Evolution .46NX in my Superstar...I am running the recommended tower super plug, that is actually made for the 4 stroke engines. 15% Nitro...from Hobbytown USA. I have noticed that the engine feels sluggish and has a slow response. If I run it very long at low throttle, then increase throttle, it spits and sputters....cant figure it out. The only time it really bugs me is if I come in to land a little hot and overshoot the strip I had set up to land on. I then pull up, advance from idle to about half throttle, and it spits and sputters for a second while trying to climb out. This engine starts very well, climbs with almost unlimited vertical, and will cruise my Hobbico Superstar beautifully at about a quarter throttle. I set the mixture like it stated in the manual, a slight turn back from the point where it made the highest RPM....

Anyone have any ideas???

I appreciate any help I can get...

Midrange needle needs adjusting, mid range is to rich.

Just yesterday I helped a new guy in the club... He has an Evolution engine in his H-9/P-51 Mustang.

My experience with that is exactly the same as you just described. I spent nearly 2 hours with this engine at the field, I finally decided to take it home with me to do some research and fix the 'Idiot Proof" engine as this was the FIRST engine I was unable to properly tune [:@]. Do a search on here for the engine tuning fix.

Hint: You'll need to remove the pins that limit the low speed and the high speed needles, that is step one.

With the limiters in place, you'll NEVER be able to properly tune the engine for reliability.

EDIT: This engine now runs like a champ... no dead-stick landings, sputtering, die from advancing throttle movement and un-even transitioning of throttle changes. It runs about as well as an O.S. engine now.

File IFR,

I appreciate the input. I have the exact same engine as in the Hangar 9 P-51....its an evolution TPS (Trainer Power System). I have often wondered how well that limiter was set at the factory...

I will definitely try that tomorrow. I have probably 15 total flights in a Nitro plane, and I am an expert at dead stick landings...after the engine quits at 30' of elevation....

I will try that and post how that goes...

Thanks to you both

Tony

I've yet to see one of these engines run well without the limiters removed. They are setup to let you start the engine and that's about all. I've seen three so far and not a one of them would tune with the limiters in place. After they were removed, they were a very nice running engine.

When you try to make something idiot proff, only idiots will be able to use it. I don't know who came up with this idea in the first place, but they should be on unemployment now.

Don

your idle is to rich, once you remove the limiter lean it a 8th of a turn, you are close.

Gentlemen this is invaluable information...I have removed the limiter pin from the high speed needle, but do not see one on the low speed....I will get my manual back out in the morning and dig a little deeper. I cant wait to see how this thing does with the engine running properly.

I cant thank you enough....

Tony

It's the chrome colored pin sticking out of the blue bezel ring at the carb's throttle arm area... pull it out with small pliers.

You'll need to set the high speed needle first, then adjust the low speed (the low speed is most likely too rich... turn it clockwise when adjusting).

You may not think it matters a whole lot, but the low speed screw is SO SENSITIVE it will drive you crazy. Move this screw (when getting close to perfect) the width of your screwdriver's blade/slot... Yes, it's that sensitive.

To check the low speed screw: Go to full power for a few seconds, then quickly bring the throttle down to idle (make sure your throttle trim is set low enough for a good low idle). Once the throttle is down, listen to the idle... if after a 10 to 20 seconds the idle slowly goes softer and softer... your low speed setting is rich. To double check yourself here at low idle, quickly bring the throttle to full power- if it trips over itself, sputters, coughs and gags it's a sign it's rich (the spraybar has too much fuel to consume).

Make your adjustments a micro movement at a time on the low speed. Don't be discouraged if it takes you a 1/2 hour of more to do this.


One other thing that can make these adjustments null and void - air bubbles in the carb feed line from the tank. Once in a while monitor the tubing during operation for a bubble-free fuel feeding.

Good luck. you'll get it.

I forgot to tell ya, Loosen the small set screw at the carb's blue bezel ring.... this will allow you to turn in the low speed screw. If you don't, it will bottom out the blue bezel to the carb body and not allow you to make a leaner adjustment.

Most people just pull the blue PITA off anyway... leaving the black low speed screw stub sticking out. I'd just do that if I were you. I did just that yesterday.

Here it basic step of glow engine tuning<h3 class="post-title entry-title">Glow Engine Tuning</h3>

The trouble Ive found is that everytime they make an engine idiot proof, someone makes a better idiot. :-p

Here is how that low-speed needle is SUPPOSED to be set from the factory:

Loosen the set screw and remove the blue collar

Open the carb ONE MILLIMETER

Close the low-speed needle.

Open the Low-speed needle 1 1/5 (One and one fifth) turns.

Replace the Blue collar so the pin is centered between the stops.

I had this same issue when I did a review of the Evo engine. I called the manufacturer and they admitted they had an issue with these things leaving the factory with improper settings. They told me exactly what I said above. I made the change and the engine ran like a champ.

YES! Extremely important point!!!

Pulling the pin alone is NOT enough. The collar prevents the needle from going in further, even if you've removed the limiting pin.

You MUST loosen and temporarily remove the blue collar. After you have adjusted the engine you may re-install it if desired.

These things used to be idiot proof then someone went out and developed a better idiot. It's been all downhill since then.[:'(]

i'm glad i found this thread. i've been looking for that set screw on the low speed needle valve for a while and just found it tonight. maybe now i can get my engine running reliably. however, i did notice some small bubbles in my fuel line today. i removed the tank to inspect the fuel lines, but i didn't see any holes. should i just replace and be done with it?

Make sure the clunk is 1/4" from the back wall of the fuel tank.

Check your lines, as you probably have a small leak.

With a full tank you should not see any bubbling.