Heat/Weather effects on HP
06-29-2010, 02:20 PM
#1
Turd Polisher
Thread Starter
iTrader: (1)
Heat/Weather effects on HP
I found this on another forum, I thought it would be beneficial for our readers to get a better grasp on how particular weather conditions can affect your car's performance.
Here's this guy's post, it explains on how to use the tool / what base line numbers you need.
http://www.csgnetwork.com/relhumhpcalc.html
I calculated out my cars horsepower based on my altitude and surprisingly, my car only makes about 94% in my neck of the woods. When I move closer to the beach closer to sea level, my car is making nearly 99% of it's crank power ..
Enjoy.
Here's this guy's post, it explains on how to use the tool / what base line numbers you need.
http://www.csgnetwork.com/relhumhpcalc.html
I figured I would share this with you all. It is not a secret that warmer air and higher elevation makes the car run sluggish. Those of you who are curious how much of a horsepower difference it makes given different temperatures, altitudes, humidity can now play with some numbers to see how it affects performance.
I was curious last night, and came across this and figured you guys would enjoy it.
It is based off if your motor has 100 hp. So if you want to know how much of a difference it would make than turn the horsepower number given into a percentage and multiply it by your current horsepower.
For instance, if the calculator says "96 horsepower", that would mean 96%, and you would multiply 240 (stock crank hp) times .96, which would equal 230.4. If the calculator says 103 horsepower, you would multiply 103 times 240, which would equal roughly 247 horsepower.
Barometric pressure in your area can be found at almost any weather site, or you can purchase a barometer. Typically barometric pressure is between 29-30.5. When it is about to storm the barometric pressure drops to around 28, but on a nice day it usually hangs around 30-30.5.
The lowest barometric pressure recorded was somewhere around 26, and this is extremely rare, and the highest barometric pressure recorded was a little over 32, which is also very rare.
Keep that in mind when playing with the calculator. I would leave the barometric pressure at 30, and play around with the other variables, than play around with the barometric pressure and see how big of a difference it can make on your car.
I was curious last night, and came across this and figured you guys would enjoy it.
It is based off if your motor has 100 hp. So if you want to know how much of a difference it would make than turn the horsepower number given into a percentage and multiply it by your current horsepower.
For instance, if the calculator says "96 horsepower", that would mean 96%, and you would multiply 240 (stock crank hp) times .96, which would equal 230.4. If the calculator says 103 horsepower, you would multiply 103 times 240, which would equal roughly 247 horsepower.
Barometric pressure in your area can be found at almost any weather site, or you can purchase a barometer. Typically barometric pressure is between 29-30.5. When it is about to storm the barometric pressure drops to around 28, but on a nice day it usually hangs around 30-30.5.
The lowest barometric pressure recorded was somewhere around 26, and this is extremely rare, and the highest barometric pressure recorded was a little over 32, which is also very rare.
Keep that in mind when playing with the calculator. I would leave the barometric pressure at 30, and play around with the other variables, than play around with the barometric pressure and see how big of a difference it can make on your car.
Enjoy.
06-29-2010, 05:45 PM
#2
Burning Brakes
Yes, density altitude (DA) has a profound effect on ET/MPH and HP. I use http://wahiduddin.net/calc/calc_hp_dp.htm to get density altitude and get my historical weather data from wunderground.com.
One important thing to note is that it works both ways. In Kansas City (~1200') in the middle of summer, it's not uncommon to see 4000' to 5000' DA conditions. In the fall, when the pressure is high, temps are cool, and the humidity low, we can see 0' DA conditions. That's a huge swing in available power.
Ever wonder why some cars post some rediculously fast ET/MPHs compared to the norm? 9 times out of 10, it's because of DA conditions. In the winter/fall/early spring in coastal areas (especially the east/northeast coast), baro pressure can get very high and have an almost supercharging effect. Factor in the sea level or near sea level elevation and it's not uncommon for these "freak" cars to have 7% to 10% more power simply because of the dense oxygen packed air. On a basic bolt-on G, that would be like adding 25whp and would be like running on a track at 2500' below sea level. It explains why some cars are going .3-.4 seconds and 3mph+ faster than the norm. There is no such thing as factory freaks anymore. Build tolerances are simply too tight and controlled. The difference, for the most part, is DA.
With my cars, I've seen differences of around .4-.5 seconds and 3 to 4mph between running on a humid 90 degree day (~4500' DA) vs running in cool dry 50 degree air (~200' DA).
One important thing to note is that it works both ways. In Kansas City (~1200') in the middle of summer, it's not uncommon to see 4000' to 5000' DA conditions. In the fall, when the pressure is high, temps are cool, and the humidity low, we can see 0' DA conditions. That's a huge swing in available power.
Ever wonder why some cars post some rediculously fast ET/MPHs compared to the norm? 9 times out of 10, it's because of DA conditions. In the winter/fall/early spring in coastal areas (especially the east/northeast coast), baro pressure can get very high and have an almost supercharging effect. Factor in the sea level or near sea level elevation and it's not uncommon for these "freak" cars to have 7% to 10% more power simply because of the dense oxygen packed air. On a basic bolt-on G, that would be like adding 25whp and would be like running on a track at 2500' below sea level. It explains why some cars are going .3-.4 seconds and 3mph+ faster than the norm. There is no such thing as factory freaks anymore. Build tolerances are simply too tight and controlled. The difference, for the most part, is DA.
With my cars, I've seen differences of around .4-.5 seconds and 3 to 4mph between running on a humid 90 degree day (~4500' DA) vs running in cool dry 50 degree air (~200' DA).
06-29-2010, 06:28 PM
#3
Thanks for posting this Tyler. As Dave said DA does have a major effect on your vehicles performance. In Tucson, AZ we have an elevation of 3075ft at our track here. I have been to the track in every season as our track doesn't close because our weather is nice year round. The best DA I have raced in is 4200ft. I was going to go to the track this past friday and decided not to. The DA at 8pm at night when the event started was 6200ft! So I figured I could test my new Jpipe in some better DA conditions. Maybe after the monsoon cooled air!
My car was running at 89% when the DA was 4200ft. I ran my 15.47@92+MPH which translated into a corrected time of 14.666@97.1MPH. So basically I don't have ideal conditions haha. The DA calculator at dragtimes.com though helps me with a more accurate projection of what my car is capable of in more ideal conditions though!
My car was running at 89% when the DA was 4200ft. I ran my 15.47@92+MPH which translated into a corrected time of 14.666@97.1MPH. So basically I don't have ideal conditions haha. The DA calculator at dragtimes.com though helps me with a more accurate projection of what my car is capable of in more ideal conditions though!
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