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Author
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Topic: Ambient air temp, oxygen density, altitude, blah blah blah
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V8 Thumper
Gearhead Posts: 3267
From: Orange, Ca. United States of America
Registered: Dec 2001
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posted 05-20-2003 08:09 PM
   
I understand the atmospheric conditions well enough, but I swear I can feel the difference in the power my motor makes in the cool morning hours compared to the 90+ degree southern California springtime afternoons... or is it all in my head? Anyone care to share some tips  ? ------------------
1965 GT coupe, 333ci aluminum headed/solid cammed stroker, four speed, 3.70:1 9" All Blue Oval, no blue bottle
http://mustangsandmore.50megs.com/V8Thumper.html
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steve'66
Gearhead Posts: 6150
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 05-20-2003 08:14 PM
Cool air is more dense (good)
High barometric pressure (good)
Low humidity, less water in the air, (good)If your car ran better in the heat,it is jetted too lean. But yours sounds right, that's why racers spend $$$ on weather stations. SteveW
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V8 Thumper
Gearhead Posts: 3267
From: Orange, Ca. United States of America
Registered: Dec 2001
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posted 05-20-2003 08:17 PM
No no, it runs like a mad bat out of hell when it's cool out  , it just dosen't feel as vicious when it's really hot out. I remember Alex being bummed about a portable weather station accidently getting run over  at an event not long ago  ------------------
1965 GT coupe, 333ci aluminum headed/solid cammed stroker, four speed, 3.70:1 9" All Blue Oval, no blue bottle
http://mustangsandmore.50megs.com/V8Thumper.html
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steve'66
Gearhead Posts: 6150
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 05-20-2003 08:20 PM
quote:
Originally posted by V8 Thumper:
I remember Alex being bummed about a portable weather station accidently getting run over at an event not long ago
Yeah, That's like burning a $500 bill. SteveW
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bluestreek
Gearhead Posts: 1202
From: Athens,GA
Registered: Jul 2001
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posted 05-20-2003 08:23 PM
Cold dry air is like free cylinder pressure. Now you know why nitrous is so awesome.  ------------------
1966 Mustang Coupe: Custom glass hood and BIG scoop sits atop a 289 stroked to 331 c.i., Steel crank and girdle, 5.4 H-beams, Forged slugs, TFS alum. heads, ported Stealth 8020 intake, Xtreme 274 Solid Roller, Holley 750 HP, long tubes, 4speed, 9" 3.50 posi.
11.86 @ 116 mph (7.62 @ 93 mph)full street trim!
DanH
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indyphil
Gearhead Posts: 642
From: Lafayette, IN, USA
Registered: Jul 2002
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posted 05-21-2003 10:26 AM
The racers could probably tell you but the air temp, track temp, humidity and wind are probably worth a lot of time on the track - several tenths if things all stack up. hence the weather stations. I guess bracket racers are obsessed with the weather because it makes such a big difference.I have felt the same seat of pants difference with the car too. ------------------
'68 coupe 289 C code
66 heads, edel 600cfm carb, performer intake, dual exhaust
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Ryan Wilke
Gearhead Posts: 1368
From: Stanton, Michigan 49707
Registered: Oct 2000
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posted 05-21-2003 10:38 AM
quote:
Originally posted by V8 Thumper:
No no, it runs like a mad bat out of hell when it's cool out , it just dosen't feel as vicious when it's really hot out....
If it runs BETTER in cool air, then that means those conditions and settings are where your carb is "happiest". If you can notice that it's not as "happy" when it's warmer out, then that indicates you are probably running richer than you need, and that you should back off on the jets a bit from the cooler setting..... I'd say you'll FEEL a difference in power if there's a 10 degree difference in temp and you don't change your carb jetting. Also as SteveW said, temp is only one factor. Power levels will also be affected by humidity changes and barometric pressure changes. Rule-of-Thumb, humidity levels will go up as temps go down; so the power level drop isn't normally a linear change. Ryan
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