j9chan

Hi guys, is there any truth to what the subject says? Is it true that the car would use more gas during the winter months? This is odd considering the fact that the A/C is used during the summer months, so it's supposed to use even more gas than the winter. Plus, winter air is colder than in the summer, thus with higher density. So as Bruno said earlier, the volumetric efficiency should go up, increasing the fuel economy.

So what's right??

bbarbulo

iTrader: (2)

fuel consumption increases of course.... cold air is denser, it contains more oxygen - for more oxygen the engine must have more fuel. The car has an IAT intake air temp sensor, and it has a ECTS - engine coolant temp sensor, and it has a MAP sensor. Based on these three, it figures out how cold the intake air is, how cold the engine is, and what elevation you are at. Off the MAP and IAT it figures out the oxygen content of the air and looks at a fuel map in the ECU and provides that amount of air... then it warms up, and starts taking reference from the O2 sensor to adjust based on it's reading. Basically, the engine burns more fuel, but it also makes more power. In addition to this, we tend to idle our cars more to warm them up, but the engine DOES in fact burn more fuel for every minute it works in the winter compared to summer. ALSO, cars run WAY better on startup when they are running rich, so to aid cold weather starting, the ECU fuel maps at these sub-zero temps are actually quite rich.

blk93si

j9chan

Thanks Bruno and Paul. I appreciate your answers. I understand that it'd take more fuel to burn in the colder, denser air. But if I'm driving on the highway and I maintain at 120 km/h for like an hour (between Toronto and Waterloo, say), wouldn't the engine be generating the same power to maintain that speed? In that case, the engine shouldn't need to work as hard to maintain that speed compared to the summer time, and thus I shouldn't be using as much gas. Am I thinking along the right line?

imported_gatherer

yes but the key is ..... O2.... there's more O2 so to stop a lean condition the ECU adds more fuel.... whether your cruising or in the city

j9chan

In that case, do CAI decrease gas milage then?

imported_gatherer

somewhat but it ain't all that noticeable... also remember that because of increased air flow you might not being opening the throttle body as much as before while cruising .. their are alot of factors that contribute to fuel milage

j9chan

Anyway, I guess the short answer to my question has been provided -- that gas milage in general goes down in winter. Thanks guys!

bbarbulo

iTrader: (2)

your thinking is interesting, but somewhat flawed. remember that your engine works on basic concepts in physics and of course some chemistry. in terms of colder air, you are getting more o2 into the chemical equation, so to maintain that 14.7 air to fuel ratio you have to add more fuel. with a CAI you maintain a the same o2 content in the air (for ambient temps) but instead of taking in the warmed up enginebay air, you are attempting to draw in more ambient air from outside. when thinking about this, keep all things constant except for what you are thinking about... so stock intake at -30 deg and stock intake at 30 degrees... only thing that changes is the o2 content of the air. then think about CAI at 20 deg, and stock intake at 20 deg. besides that you cannot compare CAI at -30 vs stock at 20 deg... cuz some effects would be negated by each other I would think. You also have to conside that a CAI supposedly reduces pumping loss in the engine - ie. the engine has to do some work in order to create vacuum to draw in air through the intake - if you make that part easier for the engine it has less of a loss in doing so. make the intake too big, and you won't be able to maintain velocity of the intake charge and you will get poor swirling in the combustion chamber and an unevenly dustributed mixture. Make it too long, and you'll have a hard time with pressure loss... it's really tough to get a good compromise, that's why I usually say OEM spend a buttload of money designing these things, esp Honda. So if you don't know better than Honda, leave good enough alone. Now that goes against hot rodding principles we live by, so here is an alternative.... measure your throttle body. Get pipe with that exact ID, have it mandrel bent with as few bends in it as possible and have it draw in the freshest air from the closest location to the throttle body (ie hoodscoop) - that will prolly straight up give you the best results. Kinda like the shaker hoods in the 60s

blk93si

just buy a 92 -93 civic VX

imported_JookSingKid

snow tires increase fuel consumption

j9chan

My snow tires shouldn't be a factor since they're 185 wide and my summers are 215...

imported_JookSingKid

well maybe theres something special about your snow tires

but i noticed a considerable loss of range when i put my snow tires, mind you I had 195 wide tires.

dropgear

ditto. with the snow tires on and the winter weather, i'm down to 410 km / 38 L, as compared to 460-480 in the summer.