cold air

1. Why would you want MORE hp in freezing weather when driving conditions suck?
2. Don't the fueling stations in Canada change to a different formulation of fuel in winter? ( I've heard it explained as the winter mix and summer mix) This could potentially be a part of the loss of MPG?
3. This has got to be one of those questions that is injected into a forum to drum up a bunch of debate and flame. Do you really care if you have more HP in -30 degree weather if you only drive to work and to the grocery store in that climate? I'm a big fan of trying to cope with driving conditions and making it safely to my destination.

If this was some sort of racing type of situation, I'd still feel the same. NOONE races in these conditions except the World Rally Cup guys.. and they are only concerned with staying on the road!

Stepping off my soapbox.. Ric

After reading all the replies, I guess the general consensus is that the advantages of cold air (denser, better combustion) are overshadowed by the disadvantages (denser air = more drag, more work for engine to stay warm) at a temperature of around 50 degrees.

This is of course, modifications aside (intercooler, ram air, boost)

Seems reasonable, except for what fbloogyudsr said about fuel not atomizing well in cold air...didn't quite understand how that works.

As for ram-air, aren't effects only noticeable at higher speeds? (some sort of linear relationship between small power gain and speed of car)

-sachin

and then:

Does that mean humidity is also a factor? completely dry air will mean higher HP?

I do understand all other factors such as colder air = denser air = more drag

but this question was posted assuming other factors are non-existent, such as heater robbing the engine of power

Posted as a theoretical question. The only factor I mentioned was temperature...not humidity or precipitation.

Wasn't talking about MPG either. Purely theoretical intake temp vs. HP question

forgive me if I imitate your style in replying:

1. This was a theoretical question. I asked for numbers to see whether or not, under other CONSTANT CONDITIONS, HP would change as a function of intake temperature
2. Not everyone has the same standards of cold air as you do. I only cited numbers as examples. Being ignorant to the answer of the original post, all I wanted to know was if cold air is better. Doesn't matter where go you, be it work or the grocery store.

don't label trolls before you properly read and understand the OP, and realize the curiosity of the original poster.

-sachin

Intercoolers are fitted to reduce the intake temperature to a reasonable level such that the engine will not overheat and explode, which is not quite the same as reducing the temperature to get more power.. your second statement speaks for itself..

It is good to know that my Jeep GC has more power when sitting on the driveway having been started in cold Canadian weather.. I am not so happy that driving away with fulltime 4x4 engaged, heater in full swing and all lights ablazing is sapping this new found power.. but I have a question.. is it true that Chinese Bingo halls in Toronto (or anyplace) number the bingo cards from right to left?.. just a theoretical thing, ya know.. lol

It is actually the depot or refinery that does the change, not the "dispensing" station where we fuel up.

It could be that this is a loss in MPG, but how much is the question. Anyone ready for a M.Sc. thesis topic in Chemical Engineering? The volatility of the gasoline HAS to be increased for winter combustion so the products will have lower BTUs and thus lower MPG. . Last week at -41C I flooded my Voyager when trying to start it, and used ether to start it up. At -41C the top of the carb had a small pool of ether just sitting there. It "quickly" evaporated, but you could see it do so, just like at that temp you can see liquid propane sizzle away.

I know, I'm just messin' with ya. -Dave

The question was "Does cold air make more power", or something along those lines. The answer is an unqualified "yes".

The fact that people drive more slowly due to slippery conditions doesn't change that.

Intercoolers mean lower temperatures, which means the air is more dense, which means you can add more fuel, which makes more power.

This is because your intercooler is much more efficient. Heat transfer, with all other things being equal (materials, distances etc) increases with increased temperature difference. So, assuming an air/air intercooler, when the coolant (outside air passing through the intercooler) is colder, it can take more heat more rapidly from the pressurized air. The same holds true for a water/air intercooler, but there is the added step of air/water (at the rad), water/air involved (at the intercooler).

I don't know this for sure, but my take on intercoolers is that the primary benefit is not to lower the temperature of the air entering, but to increase the density (PV=nRT). So, given the same n and R (specific to the gas in question), lowering the Temperature lowers the PV (Pressure time Volume), thereby increasing the amount of oxygen available in one opening of the intake valve.

Again, the losses occurring between the engine and the cold outside air, negate most of the gains of charging the intake with cold air.

Dan

Some companies make "winter gas", mostly to stop gas-line freezing. It probably does reduce efficiency.

Lots of us want more power in the winter. Hauling snowmobiles, plowing snow, cutting through snowbanks. Driving conditions don't suck, drivers do.

Lots of people race in minus 30!! Snowmobile/ATV races, ice racing (both cars and bikes). It is a whole cultural thing. Love it or die!

|>))

Came out of a meeting the other night with a transplanted American couple during a snow storm. The wife said, "You Canadians, you love this. You like the challenge" (I think they are from Florida or the Carolinas). But I thought, we don't even see it as a challenge, it is just life, it is what we do.

Dan

Absolutely. The higher observed power is entirely due to the density of oxygen molecules in the intake air. Water vapor is just un-wanted bulk that gets in the way of getting more oxygen in the cylinders.

Now, in REAL WORLD engines where you can vary several parameters, a little bit of humidity often will help suppress detonation so that the engine can run a little more spark advance and make a more power. That's why some engines (notably high-performance aircraft engines used in air racing) employ water injection. But it is an indirect effect. The direct effect is a reduction of horsepower, everything else held constant.

And your *tires* at the same ambient temperatures will, in an inverse ratio, produce a much higher 'Pucker Factor' as you enter the Esses. =8^O

-- C.R. Krieger (a BMW Guy who's been there)

Ahh, another one o' them Porsche weenies! Try Road America when it snows! You might want to swap out of the 968 for a Quattro ...

Seriously, the problem we start running into is tire compounds. As it gets colder, they get harder, so it's tough to stay *on* the track just as you're starting to make *real good* power out of that cold air. This brings on our standard Badger Bimmers' OktoberFAST morning lecture:

Cold air makes two things: *more* power and *less* traction.

-- C.R. Krieger (Been there; done that)

Interesting...however can't one assume that friction (above a certain speed) keeps the tires at a steady temperature that is not cold enough to be too detrimental to the tire grip?

Unfortunately, Dan, most of our anecdotal experiences are "unscientific". You have experience in lighting and I do tip my hat towards that expertise. No B.S., you DO have experience based on data - cold hard facts.

Unfortunately, most of us, IMHO, are not as well endowed nor as well connected as to obtain cold (no pun intended) hard facts. We can only compare in an anecdotal way what happens when we drive in "warm" temps and then when we drive in a normal on Mars day when the temps hover about -40C. Most readers, IMHO, do not use the "scientific method" to test any null hypothesis, or any other hypothesis. The average reader simply does not have the necessary tools to conduct the study and the necessary analysis in an unbiased manner. Furthermore, the average reader cannot control ALL variables. When we "make assumptions" we by necessity introduce biases - but we all know that don't we.

Yes, the textbook stuff is based on hard cold facts. Unfortunately, our cars, don't always behave as the textbook suggests they "should" behave. Assumptions mask a LOT of reality.

Lets move on to another issue. Besides, it is getting warmer since the "average' temp has bottomed out in the Northern hemisphere - it is now February after all. Racing weather is only about 4 months away in Canada and this talk of cold air will then be another interesting but of no consequence discussion, because in 4 months the question at hand will be can I "win" the next race, not what is the thermodynamic efficiency of my vehicle at 70F

Today it was about 0C (32F) and my Voyager accelerated "much better" IMHO than it did nearly 2 weeks ago when it was -41C (-43F).

Ken

P.S. I have removed the other two news groups because I do not believe > Further, your unscientific "My car doesn't accelerate as well when it's

You're absolutely right. As it gets colder its definitely a tradeoff between extra power and less grip. You have to be *extremely* careful about warming up tires in cold weather conditions and realize that they probably won't reach optimal temperature like they will when its in the 70's.

Most of the time I run Hoosiers, and they still manage to heat up pretty well when the temperatures are in the mid 50's, though they take considerably longer than usual to do so. In fact my personal best lap time at Mid Ohio came on a 55 degree afternoon. Other tires like the Michelin Pilot Sport cup simply refuse to heat up when the temperature drops below 60 degrees, and are almost undrivable in those conditions.

Jim C.