hookedonrc

As I begin my move from glow to gas engines I have been looking at the gas to oil mixtures. Right now I have a DLE20, DLE 30, and a Zenoah G26. All of these call for mixtures that allow for a 30 to 1 mixture. However, my next purchase may be the Evolution GX10 that calls for no more than 20 to 1. For those of you that have numerous gas engines, do you consider this factor? Or just understand that you will have multiple gas cans sitting around with different mixtures?

Pelle Gris

All my engines (ZG-62, GT80, King 140) runs at 50:1 mix. So only one fuel jug needed.

Zeeb

My Feedback: (41)

Well that particular engine requirement could create some issues. When I faced the same question, the "richest" oil ratio was 32:1 for one particular engine brand during break in then 40:1 after. I went to 32:1 dino oil for everything including the weedeater, leaf blower and chainsaw. Stihl didn't like the idea of that much oil in the saw but it runs fine. I'm 'bout out of the dino oil and even the new engines from DA and such can take synthetic oils, so I'll be converting to Stihl Ultra synthetic oil at 40:1 for one particular brand that is not recommended at 50:1 and all my other two cycle engines will run the same stuff.

Your new engine at 20:1 presents a problem IMHO. I'd either reconsider that engine or resign yourself to at least two gas cans. I cannot see runing other engines at 20:1 and leaner (oil mix) will probably cook the little Evo....

Truckracer

My Feedback: (19)

I run every air cooled engine I own on Stihl Ultra @ 32:1 with zero issues. If I owned one of the smaller engines that require 20:1, I'd need an additional can. But look at it this way, those 20:1 engines are quite small and don't use much gas. You can get by with a very small gas can for these smaller engines.

hookedonrc

it sounds like i may be resigned to just having separate gas cans. So that makes 3 with 1 glow and 2 gas. Of course that doesn't count the other 3 I have for the riding lawnmower for a total of 6....LOL The written information on the EVO indicates any other ratio voids the warranty. Even it if wasn't the cause of a failure I don't want to risk the warranty being voided. And as truckracer says, it won't use that much fuel anyway.

irocbsa

My Feedback: (12)

I definitely consider this factor. It's the reason I'm not interested in either of the smaller Evolution or Norvel engines. I don't want to drag a third can of fuel to the field.

All Day Dan

My Feedback: (5)

Truck,
Truck, at what point is there too much oil? I use Stihl HP Ultra at the recommended 50:1. I assume that the engine manufacturer does not know what oil you are going to use. How can they recommend a ratio? Dan.

Truckracer

My Feedback: (19)

I'm not sure I can answer your question Dan. I settled on 32:1 because some of my engines prefer that mix though others would be perfectly happy at 50:1. Frankly from looking at engine internals, for the most part I can't see any difference in an engine running the same high quality oil at 32:1 or 50:1. If anything, the engines may have a bit less carbon when running 32:1 and any carbon seems to be softer. I can't even detect any difference in the amount of oil residue on the underside of the plane which is minimal at both mix ratios. I'm sure the professionals that run engines for a living can report the effects of running too much oil but for me, I haven't seen a problem yet.

tkg

My Feedback: (1)

When I was racing Karts everybody thought that they would get more power at 40:1, including me.More gas , less oil = a more powerful fuel mix Until I stumbled across a paper by Gorden Jennings. After hours of dyno time he found 16:1 made the most power.
I changed to 16:1 and held the track record for 2 years. 16:1 might be a bit messier than 40:1, but 409 is cheap

All Day Dan

My Feedback: (5)

Truck, after running my engines for the past few years at 50:1, I decided to decarbonize the pistons using that Ethel Glycol cooking method. The carbon has covered all of their entire piston tops and is very hard. It takes over eight hours cooking them in a slow cooker set at High to get it off. Why would a mixture of 32:1 reduce the carbon build up? That’s more of an oil content. I thought the carbon was a byproduct of the oil. Dan.

Truckracer

My Feedback: (19)

More oil going through the engine seems to have a solvent action on the carbon. True, the carbon buildup is a product of combustion but the fuel flow seems to counteract that a bit. You may have noticed on the tops of pistons there can be clean shiny aluminum where the incoming fuel / air charge enters the cylinder from the transfer ports. This is even more pronounced when additional oil is used. Regarding carbon buildup on the tops of pistons, I don't worry about this very much unless it gets really heavy. Most of the time, this carbon is just the soft, almost powdery kind that partly wipes off and the remainder is easily removed by any one of several mechanical means. I do get concerned if I see a carbon buildup in the ring lands though! Most engine inspections over the last few years has shown very little to almost no carbon in this area which I attribute to quality oil and not overheating the engine.

Back in the days when Tired Old Man and the Jedi were still here on RCU, they discussed this subject several times. Maybe you can find some archives of their discussions.

All Day Dan

My Feedback: (5)

Good point, Truck, Here are images of two pistons I am working on. They verify what you have said about the intake side being clear. The carbon does not sand and can not be scraped off. The cooking process cleaned them. The others I have are much worse. I decided to do them all at once but one at a time. The others were much worse. Actually the hardest part was working with those "C" shaped clip rings. Thanks for your input. Dan.

larry@coyotenet

My Feedback: (21)

Very simple explanation. 32 to 1 runs cooler than 50 to1. The cooler you run the less baked on carbon. The engines I have had apart that had been run lean, which equals hot! had baked hard carbon deposits. The oil type can also have an impact if you get a lean run. Synthetics can develop hard deposits if overheated. Check on some of the older posts on oils when there were some really expert comments by guys who no longer post here due to the oil nazis nasty remarks.
Larry

dadragon

I wont get into the oil debate but my breakins are 32:1 then 40:1 on avgas LL100.(Penz airkooled).

Truckracer

My Feedback: (19)

Dan, from what I can see in your photos, that is not excessive carbon at all. The top of the ring is just barely visible in the photos and it appears void of carbon which is good. If you could post photos of the piston skirt and ringland areas especially the exhaust port side along with the bottom of the piston, especially under the dome but above the connecting rod. These would tell the story more completely. But at first glance, I wouldn't even bother to remove the small amount of carbon visible in the photos.

dadragon

since you got it apart you mite want to think about putting a Bowman ring on,that would be a good upgrade,just a thought.

Truckracer

My Feedback: (19)

I would agree with that statement for many engines but it is hard to beat the original equipment Sachs / Mahl components that Brison used. You just don't see poor ring seal or low compression in these engines unless there is some kind of user induced problem.

All Day Dan

My Feedback: (5)

Good recommendations. I’m done removing the carbon from the pistons in my six Brison 3.2s that I use interchangeably. None of them had any carbon down the skirt above the ring. All the cylinders were clean. The Mahle cylinders and piston assemblies have survived countless hours of running over the years with no sign of wearing out. I did change a piston ring or two just as a precaution when some dirt got in from an off field landing and nose over. Even then, the cylinders looked good. I did use Bowman’s rings as the replacements. These engines supply more than enough power for my 20 to 24 pound planes. Even if they are wearing out they are doing it very gently and I don’t notice it. I’m more interested in reliability and landing in one piece over “unlimited vertical” performance. OK, I’m convinced. I upped my oil content to 32 to one and will continue to so. While we are on the subject, does octane number have anything to do with carbon build up? I use 87. Thanks guys.

Whiskey Bravo

My Feedback: (31)

[QUOTE=Truckracer;11653539]I run every air cooled engine I own on Stihl Ultra @ 32:1 with zero issues.
+1
I also raced karts many years ago and TKG knows what he is talking about.

Nitrovein

No matter what brand you use there is some good info here; http://www.youtube.com/watch?v=f0zPhPfLpoY

As mentioned before, there have been several tests done on dyno and more oil equals more power. Here's the test mentioned before in this thread; http://www.bridgestonemotorcycle.com...oilpremix6.pdf

All Day Dan

My Feedback: (5)

Nitro, thanks for the article. The results are definitely contrary to popular belief.
“Engine output and piston cleanness improves as premix oil content is increased”.
Dan.