Tuning an YS 91 SRS RR 3D for crazy superhero powers

[GravityKills]

Hello,

the particular engine I've got is probably quite rare, but it shouldn't be too different from a YS 91 SR.
Where I am now:
* Hatori SB 19 FH-2 muffler
* Optifuel 30 %
* OS #8
* an OS bubbleless clunk, a headertank and a fuel magnet. Total overkill, at least temporarily.
* at sea level

I had to shim the engine- After putting in a second head gasket, it now purrs like a kitten and the needle settings in the manual make sense. Without the second gasket, it runs unevenly and too hot.
Right now, it gives pretty good power. It's probably the best-performing nitro engine I've ever flown. It does F3C-size loops and barely bogs. Not too bad.
But still, it's no good for tictocs. In the "hard ones" (tail rotor facing up), it bogs miserably.

I set the hover needle first, the engine remains cool as long as I only hover. Then the full needle to keep it cool at continuous full power. In hovering, it runs relatively lean.
But now I'm wondering: Would it be better to set the hover needle as rich as possible? So that the engine gets maximum cooling when it doesn't have to deliver full power?

BTW, I noticed that the governor (Aerospire multigov) seems to perform better in tictocs when I disable feedforward entirely, i.e. a flat 100 throttle curve.

Or, asking more generally, how would I tune this engine to get crazy superhero powers, so that I can start practising wheels of fortune?

[mattie-lodge]

Hi ya,

Ok after running these engines for a few years now the method that seems to work well is quite simple for max power out of the YS 91.

First of all reset all your needles to stock running in settings. You shouldnt need to do too much on the bottom end. Only small adjustments to get the transisions off idle sorted. Then what we found is the top end is the needle to tune to gain your power, so initially leaving the mid needle alone. You really shouldn't have to adjust it by large amounts to get your required power (full power climbs, tic tok and general high power moves). Once you have the power you require then the mid needle can be adjusted to improve the transisions between full power and mid range.

It seems you may have your mid too lean which is upsetting your top end.

Info I'm running mine on 30% rapicon with the stock out of the box head shim. This is on both the SR and SRS.

Hope this helps

[squeaky pete]

im gonna try that after i rebuild the sr from the bearing change lol

[GravityKills]

Thanks a lot!
I'll try tomorrow.

I had sent a mail to Rüdger Feil, and he suggested to test it without the shim and a different brand of fuel. It could be related to the Optifuel I'm using.
Unfortunately, the only other fuel in town would have been coolpower 30 % (at 'only' €48 per gallon), but it's sold out.

[robgt]

Optifuel works fine for me in my YS91SRS
It is more than likely a tuning issue, not any particular fuel you might use.
Cheers,
Rob

[Tim Procter]

Lots of YS91SRS engines running perfect with Optifuel.


Reset needles to stock (Default) and try again, only very minor adjustments needed for max power.

[mattie-lodge]

I echo what the boys have said here. I'd be very surprised if it was your fuel.

[GravityKills]

It's a bit weird that the problem is the same for me with both the SR and the SRS: Each sits in its own heli, the only thing in common is the fuel and that it's me who's tweaking the needles.

I'll reset the needles and start with the high needle this time. If it works on the unshimmed SR, I'll take out the extra gasket from the SRS and try again.

BTW, in the meantime, I screwed a 5 mm steel plate to the heli, then the V-Bar sensor on a Spartan gyro mounting kit with another steel plate. This solved the vibration problem with the V-Bar.

[barney]

Hi Grav..if your comparing the Power to weight between a 50-90 Its kinda a different kind of Power produced. A 90 relies on stored energy in the blades and is a little slower to ramp up the H/S should you over pitch it with poor pitch management. More power yes but delivered in a different manner.

It it runs inconsistant the one way vavle may be the culprit. If your not flying very regularly its worth blowing/sucking each your time out prior to flying.

Brian

[mattie-lodge]

If your not flying very regularly its worth blowing/sucking each your time out prior to flying...........Brian

Ohh errrr misses!!!!!!!!!!!!!!



Sorry couldn't resist that one

[barney]

Lol..

[GravityKills]

OK, I think you guys were spot on.
I left the hover needle at the starting setting, and leaned out the main needle.
At some point I busted a glowplug, so I guess that was then too lean...
The main [edit I meant "full"] needle ended up at about one turn open. Power was pretty good.

Next I'll try without the shim. I didn't get the opportunity today, both my 700s went sort of crazy, and each tried to dig its own hole into the ground with what looked like a lot of negative pitch. Not as bad as it looked at first glance, but I'm starting to lose faith in that radio of mine.

[Guest]

Hi,

I very much doubt it's anything to do with fuel many 3D and F3C pilots are running YS90 engines with great success on OPTIFUEL 30 and 30-SLV. It's either a tuning issue, already covered or perhaps a clunk tube issue. Overtime the silicon tubing becomes soft and will slowly reduce it's ID at higher flows and this has the effect of unexpected 'leaning' in flight, often the user will chase the needle to resolve which ends in a broken engine. I would change the clunk tubes first and test the one way valve. OS8 should be fine no shims should really be required standard YS engines work on 30% with no issues. If you use a fuel magnet check that there is no bits of sponge in the fuel system as well.

AVROBOY