redrocket600

I'm from the midwest and ethanol is not viable here, either. It's killing the livestock market...


Intake allows the engine to breathe easier, thus you have less vaccuum in the intake manifold...and the engine will fuel (more) accordingly.

Colder air means the engine is always fueling more, to keep stoichiometry...



FWIW, though, I did a cat delete on my Civic this summer...gained over 3mpg (actually, considerably mroe but since I'm not 110% srue, I won't say exactly how much) highway. It's killing my in town mileage, though....

I do recommend a ScanGauge II. You can keep track of "tank" mpgs, current MPG, MAP, IAT, etc. Then you can modify things and get up to the minute reports on whether or not it's helping. And since it can be calibrated you can get it to read MPG DEAD ON!

Running Riot

thermal dynamics say otherwise man. you can perform more work with less air when its cold. you guys take into account the air type before the combustion but remember that it doesn't JUST rely on an input signal from the AIT but from the 02 sensor as well. If not all the fuel delivered is used the o2 sensor picks it up and scales the mixture back.

gearbox

iTrader: (95)

then how do you explain a 10mpg or more DROP during the winter? by your theory, in cold weather the engine should be working much less and using smaller amount of fuel so mileage should be very high compared to summer. thermal dynamics says otherwise? lol i dont think so.

mrplow123456

See now from a scientific stand point thre are WAY to many variables. First off, do you let your car heat up begin with? Are you sure that the fuel you got in summer time is the same temperature? You know there are endless things I could list off. But I'm just gonna focus on those for now.

In the summer time, your car is already closer to idle operating temperature, where as in winter time you must run you car for a certain amount of time just to reach this temperature and if you don't let it sit, you are using ALOT of gas to start out. This is more evident if you constently start your car.

The other thing, similar to the first one, about the gas is that when it is cooler it actually burns better but it tends to heat up quickly due to running through the engine bay. This would cause a rich A/F mixture and slowly lean itself out. Then as it warms up it would fluctuate more towards the lean side again having to return to a neutral state.

This again doesn't seem like much but if you say take a 20 min trip to work everyday, it slowly adds up. Most of pricipals are just taken from pure science so maybe there is something I am missing when taking it to a car but I tried to eliminate some of the differences between summer and winter without taking the induction into factor.

redrocket600

I am a Mechanical Engineer...I've taken Thermo. Yes, ideally you would have a greater expansion of gas if you have a controlled Tfinal, and therefore more power/efficiency. BUT, the big issue with fuel economy has to do with chemistry, not thermo...

Example:

You're running xx rpm and everything else is also held constant (map, flow rate, etc). If your intake temp is 40*F you're bringing in considerably more oxygen then if your IAT is 100*F. That means with the same volumetric flow rate, you have to dump more fuel into the engine to keep the 40* air stoichiometeric. The fuel is not being used to make power, only make the O2 sensors happy (ie, not run lean and burn up your engine)...make sense??

mrplow123456

It makes complete sense but how do you explain that when I run my car with 93 octane, the ECU doesn't cut back? If it is really about the chemistry shouldn't the increased air volume and density balance out the higher octane? Yet when I run my car with 93 otane, I'm constantly running rich. I know it can be solved with a chip, but according to what you just said the ECU should balance out the A/F ratio.

gearbox

iTrader: (95)

if you use higher octane than the engine was made for, the ecu will try to adjust ignition timing accordingly. since the engine cannot properly burn 93 because it is not a high compression motor, alot of it escapes unburnt. using higher octane than required may cause fuel injectors to clog and will usually result in more carbon deposits in the engine. in addition, you get no extra power because the engine was not designed to compress 93 octane (or anything higher than 87 for that matter). why dont you just use 87??

gearbox

iTrader: (95)

best example ive heard so far

redrocket600

Which is exactly why I ALWAYS preach "run the minimum!" ...although I did run a couple tanks of 93 (when I added a ScanGauge) to see how far the ECU will advance the timing...most I saw was 30*...


Thanks

wheelspinLX

That's true only if you assume the same rate of flow. So if you have more dense air coming in you could technically get the same power from the engine with less flow and the same amount of fuel. Hence the reason why engines have throttles.

Every single thing being equal including throttle position (which isn't realistic) colder air would require more fuel than warmer air.

gearbox

iTrader: (95)

isnt that what everyone was asking to begin with? if you had a robot drive your car exactly the same in winter and then in summer, using the exact same driving style and driving the exact same stretch of empty road, in winter you will burn more fuel correct? its just the way a car works, for now anyway.

redrocket600

Yes...but I have noticed that whether I'm running warm or cold air, I can only keep the MAP so low..

IDEALLY you would be correct...but apparently something gets "lost in translation..."...I think it has a lot to do with always "warming up" the engine, int he winter...don't know. I've only take Thermo..I'm not an Automotive Eng

wheelspinLX

I never knew there was any debate over the fact that you get worse mileage in the winter than you do in the summer, but I think there are many more factors than ambient temperature. In fact I think factors that weigh in more heavily are that your car takes a lot longer to warm up and road conditions suck.

Running Riot

that i would have to say there is something wrong with your calculations. seriously wrong in your calculations friend. what your saying doesn't make sense, either your not taking into account the functions of the ecu. again, if your getting more combustion with less air volume then how are you using more fuel again?! these engines are fuel injected right? meaning the ecu is going to adjust the delivery of fuel based on demmand. so again, if the engine is working more efficiently than why is it going to use more fuel?! and yes thermodynamics prove it, i asked a PhD chem professor about the effects of lower temperatures and combustion. explain how it is the temperature has dropped to 35 here in gainesville and i stretched out a tank of fuel for a week wheras over the summer i had to fill up at least twice a week? and unless you live in arizone its generally more humid in the summer than in the winter....

Running Riot

ok i see what your saying but man, if your creating a more powerful ignition because you have more oxygen in cold air than you do in warm air, then you could get a more powerful combustion (more power) using less fuel?

Killzone2142

iTrader: (2)

i dont know if this has been mentioned or not but go buy an adjustable cam gear and retard the timing. it is called the miller cycle. (fyi my major is automive design) anyways what happens is by retarding the timing you make the spark happen after tdc(top dead center) which means your intake vavle will be open longer durning your compression and exhaust strokes. this means that the charged air or air that was already used can get pused back to the intake valve and then reused on the intake stoke because the intake valve would be open to suck in the new and reused air. but what happens is even though you lose power and torque you are more effiecent if not just as effiecnt as the Ottocycle which is what most 4 storke engines run on. im actually cgoing to try thie but with the atkinson cycle where you advance the timing to get more power


and this stuff works i just did a lab on it last week. you will be surpised what +/-20* of timing can do to an engine in terms of torque and power.

Running Riot

well if gearbox is correct then that would actually decrease economy because the engine is going to deliver more fuel to compensate for the added volume of air....

i dont particularly agree with his theory, nothing against the guy he seems pretty on the ball but ^ just goes to my point that if you can create greater combustion with the same amount of volume you can perform more work with less energy.

Killzone2142

iTrader: (2)

well an intake can increase gas mileage BUT it can also hurt gas mileage.

1. Driving style- think about it if the driver constantly keeps the engine at WOT because they want to hear the intake and get the power then gas will be burned because the engine will compromise the amount of fuel injected to the engine. but if the driver is not at WOT then the engine will only use amount of air it needs for combustion which means less work on the engine.the venturi effect in a carburator is the best way to see this concept with the mechanics of an intake in terms of driving style

2. Intake volume and design- well the truth is most intakes are not desgined to be more efficent for an engine that is street driven. yes some companies do design their intakes to conencide with an given engine and you could see better gas mileage but that is not what sells. What sells in increase in hp. so companies design their intakes to increase hp so they add volume and smooth air flow beacuse a stock intake is SOMEWHAT not TOTALLy restrictive, due to sound deading, cheap materials, and flow characterisitcs. but what happens with an intake designs (as i am learning how to design one for my formula team) they are designed for a certain rpm range. companies, not all but more than likely most, dont say the Average drive is going to be operating this engine in the ranges from 3000- 5000rpm what is the peak hp for that range. the could but more than likely they do this engine a has a peake hp at 7000rpm lets tune the engine for that. dont belive me watch a dyno test. the car on the dyno is tested for max hp

3. heat also plays a part but that is related to intake design and materials used. air has different densities in different temps. the temps affect the pressure durning the cycle which can increase/decrease gas mileage because more air is in the combustion chamber or vice versa with less air in the combustion chamber

sorry for the long reply

Running Riot

so basically it can go either way

Running Riot

i asked another chem prof with a PhD at UF and this is what he said

(basically) there are som many contributing factors that you can not attribute it to one factor. Even if you somehow found a way to get three engines in the same environtment, the condition of the engine, intake friction, fuel atomization etc that there is just no absolute way that i can see to attribute an increase in fuel economy to just one thing. One thing to take into account however is that even if you have lower intake temps, keep in mind the location of the intake manifold to the exhaust, the recirculation of exhaust gases since that is already pre heated air, if the intake air is too low or the humidity too high, fuel will not atomize correctly and will spray as a liquid and the liquid will not combust. It is sprayed into the cylinder so that is atomized into a mist or spray. In the winter, oil companies add moderators to the fuel to keep it from reliquidating when injected that can also offset any benefits from intake systems."

So frmo what he says, an increase in fuel economy is more attributable to a reduction of intake friction and not neccessarily intake temperature and wether or not the EGR systems are still in tact. Pre heated air is not conducive to good combustion, and neither is too cold air. With variations in additives in varying temperatures, you can see a decrease in winter fuel economy because of it. I live in Florida, so the additives in my fuel in the winter may be different than the amount and type of additives in the fuel in say Manitoba. So it's all relative i guess.

wheelspinLX

^ you are correct sir

Killzone2142

iTrader: (2)

1. it is not that it can really go either way its like the proffesor said there are too many factors involved. and he hit the nail on the head about too much cold air or hot air because that i what i was saying about intake design you can have a sri and suck up too much heat hurtung perfomance but if it is in the right spot you could gain. and the same goes with cai to much cold air but in the right spot it could gain. the ideal way is just to use volumetic effiency formula with intake length formula to maximumize the amount of air and fuel

turbo zombie

i know i'm reviving a very old thread, but there are other things people are completely missing on this topic.

some people are saying they are getting better mileage in the winter than they are in the summer, and some are saying they get better mileage in the summer than in the winter. it depends on location, for several reasons.

i live in va. it gets to 100*F in the summer. i use my AC like crazy. AC, as well all know, makes our cars significantly slower, because it puts a big load on the engine, causing increased fuel consumption. when it gets cool enough, say, 80*F or cooler, i run with the windows open if i can. i get better mileage that way, but i am still not getting my optimal because of aerodynamics. open windows create more drag, which increases the load on the engine.

cold weather is a completely different animal. the coldest it got where i am last year, was 15*F. at that temp, it takes a lot longer for the engine coolant to warm up to operating temp, about 180*F, and even longer for the oil to warm up. Cold oil is thicker, and flows slower, causing decreased fuel economy. The coolant temp has a different effect. There are two modes the ecu runs in, open loop and closed loop. Basically, the ecu runs in open loop until the O2 sensors have heated up and are operating correctly (they run at several hundred degrees) and the coolant temperature has reached a certain point (probably around 160, depending on make). In open loop, the ecu uses the base maps for fuel, which are usually rich (12-13:1). If your car is taking a long time to warm up because of the cold weather, it is running in open loop longer, and using an enriched fuel map longer. once the ecu goes into closed loop, it tries to maintain the optimum a/f ratio of 14.7:1. keep in mind, when the engine is under a heavy load and esp at WOT, the ecu goes back into open loop.

when i was looking around the net to verify what i wrote so that i won't look like an idiot, i found this. it explains open loop and closed loop better than i can, and explains modifying your car to get different a/f ratios.

gearbox

iTrader: (95)

yeah, ive sometimes driven around for 20 mins in -10F winters and the temp gauge still wasnt up to normal! and this was using D3 to keep it in 3rd gear. it would never warm up in 4th. i think this winter im investing in an engine block heater.

Running Riot

VA FTW

good insight, i hadn't thought of those two things either with the ECS and the oil temp. When i lived in fairfax I had to go to a higher coolant mixture then what I used in the summer. It was a pain in the *** but the car warmed up much quicker then if i had my summer mix in there. I switched to 0-30 for the winter months up there too. The guys at the honda dealership on 50 always looked at me funny for doing it too but whatevs. I have problems even here in florida sometimes (im here for school) when it gets down to 24-30º in the mornings. I used a lower temp thermostat so it opens sooner instead of waiting for 180º. As for warming it up I let it idle for 30-45 seconds then drive it since it won't ever warm up just sitting there.

Running Riot

also the humidity is usually higher in the summer then in the winter...... where i live(ed) it is(was) anyway....

Nosepicker

Reviving an old thread.

I use my Civic as a commuter so I try my best to get the most MPG as I can. I drive mostly highway but am not slow by any means but also don't have a lead foot. 65-75 mph is what I do so long as it's safe.

Anyhow, some of the comments made here are whack. Like that dr_dx guy. WTF? LOL!

And as for MPG dropping during winter, I can attest to this. I was getting 25-28 mpg and for the life of me I couldn't understand why. I switched viscosity and even went to synthetic but still nothing. Once summer hit the MPG went from 25-28 to 35-36 mpg. I can't explain it but what GB said made sense.

Just my .02