Cold Weather=More power. Why?
 

Just curious why our cars feel more powerful in colder temps? It seems the torque dip is not as noticeable and just overall better acceleration. No complaints here because I love it, but im just curious what the reason is? My last car was the complete opposite. I also have a few thousand miles on my motor now so maybe its just broken in?

Anyway, would love to hear your thoughts. Thx.

Lol, so many newbie car questions on this site. It's all good tho.

Cold weather means the air is denser, so the engine takes in more air, and more air in engine means more power.

because atoms

Yup. Exactly why people invest in COLD air intakes.

Divert A/C into intake...

Infinite POWEERRRRRR

Yep, the engine getting broken it may be part of it.

You're getting more comfortable with it may contribute.

As mentioned, colder air contains more oxygen per unit volume, which enhances combustion.

humfrz

Cooler air is more dense

because u dont have your ac on! :thumbsup:
jk jk




i miss winter when i had a turbo. +100000000hp heat soak ftl

It's the same reason your car drives better at night. :)

I'll make this fairly simple, if anyone wants a more detailed and scientific based explanation let me know and I'll write something more official up later, but as mentioned before, cold air means more dense air, or, more atoms per unit volume of air. Since air is what's required to ignite the fuel potentially more power as you can combust more fuel. Additionally, cylinder temperatures directly affect when the onset of knocking/pinging occurs. With colder air your cylinder will run slightly cooler allowing the ECU to advance spark timing a little more to gain slightly more power that way too.

The internal combustion engine is an AIR PUMP.

More air in = more power out.

(as long as the fuel delivery system can keep up with the correct mix)

Cold air = more air
Turbo = more air
:cheers:


As for all the inexperienced want to be gear heads out there there is one book that will answer all your questions about how an internal combustion engine works at a easy to understand teaching level.

Even cover clutches throw-out bearings how and when to shift, wheel alignment.


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Ford actually did this on a couple concepts. Power boost for a short time.

Its the extra oxygen molecules in the same volume of air. Its not more air being stuffed in.

Curious is this no longer being taught in schools? I'm asking as by assumption the OP may be a young fellow but obviously old enough to drive. Discussions on air density etc for me in school were far before the age of 16 so just curious is all.

You expect people to remember chemistry and physics after high school? It was a class you had to pass, not something you use in life, just like algebra and fractions ;)

Pretty sure I learned that in like grade 5 or 6 "Science" actually. :D

Sorry I guess I have had to deal with "cold air" every year of my life where I live so perhaps it was obvious as a youngster even and well can't forget when you see cold temps again and again yearly lol. Everything with a motor always is beast in winter. :clap:

I should really switch to a CAI.
I think I've been irrationally afraid of hydrolocking for too long.
I do live in SoCal after all...

Well, I learnt about the cold air thing, back on the farm; I noticed my tri-cycle would go faster, during the cool of the evenings ....... I wonder if that is related ....?? http://www.runemasterstudios.com/gra...mages/woot.gif

humfrz

I know you're kidding, but this shouldn't make any difference on any modern car - all modern cars should automatically disconnect the AC compressor when full throttle is applied, so it shouldn't make any difference in available power.

Does the BRZ have knock sensors? If it does then the engine won't make more power in cold weather.

Turbo engines do if they are intercoolers.

Not only that but the compressor doesn't run at all in cold weather because the evaporator would freeze up. Plus 3C or about 40F is the lowest temperature at which the AC can operate. There's an anti frost switch which opens at that temperature and disconnects the drive pulley from the compressor.

which make it more dense (MASS PER VOLUME) hence more air.... And it is not just more oxygen all elements in "air" are equally represented.

I wonder if this is related to the engine cutting power when it gets too hot. I remember reading about a dyno test that saw a significant power decrease after just 1 pull in semi hot conditions.

Dry Cold air is Mother Nature's version of forced induction. The difference at the drag strip is extreme. Not unusual to see a half second difference between best and worst conditions.

Yes you are right, but I am just being pedantic about the term "more air" which to me sounds like a larger volume of air, which is NOT the case unless you are FI

Air density.

/thread

You shoulda seen the hybrid forums the first summer. MPG went down because gas got warm and people were freaking out.

The tinfoil hats were being handed out at the door

Don't do it. Our stock intakes are more than adequate if you just get a decent drop in filter. Cold air intakes have to be tuned to get any real gain, and many of them have been forcing the car to throw codes and run like crap until they get tuned due to issues with the MAF sensor.

Also, I grew up in Temecula, still visit my parents there often. A city that used to be awesome for driving until they built thousands of houses and few extra or larger roads. Definitely couldn't complain about the weather, though.

When I turn on the auto climate control my A/C is constantly cycling on and off at idle regardless of temperature, even with the heat on. I don't know if it's a dehumidifying feature or what, but it noticeably affects my mileage even in cold weather when I just leave it on. It's really annoying.

Oh no, I don't drive a twin [yet]. I'm currently sitting on a Civic but a twin is in the foreseeable future. But consider it noted.

And there's still Rainbow and Highway 395 to mess around with if I happen to be coming up from the south, so it's not too bad; the streets are still well paved and the lanes wide. At least it isn't LA; absolutely hate LA driving.

:sigh:

What?

Knock sensor equipped engines develop peak bmep until they knock. Cold weather doesn't reduce the detonation point.

Intercooler equipped turbo engines can develop higher torque because the compressed intake charge is cooled effectively by very cold weather, but in the intercooler.

Cold ambient air doesn't affect combustion chamber temperatures by any significant amount. The higher the compression ratio the less the starting air temperature affects pre-ignition charge temperature. Detonation results from end gas spontaneous ignition prematurely caused by the compression wave resulting from the flame front. That in turn limits bmep which limits peak torque. Knock sensors permit combustion pressures to rise up to that point and not beyond.

Therefore, if this engine is controlled by knock sensors then it produces its highest bmep at the point the knock sensor operates.

It is true that colder intake air is denser and therefore an engine not already optimized will run better in cold temperatures than in warm temperatures. This is not the case off engines controlled by knock sensors unless turbo intercooled.

Remember that the key advantage of direction injection is charge cooling resulting from cool fuel sprayed directly into the hot compressed air in the combustion chamber. The starting temperature of that air is pretty much irrelevant now.

This is one reason "cold" air intake modifications won't produce any meaningful extra power out if these engines and because the stock air box is pretty efficient already there are no real flow advantages available either.

While an engine develops higher torque as it ingests more air mass it cannot exceed its designed detonation limit.

If you drove in the 70's and then when the first knock sensor equipped engines came out in the 80's you would realize this.

It stops when ambient temperatures drop below about 3C.

If you have auto climate control the AC light actually goes out.

You can't dehumidify freezing air using a conventional automotive AC unit because the humidity in the air blocks the evaporator with ice.

Also, unless the car interior is also freezing simply heating the air as it passes into the cabin also "dehumidifies" it by reducing the relative humidity, which is all that matters.

Going to try this right now, it's well below freezing this morning.

I'm well acquainted with the reasons why cold air allows for greater air-mass, and the functioning of intercoolers - I just really struggled to follow your logic.

The problem with this theory lies in that first sentence - this is not how the Subaru knock strategy works. It's a more reactive process - see here. It's also a curious question as to whether the BRZ is knock sensor controlled, since I suspect every ODB2 compliant vehicle since 1996 is likely to have knock sensors (I stand to be corrected).

I agree that direct injection reduces in chamber temperatures, that's the whole advantage, but DI is not used at all load ranges.

I think DI is always active. The port injection only supplements DI.

LOL wrong....

All modern cars have knock sensors.

Cold weather dose reduce the detonation point.