Trex 700N DFC with YS- 91SR 3DS

[KBaksh]

Hey guys I have this YS- 91SR 3DS motor on my Trex 700N DFC, The gear ratio is 8:1 (112MG and 14TP). What's the max head speed or sweet spot for this motor.

Thank you.

[REGULATER]

I run my YS 91 3DS around 1980 it seems very happy there . Thats a very good motor easy to tune and makes great power.

Mark

[ticedoff8]

As you know, the "practical" RPM of this engine is 2000 to 17,000 RPM.
http://www.ysengines.net/manuals-dow...YSP.pdf?6526ee

YS does not post any dyno measurements, so you don't know what the peak power RPM would be.

With your 8.1:1 ratio, the max headspeed is about 2100 RPM.
I would suggest that is your redline and should never be exceeded.
But, you should fly it around 2000 RPm headspeed, and that should do the trick nicely.

But, the reality is that anything past 2000 RPM is all noise on a 700 size heli. Even an electric.
I used YS 91SR-3DS motors in my Raptor 90 SE and 3D (converted to FBL) then in my 700N V2.

Now, I run my Trex 700N V2 w/ DFC head with a YS 120SR-X at 1950 headspeed and it flies as snappy as my Trex 600E Pro DFC with a BL750MX motor.

The 700N V2 uses an 8.0:1 gear ratio and I keep the 120SR-X motor below its max of 16,000 (a 2000 RPM headspeed).

[KBaksh]

Thanks Guys.

[Pitch-Itch]

Originally Posted by ticedoff8

As you know, the "practical" RPM of this engine is 2000 to 17,000 RPM.
http://www.ysengines.net/manuals-dow...YSP.pdf?6526ee

YS does not post any dyno measurements, so you don't know what the peak power RPM would be.

With your 8.1:1 ratio, the max headspeed is about 2100 RPM.
I would suggest that is your redline and should never be exceeded.
But, you should fly it around 2000 RPm headspeed, and that should do the trick nicely.

But, the reality is that anything past 2000 RPM is all noise on a 700 size heli. Even an electric.
I used YS 91SR-3DS motors in my Raptor 90 SE and 3D (converted to FBL) then in my 700N V2.

Now, I run my Trex 700N V2 w/ DFC head with a YS 120SR-X at 1950 headspeed and it flies as snappy as my Trex 600E Pro DFC with a BL750MX motor.

The 700N V2 uses an 8.0:1 gear ratio and I keep the 120SR-X motor below its max of 16,000 (a 2000 RPM headspeed).

What a ridiculous thing to say. To say that there aren't clear performance gains going from something like 2000rpm to something like 2250rpm is just....wrong.

[maddog7]

Originally Posted by Pitch-Itch

What a ridiculous thing to say. To say that there aren't clear performance gains going from something like 2000rpm to something like 2250rpm is just....wrong.

With a nitro motor there is an rpm point after which the engine will make less power, sometimes tapering very quickly depending on state of tune, pipe, %nitro etc, so unless you change the gearing your heli will have less punch. The ideal is to gear it so the HS is just above peak power so that when it's under load it'll drop into peak power rpm.

D