Propwash April 2019 web.pub

pressure. When that happens your pipe pressure won’t push the fuel to the carb and it will have to suck to get it. That is a lean run in the making. Nitro %: What is the best nitr o % to r un? Well, what is the humidity, temperature, your pipe length, what pipe are you running and what is your deck clearance. When it is colder you can NOT burn as high a percentage of nitro as you can in optimum conditions. When it is very humid and hot your engine will NOT make as much HP and scream as it did in better conditions. When you see a guy change his deck clearance, he is adjusting for the current conditions to get the best performance in those conditions. When he changes to a different heat range on the glow plug he is changing the timing. When he puts in a shorter or longer plug he is changing the combustion chamber volume or compression ratio which changes the timing. When he moves his tuned pipe in or out again, he is adjusting for the current conditions or perhaps a different prop. Oil %: What is the best oil %? Well is your engine new and stiff? Is it just broken in or has it got gallons run through it? Are you running an air head or water-cooled head? I have raced as little as 6% to as high as 20% oil in a nitro engine. The books will tell you the larger the engine the less oil % you need to run. Our gas racing engines routinely run 6% oil, but they are almost twice the size of the average nitro engine. You need to select your oil % based on what you are doing with it and experience. I am going to run a different oil % in my brand new $550 OS outboard (yes, they are that expensive now) then I am if I am going for a record with a properly broken in engine and I want everything it has to offer. Less oil is NOT necessarily faster. Oil types: In the old days we had one oil and it was castor . Duke Fox made Missile Mist that was 22% castor oil and it would varnish up a great engine in one contest. Today we have many different manufactures of synthetic oils and of course castor is still around from several sources. The flash point of synthetic oils varies from around 333F to 460 F. Some guys only run synthetic oils, some run a mixture of both. Like everything in life, you get what you pay for. Most fuel blenders use a UCON xxxx lubricant in their products. They are manufactured in large volume for many uses and are very inexpensive. Their labels don’t tell you what the flash point of their oil is and, in some cases, not even the oil %. Why do we care, well the cheaper the oil the lower the flash point. Why do you care, if you are operating above the point your oil flashes and goes out the exhaust port you are about to do grave damage to your favorite go fast engine. Castor oil also has different flash points depending on quality. I have seen it as low as 425 F to the best that I know of at 555 F. Again, experience will dictate what a guy thinks is best when it comes to the type of oil and the % he wants in his fuel. Good oil is the most expensive ingredient in a gallon of fuel. For some time, we have heard how great Red Line oil is, it is expensive, they have very elaborate advertising sheets BUT you can’t get a person or a spec sheet that will say what the properties of their oils are. Some fuel manufactures use Morgan oil. Morgan makes more than one type of oil for nitro blends. Many years ago, I worked with a Klotz engineer. I was very impressed that they were developing a line of oils specifically for model use. Today they have expanded that product line and they test and publish the specifications of their products. Of course, that all cost money so their oils aren’t cheap. I have attached their spec sheets. After Run Oil: Not dir ectly r elated to how your engine is going to run, but directly related to how long it will run well. Getting the methanol out of the engine is of extreme importance (Continued on the following page) Proper Care of Your Fuel Written by Rick Grim Submitted by Mark Grim NAMBA Nitro Chairman We have some new nitro boaters and some that never were taught how to take care of nitro fuel. I have been asked several questions lately about nitro fuel. It occurred to me there are several more boaters that probably would like to know so I am giving a quick history lesson and some current thoughts on fuel today. Mind you some will have a different opinion than mine. I have been blending fuel since I was a teenager. As you might have noticed that was a long time ago. Ingredients: Ther e ar e thr ee key ingr edients in our fuel, nitromethane, methanol and lubricants. Yes, some add rust inhibitors, blenders and antifoaming agents but they are not key ingredients. Containers: In the old days all fuel came in metal cans. They had metal lids and great seals. You can keep fuel in one for many years if not subjected to heat extremes. Why do we care? Well, sunlight deteriorates nitromethane. Methanol is a sponge to water. When you buy that little bottle to pour into your gas tank that swears to remove water from your gas tank it is a form of methanol/alcohol. In today’s world they sell fuel in plastic jugs. Some come with seals, some with a red plug inserted into the neck to help the seal and some with a seal that won’t even keep the fuel in the jug if you tip it over. A sealed jug is very important if you are going to keep your fuel as potent as it can be. When is your fuel its most potent? Right after all the fresh ingredients are blended and the jug is sealed. Every time it is subjected to moisture and sun after that it loses a bit more “go”. Cleanliness: I double filter ever ything that goes into a fuel jug. Why would I do that when everything is new and pure? Well over the years I have found 99.999% pure nitro or methanol, or oil has crap in it. Sometimes so much that it is scary. I don’t think the containers they put their 99.9999% product in are cleaned before use. Even with the above procedure I still use a very fine screen filter in the bottom of my jugs. You won’t see fuel filters in my models unless I need a convenient place to fuel and if that is the case, I will always fuel behind the filter. It is common practice for a guy to pull the line off the carb, fill up the tank and then reattach the line to the carb. All you have done in that case is keep the tank clean. The crud you pumped into the filter is now in the carb and you are cussing your favorite go fast engine because it isn’t going at all. Over the years I have had filters cause a bunch of issues. The less intersections you have in a fuel system the fewer places you can suck air. Fuel Tanks: In other models we isolate fuel tanks from engine vibration, so it doesn’t foam. Foaming fuel will make you crazy trying to troubleshoot as the engine will eventually go lean for no apparent reason. In boats we cram the tanks into small places well below or above the spray bar in the carb. The farther the tank is from the spray bar the more the fuel mixture will change as you burn the fuel level down. Nitro tunnels are very bad in this regard. If your engine is perfect when the tank is full on a tunnel, it will be going lean by the time you get to a ½ tank. Walt Barney, Tanks 2-U, has isolators with his tanks, and you should use them to ensure consistent runs. We don’t know what the engine is being feed when it is out there hauling on the water, but if your engine performance changes with speed you can bet it is a fuel feed issue. Pressure test your tank in a water bucket. Guys forget that the stoppers let go over time and you can only retighten it so many times until it won’t hold PROPWASH April 2019 15