Why do I get better MPG when it is hot?

[davenowherejones]

Why do I get better MPG when it is hot?

I went travelling on the Victoria Day long weekend. I wore my mesh jacket it was so warm finally.

I was getting about 80 miles per Canadian gallon when it was colder but in the warmth I got 97.8, 95.6, 97.1, 90.8, 90.1 which is great. But why?

[aguim]

The ECU relies on two Temp. sensors to determine injector opening duration (in nanoseconds) :
(a) the Engine Cooling Temp. sensor,(b) the Intake Air Temp. sensor. On cold days, even with the engine warmed up, cold air will still make the ECU provide a rather rich mixture, based on
sensor (b) data.

Only with summer weather will both sensors coax the ECU into high-mileage mixtures (that is,
shorter injector opening durations, all the time).

My own Forza goes as low as 25km/liter (spring +late autumn) then as high as 32 mid-summer.
Or from 70 to 90 mpgCan.

BTW, it is still VERY cold out here, and generally very cold in the morning, so I rarely see that
"32" showing on the dash...

[easyrider]

You can also try a hotter plug in the cold weather.That would be a lower number.. and would give you a better fuel burn in a rich fuel environment and less fouling typically found in colder climates.

[aguim]

The standard plug (LMAR8A-9) shows no sign of running any richer than 'normal'.

[easyrider]

In the cold,sensors will tell the ECU to enrichen the mixture for quicker starting.If temps are so cold that the computer sensors rather engine temps are colder than operating temps the rich fuel mixture will remain longer.A hotter plug will help retain cylinder heat more efficiently which will help in a more efficient and complete fuel burn thus translating into less fuel consumption.Once operating temps are reached a normal fuel ratio will begin and plugs will normalize .Honda utilizes a plug for all conditions mostly temperate ie Asia I would think .I would suggest trying a hotter plug for extreme cold to improve fuel burn.Might help.

[DAB]

Thermodynamics

[chicaboo]

Colder air is denser and requires more fuel to burn stoich.

[homie]

stoich.

I know you are but what am I
you, you... STOICH!

[aguim]

This is turning to METAPHYSICS, or what!

[homie]

This is turning to METAPHYSICS, or what!

https://www.khanacademy.org/science/che ... ichiometry

[aguim]

Sure has all the right proportions, isn't it.

Here, forum tech editor, dead on duty.

[chicaboo]

This is turning to METAPHYSICS, or what!

The IAT, ECT, TPS & MAP sensors all do their jobs well regardless of the environmental conditions, but the root cause for higher fuel consumption on colder days is increased air density requiring more fuel.
I've not ever seen one beyond standard cold start mechanisms, but fuel and intake manifold heaters were a makeshift way of increasing fuel efficiency at one point.
Another offshoot from colder weather is that you make more power. Not appreciable on a small scooter, but very noticeable on high revving highly strung performance car engines (particularly turbos...).

[davenowherejones]

Thanks all, I almost was ready to blame my lousy arithmetic skills.

I am not going to play around with spark plugs because our weather varies greatly within hours.

I rode over the Coquihalla Pass for supper. It was really warm when I left and a huge storm blew in while I was having supper. I should have bought some long underwear to get home. Violent winds and rain. THE Forza just takes it all. My visor fogs up and I ride by feel. Ouch on that last pothole. No wonder my front wheel is dented. (did it 40,000 km ago)

[aguim]

This is turning to METAPHYSICS, or what!

The IAT, ECT, TPS & MAP sensors all do their jobs well regardless of the environmental conditions, but the root cause for higher fuel consumption on colder days is increased air density requiring more fuel.
I've not ever seen one beyond standard cold start mechanisms, but fuel and intake manifold heaters were a makeshift way of increasing fuel efficiency at one point.
Another offshoot from colder weather is that you make more power. Not appreciable on a small scooter, but very noticeable on high revving highly strung performance car engines (particularly turbos...).

With the O2 sensor added to the lot, it runs pretty close to perfect STOICH most of the time. So
no reason to fiddle around with it. Then Dave Jones is up to 50,000 km on his , with zilch FI
issue to date (as far as I know). Enjoy, hot and cold.

[chicaboo]

This is turning to METAPHYSICS, or what!

The IAT, ECT, TPS & MAP sensors all do their jobs well regardless of the environmental conditions, but the root cause for higher fuel consumption on colder days is increased air density requiring more fuel.
I've not ever seen one beyond standard cold start mechanisms, but fuel and intake manifold heaters were a makeshift way of increasing fuel efficiency at one point.
Another offshoot from colder weather is that you make more power. Not appreciable on a small scooter, but very noticeable on high revving highly strung performance car engines (particularly turbos...).

With the O2 sensor added to the lot, it runs pretty close to perfect STOICH most of the time. So
no reason to fiddle around with it. Then Dave Jones is up to 50,000 km on his , with zilch FI
issue to date (as far as I know). Enjoy, hot and cold.

Yep, the Hondas do very well to remain stoich in closed loop. I've got an AFR gauge on my scoot, and it didn't deviate much once the o2 sensor was warmed up.
Even now I have an interceptor with my o2 sensor disconnected with just the other sensors taking care of ballpark fuelling, it's really easy to tune the air/fuel mix.
Although now I choose to run slightly richer until 7000rpm, and then beyond that I don't have the crazy over-rich mixture the stock Honda mapping does in open loop.

[easyrider]

Therein lies the problem..In cold weather the engine stays in in open loop longer burning more fuel.Based on the ambient temps outside the ECU will kick a code if not in closed loop in a specified time.There is no oxygen sensor feedback to trim air/fuel ratios until the coolant reaches a specific temperature, at which point the system shifts into closed loop operation and utilizing all the sensor inputs to optimize air/fuel ratios. In a cold dense fuel charge a hotter plug will tend to maximize the burn and waste less fuel out the exhaust and help shorten the heat up time.No need to change your plugs , but for the sake of splitting hairs and discussion we digress..

[davenowherejones]

The fuel injection system is one of the reasons I bought the Honda Forza. It is smarter than me.

I go from sea level to 5000 feet all the time. I don't have to play around with a carb. I just run the stock plug.

I tried changing things on my DR650 and it was almost always wrong for the given situation. Some times it would accidentally be correct.

46,861 km yesterday with almost no engine problems. The mpg is all over the place but so are my riding conditions. Brutal head winds drop the mpg, tail winds make things quiet. Uphill, headwind on the 120 kmph highway means the fuel drops in a hurry. But even at the worst conditions the Honda Forza uses substantially less $1.25 per litre fuel than my V8 4X4 Dodge Dakota (17 mpg).

[easyrider]

The fuel injection system is one of the reasons I bought the Honda Forza. It is smarter than me.

I go from sea level to 5000 feet all the time. I don't have to play around with a carb. I just run the stock plug.

I tried changing things on my DR650 and it was almost always wrong for the given situation. Some times it would accidentally be correct.

46,861 km yesterday with almost no engine problems. The mpg is all over the place but so are my riding conditions. Brutal head winds drop the mpg, tail winds make things quiet. Uphill, headwind on the 120 kmph highway means the fuel drops in a hurry. But even at the worst conditions the Honda Forza uses substantially less $1.25 per litre fuel than my V8 4X4 Dodge Dakota (17 mpg).

I totally agree. Many things affect fuel economy..Why get crazy over it.. I never look at at my MPG..cuz quite frankly Scarlet..I don't give a damn !!

[aguim]

Confirmation today : 8hAM, 17deg.C outside temperature. So I reset trip A, and voilà, dash
shows 30km/l (85 mpgCan,/68 US). Not bad for skidooland stop 'n go.

Curiously, my 2014 shows mpg US, not Canadian as it should...may be an american leftover !?
(the rebate was $2,000, so you bet I won't whine)

[davenowherejones]

I do not use the gauge for my mpg. I calculate it for a fuel tank every fill up.

I have forgotten if my mpg meter is Canadian or USA. I suspect it is USA. I will have to check it sometime.

I use km/litre.

Aguim you list yourself as Northern Ontario which always strikes me as funny because almost all of the people in Northern Ontario actually live south of me in Southern BC. What is the closes city to you?