Diesel Engine in a Heli

[brw0513]

I wish I could ask this question without displaying my complete lack of knowledge on the subject i.e. looking dumb. Then again, I'm getting to an age where I just don't care any more.

Why don't we have a diesel engine, instead of a gas or glow variant, in our helis?

Is there an OS91 form factor engine that is a diesel? Or could an OS91 be converted?

Is diesel fuel for this application a mix of kerosene and ether or something else?

Is this diesel engine a bad idea for some good reasons?

[poor_red_neck]

Isn't a glow engine technically a diesel? Relying on the compression to ignite the fuel.

I've seen vids of a few plank motors running on diesel, but I doubt the performance was anywhere close to a nitro blend, and therefor doubtful to work on a heli.

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Please excuse spelling/grammatical mistakes due to fat thumbs.

[desertstalker]

The power to weight ratio of a diesel engine is not great, even the modern high-pressure injection ones used in cars. I dont think you could build one light enough (with the power needed) to perform well on a heli, at least not with the current tech.

If you want to burn diesel in a heli, your going to need to use a turbine, AFAIK they can run on diesel as well as kero.

Not sure why diesel though, petrol is not exactly pricy at the quantities needed for helis, nor are flight times a particular problem (I am sure you could put a couple of hours worth of fuel onto a heli if you were not concerned about acrobatic performance.

[brw0513]

I'm talking about a glow engine converted to run on diesel.

The power to weight wouldn't equal nitro, but how would it compare to a Zenoah gas engine?

[Rc Zombie]

Davis diesel was a company in the 90's that offered conversion heads I do know some of them ended up on YouTube but I can't attest to the performance they may still be around though

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[acrow]

Originally Posted by poor_red_neck

Isn't a glow engine technically a diesel? Relying on the compression to ignite the fuel.

A better explantion perhaps is this: Diesel engines are so named due to the fuel used.

The term compression ignition is used if there is no sparking device used once the motor has been started. So on that basis, both nitro engines and diesels are compression ignition.

Regards

Acrow

[4 stroke flyer]

i had an interest in a diesel myself. I talked to some people who tried it, they all said power was excellent. But the constant tuning problems was a nightmare. I never tried it myself. for once I took the advise....... that does not happen often

[Burt37]

Originally Posted by acrow

A better explantion perhaps is this: Diesel engines are so named due to the fuel used.
Acrow

http://en.wikipedia.org/wiki/Rudolf_Diesel

Maybe this is the reason why it's called Diesel....

[mcfast]

"Isn't a glow engine technically a diesel? Relying on the compression to ignite the fuel."

NO ! glow dose not use compression ignite the fuel, it uses a glow plug to ignite the fuel, the glow plug stays white hot all the time the engine is running. plus the compression is way too low for it to run like a diesel.

[Elgyn]

If you raise the compression and nitro level you can get them to "diesel" but the pressure in the combustion chamber would be too much and you have to replace the motor after a few seconds. eg: Top fuel dragsters.

[jockstrap]

I remember the old Diesel model engines... havn't seen any around for a long time..

Most were smaller size that I've ever seen..

Instead of a glo plug they had a wrench at the top that you tuned them with - adjusting the compression to get them to run smooth.

[ngin]

Diesel R?C engines can produce a lot of power (RPM x Torque), and do so at much lower RPM because they rpoduce so much more torque at this lower RPM. That is why they are also so fuel efficient (just as they are in todays advanced deisel engines that we find in European cars).

Unfortunately, the gearing of even the gasser helis that we have in play today, are not ideal for taking advantage of this type of power delivery.

But who is to say that some may not be developed in the future to do so

[desertstalker]

Originally Posted by ngin

Diesel R?C engines can produce a lot of power (RPM x Torque), and do so at much lower RPM because they rpoduce so much more torque at this lower RPM. That is why they are also so fuel efficient (just as they are in todays advanced deisel engines that we find in European cars).

The are more fuel efficient because of the higher compression ratio, and for the car engines its not so spectacular a difference anyway (compared to a similarly sophisticated petrol engine. Keep in mind that diesel has ~20% more energy (per L) in it than petrol.

The really large diesel engines (ships, locomotives, generators, etc.) are very efficient but are also quite heavy (power to weight ratio) and operate at very low speeds.

[Azalin]

I wonder if small engines can be boosted with small turbochargers!
http://www.youtube.com/watch?v=

[Doug Darby]

Yes Turbo kits are available. I worked in one on a Traxxas truck with a 3.3 nitro motor. I am not sure if there is one out there for a Zenoah! I would bet some ingenious modeler has built one.
I just spent 4 days flying in The Denver area in the foothills of the Rockies and with the field being at 6000 ft elevation I sure could have used one. The 18% loss of power was very apparent with my 270. I just reduced the pitch a degree and it helped.