R 90 head speed

[vandelescrow]

What head speed are you guys flying on your R90s? I have a R903D and while breaking in the engine it was running real rich. I'm using the gear ratio that came with the heli 8.27:1 using a Aerospire governor, I had Normal mode set to 1800 overspeed, mode 1 set to 1900 full govern, mode 2 1950 full govern. I noticed when I would switch from normal mode to 1 or 2, the engine would actualy slow down. I know the sensor is picking up the magnet. The engine is the YS91SR. Is this due to it being so rich?

Also, what gear ratio are yall finding best on this heli. The manual for the YS91SR says 7.5:1 - 8.0:1. By switching to these gears from 8.27:1 it will cause the head to be slower at the same engine rpm right? So will I not beable to achieve these head speeds?

Lastly, has anyone found out what RPM the YS91SR is at peak power? All I'm finding is the practical rpm 2000 - 17000

Please help, I'm new to 90's and would like to get the most power out of this machine.
thanks

[miami6]

i would run normal at 1700 rpms stunt 1 or iddle up1 at 1800 and mode 2 st2 or idl2 at no more than 1890 thats my settings with the OS SZ pump motor running 690mm


multiply desired head speed x gear ration on main gear it should give you the motors RPM

[Ah Clem]

If memory serves, I have the governor off in "normal", 1850 in "Idle Up 1" and 1950 in "Idle Up 2".

I am also running the OS pumped .91 (very rich).

More power than I know what to do with!

If it is too rich at the top end, the motor can slow down when you request more power from it (same can be true if too lean). I set mine pretty much in "Normal" with the governor off, then it is good in governed mode. Again, I always run somewhat rich as I am not a contest flier and just want engine longevity.

[Dino Spadaccini]

Do not run the ys motor more than 1890 max on the head on 8.27, you will hurt that motor in the long run.

[vandelescrow]

Do not run the ys motor more than 1890 max on the head on 8.27, you will hurt that motor in the long run.

Thanks Dino, you seem to know a bit about this engine, what gear ratio and head speed would you recomend for best performance. Like I said, trying to get info on the optimum rpm for this engine is futile.

[Lota Fun R]

I had my Raptor 90 set at 1950 headspeed with a plastic head and tached it at 1920 + or - 10 rpm. The plastic head seperated in flight. You need the metal head to run those rpms.

Let me tell you about the pop it has at those rpms, it's got some pop to it.

Head temps were under 180 deg F, I'm going to install the carb smart and run it at 212 deg F with the carb smart tuning in that range. It will easily pull those headspeeds and also have performance to boot. This engine has seized on me once and I know why, I've got that sorted for the most part, and if everything is right, I'll find some new week spots.

I'll have the headspeed set at 1920 this next time out since I"ve done a gearing change to 8.27, for this heli this is the best speed to run everything. With the carb smart doing the tuning and a pro flying it.................can't wait to see one of those pro guys start using it all of the time.

I was running 7.92 and it had headspeed. But....... 8.27 is preffered from what I"m told.

It's got the whole 3D package installed and will work nicely.

[Lota Fun R]

1850 for a plastic head and use blue dampers.

[Dino Spadaccini]

stay at 1890 max unloaded in a hover on 8.45 you can push the head speed to 1900 on 8.27 which i think is a better ratio for the Sr and the OS the SR being a long stroke likes that ratio its keeping the motor loaded easier and will not run out of gear with that setup, it will just keep pulling thats the way i ran mine

[Lota Fun R]

I was using 7.92 gearing which is tall gearing for high head speeds, I changed it to 8.27 to bring the engine rpm up and the head speed down, at peak rpm 17000 it will pull 1920 head speed. With the 7.92 gearing it would pull 2021 head speed at 17000. With the 8.27 it will bog less, the 7.92 it will bog more...etc...

Curtis Youngblood and others recommend spinning the YS slightly higher rpm than the OS for the same given head speed. Check his web site to be sure.

For my OS 91 C spec I was told to use 8.27 gearing and a head speed of 1920, the guy that told me that is a Thunder Tiger sponsored pilot, I trust his opinion.