fish_antlers
Administrator
The Truth is Out There
Posts: 21895
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posted December 10, 2006 04:49 PM
Interesting technical question raised by freek (of all people!)
BC Place stadium (where the Supercross was held) is a pressurized air filled football stadium .. identical domes all across the US... Indianpolis etc etc... the stadium is at sea level.
What sort of HP advantages do the race teams gain by running their bikes in a pressurized facility? (if any?) ... one would think there must be some sort of gain...
thoughts?
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VincentHill
Needs a life
Posts: 6520
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posted December 10, 2006 04:54 PM
Lets cover the Drag Strip only when I ride! 
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ridgeracer
Pro
Posts: 1309
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posted December 10, 2006 08:17 PM
+0.3%
(sorry for the english units)
A sq ft has a 144 sq inches. a pressure increas of just .035 PSI would support 5lbs per sq ft. That pressure was in a dome spec I found online.
Feeding that pressure increase into a Relative Horsepower correction calculator came up with a difference of 0.3% or about the same amount gained by a 2 degree F drop in temperature. Given a dome is probably warmer than an open stadium you probably lose more from temperature increase than you gain from pressure increase
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MadMike
Moderator
FEAR THE BLACK FLAG!!!!!!!!
Posts: 6579
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posted December 10, 2006 09:08 PM
and I was going to say just a smidge...
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200-MPH CLUB MEMBER!
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frEEk
Administrator
ummm... yeah
Posts: 9660
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posted December 10, 2006 11:56 PM
damn, i thought there would be significant gains, given that u can really feel the pressure increase when u enter the stadium. makes me wonder, how crazy would the pressure difference between 2000 and 5000ft altitude if you made the transition in a second, cause i know that diff takes the 12 from power wheelies without even trying, to having to give it a bounce and as hard a ug on the bars as u can muster and having the front end just BARELY come up. so there's gotta be alot of HP lost in those 3000ft.
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tuusinii
Pro
Posts: 1031
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posted December 11, 2006 04:09 AM
You can find the formula for pressure vs. altitude quite easily (http://science.widener.edu/~svanbram/chem332/pdf/press_alt.pdf). From there You can pretty easily see the pressure difference and HP difference is about the same as pressure drop because You need about the same mixture of gas and oxygen. So when there is less oxygen You need less gas and get thus less HP...
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flite leader
Zone Head
Posts: 651
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posted December 12, 2006 11:23 AM
way to go ridgeracer
we have a couple of venues
in the tidewater area
1...
so close to sea level
that otherwise youd have to get wet
the other below sea level...... (im not tellin)
of course any gain is served to any & All !!
except if you are running far to lean
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blueford
Needs a job
Posts: 2984
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posted December 13, 2006 08:21 AM
quote:
damn, i thought there would be significant gains, given that u can really feel the pressure increase when u enter the stadium. makes me wonder, how crazy would the pressure difference between 2000 and 5000ft altitude if you made the transition in a second, cause i know that diff takes the 12 from power wheelies without even trying, to having to give it a bounce and as hard a ug on the bars as u can muster and having the front end just BARELY come up. so there's gotta be alot of HP lost in those 3000ft.
You would have 75% power at 6,000 ft. standard day, 65% at 8,000, so 5,000 about 80% power, these are aircraft engines, but it's all the same.
MSLP, Pressure at sea level is 14.7 psi, so a sq. ft. would be 2,117 lbs. so 5 lbs added is nothing, but just enough to support the dome fabric and lights attached to it.
Air pressure can change significantly every hour, when a pilot jumps into a cockpit, first thing he thinks is " what kind of air do I have, to work with today" the altimeter has moved a couple of hundred ft. from yesterday, what's the dewpoint, do we have dancing air? Is there a trough or cresting wave over my headd, the atmosphere is like an ocean and you're at the bottom.
I would say 5% to 8% performance shifts, same spot, any given day, the highest recorded pressure was 1086 mbar or 32.06 inches of mercury and the lowest was like 909 Mb./26.84 inches, so that's like 16% or 338 lbs. a sq. ft. deviation same altitude!!
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