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Model Forum / Radio Controlled / Air Models / March 2010Am I figuring this correctly?
I want to mix up some nitro car fuel (I finally broke down and bought a 1/8th scale nitro buggy to play with in the back yard when I can't go flying). I have some gallons of glow fuel that are 23% nitro and 22% oil. That would leave 55% methanol. Breakdown by ounces (volume) would be 29.5oz of nitro, 28oz. of oil and 70.5oz. of methanol = 128oz. If I add 64oz. of methanol to a gallon of this fuel, I end up with the same 29.5oz of nitro, the same 28oz. of oil, and now 134.5oz. of methanol for a new total of 192 oz. By my calculations, that would give me a decent car fuel of 15.4% nitro, 14.6% oil, and 70% methanol. I remember reading something about the possibility of fuel being mixed by weight versus volume. If that's the case, I'm wondering how far off my calculations would be. The car fuels I see on Tower are offered in 10% oil "Pro", 12% oil "Race", and 14%-18% oil "Basher" mixes. My 14.6% oil mix would put me somewhere on the comfortable side of the oil range if I'm figuring correctly. Thanks for any information, desmobob >I want to mix up some nitro car fuel (I finally broke down and bought a >1/8th scale nitro buggy to play with in the back yard when I can't go [quoted text clipped - 15 lines] >would put me somewhere on the comfortable side of the oil range if I'm >figuring correctly. I think we use volume rather than weight when mixing oil with gasoline for 2-stroke engines. I imagine the same would be true with the nitro-methanol-oil mixture for glow engines. Marty  SignatureBig-8 newsgroups: humanities.*, misc.*, news.*, rec.*, sci.*, soc.*, talk.* See <http://www.big-8.org> for info on how to add or remove newsgroups. >>I want to mix up some nitro car fuel (I finally broke down and bought a >>1/8th scale nitro buggy to play with in the back yard when I can't go [quoted text clipped - 27 lines] > > Marty "We" can but the suppliers we buy our fuel from do not mix by volume. That is one of the reasons my mixed 10% is better (by actual testing) than purchased 10% when 'better' is defined as more RPM on a 2 stroke engine. I think his method is the hard way, but it will work The only thing *I* would do is go high on the oil because cars don't get as much cooling via forced air. But then *I* am anal about some things. >> I think we use volume rather than weight when mixing oil >> with gasoline for 2-stroke engines. >> I imagine the same would be true with the nitro-methanol-oil >> mixture for glow engines. >"We" can but the suppliers we buy our fuel from do not mix by volume. That >is one of the reasons my mixed 10% is better (by actual testing) than >purchased 10% when 'better' is defined as more RPM on a 2 stroke engine. So you mixed by volume and liked the results? That's good! :o) >I think his method is the hard way, but it will work The only thing *I* >would do is go high on the oil because cars don't get as much cooling via >forced air. But then *I* am anal about some things. He can tell us what happens. And then we can all learn from his mistakes. :-O Marty SignatureBig-8 newsgroups: humanities.*, misc.*, news.*, rec.*, sci.*, soc.*, talk.* See <http://www.big-8.org> for info on how to add or remove newsgroups. >>I think his method is the hard way, but it will work The only thing *I* >>would do is go high on the oil because cars don't get as much cooling via [quoted text clipped - 3 lines] > > And then we can all learn from his mistakes. :-O Thanks for the votes of confidence, fellows! ;-) I was surprised to find that car fuels had less lube content than air fuels. I had guessed that the very high-revving, rear-exhaust, enclosed engines would need LOTS of oil. A lot of the mixes have only 10%, so that must not be the case. In my hours of perusing forums, trying to get up to speed on the car stuff, I read that they run poorly on airplane fuels due to the typically high oil content. Who'd of guessed it? (The car engine break-in procedure seems crazy by airplane standards, too... start by running four tank-fulls of fuel through the engine at idle!) My mixing idea seems simple enough to me... I already have a selection of air fuels and a couple of gallons of methanol. It's only for a temporary supply until I order up some car fuel. It might be a tad easier mixing it up from scratch, but I don't have any nitromethane and I doubt I could get it shipped easily or for a good price (I live in a rural area). My buggy is supposed to get here on Monday. I'll let you know how I make out. Good flying, desmobob > I was surprised to find that car fuels had less lube content than air fuels. > I had guessed that the very high-revving, rear-exhaust, enclosed engines > would need LOTS of oil. �A lot of the mixes have only 10%, so that must not > be the case. �In my hours of perusing forums, trying to get up to speed on > the car stuff, I read that they run poorly on airplane fuels due to the > typically high oil content. �Who'd of guessed it? � The only guys who replace or rebuild engines faster than car guys are control line speed flyers... the low oil content is very hard on their motors as far as wear. Most car guys are not engine guys... so they dont realize that an engine taken care of will last for hundreds of hours before needing rework. Bob >> I was surprised to find that car fuels had less lube content than air >> fuels. I had guessed that the very high-revving, rear-exhaust, enclosed [quoted text clipped - 10 lines] > hours before needing rework. > Bob Most car guys are going for performance over longevity. By running only 12 to 15% oil, they can get more power out of the fuel. If they get a whole racing season out of their engines they are lucky. Airplane engines work better with 17 to 20% oil in the fuel. I prefer 18% oil, 15% nitro, and the balance is methanol. Vance SignatureTo reply by email: vhoward1122 at gmail dot com >>>I think his method is the hard way, but it will work The only thing *I* >>>would do is go high on the oil because cars don't get as much cooling via [quoted text clipped - 26 lines] > Good flying, > desmobob The way I heard it explained is that an airplane or heli is under constant power whereas a car is given throttle for a few seconds and then slowing for the next turn. I mixed some of my own fuel by taking a quart of racing fuel mixed with 3 quarts of methanol/oil mix. I mixed it to end up with 16% oil and 7.5% nitro, I use this for my sport practice fuel but I'm not at all disappointed in the performance, it runs very good. I can mix a gallon of 30% to end up with 3 gallons of 10% or 4 gallons of 7.5%. I found someone locally that sold me a drum of methanol for $80, they bought to sell at a go-cart racing track but the track contracted a supplier and they were getting rid of what they had. For bottles, seems I can buy a gallon of Wal-Mart windshield wiper fluid cheaper than I can buy the bottle it comes in. RogerN > The way I heard it explained is that an airplane or heli is under constant > power whereas a car is given throttle for a few seconds and then slowing [quoted text clipped - 9 lines] > can buy a gallon of Wal-Mart windshield wiper fluid cheaper than I can buy > the bottle it comes in. Thanks for the info, Roger. I'm glad to hear it works well for you. It seems that I can add even more methanol and some oil to stretch my pre-mixed fuel even further..... Good flying (and driving), desmobob |
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