Emergency Duty: Gasoline and Diesel Mixture

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Originally Posted By: Pontual
I was reading this yesterday and did 5% in my Ninja ZX9R, with 12 to 1 CR. Run 150 miles without any difference. Tip of exhaust got a litler darker and thats it. 10% maybe feseable, but thats with you. I believe that at 5% it would burn lubricant 2 or even 4 stroke, imagine fuel (diesel)...


Diesel octane range is given as "about 15-25" here (but gives no source for the number)

http://www.madsci.org/posts/archives/2000-10/973012182.Ch.r.html

and here in this thread

http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/272893/Re:_Octane_rating_of_diesel_fu

which also gives a range of 8-15 in another post. Sources are given, but I can't find these numbers in them.

The scale used isn't given, but I assume its the US AKI scale rather than the RON scale used almost everywhere outside the US.

This (8-25) is a fairly wide range, with 16.5 as its mid-point.

In the abscence of any other info, I'd assume the octane of a mixture is a simple arithmetic mean of the octanes of its components, though I have heard there MAY be some exceptions, as when mixing leaded and unleaded petrol, so this assumption may not be valid for the extreme case of a diesel/petrol mix.

The fuel used is not given in the above post. Assuming its 94 AKI,( which I believe is the highest octane generally available in the US?) I THINK the resultant octane of a 5% mix of diesel at 16.5 octane would be given by:-

=((95*94)+(5*16.5))/100 = 90.125?

It is of course trivial to put this (probably simplistic and quite possibly wrong) formula in a spreadsheet so you just have to enter the values.

10% diesel gives 86.25, which I'd guess many modern engines could easily cope with by altering the ignition timing under control of the knock sensor.

If the diesel is at the upper end of the quoted octane range, (25) a 10% mix is 87.1 AKI.

If the diesel is at the lower end of the quoted octane range, (8) a 10% mix is 85.4 AKI
 
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Originally Posted By: Shannow


Personally, I think older technology might be what you need for this adventure.

Napthalene is a relatively low spill octane enhancer, not sure that a backpack full of it would solve in diesel really quick.


Wouldn't have to if it'd dissolve in the petrol. But do Tuareg housewives (tentwives?) buy mothballs?

Long time ago I read an account of a US mercenary pilot working for Castro which mentioned them running their jeeps on rum. Mothballs definitely featured but I dunno why (since alcohol is high octane). Can't remember the full recipe, but maybe they added kerosene or diesel to get the fuel value up. Think wartime jeeps were pretty low compression though.
 
Gasoline is 85 minimum octane, kerosene about 50, how would diesel be only 8-15 is what intrigues me... That could be very out. If you can burn pure (100%) kerosene in a low compression spark engine 5 to 1 CR, why 5% diesel would matter so much.
I see a chart that Diesel has 40 octane rating, not 15!
More like it
 
Originally Posted By: Pontual
Gasoline is 85 minimum octane, kerosene about 50, how would diesel be only 8-15 is what intrigues me... That could be very out. If you can burn pure (100%) kerosene in a low compression spark engine 5 to 1 CR, why 5% diesel would matter so much.
I see a chart that Diesel has 40 octane rating, as a minimum, not 15!
40 octanes is the rating of pure petroleum oil from the ground, as of the same book.
More like it
 
but you're getting all the high octane stuff out of the crude when you make diesel... kerosine is between diesel and petrol on the distillation curve, it would be logical that it's octane rating would be going up compared to diesel, and it's cetane rating down.
 
Originally Posted By: Pontual
Gasoline is 85 minimum octane, kerosene about 50, how would diesel be only 8-15 is what intrigues me... That could be very out. If you can burn pure (100%) kerosene in a low compression spark engine 5 to 1 CR, why 5% diesel would matter so much.
I see a chart that Diesel has 40 octane rating, not 15!
More like it


More like cetane
 
If you put 10% diesel in but have to give it 10% more throttle to get the same power, do you win anything?
 
Originally Posted By: Shannow


Key was to get vaporisation of the fuel...then you can run lean to reduce the autoignition potential.

Your ECM won't let you run lean, and you won't get the heat to vaporise, and a modern 95RON compression ratio won't help.

Personally, I think older technology might be what you need for this adventure.



Agreed on the old tech and running lean. Not so sure about the heat. My old-tech air-cooled motorcycles had/have pretty hot exhaust pipes. Modern exhausts might be cooler, but I'd think still hot enough to boil diesel.

It'd not be that difficult to rig/fab some kind of drip-fed exhaust heat exchanger, (coke can bashed to fit the pipe at the simplest/crudest), and feed the vapour into the air intake. (You could do the same thing with water).

The control system would (presumably) back-off the fuel injected to compensate, BUT you'd loose control over the fuelling and the proportion of diesel added, perhaps to the point where it wouldn't be drivable and/or would break.

Might JUST work well enough at a steady cruise though, with a bit of fiddling.
 
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Originally Posted By: eljefino
If you put 10% diesel in but have to give it 10% more throttle to get the same power...


We don't have any specific reason to believe that is the case.
 
This may be relevant, but,

When my brother started driving he accidentally mis-fuelled by putting diesel in a petrol car. It was a Renault Clio, fuel injected with MAF, 02, COP ignition etc.

8 litres of diesel in a near empty 45 litre tank before he realised, filled to the brim with petrol and it started/ran/drove fine with no warning lights.

Your results may vary
 
Originally Posted By: Olas
This may be relevant, but,

When my brother started driving he accidentally mis-fuelled by putting diesel in a petrol car. It was a Renault Clio, fuel injected with MAF, 02, COP ignition etc.

8 litres of diesel in a near empty 45 litre tank before he realised, filled to the brim with petrol and it started/ran/drove fine with no warning lights.

Your results may vary


This reminds me that I need to talk to my recently licensed daughter about recognizing the diesel pumps and staying away from them...
 
Originally Posted By: Olas
This may be relevant, but,

When my brother started driving he accidentally mis-fuelled by putting diesel in a petrol car. It was a Renault Clio, fuel injected with MAF, 02, COP ignition etc.

8 litres of diesel in a near empty 45 litre tank before he realised, filled to the brim with petrol and it started/ran/drove fine with no warning lights.

Your results may vary


Ditto in reverse (So less relevant:diesel Clio with probably about the same proportion of petrol) It was a hire car and a long way from home otherwise I'd probably have tried to drain it and/or add some 2-stroke oil, though that's hard to find in the UK.
 
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Originally Posted By: Virtus_Probi

This reminds me that I need to talk to my recently licensed daughter about recognizing the diesel pumps and staying away from them...


The nozzles are bigger and won't fit down the "unleaded restrictor" in her filler neck.
 
Originally Posted By: eljefino
Originally Posted By: Virtus_Probi

This reminds me that I need to talk to my recently licensed daughter about recognizing the diesel pumps and staying away from them...


The nozzles are bigger and won't fit down the "unleaded restrictor" in her filler neck.


That's the theory, but the amount of people who manage to do it suggests otherwise
wink.gif
 
Diesel S10 (10 ppm S) from Petrobras has 48 cetane rating. Regular is 46 cetane nr., on the 50ppm of Sulphur (S50).
 
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Originally Posted By: Pontual
Diesel S10 (10 ppm S) from Petrobras has 48 cetane rating. Regular is 46 cetane nr., on the 50ppm of Sulphur (S50).


I'd think cetane rating will have a very roughly inverse relationship with octane rating, so higher cetanes will have lower octanes, but they are fundamentally different, so I don't think its possible to calculate one from the other.
 
Agree, just demonstration to illustrate that 8-15 wouldnt be a good octane nr. FOR Diesel, if applicable. Somebody raised the octane of diesel as 8-15... Those numbers would make hi-pressure injection impossible due to burning while spraying in a hot cc.It would have to be 92% to 85% of pure heptane (C7H16), and it clearly isnt.
 
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Originally Posted By: Olas
Originally Posted By: eljefino
Originally Posted By: Virtus_Probi

This reminds me that I need to talk to my recently licensed daughter about recognizing the diesel pumps and staying away from them...


The nozzles are bigger and won't fit down the "unleaded restrictor" in her filler neck.


That's the theory, but the amount of people who manage to do it suggests otherwise
wink.gif



Could also have her touch a diesel pump once and see how icky and oily it is, and drive home the fact that diesel is oil and gasoline evaporates.
 
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