Fuel Economy
- Thread starter nav525
- Start date
I think the times i just gun it from stop - it does hit 3000 RPM but they are rare occasions I do that just for fun.
Overall i can only go fast as the slowest in my lane. 2500 seems very normal. But i dont think accelerating is your major problem - it is lack of any 30-60 mph driving which is sweet spot for CX-5 - if you did this for longer your avg would jump to 24 or 25 no question, 35 mph - 5th gear 1200 RPM and 45 mph (or 50 mph - not sure when 6 kicks in) 6th gear about 1500 RPM on flat road seems best.
Both my previous and current commute have a good 45 mph stretch, problem with current commute is the fastest lane is right - and it has most stop n go as folks turn right into businesses and other roads.
Does anyone know the torque pro - is it really good at FE / Fuel consumption measurement? $20 something is not bad just to kill time during driving, atleast until i get some good audio books for my CD playah!
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- 2021 CX-9 Sig
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- 2021 CX-5 GT
Think about that for another second.
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- CX5 Akera 2.2 Diesel
I dont get this at all.
If its true, why would intercoolers be added on turbo engines - with the aim of cooling the fuel/air mixture before it goes to the cylinder, so greater hp is generated?
Why would top fuel dragsters go faster in winter than in summer? More hp....
I always understood that cold air is denser than hot.....
If it was true that hotter air intake was better for efficiency, wouldnt the air intakes on our cars be located in an area that was getting heated - eg next to the exhaust headers?
For these resaons I just dont buy the generally "better duel economy in hot weather" proposition.
The only circumstances I can see better economy in hot weather vs cold would be
(a) for very short trips where the engine doesnt get warmed up properly - more friction due to cold pistons, could oil, cold transmission and wheel bearings. But these things warm up quickly, then you get better fuel ecomony due to denser air creating better combusion, more hp and improved economy; or
(b) your winter tyres are causing far greater drag than summer tyres ....
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I think winter weather is overall more unfavorable - windy. Dense cold air also has a measurable effect on aerodynamic drag on long stretches.
As far as engine temps go, there is a sweet spot for most engines - HP testing is usually done around 68-77F/20-25C. Colder conditions might have worse MPG as some energy converts to heat the engine, while warmer conditions have less dense air. Turbo intercooler helps densify the air further as compressing air heats it up.
mazdadude
ZOOOOOOOOOM ZOOOOOOOOOM
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- '16.5 Mazda CX-5 Touring
We are referring to the ability of the vehicle to move through the warmer and less dense air, not the air entering the internal combustion engine.
The air temps affect so many things, to pin it on a single variable is very difficult, unless you are willing to strictly adhere to the scientific method.
Cold temps = More rolling resistance and drag due to rain and lower tire pressure, greater air density creates more drag, less power density for fuel due to blends, running rear window defrost creates power loss due to extra alternator drag and front window defogger causes AC compressor drag.
Now once you start having some spring temps, we get the summer fuel blend back, our tires that were once 36 PSI at 30 degrees f, are now at 40 psi at 70 degrees f. In addition, since we are no longer using the defoggers, defrosters, or having the windows open, our car is more efficient.
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- 2021 CX-9 Sig
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- 2021 CX-5 GT
No, I think it is how long you drive and how long it takes for the engine to warm up. My drive to work was 8 miles. On a cold 10-15 degree morning, the blue light would not go off till I was half way there! The mileage at that point was terrible. During the summer, the light would go off pretty quickly. I think if you are driving for distance and for a while, the difference would be much smaller (if at all).
G
Guest2019C20
You are confusing efficiency (getting the most power OUT OF the gas burned) and power (getting the MOST HP out of the engine).
Turbo engines need intercoolers to avoid detonation. There have been some very low-pressure turbos (1-2 psi over ambient) that didn't use intercoolers. Turbo-compressed air gets VERY hot. Compression itself increases the temperature, and the churning by a hot compressor wheel heats it up even more. Gasoline can only handle so much temperature before it spontaneously ignites. This is also why U.S. spec 2.5 engines are limited to 13:1 compression ratios. The temperature increase at higher ratios would cause the air/fuel mixture (of crappy U.S. gas) to ignite before the spark.
Cooling compressed air (turbo or blower) allows more of it to enter the cylinders, increasing HP. There have been designs where the intercooler's restriction to flow was used to allow much higher compression (and more heat) and the restriction of the intercooler dropped the effective compression at the cylinder to be as low as needed. The higher pressure/hotter air lost MORE heat in the intercooler, and comes out cooler than an intercooler without as much restriction.
Engines DO make more power with cooler air, because dense air contains more oxygen, and the engine carb/FI injects more gas. More molecules burn, higher cylinder pressure, more power.
There have been engine designs that used hotter intake air for better efficiency. I think Smokey Yunick (sp?) had a design like this. But this makes the engine more prone to engine-destroying detonation. (I had a mis-jetted Yamaha 350cc engine melt BOTH pistons in less than a second due to detonation. I didn't have time to let off the throttle before it was too late.)
A great way to understand efficiency of fuel-burning systems is to visualize heat loss. Even in a fully-warmed-up engine, more heat will be lost to engine components in cold temps, and that means less pressure pushing the pistons down. This also makes it easy to understand why turning down your house's thermostat in colder weather saves so much money. There's a lot less heat loss when the temp difference between inside and outside is lower.
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- CX5 Akera 2.2 Diesel
Now dont take my comment out of context - the comments prior to mine where I said "I dont get this at all" were all suggesting a difference in fuel economy due to air temperature - eg ambient temp. Thats what I was questioning.
It was only after I commented, that the adverse weather conditions that accompany the colder weather in those locations came up.
I think the subsequent posts probably explained the difference between the winter and summer fuel economy over there - and its not about air temp.
Its really about the bad weather those guys obviously have in winter - with frequent rain, storms, wind and winter tyres running lower pressures. Add to that the cold weather and short runs where the engine doesnt get warmed up thoroughly, and you get worse fuel economy than you do in spring/summer, when the weather must be overall kinder and the summer tyres creating less drag with higher pressures.
All other things being equal, however, cold conditions will give better economy than hot, due to cold air being denser and engines therefore running better, as has been noted by several of us.
It was only after I commented, that the adverse weather conditions that accompany the colder weather in those locations came up.
I think the subsequent posts probably explained the difference between the winter and summer fuel economy over there - and its not about air temp.
Its really about the bad weather those guys obviously have in winter - with frequent rain, storms, wind and winter tyres running lower pressures. Add to that the cold weather and short runs where the engine doesnt get warmed up thoroughly, and you get worse fuel economy than you do in spring/summer, when the weather must be overall kinder and the summer tyres creating less drag with higher pressures.
All other things being equal, however, cold conditions will give better economy than hot, due to cold air being denser and engines therefore running better, as has been noted by several of us.
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G
Guest2019C20
We're going to have to agree to disagree on this. Unless Mazda is doing something funky like running a richer mixture in warm temps (possibly to offset the high compression ratio) or the Miller cycle is run differently/not at all, or something else is happening out of the norm.
Cold air, more potential power from engine, less MPG if you use that extra power.
Simple answer to better mpg in hot or cold is look at EVs, the leaf suffers in cold weather, even the solid Tesla's see a range drop. Cold weather means the car has to push through denser air to move forward = more fuel consumed.
Back to CX-5 - yes yrwei- the best speed for CX-5 seems to be 50 mph where it kicks in 6th gear. If you let it slow down slightly the gear is held till 47-48 mph. This would be an ideal driving style to push mpg up, 2nd best would be 32-35 mph. Anything between these two ranges are going to be good but not as phenom!
This morning - reset the odo. did my routine stuff and voila - 31.1 mpg (cricket)
Another thing about AT behavior - if i feel its hanging on to the gear for long just pull feet off throttle it upshifts
- been trying this, infact due to city driving my feet has grown so sensitive could not do 70 on the hwy with a full 4 passenger load - the car still lags in hwy mpg - I will never see 33 unless I mod the heck out, get lighter wheels / low rolling resistance tires and throw the spare out.
Back to CX-5 - yes yrwei- the best speed for CX-5 seems to be 50 mph where it kicks in 6th gear. If you let it slow down slightly the gear is held till 47-48 mph. This would be an ideal driving style to push mpg up, 2nd best would be 32-35 mph. Anything between these two ranges are going to be good but not as phenom!
This morning - reset the odo. did my routine stuff and voila - 31.1 mpg (cricket)
Another thing about AT behavior - if i feel its hanging on to the gear for long just pull feet off throttle it upshifts
- been trying this, infact due to city driving my feet has grown so sensitive could not do 70 on the hwy with a full 4 passenger load - the car still lags in hwy mpg - I will never see 33 unless I mod the heck out, get lighter wheels / low rolling resistance tires and throw the spare out.I would guess the cold batteries have as much or more of an impact than the denser air.
Thats true but they can be pre conditioned in your garage, your range will still suffer.
Cold is bad for batteries. Unless you're doing all your driving in the garage, they're going to take a hit from cold weather.
I dont deny that, you also dont drive in a vacuum - cold air is denser and takes more effort to push through. Its a combination of both but if you turn your car on and let your HVAC on heat, it will warm up your batteries in some EVs. Still your range suffers because your car is not plowing through denser air.
https://www.fueleconomy.gov/feg/coldweather.shtml
Why is winter fuel economy lower?
Cold weather affects your vehicle in more ways than you might expect:
Engine and transmission friction increases in cold temperatures due to cold engine oil and other drive-line fluids.
It takes longer for your engine to reach its most fuel-efficient temperature. This affects shorter trips more, since your car spends more of your trip at less-than-optimal temperatures.
Heated seats, window defrosters, and heater fans use additional power.
Warming up your vehicle before you start your trip lowers your fuel economy—idling gets 0 miles per gallon.
Colder air is denser, increasing aerodynamic drag on your vehicle, especially at highway speeds.
Tire pressure decreases in colder temperatures, increasing rolling resistance.
Winter grades of gasoline can have slightly less energy per gallon than summer blends.
Battery performance decreases in cold weather, making it harder for your alternator to keep your battery charged. This also affects the performance of the regenerative braking system on hybrids.
Why is winter fuel economy lower?
Cold weather affects your vehicle in more ways than you might expect:
Engine and transmission friction increases in cold temperatures due to cold engine oil and other drive-line fluids.
It takes longer for your engine to reach its most fuel-efficient temperature. This affects shorter trips more, since your car spends more of your trip at less-than-optimal temperatures.
Heated seats, window defrosters, and heater fans use additional power.
Warming up your vehicle before you start your trip lowers your fuel economy—idling gets 0 miles per gallon.
Colder air is denser, increasing aerodynamic drag on your vehicle, especially at highway speeds.
Tire pressure decreases in colder temperatures, increasing rolling resistance.
Winter grades of gasoline can have slightly less energy per gallon than summer blends.
Battery performance decreases in cold weather, making it harder for your alternator to keep your battery charged. This also affects the performance of the regenerative braking system on hybrids.
Agreed. I'm just saying you can't use an EV as proof of that 'cause it conflates the diminished efficiency of the cold battery with that due to dense air.
Most electrics have a built in heater around the battery. So turn the car on and leave it plugged into the house in the morning. That is part of the "preconditioning" that is being discussed. I looked at this extensively when I was eyeballing the Chevy Volt. Solid car, good acceleration, can do cross country without issue. Absolutely NO cargo space which ended up being the deal breaker.
Thanks for the education.
G
Guest2019C20
My tests show MPG rising as I slow down to at least 30 MPH. This is higher than when in 6th.
