OS MAX 120 FOUR CYCLE

[GiantHeli]

I NEED HELP WITH PROP SIZE AND FUEL TYPE FOR A FOUR CYCLE 120 OS MAX. I LIVE IN MEXICO, THAT'S 7,200 FEET HIGH¡¡¡¡

I INSTALLED THE ENGINE IN A HELLCAT FROM HANGAR 9



MORE INFO: THE ENGINE IS ACTUALLY A SURPASS ONE. I MISLEAD BECAUSE IT DOES NOT HAVE THE VALVE COVER IN ANODIZED BLACK.

REGARDS

[octanehuffer]

Why not use the manufacture recommendations for fuel and prop?

[WangoTango]

	Quote: Originally Posted by octanehuffer
	Why not use the manufacture recommendations for fuel and prop?

I think he means that the 7200' ASL is not letting the reccomended prop and fuel work for him. Anybody have any high altitude suggestions so this "cake can bake?"

[Texastbird]

Maybe some YS 20-20 fuel would give a little pep. I can't help much, I fly at sea level.

[Dewayne Vaughn]

hi, which os 120 do you have? and is it a current production model or one of the older versions?
Because of the altitude, you can use more pitch...14*7 or 8 three blade, 15*7 three blade, 15*10 2 blade.... you get the picture.
most of the os 120's do just fine on 10% nitro.... I always used 5% in mine. I would think that at 7200asl you would be ok with 10...I wouldn't go above 15%...Keep it tuned and you will be ok.
Luck my friend!
Dewayne

[GiantHeli]

Thks you all.

I have an old version, the FS.

I already used 10% nitro and it behaved good with a 15x8 MA prop (8,500 rpm)

I changed to 20% four cycle mix and my problem is the idle.

I guess I will go back to 10% and adjust it.

Regards

[mbacosa]

I have usually found that the 4 strokes idle better on higher nitro. I use YS 20/20 blend in all my 4 strokes including O.S.
with very good performance and a very reliable idle. Yes there will be some "needling" that will need to be done to fine tune but it's well worth it.

[octanehuffer]

	Quote: Originally Posted by GiantHeli
	Thks you all. I have an old version, the FS. I already used 10% nitro and it behaved good with a 15x8 MA prop (8,500 rpm) I changed to 20% four cycle mix and my problem is the idle. I guess I will go back to 10% and adjust it. Regards

So, you gave us no info in the first post, listed the setups you tried in your second post, found one that ran well and answered your own question? WOW

[mbacosa]

	Quote: Originally Posted by octanehuffer
	So, you gave us no info in the first post, listed the setups you tried in your second post, found one that ran well and answered your own question? WOW

[GiantHeli]

	Quote: Originally Posted by octanehuffer
	So, you gave us no info in the first post, listed the setups you tried in your second post, found one that ran well and answered your own question? WOW

I don't get it.

Do you have or not experience in OS Max 120?

[GiantHeli]

	Quote: Originally Posted by Dewayne Vaughn
	hi, which os 120 do you have? and is it a current production model or one of the older versions? Because of the altitude, you can use more pitch...14*7 or 8 three blade, 15*7 three blade, 15*10 2 blade.... you get the picture. most of the os 120's do just fine on 10% nitro.... I always used 5% in mine. I would think that at 7200asl you would be ok with 10...I wouldn't go above 15%...Keep it tuned and you will be ok. Luck my friend! Dewayne

This is what I call a very good contribution to help someone else solve a problem.

I have the Surpass one.

I will go back to 10% nitro and find out if the problem disapears...

Regards

[octanehuffer]

You should have given us all of the info from both posts. Instead of us stabbing in the dark and only for you to come and tell us what you tried after suggestions were made. Tell us what you tried and did not try in the FIRST post. You stated that you had good luck running the 10% fuel with a 15x8 prop. You then switched fuels lost performance and was questioning what to try next. Then decided to go to the setup that worked well again.
If it were me, I would run what already worked well. What is wrong with the idle? Too rich, too lean? Have you adjusted the low end?
You need to help us, help you.

[CoemnjemAvepe]

The max number you may set for N under NCycle Parameters for the N Cycle Jitter measurement is 10000. If you are worried about the memory depth and sampling rate, then do not choose such a high number for N. Choose a medium that fits both memory depth, sampling rate and also N as these are all associated with one another. If you under sample, then your jitter result will not be as accurate.