Hot weather performance ?
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Joined: Mar 2006
Posts: 80
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From: UK
Hot weather performance ?
Does anyone notice any drop in performance during hot weather temperatures. I realise that cars like cold dense air for optimum performance but i can definetly feel a lack of umph in hot weather.
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Joined: Jul 2003
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From: Atlanta
My butt dyno also detects significant loss of power on hot humid days. My theories, starting with the largest effect:
1) Knock sensors keep the ignition retarded.
2) Less air mass in 3.6 liter volume when it is hot.
3) AC on max robs about 5 hp, plus adds the rotating inertia of the compressor.
1) Knock sensors keep the ignition retarded.
2) Less air mass in 3.6 liter volume when it is hot.
3) AC on max robs about 5 hp, plus adds the rotating inertia of the compressor.
Three Wheelin'
Joined: Dec 2004
Posts: 1,779
Likes: 1
From: Halifax, Nova Scotia , Canada
The 964 has maps to reset Timing/fuelling etc when the intake air temperature
rises . That looses power but inhibits knock ! Dont know what Motec does !!!!
All good stuff
Geoff
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KS400200,the oldest 964 on Rennlist,unless you know differently !
rises . That looses power but inhibits knock ! Dont know what Motec does !!!!
All good stuff
Geoff
----------------------------------------------------------------
KS400200,the oldest 964 on Rennlist,unless you know differently !
Technical Guru
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Joined: May 2002
Posts: 8,138
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From: USVI
The ignition timing is also reduced with the increase in intake air temperature. With the standard programming and 93 octane the knock sensors shouldn't see any activity.
To reach the upper temperature scale all you need is to drive around in the summer for 30 minutes and then get stuck in stop'n'go traffic. I was kinda surprised, with an RS3.8 wing and a cup airbox the temperatures were right up there.
To reach the upper temperature scale all you need is to drive around in the summer for 30 minutes and then get stuck in stop'n'go traffic. I was kinda surprised, with an RS3.8 wing and a cup airbox the temperatures were right up there.
Racer
Joined: May 2007
Posts: 274
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From: Malaysia
From my days in aviation...
Every 4F increase in temperature is roughly the equivalent of an additional 1000ft of altitude. That is why a naturally aspirated car will perform better on a (relatively) cool day.
JNeteler
Every 4F increase in temperature is roughly the equivalent of an additional 1000ft of altitude. That is why a naturally aspirated car will perform better on a (relatively) cool day.
JNeteler
Burning Brakes
Joined: Mar 2006
Posts: 883
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From: Sydney, Australia
Originally Posted by jneteler
From my days in aviation...
Every 4F increase in temperature is roughly the equivalent of an additional 1000ft of altitude. That is why a naturally aspirated car will perform better on a (relatively) cool day.
JNeteler
Every 4F increase in temperature is roughly the equivalent of an additional 1000ft of altitude. That is why a naturally aspirated car will perform better on a (relatively) cool day.
JNeteler
