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Jul 4, 2007 10:50:14 AM

intouch1: Rennteam Master; Loc: Red Sea , Egypt; Posts: 5752, Gallery; Registered on: May 22, 2004

Heat vs Cold

was wondering what the difference in performace of our cars is in hot versus cold weather.

currently we have daytime temperatures of 38 celsius here and i feel my car runs stronger at night, when temps are down in the 28 celsius range...

any ideas ?

furthermore, i can only run 95 octane as we do ot have 98 available....how would that affect my cars performance.

all input greatly appreciated....

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Jul 4, 2007 11:22:06 AM

easy_rider911: Rennteam VIP; Loc: London , United Kingdom; Posts: 22190, Gallery; Registered on: Nov 8, 2004; Reply to: intouch1

Re: Heat vs Cold

One advantage is that when you first start the car, your liquids (engine oil, power steering oil, gearbox oil etc) are all less cold than they would be in a colder climate. It will take less time to warm up to correct operating levels and there may be less wear on certain parts during this warm up period.

As for peformance, I think on a 997TT, the different octane 95 RON (instead of 98 RON) will make a small but noticeable difference.

Remember also that other items will probably have a far bigger relative effect on performance than the higher ambient temperatures you have in Summer: tyre condition, passenger weight, fuel load etc.

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Jul 4, 2007 12:07:52 PM

eclou: Veteran; Loc: Texas , United States; Posts: 1182, Gallery; Registered on: Jun 4, 2006; Reply to: easy_rider911

Re: Heat vs Cold

heat is the enemy of turbocharged cars. The turbo relies on intercoolers and a strong cooling system to remove as much heat as possible from the intake charge and the engine itself. When the heat is retained power is greatly robbed from the motor. Our motors are also greatly reliant on good levels of octane. Lower octane leads to pre-detonation which will cause the motor to pull back ignition timing. This can also lead to a large drop in power. The worst possible combo would be high heat and lower octane. You could be losing perhaps 10-15% of the rated HP

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Jul 4, 2007 4:20:38 PM

MMD: Rennteam VIP; Loc: usa; Posts: 9652, Gallery; Registered on: Dec 16, 2004; Reply to: eclou

Re: Heat vs Cold

I have no idea why but when it's really damp and misty outside the engine seem to perform better.

I've "noticed" this for many years of driving but never understood why or if I'm imagining it.

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Jul 4, 2007 4:49:10 PM

Jim_in_Iowa: Pilot; Loc: US; Posts: 336, Gallery; Registered on: May 18, 2005; Reply to: MMD

Re: Heat vs Cold

MMD,

The air has more density when moist, hence you're not imagining things.

Jim

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Jul 4, 2007 5:13:25 PM

eclou: Veteran; Loc: Texas , United States; Posts: 1182, Gallery; Registered on: Jun 4, 2006; Reply to: Jim_in_Iowa

Re: Heat vs Cold

Water vapor in the air actually displaces oxygen molecules - thus there are LESS O2 molecules in "wet" air. The difference is that the water vapor is an excellent reducer of HEAT thru the latent heat of evaporation. When the water molecules undergo a phase change from water to steam in the combustion chamber, it draws the excessive heat out - cooling the intake charge which diminishes pre-detonation and allows more boost and timing to be used. Many tuners actually use misting devices that spray a combination of water and methanol into the intake to provide that very effect. It is almost like running a super octane level.

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