How Much Oil Should You Use In The Fuel?

[Steve Hargreaves - Moderator]

I remember when Model Technics brought out Dynaglo fuel in the 80's......people threw their hands up in horror at the low oil content but I remember engines running very well on it with good throttling & noticeably more power. I believe the extra oil is mainly to protect the unwary from setting their engines too lean....

[Jon H]

Pretty much Steve

Its difficult for us because we have customers who manage to seize engines up when running 20% oil...or at least what they claim is 20%. Home brew fuel is often an issue as working out oil % seems to fox a great many people and there is also no way to be sure if they are getting good quality ingredients.

Serious overheating and/or lean running are also not things we can control and additional oil in the fuel will provide extra protection but only in that some heat is taken away by the waste oil expelled from the exhaust.

In general, if you have sufficient lubrication to prevent seizure adding more oil will not improve the situation when it comes to lubricating the parts when hot or cold as you already had enough to begin with. The only time it becomes important is if you have a lubricant that will either burn, or evaporate above a certain temperature. In that instance you might loose a % of your oil in hotspots within the engine and so the amount left may not be enough. But, if your oil is so poor quality, or your engine so hot that this happens you only have yourself to blame anyway!

[Former Member]

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[Jon H]

Personally i would use the Laser 5 fuel in that engine too. You dont need 10% nitro and 15% oil will be fine. My saito 45 has been running on it for 3 years, and although i have not currently got any OS 4 strokes in service if i bring my OS 91 back into use i will use the same fuel without hesitation.

A number of guys at my club have converted to this fuel and are running all brands (OS, irvine, Enya, Saito, ASP) on it for over a year. One of the ASP 52 4 strokes is in a wot trainer and has run all its life on this fuel, including running in. I also ditched the running in instructions and ran it in like a Laser but slightly softer. After a full season its still got good compression and will easily run 20 minutes in the wot before a refuel is needed.

if you do switch, the exhaust oil will reduce and will be less sticky as there is no castor in the Laser 5 fuel. Fuel consumption will reduce due to reduced oil content (oil takes up space for no power) and the reduced nitro content. You will have to lean off both needles, but use my video before as a reference. Tune top end for max rpm, then throttle back to idle and stuff the throttle open. If it picks up lean it off and keep going doing this until it bogs down. A reasonable idle for the 95 should be no more than 2200rpm and if you use a big prop im sure 1800 would be achievable. Dont do a nose up test, just go and fly. If the engine goes a touch lean in the vertical land and richen by one click, at most 2, then have another go. if the engine runs leaner at the end of the flight than at the start lower the tank by 1/4 inch, retune and start again. a little time spent setting it all up will pay you back 10 fold as you will never have engine trouble again. Unless you ingest a bee or something!

Also, there is no such thing as 2 stroke or 4 stroke fuel. Its all a marketing ploy

[Cuban8]

Well, I'm sold on the idea. It's Laser 5 fuel for my fourstrokes next year; trouble is, where to get it? Mail order?

[David Davis]

I've only had two problems with engines that could perhaps be related to oil content.

One was with an HP VT 21 in a Junior 60. This engine, no longer made, is a rotary valve four-stroke, with steel cylinder and a Dykes ringed piston. I was demonstrating it to a group of lads when the piston ring seized stopping the engine immediately. I was using fuel with15% synthetic oil. The Model Engine Company of America, (MECOA) stock HP spares and supplied me with a new piston and ring. They also recommended that I use oil with a high castor oil content. This I continued to do until I sold the engine. Thinking about it, either I had weakened the mixture to much, it did seem to be running very well, or perhaps the engine had not been run in properly. I had bought it second hand.

The second engine was a Merco 35 which I flew for years in a Telemaster 66. I simply wore this one out!

[Jon H]

Posted by Cuban8 on 24/11/2016 09:56:47:

Well, I'm sold on the idea. It's Laser 5 fuel for my fourstrokes next year; trouble is, where to get it? Mail order?

I believe model shop leeds will ship it to you and there are a few others as well. Another option would be to contact model technics directly and see if they can recommend a shop local to you.

David, specialist engines like that will always be hard to recommend fuels for, but you say yourself it was 15% synthetic oil, but which one? its possible the one in the fuel was not up to the task, or, assuming this test was some time ago, it could be that it was an early synthetic which has now matured into a superior product.

ASP and Enya engines have ferrous liner/ring setups like the HP and yet they run very well on the Laser fuel.

[Manish Chandrayan]

Thanks for information on prop and fuel Jon

[Cuban8]

Posted by Manish Chandrayan on 24/11/2016 10:39:22:

Thanks for information on prop and fuel Jon

Yes, second that. Jon's info is always very informative and helps dispel many preconceived ideas that many of us just take as gospel because 'that's how we've always done it'.

 

BTW, just looked at my usual supplier's website (Southern Modelcraft) and they have their version of Laser 5; will stock up at the shows next season.

Edited By Cuban8 on 24/11/2016 11:05:22

[IanN]

Posted by Cuban8 on 24/11/2016 10:58:48:

BTW, just looked at my usual supplier's website (Southern Modelcraft) and they have their version of Laser 5; will stock up at the shows next season.

Southern Modelcraft do both 0 and 5% nitro versions of their "Laser" fuel (both 15% fully synthetic oil)

I've got a coupe of gallons of their"ordinary" stuff still to get through first before I get anymore. However, it sounds like the laser mix might be the way to go

[Jon H]

The SM stuff is pretty good and would be fine but it lacks the SICAL additive MT put in their version. The sical really does improve the running of the engines. Its not something to can see with a tacho or anything like that, the engines just seem to sparkle that little bit more. I was sceptical at first, but changing from SMC fuel to MT did make a noticeable difference, even if its only 1%. Im not saying SM is bad because its not, just that if you have an extra quid to spend (you will if you come down from contest 10!) then the MT fuel does have an edge in performance over the SM.

And Cuban you have hit the nail on the head. So much is now folklore that we dont question practices that were dubious 30 years ago.

Its not just engines, dont get me started on the misuse of expo!

[David Davis]

Posted by IanN on 24/11/2016 11:42:31:

I've got a coupe of gallons of their"ordinary" stuff still to get through first before I get anymore. However, it sounds like the laser mix might be the way to go

That's nothing I've got ten gallons of their 0% nitro Laser mix to use first!.

[Bob Cotsford]

One thing that I've noticed since changing from SMC 5% only using MT Laser 5% on all my two and four strokes is that the exhaust mess on a lot of engines has changed from a sticky brown to a much clearer residue that is easier to clean off. The outside of the engines don't get coked up with brown varnish into the bargain. However with the distinctive odour my clubmates do keep asking where I get my chipfat from .

[chris larkins]

These 2 questions are for John Harper really, firstly I have just obtained what I believe is a Laser 100 from a club member that has had it sitting in a drawer for at least 20 years (he thinks it may be far longer), it had only about 30 mins running before being laid up so is like new and turns over freely. When I say that it's a Laser 100 this is an educated guess as there are absolutely no engravings of any kind to confirm that, the distance from the crankshaft to the top of the rocker box is approx 100mm. John could you confirm that it is a 100 and also take an educated guess as to its vintage? (picture below)

Secondly once I have run it on glow and verified that all is well I am thinking about converting it to petrol (as I have successfully with an Sc 1.20 4 stroke). I know that this is not recommended but if you were to recommend an oil mix what would it be? 1:30 on fully synthetic or more/less?

[Martin Harris - Moderator]

Looks like he ran it on castor based lubrication for that 30 minutes?

If Jon is looking through the archives, perhaps he could answer something that has been puzzling me a little. I've always understood that Lasers aren't marked with their capacity but an old 62 that I have is marked with what appears to be the first owner's initials - and then the numbers 62, in what appears to be matching stamping. Was this original?

[Jon H]

Hi Chris

You have there an old Laser 90 from somewhere around 1988. We discontinued this engine in 1992 and no longer have any spares available. Frankly at this point if its not mechanically sound then its a paperweight and nothing can be done with it unless you fancy making new parts for it yourself.

As for converting to petrol, don't waste your time and money. I have been working for almost 4 years to make our engines run properly on petrol and so far am not satisfied. If I cant make it work, its unlikely to work well for our customers and that is backed up by the increasing number of damaged engines I am getting back following failed attempts to convert them. Irrespective of what you have read or seen advertised, or even done yourself, its not as simple as strapping a cdi to it and having it magically work.

Given the low fuel consumption of an engine of this size there is no advantage to running it on petrol and I would not recommend it at all. In particular, the mechanical issues you will face are going to be significant and I cannot guarantee that the engine will not suffer a mechanical failure even at 20:1 as these old engines are not built to the same spec as our current offerings. Long story short, it wasn't designed for it, we don't recommend it and I personally think its a waste of time and money.

If you wish to have a go then clearly you can, but don't expect great things from it. Sorry if I came across as rather abrupt, but I would rather be dead straight about it than give you some non committal old waffle that leads you to wasting your time and money on a lame duck.

Martin, for a while the 62 and 70 were produced in parallel and we couldn't tell them apart once assembled so the 62 was marked accordingly. For most of 2016 and from now on all Laser engines are now marked with their size.

[chris larkins]

Thanks for your reply John.

The reason that I was thinking of converting to petrol is to try to get away from 3 different power sources that I currently use (Electric/glow/petrol) and stick to just electric & petrol. I own a few petrol engines and I am always impressed with the lack of equipment needed and the distinct lack of fiddling required (usually), they also run very clean and although not quite as important with an engine of this size the fuel is very cheap.

The biggest problem that I have had, along with others, is the fact that the carb on a glow engine is just not designed for use with petrol and although it can be set to run well the needles are so sensitive that just one click either way makes a huge difference.

I am sure you are aware of this already but there is an independent guy selling conversion kits for all popular 4 stroke glow engines, ranging from a full kit to individual parts. Anyway for his Laser conversions he is using a carb from an evolution 10cc petrol engine and supplying it with a machined adaptor to fit the Laser head (picture below). I already have all the parts necessary to do this conversion with the exception of the machined adaptor (I was going to ask a clubmate with a lathe to make this for me).

There are videos of these conversions on youtube and they seem to run well, however if there is a good reason that this is not good for the engine in the long term then I would consider sticking to running it on glow. I would be interested to hear why you think this may result in mechanical failure as this might help me to make my mind up.

[Martin Harris - Moderator]

Posted by chris larkins on 27/11/2016 00:12:51:

Thanks for your reply John.

The reason that I was thinking of converting to petrol is to try to get away from 3 different power sources that I currently use (Electric/glow/petrol) and stick to just electric & petrol. I own a few petrol engines and I am always impressed with the lack of equipment needed and the distinct lack of fiddling required (usually), they also run very clean and although not quite as important with an engine of this size the fuel is very cheap.

It always strikes me as a complicated way to reduce the power output of an engine!

Just a thought - how many conversion attempts have reduced the compression ratio as part of the modifications? I don't think I've ever seen figures for model engines but in the motorcycle world, I think it was common to go from around 11:1 for high performance petrol engines to 14 or 15:1 when running methanol. If our engines are anywhere near this range they will struggle to run on petrol without detonation affecting their operation and reliability.

[Jon H]

Hi Chris

If the conversions are from the chap I think they are then they do not work very well. I have had a number of engines returned following the use of those conversions and the performance is less than satisfactory. I was able to produce the same kits after about 15 minutes work, I then realised they were not good enough about 30 minutes later and went another direction.

To be clear, I have never tried an engine using the evo carb, but given the trouble that carb caused on the evo engine itself, and the fact that horizon changed it very quickly suggests to me that it was not very good.

Like the small saitos that carb is simply a regulator and without a constant pressure behind it its unlikely to perform very well.

One final thing to remember is that a video can be very misleading. I have seen many videos showing our engines running on petrol and they are often shot in a way that shows them off at their best. They start first flick, which is easy if the engine has been run before the camera starts rolling, they show good throttle response, but only from idle to 1/3 throttle as at more than that and the engine will stop, and they show full throttle performance which is usually well down on what it should be. Mid range running is not something you will usually see and that is because they are usually as rough as a badgers backside.

Believe me, if it was a simple as it is made out to be we would be swamped with petrol 4 stroke engines, I would be selling them hand over fist and saito/OS wouldn't have gone to the trouble and significant expense of developing dedicated/custom walbro carbs for their engines.

As for mechanical failure, the risk is quite high as the crank pin was not hardened on those early engines and there is no oil hole in the big end of the rod. As the engine was designed with 20% castor in mind this wasn't a problem at the time.

[Former Member]

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[Jon H]

Hi Tom

Gordon and I have communicated regularly on the subject and I am keeping him updated with my progress and the prototypes I am working on. We have both agreed that the commercially available conversion kits are not up to the task, especially on the V twins. This is because walbro carbs are designed and tuned for each engine they are fitted to. Fit the wrong carb and it wont work properly.

While I personally believe these conversions are a con its not my job to police their sale and I have not made any effort to contact the company involved as it would only ever end in animosity and its nothing to do with me anyway. If he claimed the conversions were authorised by us that would be different, but to my knowledge that is not the case.

Even if my comments about unsatisfactory performance and engine failure are not enough, consider the costs involved. Even if the engine ran well, you are looking at over £100 to covert something like a laser 70. So that's 100 quid to convert a £200 engine to petrol. That is not good value, and given the fuel consumption of a laser 70 it would take a long time, several years probably, for see any cost advantage.

I appreciate that our bigger engines use much more fuel than a 70, but if I fly my 300 and 360v powered warbirds, and 180 powered stampe at a display weekend I may have 10 flights total and will still use only about a gallon of fuel. Personally, I don't consider 15 quid for a weekend of flying a great deal of money, and will spend more than that at the burger van I can assure you!

That said, the market wants petrol and I am working on it, but it is far more complex than it is made out to be. Sure its easy to make an engine run, but to make it run well at all rpm ranges with differing loads etc and to be easy enough to use for someone not expert in engine tuning? That takes time.

Just for curiosity, watch this video and let me know your thoughts on the performance of the engine and if you would buy ones based upon the performance you see.

 

Edited By Jon Harper - Laser Engines on 27/11/2016 21:53:58

[Martin Harris - Moderator]

It seems to tick all the boxes - started fairly quickly, idled slowly, transitioned OK and held around 8000 rpm although I have no idea what (damaged!) prop was fitted - but I bet there's a catch which will illustrate how videos give the wrong impression?

Edited By Martin Harris on 27/11/2016 21:52:51

[ASH.]

Posted by Jon Harper - Laser Engines on 24/11/2016 12:06:30:

"Its not just engines, dont get me started on the misuse of expo!"

Jon, would love to hear your take on it's misuse.

As always I find your posts most informative.

Ash

[Jon H]

Posted by Martin Harris on 27/11/2016 21:51:56:

It seems to tick all the boxes - started fairly quickly, idled slowly, transitioned OK and held around 8000 rpm although I have no idea what (damaged!) prop was fitted - but I bet there's a catch which will illustrate how videos give the wrong impression?

Edited By Martin Harris on 27/11/2016 21:52:51

its an APC 17x8 and it was a cold start, hence the priming

More details to follow

ASH, that's a topic for later and is likely to cause chaos and mahem. Should be fun, start a thread if you like and I will glady rock the apple cart/try to help folk get their settings right

[Former Member]

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