I noticed something that i had never noticed on my cavy,probably because that was a piece anyways, it was down in the 40's yesterday morning and my car didnt really want to start, then later notice my MPG went from 31.4 to 30.3 within the 5 miles i drive to work.

Heres my question, When it get to be down to the winter like temps is the outside air actually too cold for the car? And should i switch back to the airbox for winter?

 

IMO, the air isn't "too cold". It gets down to -30°F or colder here and we have guys running CAIs etc with no problems. The MPG goes down for us most likely because we let the cars warm up.

 

yeah it gets pretty cold here in Wisconsin too. Usually i dont let mine warm up i just go real easy on her for a little while til the coolant temps go up.

 

There's no such thing as air that's too cold. Colder air=denser air=more power. This power increase is even more evident in F/I cars, and is the reason why people add things like heat exchangers, to keep things as cool as possible. However, as far as the decrease in MPG goes, the explanation I was always given was that when the car's computer senses more air it dumps more fuel to keep the AF ratio constant, hence decreasing gas mileage but making more power. However, I have never found a good source to confirm or refute this theory. On the whole though, almost every car gets worse fuel mileage in the winter.

Anyways, I wouldn't change your intake at all because that's not a problem. However, driving only 5 miles in cold weather is, especially without a proper warmup. Start up in cold weather is very hard on a motor, and also is not very effecient as far as combustion goes until the block gets up to temperature. That is probably what caused your noticable decrease in gas mileage. Also, depending on when you last reset the MPG on your DIC, it can be very erratic with only small changes in driving.

 

ah yea well thats what i figured the air cant bee too cold but thats the first thing that popped into my head, and i didnt even know you could reset the MPG on the DIC

 

you gotta remember your car uses more fuel in open loop... so the longer your car stays cold in open loop... the less mpg you're gonna have.

 

Yeah, to reset it just hold down the arrow button (I think) just like you were going to reset the trip meters.

 

cold air is the best thing u can have for intake air, the colder the better, i dont know about the MPG's tho, cold air should make your engine more efficient if anything

 

Bingo

Couple that fact of longer warm up times before going into closed loop, add in people warm up cars to get into a warmer one, then top that off with gasoline thats reformulated for these conditions, and you'll drop mileage.

 

In cold weather you always use more fuel to get the car up to temp. If the ecu did not compensate for the cooler weather and add more fuel the car would just stall out from being lean or not fire at all. Cold weather tuning is a pia if you are running a standalone. It takes a ton of tweaking to get the extra fuel for warmup just right.