juniper Posted January 17, 2017 Share Posted January 17, 2017 I was wondering if someone knew how much HP increases in cold dry weather. I was driving my wife's V8 audi mid sized sedan, that usually isn't very peppy, and I can always feel additional weight when driving it, like extra passengers, or the spare tire in the trunk. I drove it the other day and it was cold and dry and it feels like there is around 35 additional HPs. So if a car has around 350hps approximately how much would it increase if it was around 5 below zero and 10% humidity. Quote Link to comment Share on other sites More sharing options...
richieb Posted January 17, 2017 Share Posted January 17, 2017 Don't know the percentage of either but conversely gas mileage goes down. Quote Link to comment Share on other sites More sharing options...
Schu Posted January 17, 2017 Share Posted January 17, 2017 Every motor will respond slightly differently to a cool charge... but they all will improve. I dont think you are going to get 10% better output... +35/350. That is unless that baseline was done in bad conditions. Also, temperature is only one component... density is very critical, probably more than temperature. Quote Link to comment Share on other sites More sharing options...
wvu80 Posted January 17, 2017 Share Posted January 17, 2017 There is no question cars have more initial HP when cold. Heat kills HP. As with any modern water cooled engine I would expect when the optimum operating temperature is achieved then HP and engine performance should be consistent. 1 Quote Link to comment Share on other sites More sharing options...
phillmartin Posted January 17, 2017 Share Posted January 17, 2017 There is no question cars have more initial HP when cold. Heat kills HP. As with any modern water cooled engine I would expect when the optimum operating temperature is achieved then HP and engine performance should be consistent.Absolutely. As the air is colder, my understanding is that the oxygen is denser, allowing more combustion to occur. Similarly, that's why Fireworks burn brighter (but shorter) in the winter.Sent from my SM-G920V using Tapatalk Quote Link to comment Share on other sites More sharing options...
JL Sargent Posted January 17, 2017 Share Posted January 17, 2017 I agree that 10% is probably not happening. I would think 5 to 7% is a real possibility. My boat has a 200hp v6 2 stroke and the performance improvement in cold weather is certainly noticeable. Quote Link to comment Share on other sites More sharing options...
willland Posted January 17, 2017 Share Posted January 17, 2017 Cold air is generally more dense than hot air. Bill Quote Link to comment Share on other sites More sharing options...
T2K Posted January 17, 2017 Share Posted January 17, 2017 There's a lot of hot air in Washington, DC. Is that why performance there is pretty dismal? 4 Quote Link to comment Share on other sites More sharing options...
JJkizak Posted January 17, 2017 Share Posted January 17, 2017 That's why the Corvette has reverse coolant flow to allow higher compression and the computer backs the timing down if pinging gets close. Then again your vehicle might be 2 quarts low on oil giving you about a 20% gain in horsepower. That's another reason why the Vette went to a dry sump system to keep the crank out of the oil bath. JJK Quote Link to comment Share on other sites More sharing options...
Moderators dtel Posted January 17, 2017 Moderators Share Posted January 17, 2017 It's not just the denser air, it's also colder fuel, remember "cool cans". The cool can went under the hood and the fuel line went through it in a coil giving as much time in there as possible. You would fill the can with ice cooling the fuel before a run, I don't know if it was just a fad that passed with no noticeable improvement or it did help but i do remember them. 1 Quote Link to comment Share on other sites More sharing options...
YK Thom Posted January 17, 2017 Share Posted January 17, 2017 I have always thought this was just in my head. I've noticed the Jeep does better in winter up here. Most definitely goes through more fuel, although some of that is warm up idling and being thrown into 4high more often. Quote Link to comment Share on other sites More sharing options...
CECAA850 Posted January 17, 2017 Share Posted January 17, 2017 48 minutes ago, dtel said: It's not just the denser air, it's also colder fuel, remember "cool cans". A lot of guys pack the turbo intercoolers with ice before a run as well. Quote Link to comment Share on other sites More sharing options...
oldtimer Posted January 18, 2017 Share Posted January 18, 2017 6 hours ago, T2K said: There's a lot of hot air in Washington, DC. Is that why performance there is pretty dismal? Yet 6 hours ago, willland said: Cold air is generally more dense than hot air. Bill Quote Link to comment Share on other sites More sharing options...
Mallette Posted January 18, 2017 Share Posted January 18, 2017 5 hours ago, YK Thom said: Jeep does better in winter up here. Crikey. Just noticed...North West Territories. God knows how anything does anything at all up there!. My people believe that anytime it's too cold to be naked, it's too cold. Dave 1 Quote Link to comment Share on other sites More sharing options...
BusaDude Posted January 18, 2017 Share Posted January 18, 2017 11 hours ago, juniper said: I was wondering if someone knew how much HP increases in cold dry weather. I was driving my wife's V8 audi mid sized sedan, that usually isn't very peppy, and I can always feel additional weight when driving it, like extra passengers, or the spare tire in the trunk. I drove it the other day and it was cold and dry and it feels like there is around 35 additional HPs. So if a car has around 350hps approximately how much would it increase if it was around 5 below zero and 10% humidity. The only way to know for sure is to put the vehicle on a dyno and make a few runs. You'll end up with an uncorrected figure for HP and torque, that is good for that day and those conditions. Those numbers would then be corrected to the SAE J1349 Standard, using 77°F, 29.235 in/Hg (or 990 mb) and 0% relative humidity. There are dyno/horsepower correction calculators all over the internet. But they won't tell you anything unless you know the atmospheric conditions. http://wahiduddin.net/calc/calc_cf.htm http://www.superchevy.com/how-to/ghtp-1109-fact-and-fiction-of-dyno-correction-real-wheel-horsepower/ http://www.dynojet.com/products/dynamometers/Automotive-dynamometers.aspx Quote Link to comment Share on other sites More sharing options...
Moderators Travis In Austin Posted January 18, 2017 Moderators Share Posted January 18, 2017 Isn't it a matter of thermodynamics? Quote Link to comment Share on other sites More sharing options...
YK Thom Posted January 18, 2017 Share Posted January 18, 2017 30 minutes ago, Mallette said: Crikey. Just noticed...North West Territories. God knows how anything does anything at all up there!. My people believe that anytime it's too cold to be naked, it's too cold. Dave You have some wise people. Not sure what happened to us. Quote Link to comment Share on other sites More sharing options...
Mallette Posted January 18, 2017 Share Posted January 18, 2017 Just now, YK Thom said: You have some wise people. Not sure what happened to us. I know what happened to us. We started walking south and kept going until it got warm. 70 here today. I'm staying. Dave 1 Quote Link to comment Share on other sites More sharing options...
Moderators Travis In Austin Posted January 18, 2017 Moderators Share Posted January 18, 2017 It's the Second Law of thermodynamics. The maximum efficiency of any heat engine decreases as the heat of the air the engine exhausts into rises. Specifically Quote Link to comment Share on other sites More sharing options...
2point1 Posted January 18, 2017 Share Posted January 18, 2017 70'-80's racing motorcycles a 20 degree change required 1 size up or down on the main jet. Quote Link to comment Share on other sites More sharing options...
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