Factory pro HDJ?

Taffy,I can follow your thoughts,
well at least half way -but I want/ need to disagree at some point

You´re 100% right:
Size does Matter - just ask the ladies :lol:
the smaller the "fuel-spray" , the less mass -> it changes Temperature faster than one with more mass

But back to the atomization cool down: I´m pretty sure you heard (or expierienced) of carb-icing, right?
So what´s happening in there? as fuel is sucked through the jet and mixes with air, it changes from liquid to spray.
And with this change in "state of aggregation"(hope it´s the correct word?) it cools heavily down.
Guess it´s same the same concept as within every refrigerator / or Air-filter-Spraycan
Just touch a carb with the engine is running and you´ll see/feel what´s going on in there


Best Regards

Peter

peter

then we agree

colder at carb and warmer afterwards.

regards

Taffy

Gokai134 said:

Taffy,I can follow your thoughts,
well at least half way -but I want/ need to disagree at some point

You´re 100% right:
Size does Matter - just ask the ladies :lol:
the smaller the "fuel-spray" , the less mass -> it changes Temperature faster than one with more mass

But back to the atomization cool down: I´m pretty sure you heard (or expierienced) of carb-icing, right?
So what´s happening in there? as fuel is sucked through the jet and mixes with air, it changes from liquid to spray.
And with this change in "state of aggregation"(hope it´s the correct word?) it cools heavily down.
Guess it´s same the same concept as within every refrigerator / or Air-filter-Spraycan
Just touch a carb with the engine is running and you´ll see/feel what´s going on in there


Best Regards

Peter

Click to expand...

Hi peter,

My two cents worth.

It's called latent heat of evaporation, it's also the same way your body cools it's self. On the body, sweat evaporates on the skin and it doing so you feel cooler because the heat in your body is being exchanged to the atmosphere..

The opposite is true for latent heat of condensation. Like when you have a cold beverage, and droplets of water form on the outside, or condensation, as the beverage warms due to the fact that the surface temperature of container is below the dew point and the cold of the beverage is being transferred from inside to the droplets of water on the outside.

And yes it's the same way with a refrigerator, the liquid refrigerant is being turned into a gas in the "evaporator" inside the fridge where it becomes very cold and the fan circulates the air across it. The heat in the fridge is absorbed into the gas in the evaporator where it then it flows to the "condenser" where a fan is blowing across it to remove the heat. I know it's kind of weird, but, refrigerators don't really cool the air, they remove the heat, then dump it outside.

So, inside the carb the liquid fuel is basically being turned into a gas and thus you have latenet heat of evaporation. Carb icing occurrs due to the moisture in the air mixing with this super cold mixture, which at that point much lower than the dew point. So not only is the water condensing, it's so cold in the carb that it freezes to the parts of the carb where it comes in contact with. That's why piston engine airplanes have adjustable carb heat, or a damper that allows the pilot to pull heated air from across the exhaust manifold into the inlet tract to either de ice the carb, or keep it from freezing.

I would resist using the analogy of a refrigerator in these discussions - as it has the difference of having an electrically driven compressor and therefore the 'system' is forced and requires energy input to operate.

Most liquids require energy input to change states to a gas at anywhere near normal termperatures. As the liquid turns to gas something has to lose energy or cool.

In my opinion people are correct in viewing this question in two parts, by the way. And I am not a fuel expert.

I think first we need to agree atomization of fuel is not the same as turning liquid into gas - rather it is turning large droplets of liquid fuel into a large collection of very small droplets with a commensurate increase in surface area.

The increase in surface area then allows the small liquid drops to rapidly take on energy/heat and change to a gas state and this near instantaneous process for gasoline would result in a very localized cooling effect - I doubt, however, this would offset the heat taken in by the fuel when atomized in the hot intake/carb environment - but I am just guessing at this point.

For an oversimplified demonstration of cooling effect due to expansion any spray can will do, but remember the contents are under pressure which would have produced heat at the time of containment and the cooling is simply a function of the energy being returned to a 'normal state' much later in time.

My simple thoughts on a interesting topic

Cheers

Mark

chilledspode said:

I would resist using the analogy of a refrigerator in these discussions - as it has the difference of having an electrically driven compressor and therefore the 'system' is forced and requires energy input to operate.

Most liquids require energy input to change states to a gas at anywhere near normal termperatures. As the liquid turns to gas something has to lose energy or cool.

In my opinion people are correct in viewing this question in two parts, by the way. And I am not a fuel expert.

I think first we need to agree atomization of fuel is not the same as turning liquid into gas - rather it is turning large droplets of liquid fuel into a large collection of very small droplets with a commensurate increase in surface area.

The increase in surface area then allows the small liquid drops to rapidly take on energy/heat and change to a gas state and this near instantaneous process for gasoline would result in a very localized cooling effect - I doubt, however, this would offset the heat taken in by the fuel when atomized in the hot intake/carb environment - but I am just guessing at this point.

For an oversimplified demonstration of cooling effect due to expansion any spray can will do, but remember the contents are under pressure which would have produced heat at the time of containment and the cooling is simply a function of the energy being returned to a 'normal state' much later in time.

My simple thoughts on a interesting topic

Cheers

Mark

Click to expand...

Mark,

I agree the fridge analogy is probably not the best.

However, I would like to kick this around. You state "For an oversimplified demonstration of cooling effect due to expansion any spray can will do, but remember the contents are under pressure which would have produced heat at the time of containment and the cooling is simply a function of the energy being returned to a 'normal state' much later in time." How about this idea, the gasoline is a liquid due to the amount of pressure on it supplied by the atmosphere. In the venturi of the carb there is low pressure caused by the speed of the air rushing through which causes the fuel to be pulled into the venturi from the float bowl, and when introduced into this rapid low pressure air flow, it is atomized or dispersed.

Left in open air gasoline will evaporate, or turn to a gas no? So the process inside the carb is really just accelerating this process, but it is more of a vapor.

No arguments with this Dale, but I might have chosen to say the fuel is actually pushed into the low pressure venturi zone by gravity working on the free surface of the fuel in the float bowl via the breather lines.

I agree that evaporation of gas takes place at a free gas/air interface. If you atomize the gasoline you dramtically increase the surface area available for evaporation to take place - thermodynamics, heat transfer, fluid mechanics and other complex topics, for which I am not qualified to elaborate on, also play a role, but I think this is accurate at a working level....

I think the fuel must arrive at the venturi area as a liquid then rapidly disperse and evaporate into a gas as one continuous process involving heat transfer, turbulence, pressure drop, etc. It happens very quickly in my opinion.

I do not know if the liquid fuel coming up the tube to the venturi, when it 'sees' the low pressure zone actually jumps directly to a gas state - it's possible...

Cheers

Mark

nb: I trust the ride went well....

Hi Gang,

Just thought I'd add some of my vague understanding of what happens and flesh out Mark's point here "pushed into the low pressure venturi zone by gravity". Gravity pulls down on the air, just like everything else, and if the pressure above the fuel surface in the intake venturi is reduced, then the air pushes down on the free surface of the fuel in the float bowel and forces the fuel up the jets into the carb throat. With less pressure, the fuel is less constrained by the atmosphere and can atomise. Its a bit like sucking up a drink with a straw. Expanding the lungs, like a piston going down, creates a low pressure zone and the air tries to equalize and the only way it can is to push down on the free surface of the drink and up the straw, and is dependant on the reduction in pressure created by the increase in volume in the lungs. Boyles Law, Pressure x Volume = Konstant in action.

If we get a state change from vapour to gas then energy is involved and that is in the form of heat. Thats why the colder an engine is, the harder it is to start, as the fuel is as cold as the engine and requires more energy to heat up to change state. What the ratio of gas to vapour is, no idea.

Without gravity, the carb won't work, but its the air that pushes the fuel up into the venturi by being pulled down by gravity.

Steve

Hi Steve,

Your explanation using the weight of air due to gravity on the fuel surface is more correct

Thanks

Mark

nb: Your point about carb's won't work with out gravity or 'seeing atmospheric pressure' is why I have never liked vent lines only going down by the swingarm pivot - I install Tees and run one down and one up to under the gas tank to ensure the carb continues to function when running in extended deep wet areas that may well submerge the stock vent line ends below the engine

Yep, T Vents of some description are invaluable, especially for water crossings. Dunno whay they are not standard, although some sugest that they are on an FCR, its just the the top hoses go down as well.

Steve

FCR or not - if they are vents and under water they are useless ...

Tees are a must if you ride in the wet stuff.

Cheers

Mark

I guess that was what I was trying to say, one up, and one down. :roll:

My bad...

Mark

Kevin Cameron, technical editor at Cycle World magazine, had an excellent article several months ago concerning the combustion event in a gasoline engine. The closer to totally atomized the fuel charge, the more complete the combustion. It is normal for a percentage of the fuel to exit the combustion chamber unburnt, unused if you wish, even when the fuel-air mixture is correct. Fuel droplets do not burn well. Fuel as a compressed vapor will burn most efficiently. The modern fuel injection systems try to provide as small a stream of fuel, in some cases multiple small streams, as possible, to assist in atomization, hence more complete combustion. More power made simple. I remember many years ago, we were building a Norton 850 for a Bonneville attempt. Using the then technically advanced oscilloscopes and such, we were appalled to find that the ignition event wasn't even happening between 2 and 5% of the time. We checked further to find this was normal, and was due to the crappy combustion chamber shape a domed piston caused. We were better off than a side-valve engine though, they were known to miss an event 8% of the time. Poor combustion chamber shape, poor atomization of fuel, and poor placement of the spark plug were normal things years ago. Our Bergs do not suffer from these problems too much, benefiting from advances in technology and knowledge. I would think that Factory Pro would put a bike on one of their dynos, with and without the HDJ, and provide some concrete proof of it's efficiency.

Hi all,

Just to add a bit more about this atomiser, I have been using one for a while now and have always had this niggling problem just as you come off idle from roll off, the engine chimes in fairly harshly you can't just feather it in, very snatchy.
Tried numerous things different FS settings different PJ different PAJ settings, lifted the needle but just can't seem to get rid of it until today when I removed the Factory Pro atomiser and refitted the OEM atomiser problem cured.
It would seem the upper holes on the Factory Pro atomiser are above the fuel height so when you just start to open the throttle there is a big lump of leanness, has any body else come accross this problem.
My aim is to block off the holes starting with the top one to see weather I can make the atomiser work, it should work ok when the holes that are left unblocked are below the fuel height in the carb.
Other comments are most welcome.

Regards

Sparks.

hi steve

so what you're going to find i think is that when you get that soft suction at low revs, the bike sucks via the easiest route which is air. it then gradually builds up the vacuum, and up, and up and then it just takes everything it can from everywhere! this will include all 8-holes in the PM atomiser and with it brings lots of extra fuel surely?

i trust that this has been helping? would be inmteresting to do some measuring of where the float stops the fuewl and where that "plimsoll line" comes to on the side of the PMA?

regards

Taffy

Taffy said:

hi steve

so what you're going to find i think is that when you get that soft suction at low revs, the bike sucks via the easiest route which is air. it then gradually builds up the vacuum, and up, and up and then it just takes everything it can from everywhere! this will include all 8-holes in the PM atomiser and with it brings lots of extra fuel surely?

i trust that this has been helping? would be inmteresting to do some measuring of where the float stops the fuewl and where that "plimsoll line" comes to on the side of the PMA?

regards

Taffy

Click to expand...

Hi Taffy,

To put it in a more crude explanation if you had a tube of water and blew air across the top the vacuum produced would pull the water up the tube but if you were to put a hole in the tube above the water line and lead this bleed off tube to the same air that you were blowing across the top you are decreasing the vacuum hence you are pulling up less water.
The same is happening in the atomiser tube.
I could of got the same result by blocking off the main air jet.
Once the holes that are above the fuel line in the atomiser are blocked off you then have more vacuum to suck up gas, there is to much air getting into the atomiser at this partial throttle opening, once it is on the needle it's fine. I think you get the idea.

Regards

Sparks.