e-sailpilot86

I was browsing the Model Engineering News website, and a guy named Malcolm Beak modified the designs to a 4-stroke ETW Kiwi. He dropped the displacement, beefed up the engine, and I think I increased the compression substantially. Guess what? After warming it up with a 5% ether, 95% kerosene start, it'll run on 100% kerosene! Is that cool or what?! Now, I don't know much about diesels, but couldn't you just use a large glow plug to warm up the engine before starting, and rely on that instead of the ether? Would that hurt the compression ignition? Anyway besides my own curiousity, the owner of the "M.E.N." website seems really happy about the potential this could bring.

link:
[link=http://modelenginenews.org/gallery/p8.html#noether]Etherless Diesel?[/link]

gkamysz

My Feedback: (19)

He also says that it suffers from preignition and I wonder if it's been run with a load of some sort.

Greg

grant-RCU

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What would be the actual CC or CI of the engine to be able to acheive enough compression heat to ignite diesel or kerosene with no ether.
Kerosene auto ignites at 410 degrees F. ether auto ignites at 320 to 338F .

My guess would be something like a 60 to 80cc would do it but would it have preignition problems from using a crab instead of direct injection? Or would it work just like the ether/kero mix engines and be adjustable via contra piston.

e-sailpilot86

aah. I see why there are pre-ignition issues now. That's why the big ones are direct injected....

To direct inject, what would you need? How much pressure? You know, I've got a wild idea that would correct the preignition problem from carburation, but it's too much mechanics, so never mind it. Hey! An easier way! What if you used the same supercharging technique that YS engines use? Use the crankcase pressure to force in the fuel just like the 1.40DZ and 1.60DZ!

grant-RCU

My Feedback: (10)

My guess to why preignition would exist is due to varation in the temp of the combustion chamber thus if the kero air mix on the compression stroke sees over 410F its going to ignite before TDC. And varying CC temps will cause the airfuel mix to sparattical combust varying ignition timing. So if you put a good load on the engine it would raise the CC temp and cause preignition.
Now i have no idea why preignition is not a issue with compression ignition models usings carbs and compressing the fuel air mix. But thats where the contra pistons comes in it controls pre igniton by varying compression. I guess??
I dont have a model diesel yet.

Direct injection is best as we all know but complicated for models[:@]

gkamysz

My Feedback: (19)

Diesel injection requires minimum 3000PSI or so. Today common rail turbo diesel injectors operate upwards of 20,000PSI.

I've had similar issues with my fourstoke conversions. Operating temperature causes the variation in ignition timing. I have my theories, but haven't tried anything yet. Mine have been operating on standard fuel mixes. Preignition or detonation doesn't seem to be much of an issue with two stroke model diesels but the fourstrokes behave differently.

Greg

e-sailpilot86

I now realize that full size diesels use a minimum of 3000psi to inject the fuel, however, if YS is sucessfully direct injecting fuel into their engines, I don't see why there could be much of a difference between a glow injection vs a diesel injection, unless YS is direct injecting the glow fuel when the engine isn't at top dead center? How serious can preignition be while an engine is still running so long as it isn't having detonation?

Anybody know how a YS injector works?

gkamysz

My Feedback: (19)

Wait a minute, that picture shows a fuel tube from the carb area to the cylinder head. I hadn't followed up on the DZ series until now. They are injecting at, low pressure, fuel into the intake port, not the combustion chamber. The fuel pump and regulator are connected to the intake pushrod so that fuel only flows when the intake vavle is open. They still use a needle valve to set fuel mixture and there must be some fuel metering occuring in the throttle body.

Preignition is a problem because it reduces engine power output and increase operating temperatures and stresses. Detonation does the same but much more violent and with more profound results, because the fuel charge explodes rather than burns.

Direct injection in diesels refers to injecting the fuel directly into the combustion chamber.

http://www.me.iastate.edu/biodiesel/Pages/bio14.html

There is a huge difference between diesel injection and gasoline or alcohol fuel injection systems. That is your assignment for tonight.
YS Engines definition is not the same. I don't even know why they are calling it injection. It's an interesting idea. I think they did it to reduce the amount of oil in the crankcase. The oil requirement in the fuel is high 20-24%.

I notice that my FS48 diesel conversion will run fine at WOT for a while than as head temperature rises it starts to knock. It gets progressivley worse until temperture seems to stabilize in a minute or so. I can reduce compression until it doesn't knock, but then it lacks power.

Greg

AndyW

My Feedback: (1)

Yes, it's doable.

http://www.rcuniverse.com/forum/m_4561055/tm.htm

gkamysz

My Feedback: (19)

I was going to try diesel(better Cetane rating than kero) and Amsoil ACB in my fourstroke conversions. I just hadn't found a source for ACB locally, the guy I called never called me back and I got sidetracked after that.

I'm glad to see it works well for you. I'm going to try it this week. Well maybe after the temps drop for the 99 degree high expected tomorrow.

Greg

AndyW

My Feedback: (1)

Hi Greg,

Diesel as opposed to kerosene,,, I'm guessing that you mean that fuel (kerosene) for diesel trucks is better, more refined, higher cetane rated? Anyone know how to get Jet A fuel?? [X(]

At any rate, yes, we'd love to see your results.

gkamysz

My Feedback: (19)

Kerosene has no cetane rating requirement. This means it can vary quite a bit and you never know what you have unless you check with your supplier. Diesel is required to meet certain specifications for cetane rating and will generally be higher than cetane rating of kero. Diesel has a minimum cetane rating of 40. Kerosene in most cities will be Jet-A as it is very abundant.

While kerosene and diesel are very similar you would not want to put kerosene into your new '06 diesel vehicle because you would probably wear out critical fuel system components due to lower lubricity and lose performance because of the reduced cetane rating.

I've looked up a lot of information online about fuels. Basically Jet-A and kerosene are identical. Diesel No.1 is very similar but a slightly heavier distillation. No.2 diesel is a little heavier than No.1. Kerosene is blended with No.1 to improve cold flow and cloud points during the winter. In the US all diesel fuels are required to have a minimum cetane rating of 40. In Europe the minumum is 49. I think most low sulphur diesel sold in te US today is closer to 45. Flash and auto ignition temperatures for kerosene and No.1 diesel are very similar.

You can run kerosene or Jet-A in a diesel vehicle but the reduced lubricity can cause problems and will void warranties. It's not recommended unles you have no choice and are adding lubricant to the fuel.

So my opinion is that No.1 diesel with higher cetane rating should work better in our engines, especialy if we are going to try to run them without ether. I'm getting things together to try some testing later this week.

Greg

AndyW

My Feedback: (1)

Greg,

Thanks to Graham for alerting me to your response and thanks to you for the information. Again, for some reason, RCU isn't informing me of new posts from time to time. Your reply has saved me a lot of work, I now recall some of what you've told us. In the end, nothing wrong with kerosene but truck fuel may have some advantages as in easier starting and consistency of cetane rating. Going to go out and get some now.

I'm going to sacrifice the .15 to this experiment. If truck fuel has better lubricity, maybe we can get away with 10% castor. Along with the better lubricity of diesel fuel and the inherent superiority of castor, this may work. More combustibles, lower compression, more power and better mileage. After all, the car guys are running 10% oil. [X(] Fun to try.

gkamysz

My Feedback: (19)

The F2C guys run 10% oil in their 2.5CC team race diesels too. That is the low limit as they pay to play at that point. Engine wear is an issue. The guys that can't afford to pay run minimum 12% oil.

10% oil in a diesel is equivalent to 4-5% in glow fuel based on fuel/air ratios. And that already takes into account the 1/3rd less volume of oil diesels already typically run at.

I think you're right, kerosene is pretty good. Diesel, might possibly be a bit better.

Greg