I have a evolution .46, The manual says to run 10-15% nitro, I have a gallon of unopened Curtis youngblood (30% nitro 23% synthentic oil) left over from my helicopter days (last year). With the price of fuel these days I'd sure like to use it. Can it be used on my evolution engine?

Buy a gallon of 0% and mix them together. That'll drop it to 15%.

zbiird68
Won't hurt a thing just a waste of nitro. Like piper said mixe it with a gallon of FAI.

I would think that you would get some diseling affect with that much nitro

That's easily solved by using a colder plug or increasing the head clearance.

Quite true but fuel consumption with that much nitro will be horrific so the best thing to do is blend it with a much lower content, preferably the zero nitro if you can find it.

30% is too much nitro. All of the manuals I have seen thus far (Thunder Tiger, OS, Magnum, Super Tigre) recommend no more than 20% nitromethane, and most of them say that if you are going to use more you need to make adjustments to the engine (timing?). Mixing what you have with some 0% will give you a great deal on 2 gallons of 15%, which is probably perfect for what you need.

The adjustment is usually a couple of head gaskets and a colder plug. Exactly what PiperChuck said.

You can mix it but I'd try to sell or trade it to someone at your club who can use it and go with some regular old 10% fuel.

Thats strange, I run it in all my airplane engines w/o problems. We get it in bulk though so cost is similar to people using 15 percent buying single bottles though.

Nothing wrong with trying and seeing how it performs I guess. Wouldn't more nitro give the engine a little more "bang"? My Evo .46 runs great on 15%. Try using a colder plug though, like others said.

All the guys (except me - 15%) run 30% in their engines.... Doesn't seem to cause a problem yet. They still use the same plug too.

Your mileage may vary.

I usually run some high performance engines and use 30%. When I fly a my introductory trainer for prospective members on training night I use the same fuel and have never had a problem. You can actually get the engine to run a bit cooler on the higher nitro as you can richen the mixture a little more without giving up power. Set the engine correctly and you shouldn't have problems.

Hi!
OK ! Here we go!
All two stroke glow engines are made to run good on 0-15% nitro. All European engines like MVVS ,Super Tigre (pre Chinese) OPS and Irvine engines doesn't like much nitro at all, if any! Some MVVS engines like the older 15cc MVVS doesn't even like 5% nitro and run best on 0% nitro, The newer MVVS 15cc with blue drive washer can cope with 15% nitro though .

All modern Chinese and Japanese engines like OS , Magnum, ASP, SC, Kyosho GX can cope with 0-16% nitro without problem. The problem using higher nitro contents in these engines is you risk getting the igniting point wrong which means that the engine will be very difficult to set properly. Setting the high speed needle will be nearly impossible because the engine will abruptly die.

Using 30% nitro is a total waste of money and will only make the engine draw more fuel, will cost more and will make the engine very hard to set properly it the engine isn't set up for this high amount of nitro.

You better mix the 30% nitro fuel with straight fuel so you at least get 15%nitro...And then mix that 15% fuel with 0% so you get 7% nitro fuel.

I accidentally fueled an OS 91FX with 30% fuel and almost cooked the engine. You could have cooked a steak on the head. Got lucky, didn't ruin it. I would cut the fuel with 0% like said and use that.

Thats because you were running it too lean. You have to open the needle somewhat, the more nitro you add the richer you need to run it. It wasn't the fuel. We routinely run 30 percent in our helicopter engines from 32's to 91's. Its a matter of proper tuning. I ran it in my 91 that was in my Funtana, all my Saito 4 strokes (they reccomend it), and my OS 108 in my Funtana 100x

Do you need it? No. It will use more fuel (see above about running a richer needle setting), it will cost more.

But higher nitro makes the engine idle better and tuning is LESS critical than with lower nitro.

Nitromethane contains nitrogen dixoide (nitrite) and as such brings more oxygen to the chamber. The limiting factor in just about any internal combustion engine is how much air you can get into the cylinder(s). This is what turbo-boosters in cars doincrease airflow into the combustion chamber (and some cool the air down on the way in, making it more dense). One can almost always introduce more fuel into the mixture by turning up the fuel pump, or opening the needle valves as it were on our engines.
So when you increase nitromethane without opening up the needle valve, you are actually running the engine leaner because there is an immediate increase in the amount of available oxygen to burn the fuel. In order to compensate for this, one would have to open up the needle valve to allow more fuel in to get the fuel to air ratio back to an acceptable level.

The benefits of nitromethane are more power (because you are able to burn more fuel at once) and better idle (more oxygen available to burn the fuel, even when the carb barrel is almost closed.

the needle setting was fine, I run 30% in all of my Saito's. Another flyer did the same thing in his FX and had the same results.

Hi!
You are comparing apples to pears!
All Saito four strokes and perhaps even some OS , ASP and Magnum engine can be run on 30% nitro but there are very few two strokes that will function properly as standard using that amount of nitro.
The problem isn't running the engine lean. As has been said above you open the high speed needle to set the engine, the problem is the ignition point. Running too much nitro makes the ignition point come to early which make the flame front hit the up going piston making the engine run very erraticly.
Try running an engine on 15% nitro that isn't set up for high nitro contents and you will see what I mean.

As the needle valve is opened more to richen the mixture out, you are introducing more fuel/air into the chamber. This makes the compression higher in the chamber because you are introducing more material to compress. If the compression gets too high, then the fuel will pre-ignige as Jaka has mentioned, and the engine will not run smoothly (car engines will knock). This can be solved by adding shims under the head (to increase the ignition chamber) or running a colder plug to try and make the fuel ignite later.

All that said, until you actually run the fuel you will not know how your particular engine responds. run a tank and see what happens. If it gets too hot, even after richening it up, then don't use it again. If it runs eratically, then don't use it again. If you find it too hard to get the needle set (because more nitro usually makes the needle valve more sensitive), then don't use it again. You can always try one tank, and then cut the rest with some 0% later if you want. I don't think you will do any irrevocable damage to the engine by running one tank through it if you keep a good eye on it to make sure it isn't getting too hot or running too poorly.

As Jaka mentioned, saito's love nitro. I think they would run on straight nitromethane if you had some LOL (J/K)

on buy 30% for my saito 125 works great and then i use it in my evo 46 (i not buying and hualing 2 gallons of fuel) the evo seems to like it alot and i use os hot plugs

That's why I suggested diluting the fuel in my first post. However, since this is a beginner's forum, rather than ignoring a follow up comment, I decided to provide additional information. And actually, the fuel consumption will go up, but not all that much.

Actually, Andy's suggestion that the engine was too lean is also valid. A third fix for pre-ignition, that I forgot to mention, is simply richening up the mixture. Adding the extra fuel keeps the air/fuel mix cooler, thus avoiding the early burn. Unfortunately, this also has the effect of wasting fuel and results in lower power output than getting the right head clearance and/or glow plug.

And since we've been discussing pre-ignition, it's important to note that in addition to making the engine run erratically, as Jan said, it will cause damage. One of the things that happens is that the explosions from pre-ignition cause pitting on the top of the piston and the head.

I once ran two engines on 100% nitro. That is not a typo - 100%. No oil just nitro. It was an accident (my brother fueled the engines from the wrong tin) but it was really interesting. One was a SuperTigre G15 and the other an Australian Taipan 15. They were in control line combat models. The Taipan ran for about 2 minutes until it seized. It was producing about twice its normal power and the model was going about 50% faster than normal. Sounded amazing. After it seized the G15 went up. It was running really lean and as a result was only running about half the time. SCREAM ... silence ... SCREAM ... silence etc etc. This lasted for about 1 minute until it threw a blade off the TopFlite nylon 7 x 6 prop. The Solafilm covered model then self destructed from the vibration in the air until my brother flew it into the ground to stop the engine. I still have the G15 and it still runs. The Taipan freed up once it cooled but it was never the same. I always thought that glow engines needed some methanol to keep the plug glowing but these two engines ran (I won't say perfectly happily) and produced vast power on 100% nitro. I suspect they were running so hot, they did not need the plug to be glowing. I have seen speed fliers use up to 70% nitro with 10% methanol and 20% oil. The resultant fuel looks like French salad dressing. The nitro will not dissolve the caster oil. They used to put their fuel on their car engines to warm it up so that it would mix better. Please do not try this at home. (It was fun though.)

I've got a G15 and 2 of the Taipans but I don't think I'll try that . I believe the Taipan was intended to run on 40% nitro and a figure I've heard said it would then give something over .6HP at around 22,000 revs. I suspect your engines kept running because the compressions were too high for straight nitro and they may have been dieseling (auto-ignition) without needing the plug to be glowing. Straight nitro will only handle 6:1 compression before wanting to detonate. Good story though .