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Discussion Starter #1
Just wondering when driving home the other afternoon, here in Ga. we are facing some triple digits, will performance suffer slightly w/ high outdoor temps? in the morning it was fine , probably around 78 degrees afternoon was ~ 101 or so , i know engine's like the cooler air and the AC was on, though, I was thinking w/ a 2.4 in a civic, Si or not, that the performance would tend to still be there.:usa:
 

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I Drive Too Much
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I notice the drop in performance at higher temps. It loses a bit for the air temp and then a bit more from the use of the A/C. My butt dyno says about 10% or so, about 17-20hp loss at 90+ deg F.
 

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Yes, definitely in any car and at those temps with the air on.
 

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Pickle Hammer Power
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yea... i can tell the difference when the temp is high or low...especially in our rigs....they dont like the heat at all.... but when you get some nice cold air in em those turbos squeal with excitement
 

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Discussion Starter #6

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Pickle Hammer Power
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The opposite, warm air is less dense, the heat excites atoms and they take up more space.

exactly..... i think about temps quite a bit... when you fly a patient heat matters alot... cold weather means more lift...more carrying capacity... hot weather greatly affects life which... basically if i got a fat patient " which these days my patients average 300+" its easier to fly them in cold weather than warm... have to give em biddger landing zone in hot weather than i would in cold weather...basically the same thing for our cars just replace lift with hp!!!
 

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The colder the air the more air molecules there are in a given space. This means more oxygen in the cylinder and more complete the
Combustion is meaning more power. Forced induction works on the same principal but increases pressure to increase the amount of oxygen in the cylinders.

If you want to try this, take a plastic bottle and fill it with hot water. Dump the water out, put the cap back on and then run the bottle under cold water. The bottle will collapse. That is the difference in how much air there is between the temps. Then think about that and the air to your engine. I can't wait to test this sucker out on a cold dry day in the winter. :p


Sent from my Autoguide iPhone app
 

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The amount of water vapor in the air also has a negative effect.
Disagree with this. Humidity has the same effect of raising octane in fuel. That's the reason WWII fighter planes were water injected. That said, higher octane in a Civic doesn't give it more HP and higher humidity doesn't reduce power in any engine.
 

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Disagree with this. Humidity has the same effect of raising octane in fuel. That's the reason WWII fighter planes were water injected. That said, higher octane in a Civic doesn't give it more HP and higher humidity doesn't reduce power in any engine.
Water injection cools the air, allowing for a higher manifold pressure without knocking and thus more horsepower.
Now humidity may make more horsepower ( I don't know ), but it also slightly increases density altitude.
 
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