I am not an engineer or an ME. The knowledge I have about mechanics and it's functions is knowledge gathered from the most part by doing research on the internet and reading magazines.

This next question may seem dumb, and probably may well be. But here it goes anyway.

I know that a conventionnal gas engine will support only so much compression before it starts to detonate, ie: 12:1 with 94 octane.

Inversely, I know that a diesel engine is basically a detonation engine.

Given also that some very high compression gas engines (with either a high CR, or lots of boost) supposedly can work with kerosene, a fuel halfway between gas and diesel used mostly for aircraft purposes, and usually very costly.

Would it then be possible that a high CR gas engine, say 12:1, with crazy boost, say 25 psi, would be possible to make it work on diesel fuel, ignite it with a spark, and have it work detonation-free?

I know some are experimenting with propane, and it supposedly has very high boost/CR tolerances, but I was wondering about diesel...

thanks.

 

Diesel detonates at approximately 18-22 bar. You would need maybe 12PSI or so of boost on a gas engine like the TSX to achieve this. Of course, I am sure other things would need to be changed (catalytic converter, valve timing, fuel injectors, etc).

Probably more trouble than it would be worth.

 

how would you achieve that initial detonation to get the engine started? I'm guessing this isn't entirely impossible, but by the time you were done working on the engine to get it diesel ready you would have been better off both in price and performance just buying a diesel car to start with.

 

I'm not sure you completely understand what I mean.

I am talking about using a gas engine with sparkplugs, so when starting, it would not detonate like it would with glowplugs. It would start just like any classic gas engine.

Also consider that a diesel has to be sturdy as hell to withstand detonation, which would be to a lesser extent on a gas engine running on diesel. Which should allow for higher revs, as good torque as diesel engines, but higher horsepower, and hopefully a longer powerband, all the advantages of both engines.

Also, diesel fuel is heavier, denser than gas. Which means it has more energy potential per volume than gas. So it should then be used more efficiently in a spark engine. No?

 

Note also that diesel combusts more slowly than gasoline, so its detonation exerts less stress on the engine. This is also why diesel engines don't generate much power above, say, 4000 RPM or so. As I've read it, the piston is literally travelling too fast for the "explosion" to exert much additional pressure on it.

FYI, 12 PSI is nowhere near enough to cause detonation in a turbo setup. This is the stock PSI in the 02 and later 1.8T, and chipheads are routinely trying (but seldom succeeding fortunately) to blow up their engines running 20-24 PSI.

 

james bond smoke screen is what you will get...

 

This is interesting...

Now I was thinking more along the lines of 25 psi and 12-15CR.

Do you think that by increasing the pressure inside the combustion chamber - and the heat as well, that the burn would be faster, or is it a constant no matter the pressure and internal temperature?

 

1. Diesel needs a really high PSI injector, gas engines don't have them.

2. Spark plugs and diesel will never mesh.

3. If you could get the diesel to ignite, it would blow the head clean off the block. Diesel engines are way beefier the gasoline engines.

Diesels are generally in the 16:1 compression ratio, doing this will kill your K series.

 

There are many much swifter engineers working for all of the car makers that would have comes up with something like this if it was feasible. Honda has some of the best engine engineers in the world - if there was a way to make this economically they would have done it already.
Diesels are more like 20:1 CR and unless you build them from the ground up as a diesel you'll get the horrible reliability of the converted GM gas V8 of the eighties. Honda modified some of the internals of their new diesel to make it work at only 18:1.
Look in the diesel thread and you'll get all the details.

 

It all boils down to the diesel principle of internal combustion and fuel flashpoints. Simply put , it has to do with how gas explodes and oil essentially burns.
The flashpoint as we know is the lowest temperature at which vapors rising from a petroleum product of a flame under specified conditions will ignite momentarily (i.e. flash) on application.
The fundamental differences between the two engines and why it wouldn't work are fundamental to the two methods of combustion in that gasoline burns due to it's vapors and its lower flashpoint and due to the higher flashpoint of the diesel you couldn't simply take a gas engine who mixes the air fuel mixture upstream in the intake manifold and instead inject oily low flashpoint diesel fuel and expect it to work. Not only would'nt the injectors work with the diesel fuel You'd only have a gooped up engine resulting from the unburnt oil dribbling into your engine instead.

Conversely , Diesel being essentially an oil as we know needs to be subjected to the higher compression ratios and resulting heat in order to burn. Because it's heavier it wouldn't flow as a vapor of gas/air mixture into the combustion chamber, thus why diesel is injected directly into the engine's combustion chamber.

So in summary, I do see your point in that you could create the necessary heat via boost and cratios but your fuel delivery system of your gas engine wouldn't work.

Check out this website where they're running diesels off of cooking oil. It'll give you some insight as to what an oilburner is all about. I found it pretty interesting.
http://www.greasecar.com/

 

Good thinking, Sauceman! You should be an engineer!

It sounds like you're trying to describe an engine that combines the good aspects of both the Diesel and spark ignition engine. The research I'm doing right now is on an engine like this. We don't know if it'll work well enough to be used on a large scale yet (we're still probing the operating parameters), but the side benefit is that we're learning a lot about the fundamentals of auto-ignition (knock) and spatial variation in the chemisty from it. BTW, we run a heptane fuel mixture (heptane is basically a 0 octane gasoline), but another group here and others around the world are doing the same thing with Diesel fuel, so your idea is possible in general.

I can't go into too much detail, but I can give you more general info if you like.

 

I didn't mean to sound negative in my last post... I just didn't want to hear you'd started swapping parts off/onto your TSX in an attempt to convert it to a diesel !

It is a good idea. Anything that lowers our dependence on petroleum is a good thing.

here's another article for Car and Driver on the Grease Diesels...

http://caranddriver.com/article.asp?...&page_number=1

 

Thanks for the post. I surely would love to know as much as I could on the subject.

So far, most of the objections have been about issues with the injection system. As far as I'm concerned, as long as I know it is a physically feasible thing, with reasonnable benefits, finetuning and adjusting accessories like the injection system is of second order, and is always something that could be adapted.

Note that I am not into such a project, I don't have the qualifications or the knowledge, nor am I too much of a manual DIY type. But I love feeding my thoughts with wild ideas and concepts.

And yes, I would have loved to be an engineer, unfortunately, I should have thought about it 12 years ago...

 

I see your idea, and to make it work you'd have to preheat the diesel for starters to bring it up to near it's flashpoint in order to combust like gas. The higher the flashpoint of your fuel the more you'd have to heat it. Since internal combustion engines generate lots of heat You could do some sort of regenerative heating method as well by using the heat from the engine's cooling system to heat the diesel fuel once everything was started.

Here's a good example of a modern day inventor. This guy has no engineering background and has a revolutionary invention with electric motors that require/use almost no electricity.
An inventor like Thomas Edison never had any college education/training as an engineer and look at his contributions to science.
Follow your dreams.


http://japan.com/technology/index.php

 

You got it. What we're working on is called a Homogeneous Charge Compression Ignition (HCCI) engine. Basically, you intake a fuel-air mixture (like a gas engine), but then you compression ignite it (like a Diesel). It's very interesting. We get efficiencies and fuel consumption levels of a Diesel without the particulate and NOx emissions.

Take a look at this webpage to get a better idea of how it works. It's from a university in Sweden, but it's one of the best basic descriptions I've seen. I'd tell you more, but it'll probably be more efficient for you to just google "HCCI" and see what you come up with. If you have questions, let me know.