Fuel for IC engines

[John-Som]

The question of choice of fuel for model IC engines is a subject that, to my knowledge, has not been aired very much on this forum. Having just completed building Jan Ridders 'Simple Two Stroke' I attempted to follow Jan's advice and use Colemans fuel used primarily for camping stoves. With no local stockists I resorted to buying online which with shipping costs worked out very expensive.

An internet search lead me to Aspen fuel available as 2T, a ready mix for two strokes and 4T, yes you've guessed it, for 4 stroke engines. As we run our engines mainly indoors then a more refined fuel such as Aspen would appear to be a sensible choice free from sulphur, benzene and aromatics (solvents).  An added bonus is that it does not smell, the exhausts does not smell, it will not smoke and you are breathing a much cleaner air when running your engines indoors.

Aspen is available in 1litre and 5 litre packs and is much less expensive than Colemans. It was far from a controlled experiment but I felt my engine ran very sweetly on a much leaner mixture extending the running time on a fill of the vapour carb. Regardless of which fuel I have tried, including unleaded petrol, there is a strong tendency for the engine to seize if left standing for any length of time. Oil added to the cylinder bore and piston rod being essential to avoid seizure.

Further info at http://www.aaoil.co.uk/environment-Aspen-2T-alkylate-petrol

Any other thoughts on this subject ?

John-Som
 

[Bogstandard]

As we have previously discussed John, when I used to run model 4 stroke ic engines, I used to use the late Bob Shores method of top end and piston lubrication, and my engines really liked the mix.

Just to let everyone know the magic formula, it was a 10% mix for running the engine in (2 tankfuls) and a 5% addition for running after that. Oh!, and the magic ingredient, WD40.

Make sure you give it a shake before use. I personally would only mix up enough for a couple of runs, I never liked mixing up full batches because normal pump gas has a tendency to go stale and not work if left for a while, but your Aspen fuel doesn't seem to matter how old it is, it will still run OK.

Now one thing I have a worry over.

This mix works great for standard carbs, as it is being physically atomised just before entry into the cylinder. I don't know if the WD40 trick would work in a Vapour Carb, it just might not get atomised with the vapour and just be left as a residue at the bottom of the tank. That would be one thing that needs trying out.

Other than that issue, the Aspen gas really looks to be the one to go for in the UK, and when I start into ic again (in the not too distant future), I for one will be using it.

Thanks for the link John


John

[raynerd]

John, I know I`m not too knowledgeable about this hobby but I agree, I`m planning on the vapour carb and expect that the WD40 will not leave the fuel tank. My understanding is that with a standard (venturi) carb, the fuel is being atomised, that being actively turned into a mist by being pulled through the carb - similar to perfume dispencer/bottle. With a vapour carb, you seem to be running off the vapour that is being generated by the disturbance of the fuel, I don`t expect the WD40 lubricants will evapourate.

This is an interesting conversation and I`d like to know more. I`m just about to build my fuel tank/vapour carb with one way return valve and my intention was to run colemans.   

John-Som - I suprised you couldn`t get colemans - I know a couple of shops that stock it near me. 

[raynerd]

John-som - where did you get your Aspen 2T alkylate petrol ready-mixed (2%) from?

[John-Som]

It is hard to imagine WD40 evaporating but you could say the same about engine oil. OK so we could give any concoction a try in the vapour carb but we wouldn't really be any wiser in terms of lubricating properties. I shall try John's WD40 a try to see if it reduces the tendency for the engine to seize up when left overnight. I was amazed at the force required to break the bond. In the case of my engine it appears to be the piston rod seal that sticks. Perhaps if I had stuck with Jan's recommended PTFE seal I may not have had such a problem. I made mine from phosphor bronze in an effort to gain an improved seal.

Apart from all that my 'Simple Two Stroke' runs happily on Colemans, Aspen or straight unleaded, which with a dash of Castrol R40 produces that nostalgic heady aroma of the pit paddock of years gone by. For the main I shall stick with Aspen on the grounds of convenience, economy and freedom from noxious fumes.

John-Som

[Rustkolector]

John,
Fuel/oil mixtures should work in Jan's vapor carb. According to "Raoults Law" of partial vapor pressures, heavier hydrocarbons such as oils, will vaporize in near the same proportions as contained in the liquid fuel mixture. I think you will find that Jan Ridder discovered this for himself and wrote about it relative to his most recent 2 stroke engine. I have tried the vapor carb and it works very well with camp fuel. I found that it is best suited for short demo runs. It gets pretty cold from the vaporization process, and prefers to warm up a little between runs. I like to run most of my engines for rather long periods so it isn't ideal for those engines. 

Don't forget propane as a model engine fuel. I have had very good luck with camp fuel, but after trying propane it has become my preferred 4 stroke fuel. It cannot, however, but used if the engine requires a fuel/oil mix. With propane, the engine exhaust is almost odorless, engines start very easily (no choking), will never flood the engine, and exceptionally clean combustion.

Jeff

[John-Som]

Hi Craynerd

I bought mine at Beaver Plant in Stamford Bridge, near York. Check out http://www.aaoil.co.uk for your nearest stockist but phone before travelling (yes bitter experience !).

John-Som

[raynerd]

Hi John, thanks for the advice but I rang around and managed to get some yesterday. I have a few local stockists and I could only get 5L which is far too much but I have it now.


Jeff, your info on Raoults Law is really interesting. So fromwiki: "as the number of components in a solution increases, the individual vapor pressures decrease". So that is why heavier hydrocarbons that normally wouldn`t vapourise on their own, will when when mixed with other fuel components they will. Wiki again "If a pure solute which has zero vapor pressure (it will not evaporate) is dissolved in a solvent, the vapor pressure of the final solution will be lower than that of the pure solvent". So WD40 could possibly evaporate when added with the other fuel components. Nice one - I didn`t know anything about that.

 

[dbvandy]

I have two vapor carbs on my two engines and the wd-40 gets sucked right into the engine with very little remaining in the tanks. 

Doug

[Bogstandard]

Thanks for that info Doug.

Problem solved before even becoming a problem.


John

[cfellows]

I can validate Doug's findings.  I too use WD40 mixed with Coleman in vapor fuel tanks on my two IC engines.  After many hours of running, I've never had a problem.

Chuck

[raynerd]

Excellent info, thanks for sharing.

Chris