i guess the tropical storm was a player in my boost yesterday??? i was only getting 20psi. i almost freaked like wtf??? then i remembered about pressures and what not. with the storm being a low pressure system,it affected by boost. am i correct on this??? yes??? no???

 

I have seen from 20ish all the way to 30 one day.....ya boost spikes. the weather really plays a big deal in these cars...

 

On average, our lovely planet is already at 14.7 psi...

Or (approx)--

• 1 atm (= 14.6956 psi)
• 101,325 Pascals (= 14.7 psi)
• 1 bar (= 100,000 Pascals)
• 760 Torr (= 14.7 psi)
• ... and so on ;-)

The pressure the turbo creates is obviously above and beyond this base atmospheric pressure. What's interesting is that the air pressure itself is partly a determining factor in how much "power" can be derived from additional boost. (Hence, one of the reasons when people try to compare boost with one another, the comparison has very limited significance... especially with "in range" numbers-- like Bubba getting 19# and Ted getting 20#, and while running the same setup, they're in different geographic locations).

As for the weather affecting boost... ABSOLUTELY!. However, something to ponder is that, when the atmospheric pressure falls, the turbo (up to its mechanical limits AND the input stream on the hot side) can create boost more easily (by spinning faster in the less dense air), thus partially offsetting the fall in atmospheric pressure. In short, the guy at sea level has more AP, and will (generally) spin up less turbo boost, than the identical setup in Denver, where the AP is closer to 12.10 psi. _IF_ the system in Denver is mechanically capable (and provided the appropriate exhaust stream), will spin up to a higher boost level. The net net of all this is STILL that high altitudes tend to be disadvantageous to making power... so don't move from Florida to Denver thinking you're going to get something out of it (other than views of the Flatirons ).

Note: Pike's Peak racers often run massive turbos in the 80+ pound boost range.

Another note: For all my caveats above... the stock BW turbo doesn't have much peak capability beyond stock, so don't get excited about the prospect of turning up the boost too much.

 

XXL is right on for the idea of what is happening. The term is called 'density altitude'. It is pressure altitude corrected for non-standard temperatures. Altimiters in a plane have to constantly be changed in terms of Hg to correct for temperature affects.

Basically it is all about air density. Hotter or cooler air will change the boost in your area as much as if it is in a higher altitude.

I believe I read a GM report that the computer system has the ability to make this correction. It was put in place so that mountain driving would be easier, or that is how they explained it. Computer can adjust from 15 to 17 to 19 to 21 based on density readings. I have not read about higher readings, and I believe they are talking about a steady reading and not a spike.

 

Decerase the mass of air because of high ambient temperature (assuming TX) minus 1.

Fool computer into thinking that air is denser because of humidity (theory, not sure how density is measured or calculated from some other measurment device)
minus 2.

Lower ambient pressure due to storm
Minus 3?


Just take it someplace above 6000 feet in the heat on a dry day and see how much boost you get there. Won't you go into limp mode if you go above 23psi anyway?

 

Here in MI I have yet to see above 15psi.

 

i won't go into limp. i'm tuned. i should see anywhere between 20-25psi and i'm at sea level.

 

I bought my turbo cobalt in Colorado Spring and drove it back to Amarillo texas boosting 20psi 150 mile after being here it went down to 17-18psi

 

I dont think i've ever seen 17 (no tune) but Ill check it out today.

 

i saw 19 down here near the gulf. it was a nasty hot day though. it would go from 15 to 19 at 5500rpm's. this was pre-tune .