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post #21 of 33 Old 11-18-2007
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Most of You seemes to be locked up in 'air volume'.
A diesel is calibrated in wheight units. If You go by mixture rate 15:1 it will mean 15 kg of air to 1 kg diesel at a given temp. The temp of diesel will normally not vary to much, usually similar to sea temp, but air temp and thereby density of air might be a different story.Not only the outside air temp but as much engine room temp is a big factor. Run on a cold day with engine room 'open' versus a hot day with engine room closed and the difference will be rather noticable.

The volume the engine sucks per stroke is 'constant' but the wheight of the volume sucked in varies a lot!
I keep out prop overload, dirty filters etc as they are not conciddered daily variables.
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post #22 of 33 Old 11-18-2007
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Another possibility for oil in the exhaust stream may be a faulty or stuck open water jacket thermostat, preventing the engine achieving the optimal operating temperature, resulting in incomplete combustion.
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post #23 of 33 Old 11-18-2007
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Haffman...

It's breathing the same stuff... air.
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post #24 of 33 Old 11-18-2007
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Quote:
Originally Posted by Rockter View Post
Haffman...

It's breathing the same stuff... air.
1 cubic air at 50C is lighter than 1 cubic air at 10C, this gives less oxygen/cubic. Engine runs rich. The engine sucks air in 'cubic' units/stroke, is injected with 'cubic units' of fuel, but variations due to temp makes a huge difference. No rocket sience, basic diesel knowledge.
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post #25 of 33 Old 11-19-2007
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"1 cubic air at 50C is lighter than 1 cubic air at 10C"

Just for my interest, how much lighter?

If thus was such a noticeable factor then trucking companies who use hundreds of thousands of gallons of diesel would have to modify their operating budgets from summer to winter. I have for many years worked for such companies where fuel is a MAJOR cost consideration and have never heard of such budget considerations.

Interesting concept . . . . . .

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post #26 of 33 Old 11-19-2007
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How much lighter depends, but why do 'hot air baloons' fly?
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post #27 of 33 Old 11-19-2007
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3, any exact same sized gas engine will use the same air volume as a Diesel as long as both are w/o a turbo or blower (naturally aspirated).
Not trying to beat a dead horse but just breaking it down a bit so I can understand it....

Take two mason jars, each the same size, and put the lids on them. Apply a vacuum of 20" on one of the jars. Which one has more air in it? (20" is the vacuum a gas motor pulls at idle) I don't think the restricted air intake on a gasoline motor can be discounted.

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post #28 of 33 Old 11-19-2007
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Here is the relation...

P1*V1/T1 = P2*V2/T2

If the pressures are the same, it becomes...

V1/T1 = V2/T2

Make the volume ratio the subject...

V2/V1 = T2/T1

Since density (rho) and volume (V) are inversely proportional, you can write as...

rho1/rho2 = T2/T1

So, if the temperatures are 10 degC and 50 degC respectively, convert both to the absolute temperature scale (just add 273 to both) and write as...

rho1/rho2 = (50+273)/(10+273) = 323/283 = 1.1413

...or about 14 percent more dense.

The motor would rather breathe the denser air.
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post #29 of 33 Old 11-19-2007
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Quote:
P1*V1/T1 = P2*V2/T2

If the pressures are the same, it becomes...

V1/T1 = V2/T2

Make the volume ratio the subject...

V2/V1 = T2/T1
Well...., yeah, when you put it that way...

Ray
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post #30 of 33 Old 11-19-2007 Thread Starter
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Thanks ERPS for your input. I think that you are right (blow back). I will see if I can capture some of the oil before kicking it back in for combustion.

As for the Diesel v. Gas air use, I think the answer is that a gas engine at full throttle uses that same amount of air as does an equivalent volume diesel (naturally aspirated in each case). However, the gas engine is using less when throttled back. Eg. you can adjust the air flow and then match gas flow as appropriate.
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