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Old 07-06-2009, 07:01 AM   #1
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More proof of HAI helping

Well, if you go to my gas log you will see that a trip to Cleveland on 7/2008 resulted in my best MPG ever recorded.... thanks to the addition of a HAI.

This past weekend I once again made the trip and again, my mileage is up way past OEM specifications. Not the 40+ I had last year, but my engine is getting loose and drinking a lot of oil these days. Haven't checked the air in my tires in about 5 months either.

SGII is reading 38.5 mpg average tank after the trip home, will fill up again soon.
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Old 07-06-2009, 06:16 PM   #2
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Forgive me, but HAI= headers, and air intake right?
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Old 07-06-2009, 06:19 PM   #3
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Nope. Hot Air Intake.
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Old 07-06-2009, 06:48 PM   #4
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the idea behind the HAI or WAI for that matter (hot air intake and warm air intake respectively) is that if you heat the incoming air that it has less oxygen in it because of thermal expansion so it takes less fuel to burn that amount of oxygen.

most intakes only run a few degrees above the ambient temperature. cold air intakes actuall try to bring that delta down even farther. my WAI has a delta of about 70 degrees over ambient. (and yes, that puts me around the 150 to 160 degree mark) some have pushed it close to 200 degrees on their intake temps.

this is accomplished in a few different ways. the most comon are to either just take air from the engine bay (raise the temps a little) or to run a tube to the exhaust manifold and run the intake air across the manifold to heat it first.

my explination isn't the best but hopefully it makes some sense
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Old 07-08-2009, 11:14 AM   #5
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the idea behind the HAI or WAI for that matter (hot air intake and warm air intake respectively) is that if you heat the incoming air that it has less oxygen in it because of thermal expansion so it takes less fuel to burn that amount of oxygen.

I thought the idea was to make the motor less effecent where you have to open the throttle more decreasing pumping loses and increase the temp of the engine which increases thermal effeciency.

in your explanation you say that your inducting less air, which to get the same afr takes less fuel. which is correct, but fuel in what propells the car. if your at a throttle position you don't increase or decrease speed ( on a steady road where the altitude doesn't change) unless you decrease throttle position which increases or decreases fuel. which makes you go faster or slower. WAI, you have to open the throttle more to get the same amount of air and fuel then before. decreasing pumping loses. if the amount of gas burnt could be calculated as horsepower or mpg.
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Old 07-08-2009, 12:03 PM   #6
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it does decrease pumping losses but it also brings in less oxygen (by volume) than the normal setup. it also gives you more play in the pedal because of this. instead of having 1/2 inch of pedal to give you the power you need, you have 1 inch. (that is just an example) this way you can meter how much throttle you give it better and you don't give it too much throttle for the task at hand.

in essense, it is decreasing the displacement of the engine.

there are probably many ways to look at it but that is the way I have always seen it. hot, expanded air holds less oxygen and thus takes less fuel to burn so every charge of air that runs through the engine takes less fuel.

another aspect of this (for me at least) is when you are sitting at a stop light. I have my scangauge set up for HP which isn't a great tool but I like it. at a stop light with an IAT temp of less than 100, I am seeing 5.X HP somewhere in the neighborhood of 5.3 or so. with the IAT approaching the 150s (usually 141 or so is my morning drive) i see it under 5HP. if the heat is roaring and I get it over the 160 mark (not usual) it will go down to as little as 4.5HP.

this within it self isn't really that important (the horsepower I mean) but the way the scangauge derives horsepower is important. the more gas used equates into more horsepower displayed.

there are many benefits to the WAI. maybe I focus on different ones than others.

I will admit that I am not an expert so take it how you will.

*edit* a few issues just to point them out. the amount of air that is taken in is the same (volume wise). your actual displacement doesn't change.

your literal air fuel ratio may actually change but the fuel to oxygen ratio will stay the same because of the O2 sensor. this is more what I am talking about. a charge of air holds X amount of oxygen, if that air is heated it will hold less (not sure what the ratio is but probably depends on temperature delta) RIDE has actually posted it before.

also, you say that it takes X amount of fuel to propel a car but that doesn't hold true if a vehicle has a few different engine options. the SUV with either the 4cyl or the V-6. if what you say is true, the only difference would be the weight difference in the motors affecting the overall weight of the vehicle. the mileage should be basically the same.
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Old 07-08-2009, 12:34 PM   #7
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Quote:
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*edit* a few issues just to point them out. the amount of air that is taken in is the same (volume wise). your actual displacement doesn't change.
Indeed. Volume stays the same, mass decreases; or to take in the same mass, an increased volume is required. That is the nature of density and an underlying concept of the WAI; by heating the air, you decrease its density.

Quote:
your literal air fuel ratio may actually change but the fuel to oxygen ratio will stay the same because of the O2 sensor. this is more what I am talking about. a charge of air holds X amount of oxygen, if that air is heated it will hold less (not sure what the ratio is but probably depends on temperature delta) RIDE has actually posted it before.
That raises this question: Does O2 expand more or less than N? N being the largest component of air (and a decent-sized dose of CO2 along with O2)...and would it change the ratio of O2-to-N? I suspect it wouldn't, the air is already committed to your engine by the time it reaches the heater portion of the WAI.

However, when the weather is hot and that's affecting your IAT, that question would come into play.

Anyway, a charge of air holds X mass of oxygen, and with the O2 sensor to fine-tune your fuel injection it will receive Y mass of fuel. As long as X mass of O2 goes in, Y mass of fuel will go in. If the air is heated after it is already in the intake, I don't think it will hold less O2; where would the O2 go? It will hold the same mass of O2, but perhaps less total mass of air will be required to convert the combustion's heat energy into piston motion, which would mean less O2 and less fuel.

Don't forget, converting the combustion's heat energy into piston motion is done by expansion of air in the combustion chamber; all the air - nitrogen, oxygen, carbon dioxide, argon, etc.

I was going somewhere with all of this, but I seem to have forgotten where. D'oh!
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Old 07-08-2009, 12:38 PM   #8
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also, you say that it takes X amount of fuel to propel a car but that doesn't hold true if a vehicle has a few different engine options. the SUV with either the 4cyl or the V-6. if what you say is true, the only difference would be the weight difference in the motors affecting the overall weight of the vehicle. the mileage should be basically the same.

yeah your right. a different vehicle is going to take more or less fuel to get to x speed and maintain that speed. efficiency of the motor, the weight. but there is a value for every vehicle. what I'm saying is if you out of the blue have less air (wai) and your in closed loop where equally less fuel is being used to get to the desired afr. your using less fuel, yes. but there's ultimately less work being done to move the car.

you still need a given amount fuel to maintain a speed in a given car. you can't just use less fuel and still acomplish this. acceleration and gear ratios and other weird factors change this, but say at a 1 to 1 ratio on flat road and the air and engine temp is constent. you cant use less fuel and accomplish the same thing. you have to increase the throttle to burn more fuel. burning the same amount of fuel at a greater throttle opening = less pumping loses.

but can you really be at a steady state?????? cause if the throttle opens more and the vehicle is more effecient, it'll add a little speed and then you have to decrease the throttle a bit. and then increase, then decrease, etc. etc................
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Old 07-08-2009, 12:46 PM   #9
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Anyway, a charge of air holds X mass of oxygen, and with the O2 sensor to fine-tune your fuel injection it will receive Y mass of fuel. As long as X mass of O2 goes in, Y mass of fuel will go in. If the air is heated after it is already in the intake, I don't think it will hold less O2; where would the O2 go? It will hold the same mass of O2, but perhaps less total mass of air will be required to convert the combustion's heat energy into piston motion, which would mean less O2 and less fuel.
but with a wai your getting your air from right next to the manifold where its less dense. as opposed to the wheel well. is that not more air in the situation of the intake being in the wheel well??
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Old 07-08-2009, 02:53 PM   #10
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you still need a given amount fuel to maintain a speed in a given car. you can't just use less fuel and still acomplish this. acceleration and gear ratios and other weird factors change this, but say at a 1 to 1 ratio on flat road and the air and engine temp is constent. you cant use less fuel and accomplish the same thing. you have to increase the throttle to burn more fuel. burning the same amount of fuel at a greater throttle opening = less pumping loses.

but can you really be at a steady state?????? cause if the throttle opens more and the vehicle is more effecient, it'll add a little speed and then you have to decrease the throttle a bit. and then increase, then decrease, etc. etc................
I would say it this way- it takes a certain amount of work to move a car at X speed from point A to point B. By using WAI, you are reducing pumping losses and so the engine is operating more efficiently and thus it can do the required amount of work (for the above scenario), using slightly less fuel.

Besides reducing pumping losses, you are also utilizing otherwise wasted heat coming off the exhaust manifold to increase the temp of the air/fuel going in to the engine. Sort of like recycling heat that would otherwise be lost to the atmosphere.
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