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      08-30-2009, 04:18 AM   #16
mixja
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Quote:
Originally Posted by ersin View Post
I read everyone talking about the heat. Higher temp = lower density air => less power. However, the whole reason forced induction (back in the early days when it was invented for aircraft) was increase the air density. So the temperature for a forced induction engine (super or turbo charged) should not make much of a difference in power delivery. There is a chance of heat soak the higher the temperature, but other than that how much of a difference could 100 degree temperatures make on an SC engine?

Don't get me wrong, 470+ whp is great, I'm not trying to downplay the numbers. But I doubt it will get much better on a cold day.

Note that this argument won't apply to normally aspirated engines -- higher temperatures (and altitudes) make a significant power drop in NA engines.
Disagree - superchargers increase air mass fed into the engine by compressing air (i.e. by increasing air pressure). When we talk 6PSI as an example, we are talking 6PSI above atmospheric pressure (i.e. a relative measure).

On a cold day, the air mass being fed at atmospheric pressure is greater than on a hot day (assuming all else is constant other than temperature). Because we have greater air mass at atmospheric pressure on the colder day, adding a supercharger running at 6PSI will result in greater output air mass than the same example on a hot day.

In other words, you'd need to run your supercharger at higher boost on a hot day to get the same amount of air mass (power) produced at a lower boost pressure on a cold day. Of course you've never actually do this because higher boost pressure will only cause higher intake temperatures already exacerbated by the higher air temperatures, causing a reduction in timing (and resulting loss in power) or detonation if timing is static.
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