Does Weather Affect Fuel Economy

rishibravo · 12th June 2007, 09:35

Quote:

Originally Posted by tsk1979

Imagine a temparature difference of 282K vs 322K
So you can have around 3-5% efficiency drop.
Add to that fuel density etc., things the difference can be upto 10%

Agreed. I have noticed a drop of nealy 10% in FE of my car. Can anything be done about it or just wait for temperature to drop.

deep_bang · 12th June 2007, 10:57

Quote:

Originally Posted by tsk1979

No problem about gas, since its filled by weight. Gas will be 10Kg whether its 10 degrees or 40 degrees, however volume may change.
But due to over use of AC and the lowering of engine efficiency, you will still see a drop in FE.

LPG is filled in liters. Not sure about CNG.

BTW.. i jus became a BHPian!

tsk1979 · 12th June 2007, 11:04

Quote:

Originally Posted by rishibravo

Agreed. I have noticed a drop of nealy 10% in FE of my car. Can anything be done about it or just wait for temperature to drop.

Get up at 6am and head over to the filling station. I don't do that, waking up in the morning is not my cup of tea

Quote:

Originally Posted by deep_bang

LPG is filled in liters. Not sure about CNG.

BTW.. i jus became a BHPian!

CNG is in kg, domestic LPG is also in kg, not sure about the auto LPG

rishibravo · 12th June 2007, 11:22

Quote:

Originally Posted by tsk1979

Get up at 6am and head over to the filling station. I don't do that, waking up in the morning is not my cup of tea

I would rather wait for the monsoons..

abhargava75 · 12th June 2007, 17:41

May be, I am not sure, but the heat wave will have an impact on the effective type pressure also. That may also have an impact on FE.

paras211 · 12th June 2007, 19:42

there is a verry noticable difference in performance drop on a hot afternoon but dosent the ecu measure the air and then accordingly pump fuel so if there is less air less fuel?

anonymous · 12th June 2007, 19:47

I think this could be the reason why I feel low power or car is sturggling to move in hot days and its very much noticable in Indica.

traman · 12th June 2007, 20:35

cold air intake. if you are running a turbo charged car a front mount intercooler is your friend else for an NA just a CAI setup would solve your problems

1100D · 12th June 2007, 21:27

Some cars (like the Ikon) - infact most recent cars - have the air intake from inside the front bumper - how much colder can you get from a aftermarket CAI?

However notice this all the time and it really gets painful to drive on a hot afternoon, having to push the pedal not only down to the floor (but to even push the floor beyond) to extract performance. Although havn't noticed much of an FE drop, if I decided on feather touch driving (for a particular end-of-the-month tankful).

theMAG · 12th June 2007, 21:33

Very interesting topic. I think Zappo's response is the most well-rounded one to answer Wolfinstein's original doubts.

paras211 · 13th June 2007, 01:12

Quote:

cold air intake. if you are running a turbo charged car a front mount intercooler is your friend else for an NA just a CAI setup would solve your problems

but a cai will reduce throttle responce too right?? so i prefer sri
also mumbai floods up too

hellspawn · 13th June 2007, 01:40

i agree with what tanveer said.when the temperature soars,the intake temperature also increases.thus the air density decreases,so the engine has to work harder to maintain the volumetric efficiency.that is why we require intercoolers to cool the air before it enters the combustion chamber.
in case of cars running on petrol,petrol from the refinery is transported to the petrol stations and the quantity is measured at a temperature of 15deg celsius.as it expands as the temperature goes up,when you fill fuel in the daytime when its hot your actually getting fuel which isnt measured at 15deg as the pumps dont have a correcting factor.so you get less quantity of fuel for the money you paid.thats how the petrol stations make money.
its best to fill fuel when its cold,either earli in the morning or late in the night when the ambient temp isnt too high.

wolfinstein · 13th June 2007, 10:31

The XETA has a CAI, located inside the Bumper on the right side.

Auto LPG Comes in liters meteric scale.

Let's see what the next FE is.

Zappo · 13th June 2007, 10:57

Quote:

Originally Posted by tsk1979

No problem about gas, since its filled by weight. Gas will be 10Kg whether its 10 degrees or 40 degrees, however volume may change.

You sure about this? I am not sure how this can be done except for by calculation. The calculation is done IMO based on the cross sectional area of the dispensing pipe and the rate of flow of the gas. That gives the volume dispensed. From that the weight is calculated based on the known density of the gas. However this setting in the dispenser is based on a standard temperature and pressure (not NTP). This is the roundabout way all dispensers calculate the weight dispensed, AFAIK.

Now if my understanding is correct, if the temperature shoots up or goes down by big margins the reduction in the weight dispensed will be perceptible. At very high temperatures the density of the gas will be lower than the standard density the dispenser units use to calculate the weight.

tsk1979 · 13th June 2007, 11:06

@zappo, if what you say is true its a problem.
Unlike Petrol and Diesel which change volume slightly on changing temperature, Gas changes volume at a much higher rate(Provided pressure is same)
PV = nRT(Ideal gas equation)
or P1V1/n1T1=P2V2/N2V2
If pressure is constant
V1/T1= V2/T2
So if at 200K a gas occupie 5L volume
At 250K it will occupy 6.25L. If we take a more realistic number 20 DEgrees vs 50 degrees 10L gas volume will expand to 11.5L(approx)

So filling gas by volume is pure wrong. If what you said is true, all CNG guys should head to the service station at 5am in the morning and get 10% increase in FE.

12th June 2007, 17:41	#20
abhargava75 Newbie Join Date: Jun 2007 Location: Indore Posts: 8 Thanked: 0 Times	May be, I am not sure, but the heat wave will have an impact on the effective type pressure also. That may also have an impact on FE.
	() Thanks

12th June 2007, 19:42	#21
paras211 BHPian Join Date: Nov 2006 Location: mumbai Posts: 646 Thanked: 108 Times View My Garage	there is a verry noticable difference in performance drop on a hot afternoon but dosent the ecu measure the air and then accordingly pump fuel so if there is less air less fuel?
	() Thanks

12th June 2007, 19:47	#22
anonymous BHPian Join Date: Jan 2007 Location: NCR Posts: 565 Thanked: 25 Times	I think this could be the reason why I feel low power or car is sturggling to move in hot days and its very much noticable in Indica.
	() Thanks

12th June 2007, 20:35	#23
traman Newbie Join Date: May 2007 Location: Sydney Posts: 12 Thanked: 0 Times	cold air intake. if you are running a turbo charged car a front mount intercooler is your friend else for an NA just a CAI setup would solve your problems
	() Thanks

12th June 2007, 21:27	#24
1100D Senior - BHPian Join Date: Jun 2006 Location: Calcutta Posts: 4,390 Thanked: 4,079 Times View My Garage	Some cars (like the Ikon) - infact most recent cars - have the air intake from inside the front bumper - how much colder can you get from a aftermarket CAI? However notice this all the time and it really gets painful to drive on a hot afternoon, having to push the pedal not only down to the floor (but to even push the floor beyond) to extract performance. Although havn't noticed much of an FE drop, if I decided on feather touch driving (for a particular end-of-the-month tankful). Last edited by 1100D : 12th June 2007 at 21:30.
	() Thanks

12th June 2007, 21:33	#25
theMAG Distinguished - BHPian Join Date: May 2006 Location: Avon, CT Posts: 7,217 Thanked: 1,807 Times View My Garage	Very interesting topic. I think Zappo's response is the most well-rounded one to answer Wolfinstein's original doubts.
	() Thanks

13th June 2007, 01:40	#27
hellspawn Join Date: Jul 2005 Location: noida Posts: 1,686 Thanked: 7 Times View My Garage Infractions: 0/1 (10)	i agree with what tanveer said.when the temperature soars,the intake temperature also increases.thus the air density decreases,so the engine has to work harder to maintain the volumetric efficiency.that is why we require intercoolers to cool the air before it enters the combustion chamber. in case of cars running on petrol,petrol from the refinery is transported to the petrol stations and the quantity is measured at a temperature of 15deg celsius.as it expands as the temperature goes up,when you fill fuel in the daytime when its hot your actually getting fuel which isnt measured at 15deg as the pumps dont have a correcting factor.so you get less quantity of fuel for the money you paid.thats how the petrol stations make money. its best to fill fuel when its cold,either earli in the morning or late in the night when the ambient temp isnt too high.
	() Thanks

13th June 2007, 10:31	#28
wolfinstein BHPian Join Date: Feb 2006 Location: New Delhi Posts: 994 Thanked: 20 Times	The XETA has a CAI, located inside the Bumper on the right side. Auto LPG Comes in liters meteric scale. Let's see what the next FE is.
	() Thanks

13th June 2007, 11:06	#30
tsk1979 Team-BHP Support Join Date: Feb 2005 Location: San Jose, CA Posts: 23,717 Thanked: 22,823 Times View My Garage	@zappo, if what you say is true its a problem. Unlike Petrol and Diesel which change volume slightly on changing temperature, Gas changes volume at a much higher rate(Provided pressure is same) PV = nRT(Ideal gas equation) or P1V1/n1T1=P2V2/N2V2 If pressure is constant V1/T1= V2/T2 So if at 200K a gas occupie 5L volume At 250K it will occupy 6.25L. If we take a more realistic number 20 DEgrees vs 50 degrees 10L gas volume will expand to 11.5L(approx) So filling gas by volume is pure wrong. If what you said is true, all CNG guys should head to the service station at 5am in the morning and get 10% increase in FE.
	() Thanks