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Performance Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Tue, 29 Jul 2003 14:02:49
In Reply to: Ari: Regarding voltage and alternator in the heat..., Patrick in Abq, Tue, 29 Jul 2003 08:09:29 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Lack of engine performance due to heat isn't due to lower voltage. The engine performance should be fine at low voltage. At some point the voltage will be too low, and the engine will just stop.
I believe from prior posts that your car is a turbo. Turbos are very affected by temperature. When you compress the air (or actually, the turbo does) it get hot. If the air is hot to begin with, it only gets hotter. A hotter charge is more likely to detonate, so you've got more of a chance that the APC will have to dial back boost to keep from knocking.
So, why not cool down that air? That's what the intercooler does. But the intercooler uses outside air to cool things off. On a really hot day, you're using hot air to cool down hotter air. So the intercooler is less effective.
Lastly, hot air is less dense - it has less oxygen per cubic foot. Yes, the turbocharge compresses it, but it's starting with less dense air to begin with.
I usually notice a drop-off in turbo response at 80 degrees, with more of a drop off above 90. You're in the desert, so the air is dry. In hot and humid conditions, it's even worse, because that water displaces oxygen. The water helps cool the combustion chamber so knock is less of an issue, but the compression/heating bit is still there.
Of course, on a nice, dry 40 degree day, the turbo performance can be awe-inspiring.
posted by 192.249....
, Tue, 29 Jul 2003 14:02:49 <-- Viewing This Message, Wed, 30 Jul 2003 07:46:11, Thu, 31 Jul 2003 06:17:49
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