Apparently cold weather really wakes up an engine
Thread Starter
Race Director
Joined: Nov 2018
Posts: 13,243
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Apparently cold weather really wakes up an engine
It's been in the 40's and I noticed the Vette seemed peppier. Tonight I was pulling away from a light and with maybe 25 - 30 mph under my belt gave it probably less than half pedal which I've done before and *whoa* - the wheels broke loose, the rear started to kick out. Got off it and straightened it out. Hmmm, note to self - definitely don't want to do that again. Can the cold air make that much of a difference?
Last edited by brassplyer; Dec 19, 2020 at 12:01 AM.
Racer
Joined: Apr 2005
Posts: 259
Likes: 45
From: Columbus Mn
Cold air can be great for power, but jetting changes etc. will be required to optimize the AFR. I wouldn't expect that the cold air is contributing to the power that allows you to spin your tires as much as the road is cold, the tires are cold and you lose a lot of grip. It's still fun don't get me wrong.
Drifting
Joined: Dec 2017
Posts: 1,306
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From: PA
Hard to say how much each factor contributed. Looking at flying, in our 4 seat 180 hp Piper Archer, on a hot and humid day, say 100 F and 80% humidity, with 2 people climb rate might be 750' per minute taking off from our airport which is 350' above sea level. Now, go to winter, a crisp 20 F day and 20% RH, and that goes to 1,100 ft per minute. So, a sizeable difference. However, even that is not just power. The denser air increases both the thrust the prop can generate at any given RPM and the lift the wing can produce for a given speed and angle of attack. The only way to isolate the effect on the engine is put it on a dyno and run at different DA's.
Also, no matter how cold it is, I've never gotten the tires on the Archer to break loose when I've hit the throttle.
Also, no matter how cold it is, I've never gotten the tires on the Archer to break loose when I've hit the throttle.
Is my vette stock?? HAHA
Joined: Oct 2015
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From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
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Thats why cld air intakes are a big deal. Normally you are getting really hot air into your motor from under the hood. NOw even the air under the hood hasnt warmed up to the normal above 100* temps so the intake sees a cooler mixture which supports more fuel and if the charge stays cooler, its denser and you can get more air into the cylinder. more air and fuel gives that boost like your getting a 40 hp nitrous boost
Le Mans Master
Joined: Apr 2011
Posts: 6,284
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From: Hermosa
Hard to say how much each factor contributed. Looking at flying, in our 4 seat 180 hp Piper Archer, on a hot and humid day, say 100 F and 80% humidity, with 2 people climb rate might be 750' per minute taking off from our airport which is 350' above sea level. Now, go to winter, a crisp 20 F day and 20% RH, and that goes to 1,100 ft per minute. So, a sizeable difference. However, even that is not just power. The denser air increases both the thrust the prop can generate at any given RPM and the lift the wing can produce for a given speed and angle of attack. The only way to isolate the effect on the engine is put it on a dyno and run at different DA's.
Also, no matter how cold it is, I've never gotten the tires on the Archer to break loose when I've hit the throttle.
Also, no matter how cold it is, I've never gotten the tires on the Archer to break loose when I've hit the throttle.
The difference is in your ground speed and your true airspeed from air density not the lift generated by the indicated airspeed. The pitot tube is also impacted by less dense air so it is registering a lower IAS for a given GS or TAS due to lack of air density.
Since the wing only knows IAS it is generating the same lift for 80 KIAS (or any given IAS) regardless of the air density.
OP, just as big of an impact on the air density due to temperature is the atmospheric pressure.
These nice cool clear winter days are dominated by high pressure as well. This adds to the air density allowing your engine to ingest more air and thereby more fuel (up to a point with a carb unless jetting changes are made) producing more power per stroke of each piston.
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Advanced
Joined: Nov 2020
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This!!
what you experiencing is lower density alt which means more molocules of air per inch of mercury
Turbo chargers eliminate high density altitude which the engine sees
as far as flying good to know we got some pik
lots here yes IAS must fenain the same at all time in a high density altitude you must increase power or lower the nose to get the same airsoeed you always see. Notice your ground speed is much higher than normal during landing so you eat up mor runway to stop.
what you experiencing is lower density alt which means more molocules of air per inch of mercury
Turbo chargers eliminate high density altitude which the engine sees
as far as flying good to know we got some pik
lots here yes IAS must fenain the same at all time in a high density altitude you must increase power or lower the nose to get the same airsoeed you always see. Notice your ground speed is much higher than normal during landing so you eat up mor runway to stop.
Race Director
Joined: Dec 1999
Posts: 11,096
Likes: 990
From: Sierra Foothills CA
Good DA can make quite a difference, assuming you aren't running lean. Add that to colder pavement with less grip and things can get lively in a hurry. I drove the '69 yesterday shortly before sunset when the temp was about 48 and the DA was 1906 (checked when I got home), which is very good for my location. I got to my usual spot to drop the hammer on a slow 1st gear roll and it was very pissed off....usually the drag radials hook and go but not yesterday. Some tire spin but enough traction to really bolt, with very quick revs through the first 2 gears. It got gone in a hurry! 
Burning Brakes
Joined: Jul 2004
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From: If your not the lead dog the view never changes Boise, Id
IAS is IAS the wing does not know the difference.
The difference is in your ground speed and your true airspeed from air density not the lift generated by the indicated airspeed. The pitot tube is also impacted by less dense air so it is registering a lower IAS for a given GS or TAS due to lack of air density.
Since the wing only knows IAS it is generating the same lift for 80 KIAS (or any given IAS) regardless of the air density.
OP, just as big of an impact on the air density due to temperature is the atmospheric pressure.
These nice cool clear winter days are dominated by high pressure as well. This adds to the air density allowing your engine to ingest more air and thereby more fuel (up to a point with a carb unless jetting changes are made) producing more power per stroke of each piston.
The difference is in your ground speed and your true airspeed from air density not the lift generated by the indicated airspeed. The pitot tube is also impacted by less dense air so it is registering a lower IAS for a given GS or TAS due to lack of air density.
Since the wing only knows IAS it is generating the same lift for 80 KIAS (or any given IAS) regardless of the air density.
OP, just as big of an impact on the air density due to temperature is the atmospheric pressure.
These nice cool clear winter days are dominated by high pressure as well. This adds to the air density allowing your engine to ingest more air and thereby more fuel (up to a point with a carb unless jetting changes are made) producing more power per stroke of each piston.
‘do you know how to tell if there is a pilot in the room? .........they will tell you.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
QUOTE=RockyL32;1602693631]‘reminds me of my wife’s favorite joke.
‘do you know how to tell if there is a pilot in the room? .........they will tell you.[/QUOTE]
Actually I usually claim to be a dry wall installer. Unless there is another pilot in the room.
‘do you know how to tell if there is a pilot in the room? .........they will tell you.[/QUOTE]
Actually I usually claim to be a dry wall installer. Unless there is another pilot in the room.
Last edited by REELAV8R; Dec 19, 2020 at 03:37 PM.
Burning Brakes
Joined: Jun 2010
Posts: 1,165
Likes: 93
From: Bellmore NY
Agreeing with a couple of posts above, yes cold air, cold fuel, and cold under hood temps can make a big difference.
For whatever reason I think it’s more noticeable on a milder lower compression motor...summertime at the track can produce a lazier response and slower e.t than earlier spring or late fall passes. Just hot lapping a car with back to back passes can show slower numbers.
and yes, density altitude/barometer plays a big role in all this.
For whatever reason I think it’s more noticeable on a milder lower compression motor...summertime at the track can produce a lazier response and slower e.t than earlier spring or late fall passes. Just hot lapping a car with back to back passes can show slower numbers.
and yes, density altitude/barometer plays a big role in all this.
Melting Slicks
Joined: Feb 2018
Posts: 2,328
Likes: 724
From: Marietta GA
Back in he day when my friend and I went to drag racing tracks, the professionals would put bagged ice on the intake manifold before each run. I don’t know if it made a big difference, but we didn’t the same on my buddy’s small block, caused it looked cool 😎.
Drifting
Joined: Nov 2019
Posts: 1,370
Likes: 99
Fun Fact: The guys with the big brains figured out around the beginning of WWII that injecting water into an engine made for a cooler intake charge. Cooler air means it is more dense (higher volumetric efficiency) and also has a lower tendency to knock (detonation).
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,171
From: Hermosa
This is the reason CAI works. Especially for carbs.
When you tune your mixture in the garage (not just idle, the mains as well) your doing it at ambient temps of the surrounding air.
Without CAI once you close the hood the temp begins to rise and the air density goes down. That cool looking air cleaner installation that sucks the under hood air is now making the mixture richer by sucking in that hot, less dense air.
The results are a two fold power reduction. Due to not only less dense air, but also improper mixture.
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,218
Likes: 9,356
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
And if you can cool the fuel before it gets to the carb you will have better results as well. heres some links to the same show
https://www.motortrendondemand.com/d...and-why/35777/
https://www.tvtime.com/en/show/31723...as%20co%20host.
https://www.motortrendondemand.com/d...and-why/35777/
https://www.tvtime.com/en/show/31723...as%20co%20host.
Race Director
Joined: Dec 1999
Posts: 11,096
Likes: 990
From: Sierra Foothills CA
Exactly correct I suspect.
This is the reason CAI works. Especially for carbs.
When you tune your mixture in the garage (not just idle, the mains as well) your doing it at ambient temps of the surrounding air.
Without CAI once you close the hood the temp begins to rise and the air density goes down. That cool looking air cleaner installation that sucks the under hood air is now making the mixture richer by sucking in that hot, less dense air.
The results are a two fold power reduction. Due to not only less dense air, but also improper mixture.
This is the reason CAI works. Especially for carbs.
When you tune your mixture in the garage (not just idle, the mains as well) your doing it at ambient temps of the surrounding air.
Without CAI once you close the hood the temp begins to rise and the air density goes down. That cool looking air cleaner installation that sucks the under hood air is now making the mixture richer by sucking in that hot, less dense air.
The results are a two fold power reduction. Due to not only less dense air, but also improper mixture.