/21# if possible. any help....appreciated
*All things unchanged*, ignores the fact that the your tune might be way off in some area, and will run best contrary to what might be expected. You have to optimize a tune for the weather, to make any comparison.
 
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