Difference in 10% and 15% Nitro?

The "Difference in 10% and 15% Nitro?" is five percent!

....just kidding. Going from 15 to 10% will not require changes in prop size. The engine will loose +/- 100 rpm at the top end and you'll probably notice that it's running a little richer than with 15%.

Using a tach reset the main NV to 300 less than peak rpm. Or.... just leave it alone and enjoy a nice "Saito smoke trail". Saitos love nitro, but 10% is still acceptable.

From theory, Nitro adds oxygen, and can make a poor breathing engine rev better. Unless the engine needs the revs, it may be an expensive waste of time. You need to drag in more fuel with nitro - the extra oxygen in the nitro will need more fuel to burn, and there will be less fuel in the fuel as the nitro takes up space.

My Saito 56 ran much better with 20% nitro, but most of the reason is that I fly at 5300' ASL and the extra oxygen provided by the nitro works wonders up here where there is no oxygen in the air to start with.

Rein

NO oxygen in the air to start with? How on earth do you breath?

He is a rare nitrogen breathing alien, only found at those altitudes.

A lot will depend on WHICH Sig fuel is used. Some Sig fuels are all castor which isn't such a great idea in Saitos. The head and cylinder is one-piece and it is very difficult to properly clean. Four strokes have a hotter combustion and tend to carbon up faster. That's why most manufacturers recommend reduced, or no castor fuel.

Many of the Japanese four strokes will LOVE more nitro. Saitos can easily run up to 30-35% with no bad effects. OS, Magnum and TT can handle 40-45%. Main benefits are more reliable idle, more power and better transition. Main negative is extra cost.

I usually don't run four strokes with less than 20% nitro. They just run so much better it is worth the couple extra dollars per gallon to me. Southern Modelcraft 20/20 doesn't cost much more than their 10% fuel.

eeeerrrr difference ???? the COST !!!! from my point of view, using 20% nitro (xcpt for racing cars : racer A/Cs or Cox engines) is an advanced form of sponsorship (as well as a cute painting killer !) Pierre

"The Natural Philos>

Take me to your leader. We come in peace.

do while ALIVE { inhale exhale }

Mark --

From a practical standpoint, other than a slight reduction in max RPM, a necessity to probably change the needle setting, and an increase in the thickness of your wallet, you won't notice the difference.

In reality, I always use 15% nitro in all my engines -- just because it's "one size fits all" -- I use a total oil content of 18% of which 3% is castor. On the other hand, our club fuel is 12-1/2% nitro with 20% oil which is half & half. No one seems to have any problems with any engines.