brjensen71

My Feedback: (1)

Just got an almost new OS 91SZ-H hyper heli engine for $143.

I seen another post about the 70 size OS heli engine working well for a speed plane. Is the 91SZ any good?

I still have to order a proper adapter, header and pipe before I can test run it.

brjensen71

My Feedback: (1)

with a GMS 76 size muffler installed and 10% nitro ( had to slot the muffler mount holes by .035") :
APC 10X10 14800
APC 11X12 12400

got a header and Pipe on order to test next.

freakingfast

My Feedback: (3)

Good idea. those numbers are quite low. When it's running right, that 10X10 may be too small. 11X10 or 11X9 at about 15K

brjensen71

My Feedback: (1)

got the pipe and header. had to actually lengthen the header to get on the pipe.

so far a little disappointed, with 30% nitro, an APC 10X10 I can get 15400 to 15600 rpm depending on pipe length.

I haven't tried my other props yet. I have APC 11X12, 11X11, 11X10 & 11X8 props to try.

freakingfast

My Feedback: (3)

Well that engine's peak power is at 15K. Now load it with more prop. What pipe are you running?

brjensen71

My Feedback: (1)

With a little help from the "Glow engine" forum I got the pipe set-up correct.

I was able to get 16200 RPM on 30% nitro and an APC 10X10 prop

bob27s

My Feedback: (19)

the pipe works like a governor too. Dont forget that.

You have a baseline. Start going up in prop size. Do not change the pipe.

When you get to a point whre the needle becosme hard to set, or if the engine refuses to stage on the pipe...... the prop is too large. Back off a size and repeat the test.

On the Jett 90LX FIRE engine, a 10x10 and 11x7 turn appx the same with the same setup (around 16K). Loading down with an 11x8 put the engine on the up-side of the power curve, so when it unloads in flight....... it gets right back up to 16K in a hurry.

freakingfast

My Feedback: (3)

Normally I need to cut off about 2" of a new Macs header (depending on the plane and engine). I never heard of lengthening a new header?

brjensen71

My Feedback: (1)

I ended up shortening the header to get to 16200. But was able to get over 15500 by lengthening it before I shortened it.