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Jun 17, 2019, 03:51 AM
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Oil percentage when running CDI and glow Fuel


Anyone have any numbers on this?
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Jun 17, 2019, 05:21 AM
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I use the same as for a glow plug ignited engine. 10% nitro methane and 18% synthetic lube.

I am sure others will chime in who use various blends.
Jun 17, 2019, 05:34 AM
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I thought I read somewhere, but can’t find it now that there is a technical reason why it can be reduced significantly.
I have reduced it slightly from 18% to 15% and can’t see any difference in the amount in the crankcase after a run.
Jun 17, 2019, 11:49 AM
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Last edited by SeismicCWave; Jun 18, 2019 at 01:12 PM.
Jun 17, 2019, 12:16 PM
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Originally Posted by SeismicCWave
I am not sure why anyone wants to reduce the amount of oil in their methanol fuel. I always believe in more oil won't hurt. You are not going to see much difference in the amount of slime going from 18% to 15% oil. Oil is there to protect the engine.

That said I run 20 percent oil in my methanol fuel no matter what kind of ignition. I run 15% oil in my E85 because that is for my big block Super Tigre 3000 only. That is on CDI. So far no problem with engine wearing out.

If you use too little oil and the engine wears out faster you will not notice it until months or years later and it is too late.
Ideally, for combustion reasons we would have zero oil in our fuel. Oil does nothing to help combustion, and in fact hinders it by fouling the plugs.
I personally don’t have an issue with the minor amount of oil I need to wipe from the wings. I was referring to the oil in the crankcase being the same.
I realise that oil is there to protect the engine and have always used 18%-20% because that is what is recommended by most.

My question was more about there being a technical reason if once on CDI that oil % can be reduced. As I said, I can’t find the piece I read regarding it now as I wasn’t to interested in CDI at the time. (I think it was something about not having lean runs anymore, as the engine will simply just stop running before damage , as compared to glow ignition )

Why is it that gassers can run 5% oil content? It’s not because the gasoline ( petrol ) has so much more lubrication over methanol to warrant a 15% drop in oil content
Last edited by sailortoo; Jun 17, 2019 at 12:32 PM.
Jun 17, 2019, 01:06 PM
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I currently run 14% oil / 5% nitro in my FT160 twin on CDI. Runs sweet, plenty of oil in the crankcase.
Jun 17, 2019, 01:06 PM
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Last edited by SeismicCWave; Jun 18, 2019 at 01:12 PM.
Jun 17, 2019, 01:54 PM
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Quote:
Originally Posted by sailortoo
Ideally, for combustion reasons we would have zero oil in our fuel. Oil does nothing to help combustion, and in fact hinders it by fouling the plugs.
I personally donít have an issue with the minor amount of oil I need to wipe from the wings. I was referring to the oil in the crankcase being the same.
I realise that oil is there to protect the engine and have always used 18%-20% because that is what is recommended by most.

My question was more about there being a technical reason if once on CDI that oil % can be reduced. As I said, I canít find the piece I read regarding it now as I wasnít to interested in CDI at the time. (I think it was something about not having lean runs anymore, as the engine will simply just stop running before damage , as compared to glow ignition )

Why is it that gassers can run 5% oil content? Itís not because the gasoline ( petrol ) has so much more lubrication over methanol to warrant a 15% drop in oil content
Your question is quite valid. For years people ran 20% to 25% oil because.. .....
Because we always did, because a little more is better than a little less, etc.

Regarding gasoline, gasoline itself has intrinsic lubricating qualities not present in methanol. Gasoline is by nature less corrosive as well. With gasoline, less fuel is passing thru the engine so total oiling is diminished as well.

Conversely, the methanol/ CDI is flowing more fuel and more oil at any given power setting. The 14% oil, at 2% castor has been completely adequate for all of my medium to larger 4 strokes. Wear is not at all a problem, these engines look great at hours where some factory fueled engines are looking bling in tooth!

In the past, when using methanol CDI, the 14% was what I used.

The one fellow who has done a load of time with 4 Stroke methanol fueled CDI is Dave, AKA " Sr Telemaster" Perhaps he can shed some light from his experience. You could try a PM, his input should be valuable.
Jun 17, 2019, 04:39 PM
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Quote:
Originally Posted by sailortoo
My question was more about there being a technical reason if once on CDI that oil % can be reduced.
I think I read somewhere that because the spark timing/ignition is more precise than glow ignition the engine runs cooler and does not need as much oil for cooling or lubrication.
Jun 17, 2019, 04:42 PM
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Gasoline/petrol has lubrication plus a gasoline engine typically spins at a lower RPM. I believe RPM is one of the main factor in the percentage of oil in an engine. Surface area ratio will be another factor. The larger the engine the less surface area as a ratio of volume.

Huh?
I acknowledged petrol has some lubrication, but 15% less oil, really?
You comment makes no sense.
Same engine One on gas , one on Methanol. If anything the gasser will have more RPM.

Just correcting , I appreciate your opinion.
Jun 17, 2019, 04:43 PM
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I've read on these forums that the mechanics of Glow Ignition mandate the higher oil content, vs the controlled ignition of CDI, however, I cannot quote the source.
Jun 17, 2019, 05:03 PM
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Quote:
Originally Posted by sailortoo
Gasoline/petrol has lubrication plus a gasoline engine typically spins at a lower RPM. I believe RPM is one of the main factor in the percentage of oil in an engine. Surface area ratio will be another factor. The larger the engine the less surface area as a ratio of volume.

Huh?
I acknowledged petrol has some lubrication, but 15% less oil, really?
You comment makes no sense.
Same engine One on gas , one on Methanol. If anything the gasser will have more RPM.

Just correcting , I appreciate your opinion.

Not sure to whom your statement was directed?
Jun 17, 2019, 05:09 PM
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Last edited by SeismicCWave; Jun 18, 2019 at 01:12 PM.
Jun 17, 2019, 05:12 PM
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Last edited by SeismicCWave; Jun 18, 2019 at 01:13 PM.
Jun 17, 2019, 05:20 PM
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The other differences can be the metallurgy, which have inherent properties related to running conditions / operating temperatures / thermal efficiency, etc. As well as the type / makeup of the lubricant.


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