Sucking hot air with an under the hood intake is a non issue. For those who have ever used a scangauge or anything else that can monitor air intake temp, as soon as you start moving you're sucking in virtually ambient temperature air. I've measured it on a few different cars, and I've even tried to suck hot air off the exhaust manifold to make a warm air intake (for faster warm up in winter, and better fuel economy), and its not the easiest thing to suck in hot/warm air. While you're at idle however, you will see the temp rise as there isn't air flowing through the engine bay. However, this isn't a bad thing as you don't need power while idling...
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View my fuel log 2015 Mirage DE 1.2 manual: 47.2 mpg (US) ... 20.1 km/L ... 5.0 L/100 km ... 56.7 mpg (Imp)