Fluid temp vs MPG

[Desert Spyder]

I've been noticing lately that the colder my water temp is the more fuel is being consumed. And of course when it is warm the less. I know on cars there is a sensor to richen the fuel mixture so to warm up the vehicle quicker. Is it the same on the Spyder? Yesterday, I went on a PG mission "down the hill" which has been enjoying 80 degree temps lately. My temp gauge on my RT showed rough half way. I drove about 120 mi and got about 35 mpg. Coming home in the desert the outside temp was in the 60's, my water gauge showed about 1/4 up (analog), and I got about 28. Why? Also, last summer I added a little "Engine Ice" to my fluid because of the high temps out here in the desert. But in the winters, when the temps drop below freezing and stay in the 50's during the day, my fluid temp may barely show any rise at all when cruising on the freeway. And of course the mpg drops. So whats going on here? I'm sure there are many owners out here who may be in the same "boat".

[Bob Denman]

Very astute of you to notice the fuel economy change correlation with the temperature change! :firstplace:
I'm not sure if it's the fluid temperature or the air temperature that enrichens the mixture to keep things happy, but I'd guess that it's the latter. :dontknow:
Quick mixture Primer...
Cold, denser air requires MORE fuel to keep the mix correct
Warm, less-dense air requires less...
That's why we get better fuel economy in the summer! :thumbup:

[NancysToy]

While mpg does vary with the air temp and density, there are too many variables here to attribute it all to the temperature. Which way was the wind blowing? How strong? Minor variations in filling the fuel? Different fuel from different staions? Uphill one way? All these can affect the mpg you calculate, especially over just a couple of fills. Gas mileage almost always is different in one direction of a trip compared to the other, due to the wind and the elevation changes alone. Only a long term, controlled study can prove that what you suspect is actually true. :)

[BajaRon]

The Spyder's temperature gauge is much more sensitive than the average automobile (or other motorcycle gauges). What appears to be a big swing in temperature is not all that much. The coolant system thermostate keeps the engine temperature to at least normal operating temperature.

I am doubtful that this is the reason for your mileage change. I usually find mileage is better with colder outside temps, which makes sense because cold air is denser and gives a better charge to the cylinder. But this is a generalization and other factors have much more effect.

[BLUEKNIGHT911]

IMHO, Colder is better power wise anyway....back in the day I knew guys who would put ice in the air cleaner housing for that little extra ???....Mike ...:lecturef_smilie:....:gaah:...:thumbup:

[boborgera]

IMHO, Colder is better power wise anyway....back in the day I knew guys who would put ice in the air cleaner housing for that little extra ???....Mike ...:lecturef_smilie:....:gaah:...:thumbup:


Don't know about the air cleaner but, Back in the 60's i made my own cool can's, I would Spiral a few feet of fuel line in it then fill with ice. Kept my ET,s down in the summer at the strip.

[bluestratos]

Yes, we used to solder in a copper coil in to an old tomato juice can that we filled with ice. it helped on the quarter mile but no differnence on trips. Not sure if I remember this correctly but I believe the cold gas takes up less space than normal or hot fuel so when the fuel enters the cylinder it expands, taking up some of the space. This resulted in a bit richer run off the line so I believe we used to compensate by leaning the air/fuel ratio bofore the run (for the street rods). Cooling the air technically would have the reverse effect, ie allow less room for fuel but with modern knock sensores, oxygen sendsers, electron timing control and all the other goodies the air temp should have little or no effect. The winter blends of fuel do make minor impacts on fuel milage both gas and diesel. It is more notible in diesel, my 2005 F250 drops from 16 in town to 14 when the winter fuel enters the scene.


Regards,

[Desert Spyder]

Wasn't there an old trick on the two barrel carbs of putting an orange peel over the throttle bottle to prevent vapor lock?

[boborgera]

Wasn't there an old trick on the two barrel carbs of putting an orange peel over the throttle bottle to prevent vapor lock?

Throttle bodies, Replaced Carburetors .

[Bob Denman]

Throttle bodies, Replaced Carburetors .
Question: Throttle Bodies... Aren't there more advanced systems being used today to get the fuel and air into the compression chamber?? :dontknow:

[boborgera]

Question: Throttle Bodies... Aren't there more advanced systems being used today to get the fuel and air into the compression chamber?? :dontknow:

You might be thinking of direct injection, but they still need some thing to get the air mix in.
Just about any [road] vehicle you can buy comes with throttle bodies,.
That said there will always be advanced systems coming along every day.
Awhile back there was a guy in India who was running a small car with an air compressor.
The cylinders were pushed by Compressed air, The compressor was run by a Kerosene? generator.
One day some nut will come up with a billion dollar idea. ie; Remember Edison:thumbup:

[Bob Denman]

http://smileys.smileycentral.com/cat/4/4_12_13.gif

[Bob Denman]

I like the way that you think, Mike! :thumbup:
But I guess I was thinking of something that us mere mortals could use without having to get too "mechanical"... :shocked: :roflblack:

[BLUEKNIGHT911]

Mike in Ga. You are absolutely right......In Antartica my Boss "429" with the shaker hood would't work worth a damn......Ford just couldn't get that right.....or the Talledaga either......:roflblack::roflblack::roflblack::rofl black::roflblack::roflblack:.....Mike...:gaah:

[Bob Denman]

Are you sure that wasn't the extra thick oil in the pan not allowing ti to spin over quick enough?? :D

[Campverdefela]

You might be thinking of direct injection, but they still need some thing to get the air mix in.
Just about any [road] vehicle you can buy comes with throttle bodies,.
That said there will always be advanced systems coming along every day.
Awhile back there was a guy in India who was running a small car with an air compressor.
The cylinders were pushed by Compressed air, The compressor was run by a Kerosene? generator.
One day some nut will come up with a billion dollar idea. ie; Remember Edison:thumbup: Yeah, but then the oil co.s put a hit on them :roflblack:

[Bob Denman]

:gaah::gaah::gaah:

[BajaRon]

Sorry Mike, but you're off a bit.........

Cold, dry, air at sea level is the most dense, with the highest oxygen content. Air with a high moisture content is less dense, as the water vapor molecules displace the air molecules, resulting in less oxygen available for combustion. Hot, humid air is the worst for performance, and dew point isn't really a factor....

Colder ambient temperatures will result in the Spyder's ECM increasing the fuel delivery to the cylinders because of the added oxygen available. This would result in better performance, so theoretically, the MPG should balance out. The mixture isn't 'richened', the fuel/air ratio would stay the same. Having fun with the increased performance might result in an MPG reduction.......

Ahh... Reason, reality and proven fact.... You don't stand a chance with this approach! :roflblack:

[NancysToy]

Well, I don't completely agree with either of you. Here is my understanding of this, partly gleaned from many years of racing.

Cool, moist air is the most dense, but moist air does not hold as much gaseous oxygen per unit volume, so it may not work the best. The oxygen (and hydrogen) in the air are not usable in the combustion process. The water is merely turned to steam. Too much moisture and the engine suffers. A little is good, though. BTW, if engines could run on the hydrogen contained in water, we wouldn't be using gasoline.

The EFI will adjust the amount of fuel delivered to match the fuel/air ratio called for by the mapping. Denser air requires more fuel to keep the same ratio. The actual volume of air taken in remains constant, as it is a product of the volumetric efficiency of the engine, but the amount of oxygen is greater in the denser air, so more fuel will be required. (Note: engines with variable valve timing can change the charge volume.) You will generally use a bit more fuel at lower altitudes and higher air densities, as a result. Other variables, like fuel mix, grades, wind, and the fuel composition will affect the mileage, too, often far more than mere air density. As was said, the peppy feeling you get from having a bit more fuel in the denser intake charge, often results in involuntary twisting of the throttle, which makes the most difference in your fuel mileage.

So, here we are with three somewhat different slants on the same phenomenon. I won't say which of us is right, if any, but I will say that I have not been convinced enough to change my understanding of the process. JMHO

[BajaRon]

After spending 33 years in the fire service I can say that I've put water on a lot of different kinds of fires, and it never burned one time. There are some fires that you don't want to put water on (like a petrolium fire) but not because the water burns.

It may be that this reference was to the expansion rate of water to steam which is a very impressive 1700:1. This will give you some substantial energy release in the combustion chamber, but as soon as you get steam you're going to put out the fire producing the heat needed to make the steam in the first place.

It does appear, however, that we may have strayed a wee bit from the original purpose of this post.

[NancysToy]

MikeinGA -
Water will merely vaporize in the combustion chamber (or any other type of fire). It does not dissociate readily, so the oxygen and hydrogen cannot form gasses that can be used in combustion. Water is a stable chemical compound, that is very difficult to break into its component parts.

HDXBones -
The air density I am talking about is that measured on an air density gauge. Moderately humid air is denser by the meter. I know what you are saying, and I was trying to explain much the same thing. Basically there is less available air in humid air than in dry air, so there is less fuel required to maintain the same A/F ratio.

[BajaRon]

I can understand why this post has pretty much become a private discussion. To add to the muddy water, there really is more oxygen in humid air (by volume) than there is in dry air. But of course, Scotty is right (and problaby HDX has said this too but I didn't have it in me to read back through all the posts). The O2 in water, be it liquid or vapor, is just not available for combustion.

The volume of H2O in the air displaces the O2 that is available for combustion thus lowering the actual, usable O2 in your fuel/air mix resulting in less power and thus, less MPG for the same volume of combustible mix in your cylinder.

Wow! It almost sounds like I know what I'm talking about! Good enough to fool my wife anyway! :thumbup:

[BajaRon]

.......now that we're up to speed on air density and the effects of altitude and humidity, who wants to discuss Bernoulli's principle and carburetor icing?.......:chat:

Wow! And I thought I was getting a headache before!

Since we are injected and not carbureted (Spyderwise that is) I think I can afford to skip this one...

[SteveMac]

WHEW! :shocked::hun:

I just turn the key, hit "mode" and off I go. Glad you guys have all this figured out. :thumbup:

[BajaRon]

WHEW! :shocked::hun:

I just turn the key, hit "mode" and off I go. Glad you guys have all this figured out. :thumbup:

You are so much better off for it too! :ohyea:

[billybovine]

I've been noticing lately that the colder my water temp is the more fuel is being consumed. And of course when it is warm the less. I know on cars there is a sensor to richen the fuel mixture so to warm up the vehicle quicker. Is it the same on the Spyder? Yesterday, I went on a PG mission "down the hill" which has been enjoying 80 degree temps lately. My temp gauge on my RT showed rough half way. I drove about 120 mi and got about 35 mpg. Coming home in the desert the outside temp was in the 60's, my water gauge showed about 1/4 up (analog), and I got about 28. Why? Also, last summer I added a little "Engine Ice" to my fluid because of the high temps out here in the desert. But in the winters, when the temps drop below freezing and stay in the 50's during the day, my fluid temp may barely show any rise at all when cruising on the freeway. And of course the mpg drops. So whats going on here? I'm sure there are many owners out here who may be in the same "boat".

OK guys now that it is settled that colder air and fuel would likely improve gas mileage, water does not burn and before someone sugests that the Rotax mill in our spyders is capable of cold fusion lets get back to Desert Spyder's original observation. In cooler temperatures his enige runs cooler and his gas mileage suffers. Maybe he has a cooling system problem, thermostat perhaps? I have heard of them starting to fail and not fully closing when cold. Could it be just in the nature of the beast to run cold in cold temps?

[BajaRon]

OK guys now that it is settled that colder air and fuel would likely improve gas mileage, water does not burn and before someone sugests that the Rotax mill in our spyders is capable of cold fusion lets get back to Desert Spyder's original observation. In cooler temperatures his enige runs cooler and his gas mileage suffers. Maybe he has a cooling system problem, thermostat perhaps? I have heard of them starting to fail and not fully closing when cold. Could it be just in the nature of the beast to run cold in cold temps?

Wow! Really!? We get to talk about the original subject again! Oh My! (You can insert 'Lyons and Tigers and Bears' if you like).

The fuel management system does richen the mixture at below operating temperatures. I suppose it is possible that if this minimum temp is not being maintained (or, if the ECU thinks the coolant temperature is too low) fuel mileage could suffer. I don't think anyone is saying it isn't possible, just unlikely if everything is operating correctly.

I believe additional fuel may also be added if the incoming air is quite cold. But this is simply to compensate for the denser air to keep fuel ratios adequate and should not cause MPG to suffer.

And I don't think anyone is saying that water burns, at least I hope not! :yikes: I thought we were having fun with the concept, but I could be wrong in that.

I think the intent was to convey that water can increase performance (fuel mileage, etc.). There are ways other than combustion to produce energy. It is true that under certain ideal circumstances, introducing water into the combustion process at just the right time and in carefully metered amounts can be advantageous in some engines.

This is quite different than oxygen robbing humidity in the air mass being used to charge the combustion chamber.

Now, about the subject of Cold Fusion! :roflblack:

[Pandy]

This thread is most timely, yesterday, we rode from Charleston to Macon GA and back. ( So where were all the GA Spyder riders) This was to accomplish two things, lunch at Nu-Way Weiners and a trip to what has to be the best Bass Pro yet. (no, we haven't been to Springfield) Now, to my point; ambient temp by the trike's indicator was never above 51F. Nighttime was down to 31F at one point. My fuel economy was down by 15 to 25%. Now, this could also be air filter, worn plugs, the machine turned over 17K miles in I-16. So, maybe there is something to the decrease in ambient temp and fuel economy. No, not what I would expect from a closed loop system, but who expects anything normal from Spyders? And they are Canadian yet!Cold shouldnt faze them! Not to hijack the thread but a great time was had by all, eh?
Patrick