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170DZ RPM Confirmation

Old 05-12-2008, 02:57 PM
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elan120
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Default 170DZ RPM Confirmation

Hi Troy,

I am in a process of breaking in a new 170DZ, after almost 2 tanks of 20oz fuel with less than 4.4K rpm with HS at around 2-3/4 turn out on the ground per your suggestion. Since the engine was running very stable, and very easy to start, I advanced the throttle to WOT after 2 tanks to check the HS setting, and found the top rpm can be as high as 8600, and seems to be able to go even higher if I continue to lean it out, but didn't. Now I have reduced the rpm down to about 8350 with the HS at 3 turns out, the idle runs very stable at 1800, in fact, engine seems to be able to idle at this rpm forever (I have tried idle up to 1 and half minutes without rpm changing). Do you think besed on the figures above, I can go flying at this setting and continue the break-in process? The main reason for the question is due to I am very surprised with the amount of rpm I am getting, and with HS needle at 3 turns out, I thought the rpm should be less and a little less stable at idle.

All of the information above were based on running CoolPower 30% Heli fuel, OS#F plug, and APC 18.1x10 propeller.

Thank you,
Kevin
Old 05-12-2008, 04:24 PM
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Troy Newman
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Default RE: 170DZ RPM Confirmation

You are golden.

The engine is running great as normal and you should be fine. I'm actually running on my 170's about 2 turns maybe 2.25turns open...

You will want to be thinking about a new glow plug here in the next few runs maybe less than 20 runs the plug will go. What will tend happen is your idle will get unstable a little rich. This is usually a sign of a plug gone bad. Normal on the new engine break in usually in the first 20 flights.

Next thing...In the air if you notice that the engine is running well but seems to be quiting in a spin or maybe a stall turn then your HS is likely too rich and its putting out the glow plug.

Flying the engine is the best for it. It allows it to unload and also get some cooling. However they can be a little unstable for a little while while you are getting the settings. So don't put yourself in a position to hurt a model. Always be ready for a dead stick, usually after a long idle or a stall or spin type of thing.

I would fly it where you are now and then start to lean it out.

To limit your power on the top end....get the mixture correct and stick one of Central Hobbies Velocity stacks in the carb...or close down the barrel a little from full open. You can close it about 20% with little change in RPM yet a huge change in noise. The velocity stack will drop about 200rpm off the top. But it will make the throttle better down low and the noise will be lower and smoother. This too will help the throttle curve out and you'll find you are not using the top end power anyway as the torque curve got lowered and the engine digs out of the hole better.

I fly that 18.1 (all the Variants) prop at about 7800-7900 and that is right on the noise limit for FAI with the 18" props. I actually go back to about 7600-7700 for the NATS. This is where I found the engine performs best and makes noise limits as well as giving me plenty and I mean plenty of power. Its insane power. I don't anybody that has seen my models fly can say they are anything but well powered. Even the Bipes

Then if at a local event where its a bit windy, you can always bump up the rpms to about 8000 and let er eat!

I tend to keep the same rpms when traveling to contests, it keeps the engine performance and throttle curves more consistent. You see going to Muncie from PHX the power and performance increases. So if I back the engine down not on the needle but on the carb opening then I'm getting the same rpm as back home and the engine curve reacts the same and the difference is much less.

I learned this little trick from Peter Goldsmith. Get to the new flying site and just dial in your RPM you need with the ATV. There will still be a slight difference in thicker air vs the thinner air but its much less when the engine is turning similar rpms.

I know that 7700 is more than enough for the task... so thats all I use.

You can also start to load the engine up with a couple of different props. The 18.1-11 or 18.1-12 are also good. The 18.1-10W is a bit harsh and tends to make the engine sound harsh. The prop flies well but the sound is not the purr and smooth sound you want. I have modified some of these 18.1-10W's to clip the tips and re-shape the tips. The sound improves on them and they still perform well. However I tend to like the 11 or 12 pitch props better.

Troy Newman
Team YS
Old 05-12-2008, 05:01 PM
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elan120
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Default RE: 170DZ RPM Confirmation

Hi Troy,

Thanks for the confirmation and additional information. I was feeling good with the engine response from yesterday's initial break-in on the ground, now with your confirmation, I am feeling great.

I am going to get the Velocity stack to try, as well as the 18.1 x 11 and 12 prop to see how they do. Meanwhile, should I wait until engine completed the break-in before using the bigger prop and the Velocity stack?

About the plug, I was using an older plug that has about 30 some flights already to do the break-in, in anticipate the early life failure as you have mentioned in the K-factor, and I will replace the plug when the engine has about 20 flights. Since I will be going to Oakdale contest in 2 weeks, I should have planty of flights to cover that requirement.

One more question, since you mentioned the stall turn, I assume there is no concern flying vertical during the initial break-in, right? Or should I wait a few flights before doing any of the vertical sequences?

Thank you,
Kevin
Old 05-12-2008, 09:38 PM
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Troy Newman
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Default RE: 170DZ RPM Confirmation

I would wait on the velocity stack until the engine is stable...it might be in a few more flights...

Don't worry about normal pattern flying stuff. Just don't go out and try to torque roll for 10mins straight.

Fly your normal pattern flights but make sure to not run it out of fuel. This makes for a lean run...

But Like I said you are golden. Give it a few flights on that prop before you start loading it down. You might be surprised at how well it flies at the current prop and rpm level. It will be just a little louder. But it should be able to make the AMA limit of 96db(A) just not the FAI limit of 94db(A)

Troy

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