Hi diesel lovers:
Is there anyone out there making diesel conversion heads?
Thanks, John

I've made a few great performance and fuel economy however I couldn't deal with the smell in my shop. No mater how careful cleaning, plugging the exhaust and carb eventually the smell permeated the shop. Even storing the fuel and 3 planes I had in the shed the wife complained the smell gave her a headache.

If you are looking for one or more, I have quite a few as well as about 12 gallons of diesel fuel. PM me if interested.

I’d be in the market for a diesel head for an OS 10FP, Enya 40CX, or even an Enya SS30BB...

But I probably should save my money for a PAW 55BR though - they aren’t cheap and get snatched up before I can get to them usually.

Just my opinion that converting a glow engine to diesel may not work as well as one would like. The higher compression ratio of the diesel creates much more stress on the connecting rods and wrist pin. I converted a K&B Sportster .28 to diesel operation. The power increase was not as significant as I expected and in fairly short order, the diesel operation beat up the cheap non-bushed connecting rod ends. Pick the glow engine carefully for a very robust rod and crank. Also glow engines ported for very high rpm don't always do as well when converted to diesel.. In my experience, it is usually better to just buy a good quality diesel to start with rather than try to convert a glow engine.

While I do agree to a point, converted glow engines are an inexpensive way to get “into” diesels. Diesels aren’t for everyone, so getting your feet wet for the cost of a conversion head and a quart of fuel is pretty little compared to a purpose built diesel. However not all glow engines make good conversions.

I disagree on the Sportster not being a good diesel conversion. It doesn’t become this adamantium infused beast, but they do gain an edge over the glow plug side with being able to pull an even bigger prop without much consequence. However, the fuel composition and needle/compression settings are critical. If you run it over compressed constantly and improper fuel composition, sure, you’ll wipe the rod out. Those rods are pretty stout even though they aren’t bushed. I have a .20 and .28 Sportster diesels - they are sweethearts with glow plugs and even sweeter as diesels.

The Sportster .28 I have used a conversion head from Davis Diesel Development . It would start and run fine. As you stated, it must not be over compressed, and plenty of ether and castor oil is needed. The Sportster connecting rod, cylinder/case and piston used a high silicon content aluminum alloy which worked OK for glow use but was not as good as bronze bushings. Without bushings, it did not last nearly as long as a diesel than it would have lasted as a glow before it got real loose. Never broke a rod, just wore out the journals. One way to tell if a diesel is over compressed is to look at the exhaust. It it is black (due to soot) then it is over compressed. Normally, when run at the correct compression setting and with fuel containing an adequate amount of ether, the engine will have a slight miss or skip occasionally and the exhaust residue should look like clear honey.

As for recommending engines designed as diesels rather than conversions, I have had better success with engines specifically designed as diesels. I have two PAW 1cc ball race RC engines that are little gems. Easy to start and will idle down to <2500 rpm, even when mounted inverted. I also have a MP Jet 1cc diesel that absolutely screams. It turns an APC 7x3 at 16,800 and makes over 0.2 BHP. Not bad for a 1cc engine (.061). The nice thing about diesels is they will idle reliably inverted just as well as upright since there is no glow plug to quench if the idle mixture is too rich. With a diesel, if the idle mixture is too rich and fuel starts accumulating, it just boosts the compression hydraulically so that it still fires.

My biggest problem with diesels is getting good fuel locally and keeping it fresh. I keep having to add di-ethyl ether to "freshen" the fuel to where it will start and run without being over compressed. Getting good ether is not as easy as it used to be thanks to all the meth labs.. Now I have to get it from John Deere as cans of starter fluid which also has butane/heptane in it too. Also, the amyl nitrate or isopropyl nitrate typically added as an ignition improver (about 2-3%) is hard to obtain because they are chemically similar to nitro glycerin and BATF takes a dim view of modelers having it. However, Diesel Clean Cetane Booster (available at Walmart) can be substituted at 4% instead.

Diesel fuel should be stored in metal or glass containers with a good sealing cap. This is the most important factor in running diesels to keep the fuel “good”. I use old acetone and denatured alcohol metal quart cans to store my fuel. The caps seal well without extra help, though I do wrap the threads of the can with Teflon tape for a little “insurance”. This has served me well - my current can of fuel is 3 years old and still runs as good today as it did when I mixed it. Diesel fuel isn’t readily available anymore, so I just mix my own just as you do - from John Deere ether. I treat the decanted liquid as pure and mix it as such, which again, has proved well for me. I mix my own glow fuel as well; mainly for the cost, secondly for putting in exactly what I want out in. The cost of commercial fuel - glow or diesel, is far more expensive to buy pre-made than to mix myself. The mix I use in all of my diesels (all conversions currently) is 30% ether, 22% castor, 46% kerosene, and 2% Amsoil Cetane Boost. The propellants in the ether cans gas off very quickly when the liquid is decanted, and the light distillate in the ether is minuscule, so it’s not even worth factoring it into the equation.

Thanks 1QwkSport2.5r,

I only keep my fuel in metal cans because I am old and tend to accidently drop things. Glass jars of ether dropped on concrete shop floors near heater pilot lights is not a good thing. I hate it when it does that.... I will try the Teflon tape... good idea... hadn't thought of that... should work fine. Do you have any information on how long diesel fuel will last if left unopened? I have a gallon of Red Max diesel fuel (metal can) that has never been opened but is about 15 years old. Shaking the can feels like it is still pretty full, so I suspect most of the ether is still in it.

David

David - as with glow fuel, if the bottle/can is totally sealed, it should stay good for a long ass time. With diesel fuel, I judge the fuel by how easy the engine is to start. If you have to crank the compression way up just to start it, chances are the ether content has dropped. If you can prime the piston and get it to fire within a few flicks, the fuel is probably fine.

I tried to find the hazards associated with long term storage of diesel fuel. Apparently the hazard is that diethyl ether can form explosive/shock sensitive ethylidene peroxide when exposed to air and light. Thus, it is not safe to store in glass bottles or jars. The Red Max diesel fuel web page says to store it in a cool dark place, the boiling point is 100 degrees F and it also warns that explosive peroxide formation is possible. This suggests that FHS does not use ether stabilizers in the fuel such as NaOH or FeSO4 to prevent formation of peroxides. It also states to not use the fuel if it is past its expiration date and to be careful opening the can. However, my cans do not have any expiration date. Anyone seen an expiration date on their cans and know when it was purchased to be able to establish the shelf life?

Kindly post what heads you wish to sell.

Tia

Super Tigre 3000 - (4)
Marked M90 - (possibly OS 90) - (2)
OS 108 (marked M108) - (1)
Marked M (possibly OS 61 FSR) - (1)
Marked M60 (same diameter as above) - (1)
Marked M40 (for OS 40/45 FSR) - (2)
Irvine 53 - (1)
Super Tigre 75/90 - (1)
Sealed Gallons of Davis Diesel Fuel - (12)

Thanks for the information.

Franchi

What do you need to get for the ST .90 head?

Indeed, there is conversion heads, and they are American made for:
Enya, OS new and old (cross flow), Super Tiger, ASP, MVVS, etc.

Enya 30 ss

Os 32 s, lapped piston

Os 10 fsr

Os 25 la