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Old 12-03-2009, 01:34 PM   #1 (permalink)
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Increase FE with warm air intake


Ive had the idea burning in my head for weeks now. Durning the winter, my personal MPG has gone down significantly. Although, most people cant wait till winter because it increases preformance. But since, with the more dense air, more fuel is required to maintain the ratio, there should be a way to prevent this.
What if one were to put fins on their catalytic converter, a circumscribed rigid air duct over them and the exhaust line to the engine bay, come off of the exhaust line, and go into the air filter box.
Of course there would need to be a servo controlled damper on the normal air inlet, as air would want to flow from the area with the least resistance. This would also allow air to bypass the heater and allow cool air in when the cat gets too cold or the driver wants more performance.

I will try it soon,
but let me know what you think,

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Old 12-03-2009, 01:49 PM   #2 (permalink)
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Originally Posted by silverhawk_184 View Post
But since, with the more dense air, more fuel is required to maintain the ratio, there should be a way to prevent this.
Yes but it still takes the same ammount of fuel and air to produce the same power and travel the same distance. You simply open the throttle plate less to burn the same amount of air and fuel. The net effect is no change in FE. Colder air also allows the engine to run its vest optimized spark timing for any given octane fuel. The only negative effect in cold weather comes from the longer engine warm up time, not denser air.

Last edited by tjts1; 12-03-2009 at 01:59 PM..
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Old 12-03-2009, 01:57 PM   #3 (permalink)
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Cold, dense air also increases wind resistance. We have so many threads about this, it has it's own acronym here - WAI.
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Old 12-03-2009, 01:58 PM   #4 (permalink)
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A lot of guys just run their intake ducting over to the exhaust manifold. With the scangauge you can monitor the intake air temps and just make sure it doesn't get too hot.
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Old 12-03-2009, 07:25 PM   #5 (permalink)
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Another way is to let the air intake suck in air that's been through the radiator.

On my car the ducting to pull air from any part of the exhaust system would be a bit tricky. So because the air filter box is located pretty much right behind the radiator, I cut holes in it and blocked off the snorkel. These days it's pulling in air about 35-40 degrees F warmer than outside temperature. That will vary depending on how much grill block you have and other factors but it's doable.

More grill block makes the radiator-heated air warmer. Best results in my car were with the lower grill mostly blocked and the upper left open - because my revised air intake is behind the upper grill area. So I want air to go thru there and get warmed by the radiator.
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Old 12-03-2009, 08:14 PM   #6 (permalink)
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silverhawk_184 -

As Daox said, exhaust manifold HAIs are very prominent. Check this thread out :



What's your EPA MPG? Go Here and find out!
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Old 12-03-2009, 11:45 PM   #7 (permalink)
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Thanks for the replies.

One thing I had already done, is to remove the radiator fan, which has helped a lot. It also has seemed to warm up slower.

From research, my little 2.3L loves to run warm (209°F). And this fall, when the temperatures fell from 80-90°F to the 60's, my mileage fell about 25%. It could just be all due to the more drag, with the denser air, but I don't think that is all it.

It is so odd, how when one starts a post and searches for relevant topics, none are returned, but as soon as it is submitted, billions of topics are automatically found at the bottom of the page.

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