With the potential nitro shortage and or cost increase, I wonder if raising the compression on common US market engines like OS 46’s to convert to methanol only would work on these engines to retain near nitro performance. I know the OS makes an ethanol engine already, but what about those in circulation. Something like an exchange program, the customer sends in his cylinder head (cherry condition or pay full price) and the customer gets back a head that has it’s deck, squish band, dome (reduced volume dome) reconfigured with maybe an anodize color to signify the conversion.

What do ya guys think?
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You'll probably find that the current crop of OS 2-stroke engines already work pretty well on 0% nitro.

Easier than making a whole new head would be to simply skim the existing head a little where it mates with the liner. This would require a lathe but I dare say that if there's a demand, someone will start offering that service.

FF,


Trying to re-invent the wheel, huh?!


All European engines, as they come from the factory, are designed to use fuel with 0% nitro, without any problem whatsoever.

Some makes (Webra), due to wanting to sell to the nitro-guzzlin' North America market, have adjusted their compression slightly, to accommodate up to 10% nitro (15% running at a richer mixture setting...).
Prior to this, all engines were designed to use just 0% nitro, with up to 5% usable for improved reliability in competition. Adding a head shim will allow using higher nitro in any engine (at a slight efficiency loss).
A small percentage of nitro, will not measurably add much power.

These engine can still use 0% with no hitch.


REMEMBER; all these (from all makes) are not 'Nitro Engines' and they never were.

They are glow ignition engines, which rely on platinum's catalytic effect of methanol break-down, to cause their glow element to remain lit. Nitromethane is not a necessity, but methanol is very much so.

Most engines and your OS46 will run nice on 0% nitro as it comes from the box. All you have to do is changing the glowplug for a hotter one OSF, Enya3 och OSA3.
If you like you can remove the head shim and see if you can squeeze out a few more rpm at peak.

I woujldn't bother the nitro shortage will be over after this summer. Unless you intend to use lower nito from now on that is.

Actually the plug also has a catalytic effect with nitro, but it is not be as strong. I know that they have ran engines with 80% nitro and 20% synthetic oil, I think 70% nitro is the max for castor oil based fuel because any more and the castor oil falls out of solution.

XJet and Flyer95, I know they run "Nice" on 0%. If I liked just nice, I would have been running 0% for years. Perhaps I should have been more clear on that.

Dar, I’m very well aware of the 0% European engines, that’s why I said "US market engines ". I wish we never had nitro in our glow engines.
I have a Moki "Mark" that likes 5% on a cool day 0% on a hot one. And I had 3 Webra 55s now only two. I lost one when the crank let go several years ago, perhaps due to too much nitro (15%).
I found out the they liked 10% max. At 15% they ran strong but even stronger on 10%, glow plug last much, much longer. (tried every heat range before) easier to tune.

Most of the engines for our market have one head gasket, and if you try to remove it / thin it, the piston is too close or will hit the squish band. (besides the head may leak with no gasket).

I guess what my main question is, is the only thing different between a nitro and a non nitro glow engine is the dome volume in the head?

Generally speaking, if you don't change the shape of the squish dome you are pretty much okay. You are just changing the volume slightly by adding or subtracting shims. Changing the shape, such as modifying the shoulder of the dome, is another story altogether.

There are so many factories that export nitro that I doubt there will be a genuine shortage. We have factories in the U.S. too.

If you want more than nice power then put a tuned pipe on your engines and gain atleast 1000rpm on the smaller ones. The piston will not hit the head if you remove the gasket otherwise the gasket would not be ramovable. No much risk for head leaking on a high quality engine once carefully tighten the head screws in cross. A fuel containing castor oil is also very helpfull when running 0% nitro.

Quote:

ORIGINAL: freakingfast

I guess what my main question is, is the only thing different between a nitro and a non nitro glow engine is the dome volume in the head?

FF,


I guess I should ask a real expert to chime-in... A racing engine builder... Bob Brassell, maybe?

Higher nitro fuel does require a larger combustion chamber volume (lower compression), but it also 'prefers' a smaller deck clearance.

Adding head shims to allow more nitro does decrease compression, but it increases the deck clearance.
This is why 'alky engines' don't run as well, if shimmed up to allow nitro fuel.


Adding shims is the easy way, but if an engine producer really wants to optimize his engine for higher nitro, a different head (lower squish-band with a larger dome) is a much better solution. This goes the other way, if lower nitro fuel is desired

But do they sell nitro for fuel? There are no US factories that sell racing fuel, though they may sell for hobby fuel. VP has quit selling hobby fuel so that they may help with the shortage for racing fuel. I doubt the shortage will last past this summer.

Idealy the squish band should be the same for high nitro and low nitro. But adding a shim makes the squish band taller, but one or two shims should not make a huge differance. It also depends on how well the fuel atomizes in the engine as well. Because of that this will make less differance in the summer than the winter.

Klotz sells nitro in gallon cans. I love "nitro guzzling" North American engines. Been using them for sixty years...love the smell of nitro in the morning.

"Smells like victory"? Sorry couldn't resist.[sm=red_smile.gif]

The "squish band" also known as the quench area of a head can have a big effect on any engine. If you look at a modern 4 stroke automotive engine you will see an almost heart shaped quench area as opposed to the older open chamber designs. Here is a photo of my new Aviastar .46 check out the quench area. These engines respond well to FAI fuel.

Quote:

ORIGINAL: C185Pilot

...I love "nitro guzzling" North American engines. Been using them for sixty years...love the smell of nitro in the morning.

C-185 Pilot,


Shouldn't that be NAPALM???

Also, engines in the USA of 20-30 years ago used to be set up to run 5-10% nitro and in fact, any engine from Europe would be usable as-is in the USA... Fox and K&B sport engines were and still are set up to use 5% nitro.

In the last two decades, a negative trait has set in, of people seeking instant gratification and having no patience and no will to learn how to do things right. Everyone wants everything to be easy; very much so, in fact.

When running on 15% nitro, which is by and large the most common and widely available model fuel in the North America today; even if you don't adjust your engine perfectly (or more likely - don't know how to do it), you would still have your engine responding decently to throttle inputs.

Do the same with 0-5% nitro and your plane would be dead-sticking 90% of the time...

Just over 20 years ago, 15% nitro was relatively more expensive than it is today, simply because it was not as popular and was only produced in very small quantities...


You were only chugging down high nitro, if you were 'rooster tailing' in boat racing, or racing in some F1 classes that specifically allowed high nitro fuels.

If not, you were probably using 5-10% like everyone else...

Don't forget cars running high nitro.

Don't forget the 1/2A engines that ran 20 to 30%. Heck I can't get a Pee Wee .020 to start on anything less than 20%!!

Actually that was only true of the engines since the early 80's. Before that the stunt engines used mostly low nitro and the high performance engines were set up for the 25% nitro Missle Mist. Many of the early K&B engines were set up for 20-25% nitro also, though they ran nice on 10%, not worth a darn on 0%.

You're both right, Barry and Jeffie.

But... I was referring only to "real" engines...


Car engines and R/C cars in general, only became popular in the last decade, or so.

With the exception of tether cars spinning a prop, with a Rossi RIRE .60, does anyone remember any model cars more than 15 years ago?


And those 'mechanical mosquitoes' that run on an eye dropper of fuel, do use only high nitro, but their fuel was never offered to someone flying a sport .40 engine (for example), because it contained too much nitro and too much oil.

Quote:

ORIGINAL: Sport_Pilot

...Actually, that was only true of the engines since the early '80s. Before that the stunt engines used mostly low nitro and the high performance engines were set up for the 25% nitro Missile Mist. Many of the early K&B engines were set up for 20-25% nitro also, though they ran nice on 10%, not worth a darn on 0%.

Actually, Hugh, the K&B 6.5 engine (tested in 1977) got top marks from Peter Chinn, in MAN magazine; throwing everyone off the podium and getting the highest RPM on a 10x6 prop... On just 5% nitro.

The later 7.5 DF engine did use high nitro, however.

The standard .40 and .61 engines did (and still do) run very well on 5% also, their recommended fuel.

I remember RC cars in the 70's, but they were not popular and almost entirely hand built. I think Dupro or someone sold coil over shocks and there were some body manufactures but you had to solder the frame togethere, there may have beens some kits as well.

I have 3 K&B Sportsters a .20 a .28 and a .45. The .20 is an early version and the others are middle of the road so to speak. All my Sporty's love lots of nitro. I am trying to find a way to make really thin head gaskets so I can up the compression a little and get them to run better on FAI fuel.

Thats almost a new engine in my book. I am thinking of the engines from the late 60's or so. They may have run on 5%, maybe very well but I recall the pattern guys were mostly using 10 to 20%. I think K&B recommended their 500 fuel, would that be 12 or 15%?

Napalm? What a great suggestion. I'm going to try it in my no nitro Euro engines...I'll let you know the results...might make the engines a little needley tho.