I'm Stupid -- Air intake info ?

[Terry Schultz]

I do not understand all this talk of air intake and cool air.



I have a scangauge and I have seen that during colder days my MPG goes down. I have also seen during rainy days my MPG goes down.



Colder air is good ?? Colder and dry OK or Colder and wet OK ??



Terry

 

[Kevin Palmer]

Not stupid.....



Basically cold air is more dense. It is more compacted compared to hot air, which is expanded. Just like you, if your hot or warm it is hard to get your rings off due to your body expanding. As opposed to if your cold it is easy to get the ring off. In both cases you don't weigh any more, you have gone thru a physical change is all. So in a not to technical nut shell you actually get more air into the combustion area than if it were hot air.



As a general rule, the more air you can get into a controlled area the better burn, or performance you will get out of that air.

 

[EddieS'04]

Cooler air makes for air denser air charge resulting in more HP and TQ...

 

[Terry Schultz]

C & E --



Then why does my MPG, according to my scangauge, go down when it is cold or wet ???



I want to understand, but I don't. There must be an optima cold, or cold and wet, to get the max performance.



I scratch my butt and wonder why ??



Myself <-- not stupid but dumb and wonders why



Terry

 

[EddieS'04]

The ECU adjusts the fuel injectors for the increased air charge, requiring more fuel for the burn ratio....

 

[Jeff C]

Just a thought from a physics standpoint, but it takes energy to heat air. Warm air is not compacted, and thus you get normal operating conditions. Cold air takes energy to heat up and expand so it can be used by the engine, thus a loss of power. Cool air and it only takes a little energy to heat, and there's more air than when driving through warm air. I've found that my ST operates optimally at the track when the temperature is between 60-70 degrees farenheit.



Just a theory.

 

[Travis Munday]

The engine makes power from the controlled combustion of the fuel/air mixture, not the temperature of the air. The air is only there to faciliate the burning of the gas; the gas enters the cylinders atomized. If there was no air, the fuel would tend to pool and 'drop' together before it even got to the cylinder. Of course, direct injection doesn't suffer that problem. The more air you have, denser or otherwise, the more fuel you can (and have to) inject to maintain stoichiometric efficency. If you try to inject too much fuel with too little air, it will cause an uncontrolled burn, as the atomized fuel will 'drop' together at various points around the combustion chamber, which can result in a very unsafe condition in the engine, like a rod through the oil pan.



The reason why you get worse MPG in cold air, and wet air, is because the engine is burning more fuel; more fuel is being injected because of the denser air. More burnt fuel per stroke, means less miles per gallon.



Horsepower and torque is a direct result of how much fuel can be burned in a controled manner.

 

[Terry Schultz]

Jeff --

I have noticed, per my scangauge, that 60 Deg is the "breaking point". It does best above 60 Deg.



Terry < not stupid --- just dumb -- BUT why not an air heater for the intake in the winter or an air cooler for the summer ???



Terry = watches scangauge too much and glad he has not hit a solid object.



Terry

 

[Travis Munday]

The breaking point is probably more a result of electronic limitations of the computer, not physical ones. In carb'd cars, they love cold air, wet air at sea level, super dense means lots of fuel...means lots of power.

 

[Terry Schultz]

Tiger ---



We're not "carb'ed" any more. We are now controlled by the "BOX".



Terry

 

[Kevin Palmer]

Ok, lets see if this helps.



On older engine there were chokes. Some manual some temperature related. But when the choke was closed it would bring in extra fuel into the intake. On our engine we have the same thing only it is done entirely electronically thru the ECM, Electronic Control Module. The temp sensor gives the info to the Injectors via the ECM.



So on cold days you are in fact using more fuel until at the very least that the engine gets up to running temperature.



Terming an item a Cold Air intake may be confusing. Maybe a better term would be "Fresh Air Intake". What a cold air intake does is to get air into the engine that is the same as or at least much closer to the ambient air temperature.



With a tradional intake you get much of your air from the engine compartment which is being heated by the engine itself.



Does this help or confuse you???

 

[Terry Schultz]

Coastie --



Thanks for the explaintion (sp). But if the ECM is doing its job, why would I see a difference ?? It sould be the same all the time (on average). I have no codes thrown at me, (still dumb) that something is not right.



This makes me wonder that the talk of "winter blends" of gas is true; or is it how the ECM reacts to the temperature changes.



Terry

 

[Travis Munday]

I know....I was simply pointing out how the "BOX" is limited into what it's able to do.



Colder air is good for power, bad for MPG. Can't get more simple then that.

 

[Dale Carter]

The colder the air, the harder it is to push the Trac through it and the increased aerodynamic drag reduces MPG.



Either that or you Tornado isn't working on cold days BWAHAHAHAHAHAHA





BTW, everything in this message is meant to be a joke, although I would love to hear a real live engineer type (preferably aeronautical) talk about the first sentence..

 

[Gavin Allan]

How about get a blower motor and "ram" the air into the intake-- kind of a poor man's turbocharger. You could even mount a switch under the dash to turn it on when you need more power.

 

[Jeff C]

dale, odds are that the ST doesn't accelerate or even have a top speed high enough for the differences in the density of the air to have a noticable increase the drag. Oh, and if you look in my profile, I'm not yet an engineer, but 2 more years...

 

[Tom Schindler]

Tiger is right. I will try to put it into simpler terms.



First off, the colder your engine is, the less efficient it is. Your engine wants to operate at a predetermined temperature. For our engines it is 192 degrees F. Check your Scanguage for proof. Second of all, if your engine is less then 192 degrees F, the engine will try its hardest to get to 192. This is done by the ECU, as Coastie explained above. The can be done by injecting more fuel into the engine. Lets say it takes 10 minutes for your engine to go from 20 degrees to 192 degrees. In the summer, it will go from 70 to 192 ALOT faster. Getting the block to warm up takes alot of energy. So while your computer is warming the engine up, you are burning more fuel.



Second, an engine is designed to run at the proper temperature. Your different materials expand at different rates. Aluminum has a lower melting point then steel does. Steel has a different melting point then iron does. All three metals expand at different rates. They are designed to fit the best together at operating temperature. When you first start your engine, you get "blow by" past your rings. Fuel does get into your engine when starting up cold. Until your engine gets to operating temperature, you loose some compression. The loss of compression is loss of power. Loss of power will require you to use more throttle (read fuel) to accellerate. That causes your fuel economy to drop.



Third, colder air is denser, like others have mentioned above. Denser air requires more fuel to keep your engine from going lean. Running lean will kill your engine quickly. The combustion chamber will get too hot, unless enough fuel is added. That also drops your fuel economy.



Fourth, oil. When it is cold, oil is thicker. It is harder for the oil pump to pump thick oil then it does to pump thinner oil. it is also true in the tranny and differential



Fifth, Here is a biggie. Reformulated fuel. MTBE, a chemical that is suposed to "oxyginate" your fuel will cause gas mileage to drop. The EPA has been "sold" (read told) that it will reduce emmisions so they require it. in the summer, MTBE is not used.



So to sum it up I will make a long winded statement that should bring everything into perspective.



When it is cold, your engine will take a long time to warm up. While it is warming up, the engine will inject extra fuel. While the engine is heating up, your engine oil, tranny fluid, and gear oil is thick and is hard to pump. Once your engine is at operating temperature, your engine requires more fuel to properly burn in the combustion chamber. An added chemical for winter gas causes your gas mileage to drop resulting in overall lower gas mileage.



Each item listed above only drops your mileage by a slight bit, but it adds up. 1/4 MPG here, 1 MPG there. Another 1/2 MPG here and another 1 MPG there. Add it up. It doesn't take long to go from 18 MPG to 15 MPG. Drive a tank full and you loose 60 miles per tankful. if you drive 350 miles per tank, you are now getting only 290 miles per tank.



Welcome to wintertime.



Things you can do to improve your MPG. Check the air pressure in your tires. I have seen tires loose 5 PSI between summer and winter. The tire isn't loosing air, the air is "shrinking". There is the same amount of volume, it is at a lower pressure.



Does that make any sense?





Tom

 

[Kevin Palmer]

Well I was going to get back to this message this morning but Tom has done an excellent job on explaining it. Last night I was typing between commercials as it was "Family Night". Too long at the computer and I get the "Look"...





Thanks Tom..

 

[TomT]

For me, winter is just the opposite effect. Once I stop using the ac my mpg goes up about 2 mpg. Of course it never gets that cold down here on the gulf coast.

 

[Kevin Palmer]

I live in a cold environment. Winter gas always costs me miles.