Fuel viscosity change with increased oil ratio

[Mark75H]

I'm trying to devise a test to see how much flow restriction increased ratios of oil present in 2 stroke gas mixtures.

I have a 50cc burette that will flow 50cc's of raw gas in 30 seconds. The outlet of the burette is about an inch and a half long and .030" bore. A lot more restrictive than a carb jet, so my theory is it should amplify any resulting difference in flow.

If I use the same gas and oil and keep the temperature constant and the weight of the mixture constant can anyone think of other controllable variables that can be acted on to make the test show accurate results?

Can anyone point out reasons this would not demonstrate whether or not the viscosity significantly changes?

[Seagull 170]

Interesting question, is it the flow rate you should be measuring or is it the fuels ability to atomize with varying oil percentages, or perhaps both.

With a wide open carb attached to a decent fan perhaps the length of time to flow 250 mls of fuel will help, but then you've got all the air temp, atmospheric pressure & humidity variations that might affect the results.

Perhaps someone on here knows a man, who knows a man who's the carb specalist at one of the big 2 stroke manufactures, now that's a call that could save you a lot of time.

The big problem with the internet is finding the man who really knows. rather than the chap who thinks he knows.

I'd be very interested in your results.

I've just tried to call Dr John Dixon who wrote "The High-Performance Two-Stroke Engine" but he's not around today, I will ask him the question, when next we talk.

[Mark75H]

One thing at a time.

Actually, I already know the answer to this question ... its the proof I'm working on.

[Tomtall]

A worthy test. I'm interested in the outcome. I was wondering if you should not maybe have a controled subtance (liquid) in your test to just make sure your numbers don't get a scew with minor changes in Barometric pressure,Temp.,etc..Like a baseline of straight water.

[Master Oil Racing Team]

I was thinking that barometric pressure could, but it might be so miniscule that it would be hard to detect without sophisticated equipment and so not really be meaningful. To counteract that, I would just run all the tests I wanted on a given day in a short period of time so that you would have the same barometric pressure and ambient temperature, then record these to check results compared to tests from different days.

BRF member Joe Flow designs, tests and manufactures valves of all types for race cars to maintain pressures and temps within a narrow range. These include fuel, hydraulic fluids, coolant, oil, and he is working on air flow for cooling as well.

[Powerabout]

Although easy to say..

How about a wet flow bench drawing through any carb and you measure the fuel flow.
Thats should be close to real world one would think?

Dont forget to try fuel only and oil only

and or get someone with an injector flow bench to measure flow with changing ratio's

Great stuff Sam
Cheers

[Powerabout]

What happens when you mix viscosities?

i.e. 50% sae 100w with 50% sae 50w what do you get?
Is the answer simple or random due to interaction of the 2 compounds?

[Mark75H]

Again you are introducing factors outside my intended test

[Mark75H]

My understanding of the physics of open containers, especially open on both ends is that ambient pressure will not affect the out come. If some one can explain otherwise with references, I am all ears.

I will do straight gasoline both first and last and keep the whole test to a short time period and monitor the temperature.

I don't see how water flow would be related. The viscosity and surface tension characteristics are so different from gas and oil. If you can point to a reference showing a significant relationship, I'll do it. The standard I intend to use is the baseline raw gas.

[Mark75H]

In the end, I can think of a reason to compare an oil that has significantly higher viscosity. That would be to show whether a dramatic flow change is possible with mixture ratios in the usable range for 2 stroke motors.

For example, if a higher viscosity oil like Klotz Techniplate reduced flow then there should be a warning on the label as such. Klotz does not recommend Techniplate for oil injection systems because it has much higher viscosity than mineral oil.

[Master Oil Racing Team]

You are right about ambient pressure Sam. I was thinking of capped off vessels. Master Oil viscosity changes dramatically with temperature change because there were no additives to keep it in a certain range. The additives were basically for extreme pressure and temperature. I don't remember exactly but it might be like 5 in the middle of a heat wave in August in Texas and 25 in a cold winter. But then it's lubricity reduces surface tension, So your mention of Klotz not recommending its product for oil injection systems due to viscosity, got me thinking. In it's early day petroleum based oils could not match the lubricity of Master Oil. But since then, synthetics have come on the market and are superior. This is what I'm wondering. Take two oils with the same viscosity. One standard petroleum base. The other a premium synthetic oil. Would there be enough lubricity difference with the synthetic to cause enough reduction in the surface tension of the gasoline to make a measurable difference?

[Mark75H]

Again, this is something well outside the original test question, but probably can be addressed with the same apparatus.

I want to show whether you have to change carb jetting if you use more oil because the increased oil slows down fuel flow thru carb jets when you make an oil mixture change within normal oil ratios used on 2 stroke motors ... Specifically 50:1, 24:1 and 18:1


PS: I don't think gas has any surface tension to speak of ... It does't stand as a bubble when you put a single drop on a plate. It runs out flat.

[Mark Poole]

Is this test going to be simply pumping/pushing the fuel through the 030 passage?
Just thinking.......might see more of a difference if the test actually flowed air through a carb and made the venturi "pull" the fuel through the jet and up the high speed nozzle.This way the mixture has to fight gravity as well as flow due to the effects of the venturi. Interested in the results either way. :)

[Mark75H]

It might be different, but would involve building and running a rather dangerous apparatus that I am not interested in building and operating. It would take a lot more gages and adjusters to run consistently.

The gas and gas oil mixture will just flow out the bottom of the burette by gravity; being run by the same height of liquid column each time. Extremely easy to accurately repeat.

The outlet of the burette is only .030" and is 1½" long, a lot more restrictive than a carb jet.

[russhill]

Sam, I think your methodology for testing and quantifying viscosity is perfect. However, with all due respect, so what? It is certainly not clear to me how or if fuel viscosity correlates to engine performance. I presume this is your ultimate objective.

I believe fuel flow can be adjusted via jet sizes and/or needle valve for infinitely adjustability. Also the oils have different viscosities. And again adjust the needle valve. I think more is to be gained by adjusting oil to fuel ratios, because quantity of oil is NOT proportional to lubricity. Isn’t lubricity oil’s main role?

I agree that atmospheric pressure would not impact your test, but it directly affects engine performance. Temperature would affect your test, but that’s easy to control. Keep us posting your testing results and your thinking. I really enjoy it.
.

[FrenchPhil]

So like will 3% oil be slower than 2.5% at a given rpm ?

[russhill]

Could be. Why at a given RPM? We're racing, so mamimum RPM/HP is what we're talking about. What the optimum ratio should be depends on a number of variables, not the least of which is the oil.

[Mark75H]

Its a matter of concern to those using fixed jets.

[fyremanbill]

The greatest loss of fuel delivery will probably be due to the displacement of fuel with oil in higher ratios. It would be interesting to know if a lighter viscosity oil in the same ratio would flow more total volume. Adjusting fuel temp is probably the best way to increase mass fuel delivery with a fixed fuel system though.

[Mark75H]

Fuel coolers don't flow more because more fuel goes thru the jet, they flow more AIR because the cold fuel cools the air going into the crankcase, shrinking the air inside ... making more pressure differential between the crankcase and outside the carb.

I talked to the 2 stroke oil expert at one of the popular 2 stroke oil companies yesterday. I'm going to talk to more companies before I'm done. Several things surprised me. First he did not try to say his oil was any better than another brand. Second, he said all the best lubricating base oils were very thick and the lighter versions were just diluted with solvent to give them pour-ability and pump-ability. The solvents also give an advantage in mixing and staying mixed, but the primary use was thinning. Then he spoke about the balancing act of thinning the oil vs lubrication, and said lighter viscosity oil is just less lubrication in a 2 stroke. Third he said he is constantly bombarded with "your oil killed my motor" from guys who ran thick oil ratios with low octane gas thinking that more oil would compensate for the junk gas. He said there is no balance between junk gas and good oil, both must be good.

He said my demonstration would be a good visual demonstration of the viscosity of mixtures as used in 2 strokes and the respective flow of high mixes and light mixes.

[Master Oil Racing Team]

What he told you about thinning vs lubrication is correct Sam, and here is just one example of why that might be necessary.

Before the advent of modern oils, sperm oil was the preferred cutting oil for the tough jobs. After it was banned, Omark Industries found that they could reduce their scrap pile significantly with the use of Master Oil due to properties coming closer to sperm oil than anything else on the market at that time. They could further reduce their losses by cutting it in half with Shell Sol 70. Why would diluting help keep their machine work within tolerance? It was because they were boring a small hole in extremely hard metal 28 to 30 inches. The deeper they got, the more circulating restrictions they had, and by thinning the oil, it was able to stay up with the bit. They were boring out rifle barrels, and that meant exacting tolerances. They had a big loss ratio until they did that.

Very interesting stuff.

[Powerabout]

M75
can you ask your guys if the oil forms part of combustion?
Does it burn once ignited?
or
Does it only support combustion
or
Does it not burn

Cheers

[Mark75H]

I asked. I was told although it is difficult to ignite, it burns as part of the main combustion.

[zul8tr]

Your testing procedure is very similiar to that used in the industry to measure viscosity but the equipment is somewhat different than what you are using. None the less the device you are using will do a good job for relative measurements but here are suggestions for use:

1. Do not drain the burette empty for each test run only measure the time for a volume to release say 30cc that keeps the fluid released in the graduated constant cross section region of the burette. There are dynamic flow regime reasons for this control. In doing the test start the flow at the full mark of the burette and start the timing when a selected top mark is reached and stop the timing at the lower mark. Repeat to get average time per each fluid test. This will eliminate the transient starting flow conditions and eliminate the dynamic flow conditions at the nozzle outlet and confine the flow release to the constant area section of the burette and hopefully laminar flow conditions. If flow times are to quick reduce the size of the exit orifice to assure laminar flow in the burette measuring region.

2. To maintain a nearly constant temperature of the tested fluid place the burette in a surrounding container of water of large enough volume to maintain the temperature of the fluid you are testing. Devise a sealed means to have the burette discharge out the bottom of this container. This is the temperature control procedure used by ASTM for the Saybolt device described below.

The most popular measuring device for low viscosity fluids is the Saybolt Universal Tester Viscometer. With it a 60 cc of fluid is drained thru the graduated portion and the time recorded. The device is calibrated with a known viscosity fluid but equations are available if calibration is not done. The calibration or equations will provide the kinematic viscosity in units of Centistokes (cSt) which if needed can be converted to Centipoise (Cp) knowing the specific gravity of the fluid. Both units are used in the industry.

Details are provided in Section 1.11 and Section 14.21, "HandBook of Fluid Dynamics" by Victor Streeter Ed. In Chief, 1st Ed 1961 McGraw-Hill Book Co, .

[7500Blizzard]

While the results of this test will be interesting i just don't see how it will help you decide on any tuning as it in no way replicates what your motor will be or is doing. To say that it takes point .001 seconds longer to flow 60cc's means nothing. There are 100+ different things that'll effect your fuel system. 1st your system is pump fed not gravity, than anything from how many hard bends in fuel lines, condition of inside of line, strength of pump/s condition of carb and so on. As stated above the biggest concern of extra or over oiling would be the leaning condition.

[Mark75H]

While the results of this test will be interesting i just don't see how it will help you decide on any tuning as it in no way replicates what your motor will be or is doing. To say that it takes point .001 seconds longer to flow 60cc's means nothing. There are 100+ different things that'll effect your fuel system. 1st your system is pump fed not gravity, than anything from how many hard bends in fuel lines, condition of inside of line, strength of pump/s condition of carb and so on. As stated above the biggest concern of extra or over oiling would be the leaning condition.


It looks like you are saying extra oil slows down flow thru your entire fuel system including the fuel pump. If that was the case not even increasing jet size would help.

I'm not clear on why you say viscosity only applies to gravity induced flow

[Mark75H]

only measure the time for a volume to release say 30cc that keeps the fluid released in the graduated constant cross section region of the burette.

That's the way I've been doing it and plan on doing it for the better video


2. To maintain a nearly constant temperature of the tested fluid place the burette in a surrounding container of water of large enough volume to maintain the temperature of the fluid you are testing. Devise a sealed means to have the burette discharge out the bottom of this container. This is the temperature control procedure used by ASTM for the Saybolt device described below.

Rather elaborate and necessary for assessing to a standard ... but I am not assessing to a standard, I only want to know how the particular mixes flow relative to each other, so I will only take it as far as monitoring and recording the temperature room temperature and the mixes to assure there is no change more than 2° at most. Since room temperature puts us squarely on the flattest part of the temperature/viscosity curve of the stuff being tested, that should be pretty good.

Is there any barometric pressure concern in the standard? I would think there is not.

[7500Blizzard]

No i'm not saying oil slows it down throughout your system although it most likely does atleast minutely in a gravity fed system. What i'm saying as it will prove nothing to help in tuning as it will not replicate anything your motor does. In order to prove anything you would have to replicate a typical fuel system to get any real usable data, and even then it would still vary from motor to motor.
I am also not saying viscosity only effects gravity fed systems although it will more than a pressurized system again all i'm saying is this test will give you nothing to use in the aid of tuning your motor.

[Mark75H]

I agree with that.

It will only show one particular aspect and how much that aspect can affect tuning.

[zul8tr]

That's the way I've been doing it and plan on doing it for the better video



Rather elaborate and necessary for assessing to a standard ... but I am not assessing to a standard, I only want to know how the particular mixes flow relative to each other, so I will only take it as far as monitoring and recording the temperature room temperature and the mixes to assure there is no change more than 2° at most. Since room temperature puts us squarely on the flattest part of the temperature/viscosity curve of the stuff being tested, that should be pretty good.

Is there any barometric pressure concern in the standard? I would think there is not.

ASTM has no barametric standard for the viscosity test that I am aware of.

Along with room temp also measure the gas oil mix temp but if gas and oil containers are stored in the same room that not be needed.

What will you be using to measure the temps: simple small mercury thermometer, infra red gun or other? :)

[Mark75H]

I will use a Fluke 87 thermocouple thermometer. I don't think I will do any testing if the oil, gasoline and room temperature aren't the same to start with.