Hello,
Today, I have tested my RToucan ( based on Score ARF) with muffled Evo60NX modified for C/L.
I wrote before about my attempt to make Evo60NX adequate for stunt and this is the continuation of the story.

In today's flights, the liner's button was raised by 0.45 mm. (0.018") using two shims for the engine to run "softer" and it did but....

1. I could not set the stable 2-4-2 stroking target RPM about 8,300-8,600 with Zinger 13x6 prop.
    The RPM kept fluctuating + - 1,000-1500 RPM no matter what I did to the needle setup.
   Comment:: I know that Zinger is not the highest quality stunt prop. but it does the job adequately for me when the engines run well.

2. The launch RPM that were more or less stable but I did not know if they were 2 or 2-4-2 cycle , were about 9,700 and I launched the plane expecting the laps
    to be too fast on 65" lines.
    Instead, the RPM dropped immediately in the level flight with lap times 5.7-5.8 seconds.

3. The engine was 4 stroking in this very slow level flight with not enough lines tension but when I was trying to "wave" the plane up and down, the RPM were 
    audibly increasing while the nose was up 45-50 deg. ( I did not risk the wingover), and decreasing when the nose was down 45-50 deg.

The engine is mounted with the cylinder pointing outside of the circle and the tank is 8 oz. Sullivan with the clunk. The tank is pressurized by the muffler pressure.
The tank horizontal center line is exactly at the spray bar level what is the default tank configuration but the tank can be raised or lowered within + - 1/2 inch.   

This engine has the exhaust timing about 150 degrees but I cannot assess the effect of the fuel intake port geometry/timing and the transfer ports geometry/timing on the engine performance. It is very likely that Evo60NX, being the RC engine, likes to run at stable RPM when the RPM are higher and, by depressurizing the combustion chamber using 0.45 mm. ( 0.018") shim, I made the engine UNSTABLE at LOWER RPM.

Possible solution 1: remove the shims and repeat the flight tests at the LOWEST stable launch 2-4-2 cycle RPM. (if 2-4-2 cycle launch stable RPM are possible for this engine), watching the level flight RPM and the lines tension.
 
Possible solution 2: change the prop to Zinger 12.75x4 and launch at HIGHER RPM.(10,500-10,800) without shims. It will be full 2 cycle on the launch so no 2-4-2 break in maneuvers but my Evo36 C/L run at 10,500 RPM. full 2 cycle on the launch with APC 11x4 prop. and my Parrot with this engine flew adequately for the entire pattern training with 5 sec. lap times on 60' lines.

Any other suggestions or comments?
Thank you.
Matt
 

Hi Chris,
What are the launch RPM of your Evo60NX with 13x4 propeller?
What is 2/2 break?

Do you know if somebody published the torque v/s RPM and/or power v/s RPM curves for this particular engine?

Thanks,
Matt

Hi Chris,
I have already removed the added shims and will try Evo60NX with 13x4 APC, setting, if possible the launch RPM in the 10,000 range or even higher.
Something tells me that Evo60NX, that was build for R/C, has the Torque v/s RPM curve peak shifted far to the right and cannot perform well at lower RPM like engines having the timing purposely set for C/L stunt. After yesterday's tests, I suspect that Evo60NX fuel transfer suffers if the RPM are in the 8,000 range, causing the engine to become erratic with unstable RPM on the ground and lower (!) RPM in level flight.

Comment: the removed shims (total thickness 0.018" and this is a lot...) were added on recommendation of the best stunt pilot in our club so I listened but...the guy runs muffled ST60 and other presently hard to get engines build purposely for stunt and also RoJett 91 with header/muffler. Consequently, I believe now he suggested the solution that was instinctive for him but does not work with EvoNX60.

The tests will show if this engine can give me 5-5.2 seconds lap times for RToucan that weights ~65 oz. and flies on 65.5' lines ( handle to CG.). I like to feel the lines tension everywhere in the semi-sphere and do not mind if the plane is flying a bit faster.

My other Evolution engine (Evo36C/L) runs well with 11x4 APC, with the launch RPM around 10,500 and with easy starts on stock Omega 10% nitro fuel.
With this prop and at this launch RPM., Evo36 C/L runs is full 2 cycle in the level flight and pulls the 40 size trainer easily through maneuvers on 60' lines with the lap times around 5 sec. During first phase of Wingover, Evo36C/L 2 cycle RPM go a bit up what confirms 2/2 break - I simply was not familiar with the term.

Evo60NX seems to work ok on stock Omega fuel without extra castor added and Omega is easily available here (Toronto, Ontario, Canada). I know some people say it is c*ap fuel but I am running my Evo36 C/L for the last two years on it and the engine is actually getting slowly better and better so...

I am going to fly tomorrow and we will see.

Regards,

Matt

P.S: we used to ski in the Colorado Rockies a lot when our son was racing. He moved to Switzerland 10 years ago to ski the mountains that are so big and steep it is scary but married recently the Swiss girl so perhaps the circumstances will tame him a bit?

I use a BY/O 12 x 6 on my evo 60 c/l engine 10% nitro 22% oil and launch at 7800 or less. Any higher and it runs like yours.

I am very pleased with Evo60NX performance today and believe that so called 2/2 break with higher RPM can be effectively used in stunt.

    Yes, I think we know that.

     I would strongly urge you to try something like a 13-4.5  or 12.5-4.5 graphite 3-blade. The performance will be much better than a Zinger of any type. The only reason that all that pitch works with a 9600 rpm launch is because the engine is SO severely bogged down due to the crude propellor that the unload is minimal.

       Brett

Brett,
You know and other experienced people know but some guys in my club are 2-4-2 break lovers and if you try something else it is like breaking a taboo.

    I just hate to see people thrash with things like it is 1975 again.

 
     Brett

Chris,
I have not tried APC 13x4 yet - I have to buy it first. I have MAS 13x4 (black with white tips) though and will try it.
There is another problem: I have discovered that the ST60 NVA I am using with my Evo60NX cannot stop the fuel flow through the spray bar completely even if the needle is screwed in to the very end.

Simply put: I can keep turning the needle clockwise until it stops and in this needle position the engine still draws enough fuel to run at 8,200 RPM on my Zinger 13x6.

Correct me if I am wrong but the needle should stop the fuel flow in this position completely and the engine should stop being starved of fuel.

My OS Max 40 NVAs allow for complete closing of the spray bar fuel flow with needles and the engines stop but I cannot use them with Evo60NX venturi as they are too short.

Matt
 

Hi Chris,
I have ground tested my Evo60NX with MAS 13x4. RPM 11,300-11,400 on stock Omega 12.5% nitro (no castor added). This time the engine was equipped with a light muffler build by me using the Al tubes from the camping chair. I was also flipping the plane quite rapidly to check the nose up and inverted RPM and they were very stable - I could not hear any RPM increase with nose up so probably no 2-2 break.

Needle is fixed. It is possible now to close the fuel flow completely but, ironically, it is not necessary. At 11,300-11,400 RPM, the engine runs with the spray bar fully open and turning the needle even 720 degrees CW or CCW does not do anything.

APC 13x4 is coming and I will test the plane in the air.

Comment: I feel that my Evo 60NX, being the R/C engine, likes to run at higher RPM with the muffler. I forced it to run at 9,500-9600 w/o muffler with Zinger 13x6 and the RPM were stable, now the same propeller turns at 8,500-8600 with the muffler, with audible dip in RPM when the nose goes up.   

Again, I would love to see the Torque/Power v/s RPM graphs with different props.
Regards,
Matt