My wife and I are moving about 80 miles south of where we now live in Alexandria, Va. to a wide open area called Colonial Beach. At the back of my new shop is an approximately 100 acre field and houses to the side are about 400 feet away and well forward of the new house and shop. I believe I can run engines there uninhibited. I want to do a torque Vs. nitro test using my Saito .82a and a 14x6 APC prop. I am going to order a case of WildCat fuel with one gallon each of 10, 15, 20 and 30% nitro. I rarely use more than 10% nitro so I have little to no experience with 20% except in YS's and none with 30%. So. a couple of questions for you higher nitro users.

Does this sound like a useful test?
Should it be done at peak rpm or 200 to 300 rpm rich?
Would trying different plugs be useful, I have H9 SuperPlugs, Fox Miracle plugs, OS-f and whatever comes stock in an Enya fourstroke.

I chose the .82a because the American Hobby Products Dyno has a .91 sized max capacity, the .82 should operate in the most accurate portion of the Dynos scale.

Lets hear what you think.

Well I learned in my brief rc history that my OS 46fxi and Saito FA 56 both like 15% better than 10%, they ran better and are more reliable.

Hello; That sounds like something I might do. of course we all know that there is more to an engine then just measureable thrust, although it is the easiest to measure. I usually buy my fuel in a case, and search for the best deal, rather then the highest nitro content. I will be interested in your results.

I would run the test with the engine tuned just the way I would fly it, not peaked to within an inch of it's life.

I assume you plan to tune both high & low needles with every change in fuel. I run Magnum I (20%+ nitro) routinely in my four-strokes (YS, OS & Saito) with YS or OS-F plugs. On occasions when I've used Magnum II (higher nitro) I find that the added power is significant to the extent that I fly my routines with at least a click or two less throttle, and when I land I have more fuel left in the tank than with the Magnum I.

When I finish up my stock of Magnum I, I plan to order a quantity of Magnum II next time, since my experience is the engine runs stronger by a margin that more than compensates for the higher cost of the fuel. In other words, Magnum II is the best performer and more economical.

Who owns the field? Will you have flyover access? Can we come watch you fly?

I'm not going to fly there, it's just that the Farmers buildings are a good half of a mile a way so he won't worry about me running engines. I fly at CCRCC in Waldorf, Md. The Farmer behind our new house has a 60 foot high silo there, I hope my Saito 2.20 doesn't blow it over.

For a valid test, every run should have only one variable?

Every run should be peaked and then reduced by the same rpm? (or not reduced any?)

This test would only be valid for a 82? Possibly Saito's in general? and not necessarily applicable to other brands and types?

Enjoy,

Jim

As for my experience with 4 strokers, I´ve found 2 combinations that gives the best on my FA-80:
Byron´s fuel at 25% nitro with custom blend of 23% oil using an O.S. F glow plug and the best combo for this engine is using Power master Heli fuel with 30% nitro and 23% synthtetic ("low vis") oil with same glow plug.
With this combo I´ve my FA-80 turning an APC 14X4W at 10,800 rpm on the rich side with 11,100 rpm at peak.
Never had a dead stick and idling at no more than 2,000 rpm.
Those numbers are at 9000 ft over sea level with an average temperature of 85 F.

Best regards.

Hobbsy,

Great idea. I have always wanted to see what effect nitro has on an engine's peak power, torque and the shape of the torque curve. Here are my suggestions:

1) Take peak readings only, as to richen so many revs from peak introduces another variable.
2) Use a series of props on the same fuel test to plot the torque at different rev points on the graph. Suggestions in addition to your 14x6 are lighter loads like the 13x7 and 13x6 and as a nominal heavier load, the apc 14x7.
3) Cross check your readings with prop-power.xls (calculate the torque from the horsepower), to see if these two different measurement techniques produce the same numbers.
4) I know you've got lots of engines - try another brand .70 to .91 to dispel the "brand x responds much better to nitro than brand y" myths

Most importantly, don't forget to let us know how the testing went

I would do the test at full rpm....don't forget, there is a range of a few clicks
at max rpm that can go from slight/rich to slight/lean....all at the same rpm.
Just run it at the richest it will run, and still sustain Max rpm.

I think the torgue test will be interesting.

Dave.

Thanks for all the tips, the only other brands I have close to that range are my Enya .53 TN, RCV .58 or YS .53, I'll have to think about that. Maybe Jim will loan me an engine for that.