peteyjr Posted April 21, 2009 Share Posted April 21, 2009 Everyone knows that heat makes our cars run worse. Pulls timing and we lose power. So what is the relationship between humidity and how our cars run. Seems to me everytime it gets humid here in South Florida (which is quite often near summertime) my Leggy runs with a mild stutter and slower. This is something I have noticed with every Subaru (and just about every car I've ever had). Today a late season cold front came to town but with rain. Temps were a cool 68-72 deg. A range in which our cars run good. So why did the Leggy run bad? Any theories? Link to comment Share on other sites More sharing options...
snow05gtRI Posted April 21, 2009 Share Posted April 21, 2009 more humidity makes less oxygen density in the air charge is my take on it. you're still getting the same amount of air, just less oxygen in it, so less combustion. i have no scientific backup, this is just me making assumptions. GTTuner was talking to me about this the other day when he was doing some work on my car, noticing the same things that you pointed out. Link to comment Share on other sites More sharing options...
peteyjr Posted April 21, 2009 Author Share Posted April 21, 2009 Good explanation, pretty much what I had in mind. Now if we could only figure out why people joints hurt when the humidity is high ( I work in an orthopedic rehab facility) Link to comment Share on other sites More sharing options...
mwiener2 Posted April 21, 2009 Share Posted April 21, 2009 ^^ that's easy. Storm fronts change the barometric pressure when they move in. this fast pressure change creates an imbalance in the pressure on the outside and inside of our bodies. Some people, usually with prior injuries, are sensitive to this pressure change. My Mods List (Updated 8/22/17) 2005 Outback FMT Running on Electrons Link to comment Share on other sites More sharing options...
peteyjr Posted April 21, 2009 Author Share Posted April 21, 2009 The pressure change scenario is well documented. Pressure will always move from a high pressure state (given a semipermeable membrane) to a low pressure state . This is why when the weather and pressure really drop like in a hurricane in our area, Pregnant females start dropping babies and hospitals/maternity centers are ready ( the internal body pressure wants to equalize with the lower outside pressure and presses on receptors that think the baby wants to come out). Arthritics also go thru the roof and old injuries come out and pain you. Humidity on the other hand has been challenged by the medical community. I read a study that refuted humidity as the cause of pain in arthritics. Another one theorized that similar to low barometic pressure, there is an osmotic (water) pressure gradient difference which causes the pressure and therefore pain. In an engine there is little to almost no water content so that theory does not hold well with why an engine runs different with humidity . Our Subarus are subject to Heat, barometric pressure and humidity. All these factors make a complex interplay of forces that really affect the way our cars run. I'm not looking forward to summer in South Fla. Link to comment Share on other sites More sharing options...
abcfob Posted April 21, 2009 Share Posted April 21, 2009 Good explanation, pretty much what I had in mind. Now if we could only figure out why people joints hurt when the humidity is high ( I work in an orthopedic rehab facility) I would have guessed that high humidity and high temps usually go hand in hand, and high temps will cause body parts to swell. I know my fingers swell on hot days, making rings tight. Link to comment Share on other sites More sharing options...
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