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Old 10-08-2008, 10:43 AM   #1 (permalink)
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Hot Air intake vs. Cold Air... why or why not?

As I'm going through the posts here and other places. I'm seeing a split between people who feel hot air intake is better vs cold air intake for FE.

When I was a kid, I had a step-uncle who was a diesel mechanic and he loved to build and run high output gas engines for racing. In favor of nitrous oxide, he told me that one benefit of nitrous was a colder burn. He said that for every degree he burned cooler, he gained 3 HP...OR, since it was so long ago, it could have been 3 degrees cooler gains 1 HP. I don't remember which but he was in favor of a colder burn.

I'm not sure how that applies concerning intake air temperatures but I have seen several posts that have stated that cold air intakes are less efficient and that it has been proven. Is this true? I'm asking because out of all the mods I've seen talked about here, the hot/cold air intake mod seems to be the easiest to start with for a nooblet like myself.

So, if you're in favor of hot air intake, what kinda hot air we talkin' about? Just something drawing from somewhere around the exhaust manifold or a conductive metal running directly along the engine block? I bet there would be a big difference between the two.

Have you seen it's benefits? Got pics, links or quotes? What are the dangers?

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Old 10-08-2008, 08:34 PM   #2 (permalink)
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Link to one article that mentions it:
http://ecomodder.com/forum/showthrea...amics-312.html

Sorry the thread is so long, but it's definitely one that I remember showing results. You'll have to dig through the thread. The modder ran a dryer vent hose from his intake to in between his exhaust and the engine block. Noticeable gains in fuel economy.

Cold air does make more power. It does this by allowing you to burn more fuel at a given throttle opening.

To get the same amount of power as you'd get with a "normal air" intake, you indeed close the throttle some. But you're burning about the same amount of fuel you burned making that level of power, and a more-closed throttle means that your engine has to work harder to draw the air through that opening.

Warm air makes you open the throttle more for a given amount of power. But you are still burning that same basic amount of fuel, more or less. But since your throttle is open wider, your engine doesn't have to work as hard to draw the air in. This reduces "pumping losses", making the car slightly more fuel efficient.

-soD
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Old 10-09-2008, 09:16 AM   #3 (permalink)
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Quote:
Originally Posted by some_other_dave View Post
Link to one article that mentions it:
http://ecomodder.com/forum/showthrea...amics-312.html

Sorry the thread is so long, but it's definitely one that I remember showing results. You'll have to dig through the thread. The modder ran a dryer vent hose from his intake to in between his exhaust and the engine block. Noticeable gains in fuel economy.

Cold air does make more power. It does this by allowing you to burn more fuel at a given throttle opening.

To get the same amount of power as you'd get with a "normal air" intake, you indeed close the throttle some. But you're burning about the same amount of fuel you burned making that level of power, and a more-closed throttle means that your engine has to work harder to draw the air through that opening.

Warm air makes you open the throttle more for a given amount of power. But you are still burning that same basic amount of fuel, more or less. But since your throttle is open wider, your engine doesn't have to work as hard to draw the air in. This reduces "pumping losses", making the car slightly more fuel efficient.

-soD
Thank you soDave. I will definitely check that thread out.

So, to recap, what you're basically saying is that a hot air intake which is constructed correctly will reduce available HP and top end speed but cause greater FE at normal speeds with normal weight... Sounds good and sounds like it's definitely for me as a first time modder.
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Old 10-09-2008, 10:01 AM   #4 (permalink)
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Eh, sorry for cloggin' up the forums guys. A simple search would have landed me two threads on this threads on this, one of which explains what Dave explained and a little more. I reckon I need to shed some laziness and SEARCH.

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