DEF going away ?

[rScotty]

I want you to conduct an experiment.

Go to your diesel engine and remove the air filter. Spray some diesel in using a water bottle. Does the engine automatically increase in RPM.

Report back.

Experiments are always a good idea. But squirting liquid diesel into an air flow isn't quite the right experiment because raw diesel fuel just doesn't make much in the way of combustible fumes at room temperature. That's why diesel is a "safe" fuel and keeps well when stored.

For your experiment, we need to be mixing intake air with a combustible fume....that is, we need to be mixing a gas with a gas, not a gas with a liquid. We need something to burn that is already in the gaseous state.

I suggest we either fill the spray bottle with boiling diesel, or with some kind of fuel that makes lots of fumes at room temperture. A gasoline soaked rag or a can of spray ether are both good sources of room temperature fumes to mix into the intake air.

I've used both of those to increase a diesel from cranking rpm to running rpm. I'm guessing most of us with older diesels have done the same.

Good experiment, thanks.
rScotty

 

[Snobdds]

No need for that "experiment", really.

The same basic thing happens every time I spray ether into the intake tract, since I'm adding "fuel" through the wide open intake, in addition to what the injectors are supplying. No need to remove the air filter eit

We do need the experiment.

If the throttle is set to idle, does the spraying of either raise the RPM?

I have never had the RPM increase...

The removal of the air filter is for diesel to be sprayed as it's not a gas to make it through the filter.

 

[Snobdds]

Experiments are always a good idea. But squirting liquid diesel into an air flow isn't quite the right experiment because raw diesel fuel just doesn't make much in the way of combustible fumes at room temperature. That's why diesel is a "safe" fuel and keeps well when stored.

For your experiment, we need to be mixing intake air with a combustible fume....that is, we need to be mixing a gas with a gas, not a gas with a liquid. We need something to burn that is already in the gaseous state.

I suggest we either fill the spray bottle with boiling diesel, or with some kind of fuel that makes lots of fumes at room temperture. A gasoline soaked rag or a can of spray ether are both good sources of room temperature fumes to mix into the intake air.

I've used both of those to increase a diesel from cranking rpm to running rpm. I'm guessing most of us with older diesels have done the same.

Good experiment, thanks.
rScotty

Super rich air/fuel mixture starts a diesel easier.

The question is...does that automatically raise the RPM if the throttle is set at idle.

Everyone is missing the issue at hand.

 

[Hay Dude]

Super rich air/fuel mixture starts a diesel easier.

The question is...does that automatically raise the RPM if the throttle is set at idle.

Everyone is missing the issue at hand.

And a warm combustion chamber

 

[Snobdds]

And a warm combustion chamber

We'll assume it's summer to avoid one extra variable.

 

[rScotty]

Super rich air/fuel mixture starts a diesel easier.

The question is...does that automatically raise the RPM if the throttle is set at idle.

Everyone is missing the issue at hand.

Snobdds, I get that you have always enjoyed arguing.
I do think your questions are good, since they give us a chance to get technical about how diesels work.

Yes, of course rich fuel in a diesel raises the RPM. For that matter, starting the motor from cranking to running speed is nothing more than raising the RPM at idle.

The problem with your original experiment is that to change your diesel squirt into a vapor it has to be heated above boiling....and diesel doesn't boil untl 400 to 600 degrees F. The high boiling point is a large part of why we can store it for long periods. Diesel fuel is just not volatile at room temperature.

Inside the engine, the compression heats everything, including the mixture each time the piston comes up and compresses the mix. So the compression stroke boils the diesel.
In fact the heat of compressing the air alone can raise the air temperature alone more than that ...without there needing to be any fuel in there to burn at all.

BTW, here's a weird fact: That extra heat of compression is why you see the pressure gauge continure to rise on a compression test when you crank the engine too long. It's why when a mechanic does a compression test he either counts strokes or uses a timer to equalize the cylinder readings.

rScotty

 

[Snobdds]

Snobdds, I get that you have always enjoyed arguing.
I do think your questions are good, since they give us a chance to get technical about how diesels work.

Yes, of course rich fuel in a diesel raises the RPM. For that matter, starting the motor from cranking to running speed is nothing more than raising the RPM at idle.

The problem with your original experiment is that to change your diesel squirt into a vapor it has to be heated above boiling....and diesel doesn't boil untl 400 to 600 degrees F. The high boiling point is a large part of why we can store it for long periods. Diesel fuel is just not volatile at room temperature.

Inside the engine, the compression heats everything, including the mixture each time the piston comes up and compresses the mix. So the compression stroke boils the diesel.
In fact the heat of compressing the air alone can raise the air temperature alone more than that ...without there needing to be any fuel in there to burn at all.

BTW, here's a weird fact: That extra heat of compression is why you see the pressure gauge continure to rise on a compression test when you crank the engine too long. It's why when a mechanic does a compression test he either counts strokes or uses a timer to equalize the cylinder readings.

rScotty

Debating scotty, debating.

You still are skirting your initial statement of diesels are at full air 100% of the time and fuel dictates everything. I don't believe that to be true at all.

Nothing you have presented has confirmed this. I have presented turbos, MAF, Baro sensors, jake brakes, and even throttle plates to say, nope...you're wrong. I have even offered up an experiment and now you say the diesel needs to be boiling. What?

At some point, you need to refute diesels are an air pump and the air is regulated with something.

 

[Too many Kubotas]

....diesels are an air pump and the air is regulated with something.

That something would be the speed of the pistons moving up and down.

If there's no supercharger involved, the air will fill the voids in the cylinders to near atmospheric pressure.

 

[rScotty]

Debating scotty, debating.

You still are skirting your initial statement of diesels are at full air 100% of the time and fuel dictates everything. I don't believe that to be true at all.

Nothing you have presented has confirmed this. I have presented turbos, MAF, Baro sensors, jake brakes, and even throttle plates to say, nope...you're wrong. I have even offered up an experiment and now you say the diesel needs to be boiling. What?

At some point, you need to refute diesels are an air pump and the air is regulated with something.

Ok, debating..... I'll go with that. But no....I can't refute that diesels are an air pump. That is exactly what they are. Adding fuel to the air being pumped is what creates additional useful energy.

That's not to say that you cannot regulate the air or do other things with that incoming airflow....but a diesel will work just fine when the incoming air is not regulated at all. And the engine will accelerate when more fuel is added because the mixture becomes closer to optimum - take another look at the original graph.

Boiling? Well, since diesel fuel is not very volatile - i.e. it doesn't make vapors easily - at room temperature, then we need to raise the temperature somehow to get enough combustible diesel vapors to mix with the air. Compression heating is handy, and is an convenient way to raise the fuel/air temperature so it will mix and full combustion will take place. When running, the fuel/air mix passes through the boiling temperature very quickly as sprayed fluid droplets turn to vqpor.
I just use "boiling point" as an example because I think everyone understands boiling to be an efficient temperature for converting liquids to gases.
In fact, some small amount if vaporization does happen at any temperature, and the heat of compression from the rising piston actually heats the mixture far above diesel's boiling point before it combusts.

rScotty

 

[Hay Dude]

Just goes to show you how different a turbo-diesel and an N/A diesel are.