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Android Users - Coming Soon! - Migrating from aCar 4.8 to 5.0

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Old 07-08-2009, 03:10 PM   #11
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there is also the idea of better atomization of the fuel with warmer air coming in. I don't know much about this so I will simply throw the idea out there for those who do understand this (at least better than me)

I do agree that pumping losses is a factor and that it takes a certain amount of work to move a given object at a given speed (all other factors being equal). all of the above being said, there has to be more to it than just pumping losses. I have always heard that the warmer air made the vehicle more efficient. though I don't have much to back that up right off-hand
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Old 07-08-2009, 04:08 PM   #12
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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??
Thank you for pointing that out. I was thinking of a WAI design I've seen where the air is heated once it's already in the intake. It's still an enclosed area when it comes from the manifold without an upstream snorkel, but not quite that enclosed.
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Old 07-08-2009, 05:04 PM   #13
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Better atomization can be understood by looking at air conditioning. Refrigerant is atomized and absorbs heat, then its compressed and the heat is removed by the condenser.

Fuel when injected absorbs heat in much the same way as refrigerant. The warmer the fuel and air, the better the atomization. Ideally with complete atomization the efficiency would increase by almost 25%.

That is what is being pursued with HCCI or Homogeneous Charge Compression Ignition. This is where fuel and air is perfectly homogeneous and you can ignite gasoline through compression alone. HCCI when perfected will produce almost the same power in a gasoline engine as in a diesel. Not quite, but very close, because diesel fuel contains more energy per unit of volume than gasoline.

While not directly related to this post you should also consider the restriction of air flow over the radiator, which serves to increase the temperature of the coolant entering the engine to a point where it is about the same as when ambient temperatures are in the range of 100 degrees.

In winter when WAI and radiator blocks work best, the combination of the two mods serves to closely duplicate summer conditions in the winter, at least as far as the temperature of the intake charge and the temperature of the coolant entering the engine after the radiator removes some of its heat energy. Controlling the heat energy lost in the radiator means coolant is fairly hot when it enters the engine, like it is in the summer.

A thermostatically controlled radiator block, that maintains the inlet coolant temperature around 110-120 degrees (like it is in the summer) and a WAI that duplicates the intake air temperature to the same as summer, would go far to rectify the loss of mileage experienced by all of us in the winter.

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Old 07-08-2009, 05:14 PM   #14
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Personally I would tend to think if you heat the intake air beyond a point that occurs naturally it COULD reduce efficiency (emphasis on could).

That would depend on the particulars of the system in your car, and I have read her that some work well in much higher temperatures than occur naturally, which is about 140 degrees.

Air density from 32 F to 200 F is reduced by 25% so yes you are in effect reducing the displacement of the engine. With most of our cars either under geared or overpowered reducing the effective displacement makes the engine more efficient.

Offsetting that improvement is the fact that larger displacement engines have to work harder to just move their more massive components in order to reciprocate them to create compression for combustion. This is why a small 4 cylinder engine will only need .2 gallons of fuel to idle for an hour, while a V6 will need about .35, and a V8 will need .5 or more. That's just the engine, with no outside loads applied. Pumping losses should include reciprocation losses as well as all other losse necessary to create pumping losses.

Monroe 74 and I had a heated debate a year ago about the amount of energy required to create compression being much greater than the energy losses in creating a vacuum.

Wish he had not stopped posting on this forum.

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Old 07-09-2009, 05:08 AM   #15
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That's how I always understood it... better atomization due to warmer air and a less dense mixture of fuel resulting.

Anyway, despite what scientific reasons are behind the functionality here... point is: IT WORKS.

I might also add that I've got a failed rear o2 sensor (P0141) and have had it for roughly 4 months. I bet if I replaced it prior to this trip I would've seen 40/41mpg. Had I checked tire psi I bet I could've matched the MPG recorded from last year's trip over the same weekend. All other conditions were nearly identical, ambient, intake temp, 1 passenger, same amount of cargo, no A/C, mild drafting.

I really don't try to hypermile anymore. The car just uses so much oil and is so far down on power (bad rings), it takes a lot of pedal use to get the car moving. If it dips into the low 20's I'll rebuild, if not, I'll keep driving it until something else comes along.
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Old 07-09-2009, 05:35 AM   #16
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I might also add that I've got a failed rear o2 sensor (P0141) and have had it for roughly 4 months. I bet if I replaced it prior to this trip I would've seen 40/41mpg.
Would a rear O2 sensor affect FE at all? I thought its only job was to monitor the catalytic converter to make sure it's working right.
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Old 07-09-2009, 09:44 AM   #17
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I assume the rear in my Saturn has just as much if not MORE to do w/ FE because of the wiring. The front only has 1 wire. The rear has 4 or 5 if memory serves correct. I figure it's monitoring things more closely than the front. IDK? I could be wrong.
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Old 07-09-2009, 10:30 AM   #18
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I assume the rear in my Saturn has just as much if not MORE to do w/ FE because of the wiring. The front only has 1 wire. The rear has 4 or 5 if memory serves correct. I figure it's monitoring things more closely than the front. IDK? I could be wrong.
A rear O2 sensor will probably require a heater to reach operating temperature, wheras the front one typically doesn't.

If the factory was going to spend money on a wide-band sensor, they'd put it in front of the cat.

-BC
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Old 07-09-2009, 10:46 AM   #19
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Better atomization can be understood by looking at air conditioning. Refrigerant is atomized and absorbs heat, then its compressed and the heat is removed by the condenser.

Fuel when injected absorbs heat in much the same way as refrigerant. The warmer the fuel and air, the better the atomization. Ideally with complete atomization the efficiency would increase by almost 25%.

That is what is being pursued with HCCI or Homogeneous Charge Compression Ignition. This is where fuel and air is perfectly homogeneous and you can ignite gasoline through compression alone. HCCI when perfected will produce almost the same power in a gasoline engine as in a diesel. Not quite, but very close, because diesel fuel contains more energy per unit of volume than gasoline.

While not directly related to this post you should also consider the restriction of air flow over the radiator, which serves to increase the temperature of the coolant entering the engine to a point where it is about the same as when ambient temperatures are in the range of 100 degrees.

In winter when WAI and radiator blocks work best, the combination of the two mods serves to closely duplicate summer conditions in the winter, at least as far as the temperature of the intake charge and the temperature of the coolant entering the engine after the radiator removes some of its heat energy. Controlling the heat energy lost in the radiator means coolant is fairly hot when it enters the engine, like it is in the summer.

A thermostatically controlled radiator block, that maintains the inlet coolant temperature around 110-120 degrees (like it is in the summer) and a WAI that duplicates the intake air temperature to the same as summer, would go far to rectify the loss of mileage experienced by all of us in the winter.

regards
gary
regrigerant isn't atomized. atomization is mixing with air or being suspended in air. the a/c system is put under a vacuum to remove all the moisture,,,, but that's not air, but its induced under pressure. I don't think there's any air in the system.

the main way a/c works is the latent heat of vaporization. the change of states and pressure reduces and increases heat.


but now I get it. the warmer air more spread out, expanded, its easier for the fuel to mix with the air and there's less likely of a chance to miss fire, or all the fuel being burned.
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Old 07-09-2009, 10:56 AM   #20
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Would a rear O2 sensor affect FE at all? I thought its only job was to monitor the catalytic converter to make sure it's working right.

I've been told that the rear is what's use for LTFT.
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