Graham,

Yeah, CT's Cetane booster seems suspect in light of this.

http://householdproducts.nlm.nih.gov...bl=chem&id=188

I looked into the components of Mineral Spirits and found that the trimethyl stuff was in there already in about the right amounts. I'll elaborate further why I looked into what mineral spirits are.

But notice that this stuff (trimeth) is used in a wide range of products, including its use as an OCTANE booster. ***?, as they say in less polite circles. Don't know. Going to have to revisit the issue. Maybe call the company on Monday. That should prove to be interesting.

Agree to all comments re using at least some ether. But the issue in that, is throttling. The less we have of the ether, the greater the difference between idle and top end as far as optimum compression ratio. Recall that as we idled down, the engine ran with a burble and sometimes didn't accelerate cleanly. Upping the compression at idle smoothed things out but then we find the compression too high for full bore.

So it appeared that as we reduced the cetane number of the mix, as in less ether, compression at idle became inadequate. However, in some mixes, the Amsoil "cetane booster" was upped to 10% and this supposed boost in cetane, made the situation worse. This is contradictory to adding ether to boost cetane.

So it begs the question, are "cetane boosters" like the Amsoil product really boosting the cetane number of the mix? Or, as the above implies, they don't actually do that but operate by being ignition improvers.

To clarify that.

Adding ether makes starting easier and running smoother by raising the cetane number of the overall mix.

Adding diesel ignition improvers do the same but really don't raise the cetane number of the mix but operate by improving ignition in some entirely different fashion.

But note that unlike Amyl nitrate, more than 2% of the Amsoil CB was good,,, didn't hurt, for smoother running.

It appears that with lots of ether to boost the cetane, the ether acted to cool the engine at full bore more than at idle. At idle, the cooling effect of the high ether was less effective (less fuel being processed) and so the cylinder temperature was more constant between full bore and idle and thus didn't require a higher compression ratio at idle.

Using lots of Amsoil "cetane booster" to boost the cetane, didn't have this cooling effect and so, it ran hotter at full bore and required a looser compression setting. At idle, as the engine cooled considerably, the compression needed to be tightened up to get a smooth run.

Using no/low ether, the engine runs hotter at full bore and so, the compression needs to be backed off. At idle, the engine cools considerably and now the compression needs to be tightened up to get a good run.

In the experiment on the .074 where I added considerably more fin area, the effect was to keep the engine cooler at full bore, (because of prop blast) and mimic the action of a high ether mix. Reduced prop blast at idle, allowed the engine to run a bit hotter, and thus the cylinder temperature between full bore and idle was closer, one to the other. And thus, the compression setting required between idle and full bore could be closer to each other allowing for more consistent throttling.

The final solution to no ether mixes may be more cooling fin area along with a mix that mimics the action of the ether. This is why I tried the lacquer thinner in one of my tests. We aren't really wanting to run an all kero mix necessarily but want to eliminate the ether as it's a troublesome, expensive ingredient. A cheaper, more readily available ingredient along with engine design may be the direction we need to go in.

As suggested by Kelly, maybe white gas or an Aliphatic thinner or BBQ lighter fluid will be that ingredient.

Yesterday, we tried most of the above. The results were quite interesting and will be reported on in due course.

BTW, coconut oil remains in suspension in kerosene at below 70F at 30% concentration. !!!! Hmmm. Looks like the fat man is lingering at the stadium. Maybe, as coconut oil is radically different from other SVOs, we have some possibilities here.

Just to stir things up more, Luke, local tinkerer extraordinare, converted his OS .40 to diesel. He's reported smooth running, good power and excellent idle on a mix of 80% kerosene, 10% ether and 10% corn oil straight from the fridge. [sm=50_50.gif] Yeah, I know, but that's what he said.