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riv
Dodge Dakota
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9/26/2004
22:03:27
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 Subject: Humidity
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Is it just me or are these things super sensitive to humidity(see tempremental).
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Vic
Dodge Dakota
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9/27/2004
00:47:00
| RE: Humidity
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What things??
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mcarthey
Dodge Dakota
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9/27/2004
09:43:35
| RE: Humidity
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His cakes he just pulled out of the oven. And yes, they are.
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N56629
Dodge Dakota
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9/27/2004
13:13:49
| RE: Humidity
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I read your previous post http://www.dodgedakota.net/boards/per/11059.html and yes, humidity does affect it, because it is a factor in air density.
Try this http://www.westechperformance.com/pages/Tech_Library/Performance_Calculators/calc.html
Theoretically, all else being equal, you can predict your performance.
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Seriously
Dodge Dakota
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10/02/2004
11:28:05
| RE: Humidity
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Humidity affects these trucks more than any other vehicle I've seen.
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N56629
Dodge Dakota
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10/02/2004
15:16:11
| RE: Humidity
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"Humidity affects these trucks more than any other vehicle I've seen."
Seriously, it affects all internal combustion engines equally. It is a variable in air density.
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einstein
Dodge Dakota
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10/02/2004
16:19:52
| RE: Humidity
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the piston does not suck in air,the sudden vacuum is filled by atmospheric pressure alone. thats why you will make the most horsepower on a cool dry day with a high pressure area in control of the weather. sensors will lean out the mixture on hot days and the air won`t be as dense as on a cool day.
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peedee
Dodge Dakota
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10/03/2004
06:52:02
| RE: Humidity
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I really hope that einstein is kidding....pretty much the opposite is true.
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N56629
Dodge Dakota
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10/03/2004
10:02:11
| RE: Humidity
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I think this is what einstein meant.
Sensors will lean out the mixture on hot days [when] the air won’t be as dense as on a cool day. I jumped to the same conclusion as you.
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Riv
Dodge Dakota
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10/06/2004
21:50:06
| RE: Humidity
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What I meant is that by comparisson my truck ran a 15.008 @90mph at 9pm. A half hour later when the dew came in and the humidity increased it slowed to a 15.38@87mph. The 60 ft times were both 1.197 and 1.196. Yet I watched a carbed camaro who ran behind me both times only fluctuate by a tenth.
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N56629
Dodge Dakota
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10/07/2004
06:45:19
| RE: Humidity
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"Yet I watched a carbed camaro who ran behind me both times only fluctuate by a tenth."
You seem to be assuming that everything was identical on both vehicles during both runs. Changing the humidity is no different than changing the temperature. You are always working with air density.
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peedee
Dodge Dakota
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10/09/2004
06:30:50
| RE: Humidity
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If "the dew came in", then the air was actually of the same 'relative' humidity or less. The "dew" is the moisture that was in the air but has now condensed on objects that are cooler than it is. The air "gave-up" its heat, and what is left behind is moisture. So you had a certain temp of air and objects. Then the objects were cooled (probably by cooler air or air with more moisture, OR the air was now warmer and more moist, BUT the air then left its moisture on the objects, so it isn't so moist anymore. it is actually drier or the same 'actual' relative humidity than at the time of your first run. Just like a big air conditioner or dehumidifier, and your engine was drinking drier air, or air with the same relative amount of moisture but cooler. Maybe the camaro intimidated your and your foot slipped.... lol Kidding just kidding, don't hit me. BTW, for those who don't know.... The humidity #'s we all hear on the evening news are that of relative humidity. Relative meaning relative to temperature AND actual content (or lbs per cubic inch) of moisture. The same amount of pds/cu in moisture in air that is suddenly heated or cooled will have a different relative #. In the case of an aspirated engine, and lets say cooler air. In the case above, the air may be cooler because it gave up its heat, but it also lost its humidity or moisture. So the air is relatively the same as it was when measuring lbs/cu in moisture. The only real diff is the fact that it is cooler, and cooler air with equal relative humidity will perform differently.
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N56629
Dodge Dakota
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10/09/2004
07:35:45
| RE: Humidity
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Good point, I knew that. LOL
"The only real diff is the fact that it is cooler, and cooler air with equal relative humidity will perform differently."
However, it still boils down to calculating your air density or density altitude and determining what affect it will have. And, bottom line, it affects all internal combustion engines, not just some.
I'm going to have to think about this a bit, but there may be one possible area that would cause humidity to affect one engine more than another. What if one engine is running leaner than another. This applies more to forced induction engines than NA unless you are running high compression. We all know that water jection can help, but might it not also be true that added humidity could have the same or some affect on a lean burning engine and a detrimental affect on an engine that is running too rich?
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peedee
Dodge Dakota
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10/09/2004
08:05:07
| RE: Humidity
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I agree that diff engines are affected differently. Many variables involved. In an earlier post I had shared my experiance with diff octane during diff weather while traveling long distance. I usually adjust my octane purchase according to the current weather while traveling, lets say from MA to FL. It does make a diff because of the diff temps and humidity encountered, and the load on the engine. In the city I get 14 with Mobil Regular, about 14.5 with Sunoco, but 13 with premium or middle grade. On the highway I get 16.5 with reg, but 19.5 - 20 with middle or premium. But during times of warm relatively dry weather I get the best with middle or premium while I get the best with regular during warm or cool higher humidity. Others may encounter a difference than I do, so it is good to experiment. BTW the comment I posted here was directed more towards RIV, for his/her comparisons. You are correct about the density. Temperature affects it and moisture content is more key than the oxygen. One of the most important factors of high altitude is oxygen, but the air is also 'drier' at higher altitudes because of the thinness and lightness ofthe air, that it cannot hold as much moisture as air at sea level. With a gas stove (external combustion) it is the oxygen that is most important, but with an internal combustion aspirated engine the moisture and oxygen influence is pretty much equal with the moisture having slightly more influence. It retards spark like higher octane while at the same time increasing compression. Get the right balance of compression, spark timming and octaneand performance is greatly increased or decreased.
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N56629
Dodge Dakota
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10/09/2004
10:35:23
| RE: Humidity
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" BTW the comment I posted here was directed more towards RIV, for his/her comparisons."
I understood that. You where pointing out his comment "A half hour later when the dew came in and the humidity increased it slowed to a 15.38@87mph." Your point was, that the humidity had actually decreased at that time, not increased, making it most likely both cooler and drier.
Let's face it, RIV was just out of control. ;-)
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Riv
Dodge Dakota
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10/14/2004
15:37:50
|  RE: Humidity
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Your right I am out of control(HA!) No seriously I understand the whole humidity/ internal combustion engine deal, I was simply wondering if any body else with dakota's experience this much of a fluctuation. It may be the sensors, or as stated, and most likely, a combination of octane level's, humidity etc.
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