Does anyone else ever think this?......
#16
04-23-2005, 06:18 PM
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Originally Posted by Gsedanman
There are many atmospheric variables that can affect performance- it's not your imagination. Hot dry days, your perfornance is off a little from cool damp days.
Altitude affects it too, sea level being the best.
Only other thing I can think of is gasoline variances and brands. (within the same grade- ie 91 octane). Some brands seem to run better than others in our engines.
C.
Altitude affects it too, sea level being the best.
Only other thing I can think of is gasoline variances and brands. (within the same grade- ie 91 octane). Some brands seem to run better than others in our engines.
C.
i just fill with 93 exxon..
#17
04-23-2005, 09:37 PM
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04-23-2005, 09:53 PM
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04-23-2005, 11:46 PM
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Originally Posted by Gsedanman
There are many atmospheric variables that can affect performance- it's not your imagination. Hot dry days, your perfornance is off a little from cool damp days.
Altitude affects it too, sea level being the best.
Only other thing I can think of is gasoline variances and brands. (within the same grade- ie 91 octane). Some brands seem to run better than others in our engines.
C.
Altitude affects it too, sea level being the best.
Only other thing I can think of is gasoline variances and brands. (within the same grade- ie 91 octane). Some brands seem to run better than others in our engines.
C.
Well noted, but on the same day in the same conditions, I can feel this? I thought about the gas as well, I usually use Unocal 91, or what ever it is here in Ca. and I know there is a difference in the gas when summer time arrives.
I am glad many here feel the same way, I will ask the master tech when I take my car in next week?
#22
04-24-2005, 07:47 PM
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Originally Posted by geioushi
I agree, my physics professor mentioned this before...even though the atmospheric variables may be only slightly different, they have a significant affect on performance. Its not just the G, but all cars. Maybe some of the mechanical engineers can elaborate more.
When your engine draws in air, it fills the cylinder with air at whatever properties the outside air is at, such as temperature, pressure, and humidity (neglecting changes due to it traveling through the filter, intake, etc.). The more air you can cram into the cylinder, the more gas you can add (keeping the air/fuel ratio the same) and thus the more power you can make. What happens is that the colder the air, the more dense it is. For those not scientifically inclinded, this means that you will have more air molecules within a given volume, the volume being the cylinder in this case. At a higher pressure (this is where altitude changes come into play), the air will also be more dense. With humidity, the water molecules take up part of the space within the volume that in 'dry' air would be where more air molecules would be. So the dryer, higher pressure and lower temperature you can get, the more air you can put into the cylinder, thus making more power.
This is the basis for turbos and s/cers, You compress the air, making it much, much more dense, allowing more fuel and resulting in more power.
Last edited by msd3075; 04-24-2005 at 09:54 PM.
#23
04-24-2005, 07:48 PM
#24
04-24-2005, 07:53 PM
I also noticed the cleaner mine is the faster it goes. 
#25
04-25-2005, 12:02 PM
Originally Posted by depechek
car motors run more efficiently when the air is cool and moist. That is y your car runs better or "faster" in the morning or just after it rains.
Water only displaces oxygen molecules needed for combustion.
Our cars are very susceptible to heat soak and environmental variables. Fluid/air temps play a large part in how much power the ECM makes in any given moment.
This is why dyno operators need to keep an eye on oil/water temps when making a pull. An unscrupulous operator could manipulate final numbers easily by choosing when to make the pull based on temps.
Last edited by ChicagoX; 04-25-2005 at 12:08 PM.
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04-25-2005, 12:54 PM
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04-25-2005, 02:08 PM
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#29
04-25-2005, 02:55 PM
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), then a full 20 gallon tank of gas will make your car weigh 120 pounds more than it would when you are next to empty.