AMB

Here is a ASP 52 4 strk converted to diesel the engine was modified to raise the compression and the glow plug replaced with a vari compression adjustment unit that just went in the glow plug location Greg I think restricted the carb intake also, think he miiled down the head and shortened the push rods and their covers and yes it valve covers fit on nice job


^^%^^%%$ sorry will try this again photo nice family gathering but we did get up the engine pix

ASP 52 conversion done by AJ Coholic certainly more flexible than changing head gaskets on an Enya
Now it seems to me that without a lot of effort Saito or OS could do this, Saito goofed on the 80 a few years back and a few very high compression 80s got out Davis had one ran fine on diesel, Hobbsy has one also runs fine on diesel of course fixed compression and required some prop matching
again OS could certainly crank one out. I have had this several years and do not have the rpms or prop numbers but will rerun and write them down. It runs great Davis ABC fuel
right off with a quick shot from the electric starter no issues> I did not want to spend the bucks on the Enya and nothing to change, assemble, just fuel start and very easy to adjust

martin
he made new push rod tubes due to the collars on the old ones which could not be shortened

Recycled Flyer

Does it work well mate?

I am interested in hearing more about 4 stroke diesel conversions!

Cheers.

AMB

Recycled flyer, quiet ( 4 strks are anyhow even on glow quiet only this has a nice mellow tone) and less crap coming out the exhaust as I remember than running my 4 strk glows
this was a NIB engine I sent him I doubt it ever saw glow fuel
Of course Davis could do this but the time and machine work to do this would just require a high price tag and he is sticking to conversion heads, I strongly suspect he has done one
but the economics just are not there as a production issue

OS a 30 and 56 would be nice wishful thinking?

Hobbsy

My Feedback: (102)

LASER also made an .80 Diesel a few years ago but will not make another run no matter how many people ask.
Here is my Saito .80 turning a MasterAirscrew K-14x8 at 8,700 something and idleing at 1,400. I want to do it again and then fly it on something

[email protected]

Here is a photo of the Laser .80 four stroke diesel I lifted from the web a couple years back. Jack

AMB

Besides being a great engine looks like an art piece with its design features well just "very clean" martin

fiery

My Feedback: (2)

I am the proud owner of a TT75 FS converted to diesel by Greg Kamsyz

You can see a video of it here

www.dieselrc.com

Cheers

Mr Cox

Here is a video of a converted ASP 1.20 (not mine), nice tickover at idle; [link=http://www.viddler.com/explore/Diesel/videos/16/]ASP 1.20[/link]

Motorboy

Now i am back to forum due i was at move from former flat to a own house with garden.

Here are my movie of 4 stroke diesel engine with fixed compression.

[youtube]http://www.youtube.com/watch?v=lCSGvyUnU68&feature=related[/youtube]

[youtube]http://www.youtube.com/watch?v=FTmmTLAsEas&feature=related[/youtube]

This is the engine with too low compression ratio due fault from Enya Mfg before i improved the problem with compression ratio. Sound as a old boat engine, pop pop pop pop...
My biggest recommentation are to add the variable compression by contrapiston and compression screw in the Enya stroke diesel engine. It is a fault of Ken Enya do not make compression ratio adjusted by operator due weather and fuelmix.
[youtube]http://www.youtube.com/watch?v=bjSi4vzK6sc&feature=related[/youtube]

Mr Cox

Most 4-strokes on diesel seem to have problem with pinging (?), not sure about the correct name in english, but when accelerating from idle there is a metallic noise as if the ignition is to early. Can that be removed with proper tuning or is that something that one would have to live with?

I would like to convert an FS30 or even an HP VT21, if one can just get rid of that metallic noise...

gkamysz

My Feedback: (19)

Martin, what are you going to fly it in?

I have an Avistar 40 set up with the FS-48 diesel. With a 13 oz tank I expect it to fly for over an hour at WOT. Maybe get some video tomorrow.

Knocking upon opening the throttle is pretty much unavoidable, but the smaller ones, FS-26,30, are not as bad. In larger engines this gets worse. I think the largest that can be tuned well is around .80ci. I've not worked on the FS-91 for a couple years, but it was difficult to get tuned to where it didn't sound like it was going to punch a rod through the block any second. I think the knocking is simply due to better scavenging in a four stroke. It's just over compressed for the short while RPM hasn't caught up to the throttle setting. And two strokes are tuned so rich that we just don't experience it.

VT-21 probably can't be converted. I haven't measured one, but by looking I don't think the compression ratio can be increased enough.

Here are some youtube four stroke diesels.

The first is my FS-48 conversion.

http://www.youtube.com/watch?v=qHySiHjCUuY

These two are not mine.

DeVries VT-1D

http://www.youtube.com/watch?v=MRJ05ucMii8

Laser 80 diesel
http://www.youtube.com/watch?v=huVUhkl16fE

Recycled Flyer

Hi Mr Cox,
Current theory holds that when a model diesel fuel charge ignited it did it all in one go - as in the entire combustables either ignited or they didn't.

But something that Bob Davis alluded to ages ago with baffle top piston being unsuitable for diesel conversions due to partial pre-ignition makes me think of your situation.

When you have an irregular combustion chamber shape then parts of it will be very much hotter than others, parts like the exhaust valve.

Now I don't know for sure but perhaps when a rapid change from idle occurs it excerbates (makes the difference more apparent) a condition that is only present in a very small amount when running under full throttle.

Ibeleive that a diesel charge can ignite from multiple point sources - and is not always a singular global 'bang' eminating from a central area. Whatever is hottest or more compressed will be the source of combustion.

So perhaps you have, under steady idle, just one point of initial combustion and when you accelerate that point shifts or doubles up when a wetter mixture temporarily increases the compression ratio.

Hard to prove any of this of course sinc e its just my opinion and I don't know of any way to solve it either.

Cheers.

[email protected]

Here is my Enya four stroke .41 diesel on the test stand. My first four stroke. Easy to start by hand with a Zinger 12/7 prop. Would be nice to have variable compression. Jack

AMB

Greg and the rest of the group have an ASP 52 4strk mounted on its side in a VMAR Apache lll . easy swap 4 engine mount bolts and change out the fuel and clunk lines for diesel fuel this is a new airframe never flown only static run.wth engine on its side
cowled over the top does not have that trainer look with engine sticking up in front of the windscreen looks pretty clean martin

Mr Cox

Thanks for the Youtube links. The HP VT is probably unnecessarily tricky with the rotating cam. I do like their softer exhaust tone though.

Looking at the movies, it seems that there is also lot of smoke when there is knocking. So it is not simply an early ignition (that would not give any smoke as the fuel is burnt, just a bit too early) but more like it is too rich. So it might just be getting too much fuel when the carb is opened from idle?
There might not be any need to get into details about hot spots in the combustion camber, etc.

Hobbsy

My Feedback: (102)

The first time I ran my Saito .80 on Davis ABC mix, actually the 2nd time too, at about 5,500 rpm it sounded like it was going to become a Black and Gold grenade. This was using a 13x6 Scimitar prop. I thought a larger prop would make it worse but much to my surprise a Bolly 13.5x8 and a Master Airscrew K-14x8 eliminated the awful knocking. I'll see if I have a 15x6 to try.
Martin, I'm taking Lynda to Richmond today for her final cast, this one custom fit for her to wear the rest of her life.

gkamysz

My Feedback: (19)

Mr. Cox, it sounds like you have a four stroke diesel conversion in your future.

Mr Cox

Yes, damn, another thing I didn't know that I needed...

I have recently moved and I "found" enough engines to last me a lifetime. [X(]

AMB

Seems the 4 stroke does have that occasional metallic ping on mine that Greg converted most goes away on adjusting compression
but you still get a few, interesting enougth the video of the Laser 4 strk 80 diesel made the same sound the combustion area in the 4 strk being different that the 2 stroke may set off a pre-ignition now and then but do not think any cause for concern, I have heard it in full size diesels too martin

gkamysz

My Feedback: (19)

I really do think the clatter is unavoidable to some extent. It could be simply cycle to cycle variations in mixture that cause the occasional ping even at a steady RPM. I will have new video later.

gkamysz

My Feedback: (19)

Here you are.

[youtube]http://www.youtube.com/watch?v=hs4SZtYY9Io[/youtube]

DeviousDave

I forgot what a nice field your club has...

I'm gonna call you tomorrow, Greg..