Diesel Engines

Not being a mechanical engineer, some of the things that I believe are probably incorrect. I always thought that that cracking sound was the detonation of the fuel/air charge in a Diesel engine, thus slamming the connecting rod hard and generating a sound that is uncommon in gasoline fueled engines.

The analogy may not carry over between full size compression ignition engines and model compression ignition engines (specifically what we call Diesels), but model Diesel engines have a very much quieter exhaust than glow engines. It has been said by some folks in the know that the reason for this is because in the model Diesel engine, the combustion process is very nearly completed before the piston uncovers the exhaust port, whereas, the glow engine still has some fuel burning when the port is uncovered. The latter allegedly generates the louder exhaust note of the glow engine.

Ed Cregger

gasoline

whereas, the

engine.

Ed, It's not mechanical noise at all, its the rapid burning from the extra lean mixture that a diesel has at idle, it's not actually knocking but very close. I did not find this on the web. I could not find anything that says that diesel burns slower than gasoline, in fact they are about the same with some high test gasoline burning slower. The main differance is that diesel ignites at a slightly lower temp, the high test gas ignites at the highest temp which helps prevent knocking. Also I recall that diesel fuel is made to ignite as soon as it leaves the injector, the lag time of ignition and the constant pressure cause the diesel to run at lower RPM's. Not the same reason that model diesel's run at a lower RPM, that is mostly due to the lower per volume energy of the fuel mixture.

Thanks for sharing your knowledge.

In the strictest sense, all noise is generated mechanically, but I'm sure you know that and I understand your point. I hadn't thought that the ignition of the fuel/air charge was violent enough to sound through the cylinder walls, but why not? It is all a matter of degree, so to speak.

Ed Cregger

Well yes it is mechanical, but it's the pressure wave vibrating against the cylinder and head walls. Not the con rod or bearings. If you think about it the engine is idling, there cannot be much stress on the con rod

Amyl or Butal but nowadays you need a prescription to get it. Ether is getting hard to buy as well.

Don.

There used to be a guy in Phoenix, Az. that imported Diesels for sale here in the States. It was called "Carlson Engine Imports". He had quite a few different diesels. I bought several different types from him. This was several years back. Ed was very helpful and knowledgable in diesels.

When glow plugs first came out, I ran normal gasoline fuel with little problems. Glad to know it would not work or I would never have tried.

Ray S.

I have seen folks try to do this with modern glow plugs, Ray. None of them had any success. One fellow got his to run as long as the booster voltage was still being applied.

Most of them managed to set fire to their models eventually.

I wonder what was different between what you were doing and what they were doing?

Ed Cregger

I have heard this story before, but if you go to RCUniverse and look under the engine conversion forum, you will find a year old or so thread of people running gas with glow plugs. Not sure but I think they were using cold plugs. The engines ran but not as well as with ignition. Some did as well if they mixed a small amount of methanol. Gasoline has a much lower ignition temperature so I figure it needs a colder plug.

The current mythology is that the platinum in the glowplug and the methanol react, causing the glowplug to remain glowing after the booster voltage is removed. Obviously, gasoline would not cause that reaction and the engine would quit upon removal of the booster voltage.

I haven't performed any experiments in an effort to determine if this is true or not. Just like everyone else, I tend to believe what the modeling experts have told me over the years. Modeling experts such as Clarence Lee and Duke Fox.

If someone could figure out how to make their glow engines run reliably on an all gasoline and oil mix while using an unpowered glow plug, I would be interested in duplicating their efforts, just for the fun of it.

I have heard of folks using glow fuel with gasoline added in an effort to run in very cold weather. Also, some folks claim to get much longer engine runs for a given amount of fuel by adding gasoline to their glow fuel mix. These two things are somewhat believable. But I have never heard of anyone having luck running today's glow engines and glow plugs on an all gasoline/oil mix.

I'm not too old to learn, so if anyone has tips on how to make it happen with today's gear, I'm all ears/eyes.

Ed Cregger

platinum

methanol.

voltage is

Clarence Lee

reliably on

effort to

Ed,

I checked RCU last night and they are having to use hot plugs and getting small to moderate RPM drops when the battery is removed, and a rough idle. Platinum reacts to all hydrocarbons, actually it reacts to the combusted gas not the fuel itself. We know our glow plugs also work with pure nitro fuel, though it needs a much colder plug. It also reacts to the nitrogen, by attracting the nitrogen and carbon molecules to the element oxygen and hydrogen are more exposed to each other. Likely the effect is more pronounced with alcohol because of the high hydrogen componet and the oxygen in the fuel. But it is an exaggeration to say thay there is no catalytic reaction with other fuels. Besides the catalytic reaction only enhances the glow plug and makes it hotter, Ray Arden started with ni chrome elements which had no catalytic reaction, but to get them hot enough they would not last well.

There is a company that has a web site makeing a high tech glow plug, I think it is called smart plug.

They use a small interior chamber which is exposed to the plug, the fuel mixture ignites in the chamber and the hot gasses leave through small orifices with a small blow torch effect to ignite the remaining fuel. The size of the chamber and the size and length of the orifaces affects the timing.

Well, this is why I responded to Ray's post. It looks as though I can learn something today. Thanks.

I'll skoot on over to RCU. Any hints on what thread this information is in, off the top of your head? TIA

Ed Cregger

It is under engine conversions. I think you can do a search on subject only as the title is something like Gas engine with glow plug and gas, no ignition. I think if you included ignition gas and glow plug you will find it.

Thanks.

Ed Cregger

Its parrtly true. Its also true that antything that stays red hot can compressioin ignite most fuels provided the compression is high enough.

And things can compression ignite on their won as diesels do.

Is mostly true, but teh reaction is not the only source of heat, otherwise we wouldn't need a starter battery.

"Sport Pilot" wrote in news: snipped-for-privacy@z14g2000cwz.googlegroups.com:

I went to their website. They have suspended sales until they retool for increased production levels. Uh-huh.

The added cylinder volume of the device would substantially decrease the compression ratio, which is what is needed if burning gasoline for fuel.

Something smells fishy to me, but I can't quite put my finger on it. I hope it is legitimate and that it does work. I don't think I would like to be out in the wilderness on an ATV equipped with these devices without several spare glow plugs onboard.

Ed Cregger