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Horsepower and cold weather


juniper

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the difference would be mainly due to the increased air density.  There is a 2% increase in density for every 10C decrease.  So maybe 6% difference from warm summer to freezing.  Modern fuel injection have an air mass sensor so it would increase the fuel proportionately.  This is a very rough estimate and who knows what the real world results are.   As for the thermodynamic efficiency based on the difference in input and output temperature, yes but it is air intake temperature to exhaust out of the cylinder. Basically assuming that the temperature difference is converted into mechanical energy. But considering exhaust exit temp is rather high compared to ambient, I doubt this will add much. 

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 You missed my point.  Unless the OP is out on a track with his wife's Audi, which I highly doubt or is WOT from stop sign to stop sign everywhere here go's....  There can be a noticeable difference with the compressor off just sporting around. But like mentioned, the big gain comes from cool, dense air, added timing and fuel mixture the ECU is allowing

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5 minutes ago, Max2 said:

You missed my point. 

I didn't.  I was just answering a question.  It's a given that it takes HP away from the wheels to spin a compressor.  Same goes for a power steering pump and is the reason many manufactures are going to electric power steering pumps.

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35 minutes ago, CECAA850 said:

I didn't.  I was just answering a question.  It's a given that it takes HP away from the wheels to spin a compressor.  Same goes for a power steering pump and is the reason many manufactures are going to electric power steering pumps.

Apparently I didn't get my quote in for Justus

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54 minutes ago, CECAA850 said:

The old quote system worked better for me prior to the software update.  It would quote the quote within the quote which I liked.

Maybe so.  I just wasn't paying attention though.  I'm really good at starting a response, getting side tracked with work and posting it half completed or 2 hours later loose interest, not have time and just leave the site or go home. I'm all over the place these days

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On 1/18/2017 at 11:36 AM, Don Richard said:

When drag racing motorcycles, the last race of the year in mid December, 12.24 @106.8. In the summer it was 12.60 @105.3. I don't know what the HP difference was but the performance increase was real.

You must be in a warm climate. Mid December can be pretty cold. I did a few 1/4 mile runs on my bike. My best time was a 10:80, mostly stock bike.

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Im sure my truck also will make a few more ponies since i fixed the dealerships screwup.

 They left a plug in the inlet of the heat exchanger. Thankfully i dont drive too hard, l live between sea level and 900ft, and on the central coast.

 Dealer replied "no way we could have done that". 

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On 1/18/2017 at 10:36 AM, juniper said:

Thanks gentlemen! I am going to do some 0-60 tests one warmer day and one cold dry day.

Read this article from a peer reviewed engineering journal, they did exactly what you are proposing to see if the know correction factors were accurate, and whether temprature or atmospheric pressure had more of an effect.

 

You will need to know what the barometric pressure is at the time you run your acceleration tests as it has even more of an effect than temprature which is inversely proportional to the square root of temperature  (absolute, which for centigrade would be in Kelvin)

a10v25n3.pdf

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I say that everything performs better when it's cold, my girlfriend will disagree.

 

Flying an airplane, it's better all the way around. On cars, why do they put intercoolers on the air intake? 3, 2, 1... Not sure if they still do, but Jaguar used to have a heat exchange for the fuel that they ran the chilled AC freon through. 

 

They always made things so simple to work on.

XJ12_Motor.jpg

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