I have come into the possession of a new, in box Evo.36. I had one of these when they first came out and called it the Evil.36! It came with the PT-19 that Horizon was introducing at the tome (also a less than stellar product.) I tried to break in the engine as per instructions but the thing ran away soooooo bad it wasn't funny, and was in fact scary. I have recounted the story several times here on the forums. At the time I was wondering if the crank case was porous and leaking air really badly some where. I eventually added a back plate gasket, and took the large venturi and drilled it for a OS needle valve assembly and did away with the rear needle valve. The engine was better but still didn't act right. I should have just packed it up and sent it back to the factory at my first troubles, but by this time it was too late. The only prop I had any success with was the APC 10.5-5 stiletto shaped prop. Eventually, a guy who used to hang out at our field just HAD to have it, so I traded him the engine for a ready to fly Sakitumi and LA.40. One of the best deals I ever made!
    I can't remember too much about that first edition of the engine. The one I have now has three venturis with rear needle valve set up like the original. The venturis are tall, and have a spigot type fitting on them for the fuel line to hook up to.  The box art shows a short venturi with a spray bar installed behind itto hold it it in true venturi fashion. I'm thinking that is what my first version was like.  Is there anyone out there that has used these thing extensively that is familiar with the breed and history? I thought that they quit making them but Horizon still shows them on their website and those photos look like my engine. I'm curious as to whether or not a major change was made to the engine and may have been part of my problem. I'm not sure I want to go through the break in drill and get re-acquainted with these again or not. Maybe somebody has something out there that I can use and would trade me for it. I don't like having just one engine of any kind.
   Type at you later,
    Dan McEntee

Dan, my experience with my first Evo 36 was the same, ran away on a twister and shook it bad. I did not give up on this engine and one day after about another  quart of fuel on the test bench it just changed. Runs smoothed out just like it broke in all of a sudden. I have one on a P-40 that I love, tons of power. I used the medium sized blue venturi and screwed a os 1a remote needle in it.

This is a great example of being able to learn something or confirm your theories by just paying attention to what other people are doing. People had all sorts of problems with the Evo 36 and almost universally concluded that the venturis were all way too big.

      But the real problem was that it was developed using Cool Power - which has much less viscosity than normal stunt fuel. With the large venturis it just couldn't manage to suck enough stunt fuel to keep running, hence, runaway after runaway.   The corollary is that you could run much bigger venturis if you could reduce the fuel system drag, or alternately, get much smoother runs with the same venturi/power. This more-or-less confirmed what David and I had been fiddling with for years, specifically, that reducing the drag on the fuel system could have a marked effect on the run.

   BTW, I got the first real data about this running a 20FP on the bench using heated Wesson oil instead of castor (for my friends kid's science project) - it ran great, but as the fuel cooled down, the needle had to be moved further and further out until it finally just fell out, well before the fuel got to ambient. That's when I got the idea for the fuel pre-heater.

       Brett

     Have they changed the style and size of the venturi? This is just a curiosity on my part. I think the originals looked like the one in the box art. I tried ALL sorts of fuel with that first one and got the same results. The first run was on SIG Champion 10% with no muffler, like I think I remember the instructions saying. When I started it, it was just screaming and like I mentioned was kind of scary. The first ones had a pin in the needle so it would only turn one way or the other 1 turn. That came out with a pair of pliers and the next attempt had me backing the needle all the way out with the engine still screaming. The current instructions still mentions this limiter, and that it was meant as a diagnostic tool. If you couldn't get the engine to run satisfactorily with the factory settings, you were to contact Horizon. I don't know how they expected engines to run the same at different altitudes all over the country as they ran  wherever the "factory" was.. This engine doesn't have the limiting pin. I still think the first one was defective in some manor as it just wouldn't needle at all. Fuel might make a difference in a stunt model in flight with prop load being a variable, but on a bench, I figure you should be able to at least run it and get it to follow a needle valve setting up and down. I've never had an engine of any other kind do that even with a pin hole in the fuel line. The instructions mention using Cool Power, Omega (both Morgan fuels) or Powermaster 5 to 10% nitro. One other consideration is that to me, it's just not a pretty engine! All those finms going every which way and such, and not the lightest thing on  the market. I'll have to give this some more thought. Fred Kreoger was here in February for our Ice-O-Lated contest and he had one that he said he retimed, and had done a lot of them that way to get what he wanted out of them. If I remember correctly, he said that the timing one each individual engine was different as he checked each one at the time he did the modifications. I'll have to contact him again just for the information.
   Thanks a lot,
    Dan McEntee

I asked what fuel are you using, because I initially ignored the instructions in the manual stating to use Cool Power and instead ran GMA Powermaster 10/22....and got the same sort of results I've read about on these forums. Once I made the switch to Cool Power the change was like night and day. I drilled the case for a conventional NVA going through the venturi (Delrin. .272" bore, .156 diameter spray bar). I wasn't crazy about all the goofy fins either, so machined the outside of the head round and then used a disc sander to sand the fins on the back of the case even with the head. Dropped the weight to 8.2 oz. and in my opinion looks better. This is one of my favorite engines (I've got six of them now). Other than drilling the case for the NVA, this engine has dead stock timing and compression. One big advantage of running the Cool Power is the increased fuel economy. It is significant. I've also got 6 of the Magnum XLS .36, 4 Thunder Tiger Pro .36 and 2 Aero Tiger .36 and have had plenty of time spent running them back to back. The Aero Tigers are way more flexible in all the different ways they can be set up and run. After that, I like the Evolution .36, then the Magnum .36 XLS followed by the Thunder Tiger Pro.

I've also run one with the Jim Lee Venturi and NVA (true Venturi) and it runs just the same as mine. I just don't like how it positions the needle valve height.

Chris

    I'm bringing this back up for some more discussion because I have had some more experience with these in the last month. A local guy who, along with his dad, have joined our club. His dad is a retread having flown models of several kinds over the years but his son is new to C/L models. He has a Twister with an Evo .36 on it. The first time I saw him fly the airplane, it sounded just like mine, running erratic on the ground and in the air, turning 4 second laps and he was just white knuckle flying it and hanging on. He crashed the model once because it quit in a loop on him, and he repaired the model and has it flying again. That first time I saw the airplane I suggested a APC 10-4 prop be tried out on the engine ( he had a Zinger 10-6 on it) and explained what was happening  when it was running to him. We started the engine and it still ran away a bit on the ground and was erratic, but got it launched and in the air. After about two laps, it cooled off and settled into a really nice run and it slowed down to a 5 or 5.2 lap time. He can't do anything other than loops, but I could see an immediate smile on his face as he maneuvered it around in climbs and dives and a loop or two. When he landed, he was still all smiles and asked what happened! I explained it all to him again and I think he understood what I was telling him. About a dozen or more flights, all with SIG Champion 10% fuel, and it has broken in to where it sounds the same sitting on the ground before launch as it does in the air. He has a Perfect 4 ounce wedge tank on it and only gets about 4 minutes run time, but now that he is flying more relaxed and confident, I'll work him up to a Sullivan 6 ounce RST tank plumbed for uniflow and we'll start work on other maneuvers.
   Seeing and experiencing all of this has given me new hope for the Evo .36 I have in my stash. I got it out this weekend and put it on a test stand with a 9-4 prop and a 4 ounce tank and fired it up. I did put a sleeve made form 7/32" aluminum tubing in in the smallest venturi ( I think it measured .225?) to help with fuel draw after reading what was posted on this thread, and used Cool Power 10%. It started right away and ran quite nicely, needling any where I wanted it to go. The EXACT opposite of what my first experience was with an Evo.36! I let the tank run out after running in a wet 2 stroke for the duration of the tank. With all those fins, it cooled off to where I could hold the cylinder with my hand in about two minutes. I pulled the sleeve out and filled the tank with cool Power again and fired it up. I adjusted the needle for the same run and it was in the upper 12,000 RPM range with that prop, but running in a nice wet-2. I let the tank expire again and cooled it off.
   i ran about two more tanks full of fuel that way and the exhaust was already running clean and when I pinched the fuel line, even on the second run, it came back to the needle setting immediately. After about 6 tanks of fuel, I tried Omega 10% and it ran exactly the same, almost to the single digit on RPM. Then I ran it on SIG 10% Champion, and again, it ran exactly the same and at the same needle setting. Needless to say I was quite pleased. I've mounted the engine in my Hanger 9 PT-19 where I had the first one and will try flying it next time out.
   All this still leads me to believe that I had a defective engine on the first one. and that leads me back again to the reason for this thread, and that is, have there been any significant changes in the engine since first introduced? My current instructions had NO mention of any break in, where my first one did, I'm pretty sure, and recommended Cool Power,  Omega, and Powermaster fuel, although it didn't state what blend of Powermaster fuel. It didn't even give a basic needle setting. But the end result was that through my experience with engines, I was able to get it started and running in what I called an acceptable run.
   I noticed in almost all of the responses from you guys that like the engine, none of you are running it in an "out of the box" form, and have all done some sort of modification to it. I think that since it's marketed and sold as a control line stunt engine, it should do the job to a certain level with out a lot of hassle. Even the venerable Fox .35, if operating instructions were followed and operated per those instruction, would perform as advertised. I have had good luck with the ST.51 in stock form right out of the box. I have hopes that, from what I have witnessed in the new guy's model, that mine will  perform as advertised in stock form right out of the box.
   I had been thinking about the comments that the engine was "designed around Cool Power fuel."  I just couldn't wrap my mind around that, even though I know you need different fuels for older, iron engines, modern ABC types, etc. We talk and concentrate mostly on total oil content, and my thinking was all in that context as far as model engines go. I also mess around with vintage dirt bikes. In fueling those, I have been using a concentrate oil in my premix that is a synthetic, and that allows you to mix it it a ratio up to 100 to 1. I never mixed it in those ratios but know guys that have and had no issues. I had read comments that if used in mixtures in that ranges, the carbs needed to be re-jetted leaner, because now there was more gasoline in the mixture and the bike would run rich. Some vintage bikes were run on oil in as much as a 32 to 1 , or more or less 30% oil I think, and on a few bikes I had like that, I experienced just that problem. I had to significantly jet the carbs leaner to get a good, clean burn and good looking spark plug. I applied that kind of thinking to this fuel discussion and realized that we are dealing with the same thing some times, only the opposite.  Brett put it in terms that call it "fuel viscosity" and that is what I could understand. But in thinking about it in terms like my dirt bikes, on a modern model engine with the different metallurgy and closer tolerances, the higher oil content fuels meant LESS alcohol, the fuel, and thus will run in a leaner condition, and with less room for the oil to do it's job to lubricate and carry away heat, the engine heats up and runs away. The alcohol in itself has cooling and lubrication properties and with less of it in the mixture, the engine can't perform as designed.
   What I don't understand now is why this new engine seemed to run the same on the higher content oil fuels, as it did on the lower content fuels. unless the first two or three runs were enough to run the engine in to where any fuel will "fit" inside the engine. Frank McCune had a thread where he had a batch of fuel he mixed up that would not start in his engines. He thought he had a component problem, but it turns out he added twice as much oil as what he needed. He could prime the engines with other good fuel to start and it would then run on his incorrect mixture. I just wonder that if my thinking is on the right track, if he had opened the needle valve far enough, he would have reached a point where he would have had enough alcohol in the mix for the engine to start on the incorrect mixture? This all isn't incredibly ground breaking territory or earth shattering news but may help me figure out a problem in the future with a problematic engine. I hope to get out with mine as soon as possible to see how it runs in the air now after a dozen or so bench runs.
  Type at you later,
  Dan McEntee

Dosnt it Go Well , Fred K.

If I had one Id send it to YOU . 

Doesn't running higher content oil raise the compression since the oil doesn't atomize, in effect reducing the effective volume of the combustion chamber? Adding head shims compensates for that at the cost of changing the timing. Running a 10 x 4 prop at higher rpm may allow a fuel mixture with more oil to run ok since the prop doesn't load the engine as much and can be run leaner without heating up as much. My Magnum .28 will turn an APC 10 x 4 at 12000 rpm. I'm curious how it performs in the air with the higher content oil...especially would like to hear the results with a larger prop launching at about 10000 rpm.
Chris