Author Topic: Nitromethane  (Read 4149 times)

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Offline EHP

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Re: Nitromethane
« Reply #60 on: November 27, 2016, 08:58:31 am »
first thing , hold throttle wide open with switch turned off will kill most run ons , next ALWAYS have your squirt bottle you prime the saw with to start it with you , just squirt your mixed gas into carb on saw that's running on , it will quit . Are you guys cutting the ends on your spark plug , if you that's your trouble , the end of your plug will glow when running nitro/alcohol and will not shut down until its flooded , you can turn your switch off but it will not matter . Next if your running a pipe with wide skirt piston and ports to match you donot need or want big compression
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Offline trappermike

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  • 40 years mechanical and 2-Stroke racing experience
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Re: Nitromethane
« Reply #61 on: December 29, 2018, 03:00:47 pm »
Back around 1989 I was mechanic in a large Stihl shop and had my own fleet of competition saws for each class. In my archives I had some old data on running Kart motors on Nitro mix,it said 25% nitro was the hottest percentage you could use. So I made a 25% nitro/75% methanol mix,I used synthetic Amsoil mix oil because I know mineral oils will not mix with methanol,so that was my fuel/oil mix.
For information I went to the master mechanic at a local Speed shop,This guy had experience in building drag cars on alcohol or Nitro. He told me that to rum alcohol you needed twice the fuel flow and nitro needs almost 3 times the amount of fuel flow. I was using my 084 hotsaw as a test mule,and I knew I would have to modify the carb and circuits to flow a helluva lot more fuel than for gasoline.So I would pull the carb off,enlarge the fuel circuits,then test run the saw but still too lean.I had to repeat this process about 8 times until finally the carb would actually flow enough fuel and I could richen or lean the HS screw and make the saw rev to whatever top rpm I wanted-success!
However I discovered that 2-strokes aren't really a good design for running nitro on,because during it's normal cycle you have fresh mix entering the cylinder while burning exhaust is going out,and with nitro fuel this results in the incoming nitro fuel being ignited,causing"Auto-igntion"-the nitro fuel is ignited before the spark plug even fires. So what happens is about 10 seconds after you start the saw the motor will start racing like crazy,10,000 plus rpms while your finger is off the trigger! So when this first happened I was freakin' out and immediately hit the stop switch but the motor kept screamin',so in a panic I yanked the spark plug wire off and got a helluva shock but the motor kept revving and was obviously running without spark,then luckily I tried closing the choke and the motor stopped. So in tests after that to shut off the saw I merely snapped the choke shut and opened the throttle at the same time it it would quit nicely. So unlike my other race saws I had to leave the choke assembly in the carb.
It was just a week before the annual local Loggers Sports competition,then I found out the rules clearly stated gasoline fuel only allowed,so all my hard work was in vain. I did have a can of Klotz Nitro Power Additive and I added it to my 090 hotsaw at ratio recommended on the can(which is a very low percentage),but when I ran it in my 090 at the event there was a very strong chemical smell in the exhaust,and quite a few other competitors immediately asked me what I was burning in the fuel,I suggested maybe it was from some anti-friction additive that I had in the fuel,but I don't think anyone believed me,but the fact is nitro isn't legal in the fuel and even a tiny percentage the smell is a giveaway...
I guess it's possible to build another nitro-burner like my 084 to do some interesting demonstration runs at an event... That would be cool.
Experience builds real horsepower...
When the hammer drops the BS stops:Loggers sports competition!
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Offline SquareFile

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Re: Nitromethane
« Reply #62 on: May 04, 2021, 03:02:50 pm »
This thread makes me lol everytime I read it. If you've got enough fuel, non of the above lean situations happen. Runons, glow plugging, auto ignition is all lean situations,  period!

No side gapping, 180psi on pipe, big ports, 20% nitro in over 10 second long cuts with WG carb.

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