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Old 12-14-2004, 03:30 PM   #1
alleninpa
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Default Better Fuel Economy??

Have you ever noticed that your fuel economy goes down in the winter, then back up in the summer. It makes sense if you think about it because cold air is more dense, meaning the engine adds more gasoline to have the correct fuel/air mixture.

Ok, now on for the question.

What if hot air instead of cold air was used in the winter. I origionally thought that I could just use a cold air intake and modify it so it is behind the radiator. Should get great fuel economy, but poor power.

So, my next step in this is to have 2 air filters, one in the cold area, one in the hot area. Use a switch attached to the throttle that would activate when WOT was hit. Then, a solenoid would flip a baffle, switching from the hot air side to the cold air side. The temp sensor would be located down stream from the baffle.

Any comments? Am I crazy, or is this an awome idea?

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Old 12-14-2004, 05:08 PM   #2
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Default Re: Better Fuel Economy??

I think the winter formulation of gas has more to do with the mpg loss than anything really. As long as you don't hammer the gas in the winter to actually utilize the greater power because of the colder air, you really shouldn't be using that much more fuel (due to the air temp).

Joe

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Old 12-14-2004, 06:11 PM   #3
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Default Re: Better Fuel Economy??

Quote:
Originally Posted by MightyJoe
I think the winter formulation of gas has more to do with the mpg loss than anything really. As long as you don't hammer the gas in the winter to actually utilize the greater power because of the colder air, you really shouldn't be using that much more fuel (due to the air temp).

Joe

You will however use more fuel on startup due to the colder temperatures causing the computer to hold the car at a high idle for a longer period of time on initial startup.

...
Kevin

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Old 12-14-2004, 06:34 PM   #4
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Default Re: Better Fuel Economy??

You're forgetting there is much COLDER air going through the radiator to cold your engine down constantly in winter than it is summer. This is the main reason why your gasmilage drop more.

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Old 12-14-2004, 07:24 PM   #5
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Default Re: Better Fuel Economy??

Quote:
Originally Posted by amazinghl
You're forgetting there is much COLDER air going through the radiator to cold your engine down constantly in winter than it is summer. This is the main reason why your gasmilage drop more.

CARDBOARD.... ... Heat is a good thing. Apparently my car doesn't have much. Now we can run 1/2-way up the temp gauge in the winter. Cheap Solution.

...
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Old 12-14-2004, 09:14 PM   #6
alleninpa
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Default Re: Better Fuel Economy??

The air blowing over the radiator really doesn't effect the engine performance. The thermostat controls the temperature. Have you ever seen a car overheat in the dead of winter? Sure, they use water in the radiator, instead of antifreeze. The radiator freezes, and the engine can't cool.

The computer sets up a ratio of fuel to air mixture. Since the O2 sensor will read more air, since the air is more dense, it dumps more fuel in, no matter what the RPM, or how hard you accelerate.
By the way, there is 15% more oxygen in air at 32 degrees compaired to 100 degrees f.
Therefore, your fuel economy will go down by 15%
I set a thermocouple in the engine compartment for tomorrow morning. It will be 18 degrees f in the morning, and I will report back about the engine compartment temp versus speed tomorrow.

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Old 12-14-2004, 09:33 PM   #7
Nowhere Man
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Default Re: Better Fuel Economy??

In the winter time they also use a gasoline/ethanol mix. This makes the gas mileage go down as well. I noticed when they switched to winter gas a few weeks ago when it was still in the 80's here. Tank before was 33.4 mpg, and tank after the switch was 30.2 mpg. I think the ethanol mixture around here is 5%. Why do this?
Well, as stated above the poorer gas mileage results from the denser air. To counteract this and reduce emissions, ethanol is added in the winter. Which ironically, makes the gas mileage go down even more.

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Old 12-14-2004, 09:56 PM   #8
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Default Re: Better Fuel Economy??

I see that every winter here in Maine; my '95 SW2 usually drops down to around 32-33 mpg this time of year, and back up to 37-39 mpg during the warmer months. It's a combination of the colder weather, harsh driving conditions (i.e. snow/sleet), and winter blend of gas. Sometimes, though, it will surprise me...last Christmas we took a trip out to NH to visit relatives, and the car returned 39+mpg.

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Old 12-14-2004, 10:23 PM   #9
emptypockets
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Default Re: Better Fuel Economy??

Quote:
In the winter time they also use a gasoline/ethanol mix. This makes the gas mileage go down as well. I noticed when they switched to winter gas a few weeks ago when it was still in the 80's here. Tank before was 33.4 mpg, and tank after the switch was 30.2 mpg. I think the ethanol mixture around here is 5%. Why do this?
Well, as stated above the poorer gas mileage results from the denser air. To counteract this and reduce emissions, ethanol is added in the winter. Which ironically, makes the gas mileage go down even more.
I always thought the ethanol was in there to mix with the water and condensation to keep your fuel lines from freezing up. Also the snow and ice makes the tires spin more and causes higher RPM's. The colder/denser air still has a factor in it though.

I would think that putting a second air filter behind the radiator would help because of the warmer air. The radiator would put off warmer air then the outside air so you're engine would be getting less dense air. It might not noticeably change gas mileage though. You would have less power because cold air raises compression. I don't understand the switch at WOT though. I would think that maybe you could just install completely different intake tubing so it's behind the radiator in the winter.

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Old 12-14-2004, 10:44 PM   #10
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Default Re: Better Fuel Economy??

Quote:
Originally Posted by emptypockets
I always thought the ethanol was in there to mix with the water and condensation to keep your fuel lines from freezing up. Also the snow and ice makes the tires spin more and causes higher RPM's. The colder/denser air still has a factor in it though.
True, this may be the case up north (where the mixture can be as high as 10% ethanol). But the reasoning in Florida is mostly emissions realted.

...
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Old 12-15-2004, 03:35 AM   #11
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Default Re: Better Fuel Economy??

Reinstall the stock air intake. That large box that sits over the rad is for getting warmer air to the engine to help with startup, warm up, and driving.

Other than that, the winterized fuels will have an effect too.

Did you switch to winter tires? Were they stored over the summer? if so double check the tires pressures are correct. A low tire will make the biggest difference in fuel economy. The specs are on the end of the driver's side door or in the trunk lid. usually 30lbs is good. I run a little more in the fronts as they are doing most of the work.

Hope you solve your problem. ir get some better mileage.

Giuseppe

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Old 12-15-2004, 03:23 PM   #12
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Default Re: Better Fuel Economy??

Sucking in colder air won't make a difference in MPG if you don't drive at WOT very much. Since it's denser you'll use a lighter foot because you get more power from the same volume of air. The car* will keep an ideal fuel mix summer or winter. Now if you're drag racing you'll get more power and less MPG... but less than WOT, no difference. Note the intake air temp sensor... that's what it's all about.

*I'm talking warm engine long road trip mileage here; warmup time is a huge MPG buster in the winter.

Another way to look at it is: Yes, the computer does add more fuel when it's colder out for a given throttle position. But since more oxygen molecules squeeze past that throttle plate, you go faster, lift the pedal, and it all evens out. You can use a hot-air intake if you want, but it will limit your max power without any benefit.

Look at the "stoves" in early 80's carbureted junk that get warm air from around the exhaust manifold when needed. That awful technology would still be in service if it offered some benefit in economy/emissions/driveability.

Since the warm air is thinner in the summer, your drag coefficient through the air gets better. You can't escape this no matter what you do under the hood. Since one needs windows down or A/C when it gets hot this negates this. Sometimes the best mileage I ever get is in the spring/fall.

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