<span class="Apple-style-span" style="color: rgb(0, 38, 94); font-family: tahoma, verdana; font-size: 11px; -webkit-border-horizontal-spacing: 1px; -webkit-border-vertical-spacing: 1px; "><span class="oldpost" style="font: normal normal normal 12px/normal Verdana; ">Difference between 30% and 33 % fuelnitro ?????</span></span>

Not much, about 3%.  I suspect 33% is a bit more expensive.  I would not expect a great deal of difference in performance.  Maybe run a bit cooler.

Chip

You have spent three posts concerning the same question. Go on like this, and no one will take you serious any more.
Your action is called crossposting, and is a no-no (thing not to do)

pe,

Give the guy a break, He just joined today andhe'snew atposting.
He'll get the hang of it, but he won't be around long if folks like you start out bustin' his butt.

Happy flying, Oscar</p>

Not a real boost in performance, however way too much nitro for an aircraft engine. More suited to a car engine, with an extra head shim.

Also - the more nitro the more heat is produced. The methanol content has a lot to do with how hot or cold an engine runs at optimum mixtures. Nitro adds fuel to the flame creating more heat and the need for a richer mixture and thus lowering fuel economy.

In a car engine not being raced, 20% nitro is all you need. The performance between 20% and 30% is not going to be dramatic. Not to mention the price of 20% is around $32 and 30% is $38-$40 around me - thats expensive!

As an oxygenator, nitromethane creates oxygenduringthe combustion process.
This why the mixture needs to be richer so as to add more fuel tocompensate for the increase in oxygen.
A more intense combustion thus creates more heat.
Although less fuel economy occurs, the increase in throttle response andhorsepower is often worth the sacrifice.
This of course,depends entirely on the efficiency of the engine design.


Happy flying, Oscar

That is essentially what I meant by "adding fuel to the flame" but got side-tracked and didnt elaborate.
The problem with box-stock RTR type car engines is they tend to run hot on 30% nitro without shimming them. Though many owners manuals say 10%-30% is okay, I think 30% or even 33% is too much without adding a head shim or two. I've tried running 30% nitro before (no added shims) and I didn't like to see the engine temp hovering around 300°F (with temp measured at the glow plug). Preignition is no good either. Richening the needle to get preignition to stop meant sluggish performance and wasted fuel.

I know from my own experience changing bearings in nitro engines - at about 315°F the bearing races in the engine crankcase have expanded enough to release the outer ring of the bearing. One good run through the grass could get the temp to climb above 315° easily if tuned to peak performance to start with.

Perhaps this is a bit off-topic - sorry.

1QwkSport,

300+ degrees F is pretty scary, at those temps castor is starting to polymerize.
Thank goodness for synthetics!

I didn't realize you are running cars, I am running much lower temps as I am running my engines in aircraft
although I don't know precisely how much lower. I have run 30% nitro in my YS four strokes and got
great performance but have switched to20% nitro 20% lubricant fuel so I can run the same fuel in both my
two stroke and four strokes. The drop in nitro for the four strokes had a very small effect.

Happy flying, Oscar

I personally have cars and airboats but I am guessing the OP was posting about 30 and 33% nitro fuel. The OP didnt say if it was helicopter fuel or not, so I assumed he/she was talking about car fuel.

Obviously the lower compression engines (YS for example) can run higher nitro, but most aircraft engines run best on 5%-10% nitro.

Temperature is more critical with car engines since they dont have props to cool them off. Also they aren't loaded as much so their fuel has less oil in it too. I usually run 25% nitro/12% oil which is pretty typical of the market, though there are some race fuels with as little as 8% oil and some higher at around 16%. My Failsafe has shot me some temps in the area if 310°-320°F after a good run through the yard. Let it idle for 15 seconds and it will drop to 260-270° quickly. I have my engines tuned to peak performance and usually average 270°F. My TT .46 Pro runs up around 280-290° after a good wide open run on the test stand. I do not tune my engines to run at a specific temp - I tune them so they run good. If it sounds good, and throttles well then whatever temp it runs at is the temp its supposed to be. Some feel 300° is scary, but I dont think so as long as its running the way it should.

I'll be mixing my own fuel this summer and I'm getting away from the synthetics and going all castor in both cars and airboats.

Yep, while the castor is starting to polymerize the synthetics are well past beginning to vaporize. Make no mistake, where heat is concerned, nothing even comes close to castor. Those polymers that are formed and that stick to the metal are still a lubricant. Almost all of the fuels sold in the US with synthetic oil are using PAG type oils. (As opposed to Ester based oils) I'll keep on using a blend thank you very much.