GLOW to PETROL

[Rich Griff]

I though I had asked about this before....

I am on a tight budget, and have in the past bench run a Magnum gp40 glow engine on petrol with about ten to one two stroke oil.

From memory it ran quite well but the glow plug was permanently powered.

I know you can get glow plug size spark plugs and ignition system.

Has anyone experimented with this cheaper and more easily bought fuel ?

[Martin Harris - Moderator]

I believe that many have tried but few have had good results. The main problem seems to be carburation with the smaller fuel volume being very finicky - one click of the needle may take it from too lean to too rich...

[Jon H]

Its really not worth it on an engine so small. You would be better off just buying the glow fuel as its likely to take 10 years to see a cost advantage running petrol. And that assumes you dont bust the engine doing the conversion.

If you want a petrol engine, buy one. Converting glow engines is not as simple as you may have been lead to believe.

[Frank Skilbeck]

You could always try the OS G5 Petrol glow plug and see if that works.

[Rich Griff]

Thanks for the replies.

Will do some more research, to include that is G5 plug.

I live miles from the nearest club who usually stock glow fuel. I know of Weston glow fuel but carriage can be expensive. 4 gallons and it's carriage free, or was, but 4 gallons...

Petrol I can get easily.

The clunk tanks I think can tolerate petrol but what about the clunk fuel pipe which needs to be flexible for the clunk to "clunk" ?

Is the yellow fuel pipe which is petrol tolerant flexible enough ?

Edited By Rich Griff on 15/01/2021 08:20:58

[Frank Skilbeck]

You will need to change all the fuel tubing, including the clunk line. If the tanks have rubber bung or use O ring seals then you will need to change them to petrol compatible ones.

A few years ago a friend built a 1/5th scale Zero he had originally planned to use a big Super Tigre, but changed to a DLE 30cc, he changed all the fuel tubing but forgot the bung which then broke down and petrol leaked inside the model.

[Cuban8]

In over 40 years of being involved with aeromodelling and model glow engines, I've never seen a glow to petrol conversion work satisfactorily. I've seen several very experienced modellers try to go down this route but none have had results that would convince me to bother trying - even with a 'conversion kit' from a well known supplier who advertises such devices widely. I could be wrong but I never recall the late, great, Brian (one flick) Wynch being a big fan of anything other than petrol engines that were actually designed from the outset to run on that fuel and for model use rather than modified weed wackers or whatever.

Shop around for mail order glow fuel, there is quite a difference between suppliers. With no shows to visit last year I got a couple of gallons of Laser 5 delivered by courier for not much more than what it would have cost me to get it personally. Not possible anyway as what model shops that there are within an hours drive didn't stock it or were closed to callers because of you know what.  I got mine from Model Shop Leeds as they had no minimum quantity and 48 hour delivery was only a tenner IIRC.

 

Edited By Cuban8 on 15/01/2021 12:26:10

[Jon H]

Model shop leeds post fuel, as do a few others. Cuban's suggestion of laser 5 is a good one and it would suit your engine very well.

If you buy 4 gallons as long as you store it correctly it will last a year at the very least and likely a good while longer. I have a gallon of fuel for my nitro car which is probably 3 years old and its still ok to use.

[Martin Harris - Moderator]

Dave from Southern Modelcraft told me that if stored in the dark and in sealed containers, unused model fuel (including that containing nitromethane) will last indefinitely.

[Nigel R]

Assuming the container doesn't permit any moisture transfer that makes perfect sense. Only thing that would significantly degrade it is methanol absorbing moisture?

I have 4-gallons-in-one-go (of the fuel that shall not be named) which is now about 3/4 gone after 18 months.

OS 40 FPs seem quite happy on it.

[Phil McCavity]

Posted by Martin Harris - Moderator on 15/01/2021 13:05:41:

Dave from Southern Modelcraft told me that if stored in the dark and in sealed containers, unused model fuel (including that containing nitromethane) will last indefinitely.

I buy fuel from Southern and he told me the same. There seems a lot of urban myth around old model fuel despite being told by producers and credible sources that last seasons fuel and older is fine, the club old sage will still advise to dump it after a year despite this, Model Technics have even quoted that excessive moisture content in fuel is not a major problem because Methanol and Nitro is only "Mildly Hygroscopic".

 

 

Edited By Phil McCavity on 15/01/2021 13:48:22

[Luke Lane]

Weston's fuel is fine, been using it for years. I normally buy 4 half gallons as with low usage it's less likely to get contaminated. Also, when you're about to place an order, ask your club mates if they require some, to share the costs. You'll never get the same power from an engine running on petrol as opposed to glow fuel. I have found that petrol engines below 15cc aren't worth the bother. I dare to say, you can always try one of them new-fangled electric engines.

[Peter Jones 21]

Two problems with glow to petrol conversions and both really relate to the big differences in calorific value.

Basically petrol has much more energy than methanol per unit of measure.

So most glow engine hose the fuel through, this means the jet size is quite big (the needle valve is well out) this high fuel consumption means that to a degree (particularly in 2 strokes) the fuel is contributing to the overall cooling effect in the engine.

So it will come as no surprise that the OS petrol engines have much larger cooling fins than similar glow engines to manage the running temperature.

Get the cooling fins under control and reprofile the needles and use OS specific plugs and you will stand a chance.

Not worth it though IMO.

[Mike T]

Posted by Martin Harris - Moderator on 15/01/2021 13:05:41:

Dave from Southern Modelcraft told me that if stored in the dark and in sealed containers, unused model fuel (including that containing nitromethane) will last indefinitely.

It's a pity, particularly in the current circumstances, that SM are so unbending in their refusal to do mail order. Their fuel is excellent and by far the best value.

Re petrol conversion, I'm not going to repeat what I've posted before (seek and ye shall find) but suffice to say if you have the right engines (big Super Tigres and Mokis are the best) the riht Walbro carb and access to a lathe to turn a simple carb adaptor spigot, then a very satisfactory result can be achieved. I've also used the G5 plug, which works but with a slightly lumpy (and higher rpm) idle. Forget it on anything less than 20cc...

BTW - the primary driver for me in converting was not cost, but reduced mess!

[Phil McCavity]

Posted by Mike T on 15/01/2021 16:36:41:

It's a pity, particularly in the current circumstances, that SM are so unbending in their refusal to do mail order. Their fuel is excellent and by far the best value.

As far as I'm aware Southern Modelcraft have never offered home delivery, only pickup from his home and sales at the shows.

[Jon H]

Posted by Mike T on 15/01/2021 16:36:41:

BTW - the primary driver for me in converting was not cost, but reduced mess!

If that is the goal then its a bit of a waste of time. Small glow 2 strokes converted to petrol tend to need quite a decent slug of oil and they spew said oil (now black) all over.

You are likely to get a decent reduction in the oil residue from the engine by choosing a glow fuel with less oil in it. Certainly 15% is more than enough and it makes a big difference dropping from 18/20% to 15.

[Mike T]

I agree re small engines, which is why I wrote: "big Super Tigres and Mokis are the best..."

When I first got my Moki 210 (the engine I converted), the advice from JE was to run it on no less than 18% oil. It now runs on 5% petroil mix, post-conversion. Yes, the 'effluent' is black, but there's a lot less of it...

[Jon H]

Posted by Mike T on 18/01/2021 14:47:38:

I agree re small engines, which is why I wrote: "big Super Tigres and Mokis are the best..."

When I first got my Moki 210 (the engine I converted), the advice from JE was to run it on no less than 18% oil. It now runs on 5% petroil mix, post-conversion. Yes, the 'effluent' is black, but there's a lot less of it...

most retailers and manufacturers have been very cautious with oil recommendations and glow engines will run on considerably less.

Much is made of the lubrication properties of petrol vs methanol but although petrol is measurably better, its still completely useless in real terms.

In theory, glow engines (4 stroke especially) should need no more oil than a petrol and that is why i am working on testing Lasers with less oil. So far we are down to 7% with total confidence but i am working to lower that further.

[Mike T]

Yeah, I'm pretty sure our relatively high oil content is down to a combination of history and manufacturers/distributors playing it safe. Although you'll doubtless warrant your engines on lower oil, I can't see any others rushing to do so - particularly in the current climate. As an aside, I'm pretty sure that the Saito petrols have bushed little ends, like their glow equivalents, when one might expect them to have rollers....

Any rule-of-thumb on oil content for more 'cooking' motors, like old OS' and ASP/SC? I vaguely recall SM doing a "Double Lube low" oil which was a Synth/Castor mix totalling 12%, but they don't seem to do it any more.

[Roger Jones 3]

Posted by Jon - Laser Engines on 18/01/2021 15:30:50:

 

most retailers and manufacturers have been very cautious with oil recommendations and glow engines will run on considerably less.

Much is made of the lubrication properties of petrol vs methanol but although petrol is measurably better, its still completely useless in real terms.

In theory, glow engines (4 stroke especially) should need no more oil than a petrol and that is why i am working on testing Lasers with less oil. So far we are down to 7% with total confidence but i am working to lower that further.

Your post above and your earlier one are interesting. However, despite what you say, reducing oil content from 20 or 18% to 15% makes very little difference to residue.

But model petrol engines typically use 5% oil and coupled with their much lower fuel consumption the residue reduction is VAST.

And what 'Dave' of Southern Modelcraft says about glow fuel not deteriorating is wrong. Unlike petrol it shouldn't deteriorate  in theory but in practice it most certainly does.

The symptoms are obvious. Detonation (more severe on four strokes) and particularly erratic running on small four strokes - my two OS30 FS engines won't even run steadily on the bench, let alone in the air,  with old glow fuel, but are fine on new fuel.

Both fuels absorb water but this can be avoided by keeping them in metal cans.

One poster suggested moving to electric. Like many others I have done this on small planes. But it's a tremendous faff compared to glow or petrol. Our site is 'public' and has about 300 'registered' fliers in total, though only 5 to 10 turn up at any one time. Over the last three years or so I have noticed that the move from glow to petrol is far larger than the move from glow to electric.

Edited By Roger Jones 3 on 25/01/2021 07:33:42

[Jon H]

In fairness, the cleaner running of the 15% oil fuel i mentioned was coming from an 18% klotz super techniplate oil fuel with 20% of that being castor. The removal of the castor and reducing the synthetic component slightly makes a big difference to the goo, especially if the nitro is also dropped from 10% to 5%.

A number of people i have recommended it to have commented on its cleaner running, especially in their 4 strokes.

On the glow fuel storage, a full never opened bottle will last a long time. not forever, but a long time. You are right though Roger, even totally sealed it can deteriorate and the running problems you mention are what i would expect to see, especially from smaller 30 size 4 strokes.

In the end, a glow engine will never match a petrol for pure fuel economy performance but they have other advantages in other areas. They are certainly easier to cool and we get customers frequently saying they have had to ditch their petrol engines due to noise/the cost of silencing being more than the whole thing is worth in terms of faff, when a glow 4 stroke will do all they need to meet their other criteria.

I guess you pay your money and take your choice!

[Roger Jones 3]

Posted by Jon - Laser Engines on 25/01/2021 08:56:20:

In fairness, the cleaner running of the 15% oil fuel i mentioned was coming from an 18% klotz super techniplate oil fuel with 20% of that being castor. The removal of the castor and reducing the synthetic component slightly makes a big difference to the goo, especially if the nitro is also dropped from 10% to 5%.

A number of people i have recommended it to have commented on its cleaner running, especially in their 4 strokes.

On the glow fuel storage, a full never opened bottle will last a long time. not forever, but a long time. You are right though Roger, even totally sealed it can deteriorate and the running problems you mention are what i would expect to see, especially from smaller 30 size 4 strokes.

In the end, a glow engine will never match a petrol for pure fuel economy performance but they have other advantages in other areas. They are certainly easier to cool and we get customers frequently saying they have had to ditch their petrol engines due to noise/the cost of silencing being more than the whole thing is worth in terms of faff, when a glow 4 stroke will do all they need to meet their other criteria.

I guess you pay your money and take your choice!

I haven't tried petrol yet - many of them are still crude and heavy modified chainsaw engines or things of 'doubtful parentage' and probably non-existent spares availability.

And the price of ALL OS engines have become totally nuts and their spares availability isn't too good either. But most of their clones are total rubbish. You seem to be a valid and not too pricy alternative to OS.

[Chris Walby]

IMHO I can't see the point. Some people irrespective of manufacturer have spent a lot of time and money developing an engine to run on a certain type of fuel be it petrol or glow. These are not just thrown together, but a lot of clever stuff to achieve a powerful, well performing engine that nearly no one can break (if operated as per the manufacturers instructions).

Technology advancements in materials and lubrication allow improvements to be made in a considered way by the manufacturer.

Sorry but I have seen too many JABS in my day that were no more powerful and were less reliable than the original version.

If you want petrol buy that, if you want glow buy that or any other fuel type but why mess with a good engine.

PS - JABS (Just Another Butchered Special)

[Nigel R]

"And the price of ALL OS engines have become totally nuts"

The prices, accounting for inflation and exchange rates, are about what they always used to be.

[GrumpyGnome]

In my opinion, I am not sure all petrol engines are crude or converted chainsaw engines tbh ..... seems to definitely be a growth area and manufacturers are responding.

Similarly, not all OS clones are bad - I have had a number of SC 2 and 4 strokes that were excellent........maybe I have been lucky and had all good ones whilst others have been unlucky and had all bad ones.....

OS engines, and spares have always been, in my opinion, excessively high but if people are willing to pay, why would any manufacturer one not keep prices at that level.

GG