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.