Adding Diesel to gasoline

[FourBinLabs]

Originally Posted by Odin

one thing i think you are forgetting diesel is injected at very very very high pressure which is one of the reasons it burns the way it does (in my benz its 5500psi) it only gives off a clean and controlled burn under these pressures because its atomized into a super fine mist if you just shot it in with the intake you would not get the same results

I'm definitely not forgetting how/when diesel fuel in injected into the cylinder in a diesel engine. What I keep trying to back to is how each fuel would perform under identical conditions (this particular situation revolving around a gasoline engine. I don't have an interest in why diesel fuel can be used in diesel engines.

It boils down to this. It takes ~600°F to auto ignite diesel. It takes 495°F to auto ignite gas. If a gas engine has enough compression to make diesel fuel auto ignite, then the cylinder temp must reach ~600°F during compression. If the cylinder reaches ~600°F, then it must invariably reach 495°F on it's way there. If it reaches 495° The gasoline wile auto ignite long before the diesel will.

If putting diesel in a gas engine would make it knock, then it seems putting gasoline in the engine would make it knock worse.

[dcb]

Originally Posted by FourBinLabs

...
I'm confused as to how it's possible that a diesel engine may have double the compression of a gasoline engine, and not require more resistance to detonation.

Has this question been sufficiently answered?

[NachtRitter]

You have it right here...

Originally Posted by FourBinLabs

If once diesel fuel ignites, it is an uncontrolled explosion, that sounds like detonation. If when gasoline ignites, it's a controlled explosion, then does this mean that gasoline burns slower than diesel?

Once diesel ignites, it burns significantly faster, and in a more uncontrolled fashion, than gasoline. As well, there are additional points of secondary ignition when the diesel burns. The higher the octane, the slower it burns, and the lower the chance of secondary ignition points.

Originally Posted by FourBinLabs

It boils down to this. It takes ~600°F to auto ignite diesel. It takes 495°F to auto ignite gas. If a gas engine has enough compression to make diesel fuel auto ignite, then the cylinder temp must reach ~600°F during compression. If the cylinder reaches ~600°F, then it must invariably reach 495°F on it's way there. If it reaches 495° The gasoline wile auto ignite long before the diesel will.

Read the Gasoline FAQ link I posted previously... no, really, read it. You're still equating the octane rating (RON, MON, AKI) with initial auto-ignition under temperature and pressure. It is not the same, as I said in my previous post.

Octane rating conveys what happens once the fuel has been ignited, not how difficult it is to ignite the fuel initially, according to the FAQ.

[UFO]

This "discussion" has still not rendered any light, just a bunch of heat. I can't think of a single good reason to put diesel in a gasser. The engine was designed for gasoline - use it. Diesel is not going to improve anything.

[FourBinLabs]

Originally Posted by NachtRitter

You have it right here...

Once diesel ignites, it burns significantly faster, and in a more uncontrolled fashion, than gasoline. As well, there are additional points of secondary ignition when the diesel burns. The higher the octane, the slower it burns, and the lower the chance of secondary ignition points.

Read the Gasoline FAQ link I posted previously... no, really, read it. You're still equating the octane rating (RON, MON, AKI) with initial auto-ignition under temperature and pressure. It is not the same, as I said in my previous post.

Octane rating conveys what happens once the fuel has been ignited, not how difficult it is to ignite the fuel initially, according to the FAQ.

I was under the impression that auto ignition was only a result of temperature and pressure (that and carbon deposits). But looking closer at the below definition, I see that octane rating may only be in reference to a spark-ignition system

Originally Posted by Wikipedia

The octane rating is a measure of the resistance of petrol and other fuels to autoignition in spark-ignition internal combustion engines.

I'll spend some time reading the article after I get home from work and post back later when I'm more informed. I appreciate you taking the time to help.

Originally Posted by UFO

This "discussion" has still not rendered any light, just a bunch of heat. I can't think of a single good reason to put diesel in a gasser. The engine was designed for gasoline - use it. Diesel is not going to improve anything.

The above quote has not rendered any light, just a bunch of heat. Not one piece of substance here, just an opinion with no backing.

[gone-ot]

...OCTANE rating is a "referenced" number that equates to the gasoline's ability to resist "pre-ignition" prior to the precise moment that ignition IS DESIRED to occur. NOTE that "pre-ignition" is any combustion that occurs before it was intended to occur, ie: pinging, detonation, etc.

...CETANE number is a statement about "how well" the diesel fuel combusts (smoothly vs. irregularly or sputtingly).

...OCTANE and CETANE are not the same, just as gasoline (spark-ignition) and diesel (compression-ignition) are not the same---although the two are murging with HCCI.

[NachtRitter]

Originally Posted by Old Tele man

...OCTANE rating is a "referenced" number that equates to the gasoline's ability to resist "pre-ignition" prior to the precise moment that ignition IS DESIRED to occur. NOTE that "pre-ignition" is any combustion that occurs before it was intended to occur, ie: pinging, detonation, etc.

That's the misleading part... Based on what I read on the Gasoline FAQs, the 'ping' / 'knock' is not a result of pre-ignition of the fuel prior to the ignition point... from the link:

...the knock did not arise from preignition, as was commonly supposed, but arose from a violent pressure rise *after* ignition...

The knock happens when the fuel is ignited by the spark, and then after that point the unburnt portion of the fuel (at the outside edges of the mixture) pre-ignites and produces a secondary wave front. The point at which the two (or potentially more) wave fronts meet create the 'knock', producing much higher pressures at the wrong time.

Indicating that the fuel pre-ignites *before* any ignition source is exactly what confused FourBinLabs ... quite understandable. But that is not what the octane rating is measuring.

Read the FAQ... no, really, read it. It is quite good and very understandable. Link again: Gasoline FAQ - Part 3 of 4

[gone-ot]

...from that same source:

"Knock and preignition are both favoured by high temperatures, so one may lead to the other. Under high-speed conditions knock can lead to preignition, which then accelerates engine destruction
[27,28]."

...bold emphasis is mine, not the author.

[arcosine]

I surely would not want to be following you! PU!

[UFO]

Originally Posted by FourBinLabs

The above quote has not rendered any light, just a bunch of heat. Not one piece of substance here, just an opinion with no backing.

Oh very good. And how is my statement "The engine was designed for gasoline - use it." an opinion?

Come on now, what sort of benefit is expected or documented? Diesel reduces the octane, so you will now knock when you compress this brew, so you either damage your engine or your ECM reduces timing for poor mileage.

This forum usually sticks to sound experimentation looking for effective ways to reduce petroleum consumption, but this thread is almost as far into the weeds as HHO. Sorry to have to be the one to point it out, but now the rest is up to you.