09-15-2006, 11:29 PM
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Active Enthusiast
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Hybrids: Toyota Highlander
Posts: 80
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Re: FE hit cuz of cold weather starting.
Cold weather has benefits for gas engines. First of all, your engine will provide more power when colder since the cold air flowing into it will be more dense which will result in more fuel being packed in with this dense air to keep the air-fuel mixture properly balanced. This will result in more horse power output.
This effect is like a very mild form of turbo charging as more air can be packed into the engine cylinder when it is cold and dense. Air reduced by 30 degrees is equivalent to 1 PSI of turbo boost. With cold weather you get this effect for free.
Intake Air Temperature
Engine Power Loss
Example Power Output
20C
%0
224 hp
40oC
3.50%
216 hp
60oC
7%
208 hp
80oC
10%
202 hp
100oC
13%
195 hp
Toyota and most automakers take advantage of this effect by placing the engine air intake at the very front edge of the engine compartment under the hood to avoid pulling in hot under-hood air into the engine. The table below describes the relative power loss expected by a gas engine as outside temperatures increase:
The second advantage of cold weather is that the engine can run on lower octane fuel before experiencing engine knock. Thus, when the temperatures are in the 30's for instance, you can notch down to a lower grade of gas without reducing gas mileage and performance. I typically use premium gas in spring through fall and mid-grade in winter (Chicago area)
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