Changing Nitro Content
 

At our Christmas party I won 2 gallons of 10% nitro fuel.
I have had trouble with my OS LAs on 10% but they run great on 15%.
If I just add 6 ounces of nitro I'll also be changing the oil content ratio.
20% of 6 ounces is 1.25 ounces.
Is it enough to cause a problem?
How much of what kind of oil to add?

Thanks for your help,

KW_Counter

Hi!
Strange...The OS LA series of engines run perfect on 5% nitro!
Which OS LA is it you have?

We are forced to use 10% on our LA .25's and they work great. My .10's .15's and 40's work great too. I usually take out a head shim if I think I want to go faster or keep the heat in for a better idle, but I would just use up the fuel and say thank you. As long as there is at least .012" between the head and piston, you will be good. My .10 had a very thick shim, and no shim would have made it aroun .006", so I made up a .005" shim and it is quite lively on 10 % fuel. 4 parts of nitro and one part of oil will keep the overall ratio of oil close. I normally add 3 oz. of castor to a gallon anyway, not because it needs it, but because everyone says to, but Klotz or whatever your favorite is will do.

When I lived below sea level my .40 & .46 LAs ran fine on 10% fuel.
When I moved to the mountains there was no mid range and would die on acceleration.
Spent a lot of time on the test stand trying to dial it in.
Went to 15% and the problem disappeared.
I have not tried the 10% on any of the engines I acquired since then.

KW_Counter

Air at higher altitudes has less oxygen. The extra nitro adds the necessary oxygen for the engine to run properly. I've heard of using more than 20% nitro at 6,000-8,000' ASL to get the same performance as 5% at sea level. Makes perfect sense to me.

Adding a couple ounces of nitro won't affect the fuel much in terms of oil because the richer needle setting needed for the extra nitro makes more oil move through the engine since more fuel is going through it. That's why the RC car guys run 30% nitro and only 8% oil on 35,000rpm engines and don't grenade them. My little .28 car engine can burn 7oz of 30% fuel in about 4-5min. At idle it spits many little oil droplets on the ground.

Might be worth trying the 10% again before going to the trouble of raising the nitro. I run my 40LA on 5% and 0% without any issues. Granted, my field is about 600' MSL.

Alternatively, buy 2 gals of 20% and mix them with the 10%.

You will have to lean out the needles a bit with 10%.

1QwkSport25 is my "go to guy" for fuel formulas ever since i started mixing my own fuel (we use high nitro fuels for competition) and he has never been wrong......some of the requests surely would make my head spin too.
not sure if he sent me this or not, but it works and is a great calculator for changing the nitro/oil content in fuel you already have............

http://www.nitrorc.com/fuelws/allmix.asp

Summerwind,

Awesome! In my Favorites!

Thanks,
KW_Counter