YS91/MP2/8:45

[bkervaski]

We've been having a heck of a time getting my YS91/MP2/8:45 combo tuned. I got Don "The Ear" Wade helping me out and it's still not there. Running Powermaster 30%.

I ordered a two plug Viperhead hoping that would help. Any feedback would be appreciated!

Bill

[3DME]

I belive 8.45 is a little high on the YS/MP2 combo. I think Curtis recomends 8.0:1 but I am not sure as I run a Hatori. I am not sure if this has anything to do with your problem, but it is just a thought.

Mike

[tnreefguy]

I agree the 8.45 on the ys 91 is recomended for the hatori pipes the lower ratio would work better.

[ColinB]

I'm running my YS.91/MP2 combos on the 8.27 ratio and both work extremely well.

Give the 8.27:1 ratio a try.

Colin

[Yellowjacket]

On one of my Fury ex.I run the YS 91 with a Viper head on 30% Powermaster with the Cutis pipe @ 1800 head speed. That puts the motor @ 15210 rpm and it makes tons of power.

Depending on the time of year the YS motor temp ranges from around 110 to 160 with the sensor wrapped around the top of the cylinder were the head bolts on.

I have always used a MIP or Venom temp gauge to monitor the motor temp.
Not because they run hot I just like to know where they are running on any particular day.

It takes time to acquire an ear for tunning and can be frustrating.
It’s been my experience that YS motors tune differently than my OS motors.
I can lean my YS down to where there will be a noticeable power drop off and it still doesn’t really run hot. On the other hand my OS will keep making power until the temp spikes and the heli starts shaking from being to lean.
In my experience my OS has always run hotter than my YS to get the power out of them.

I was at a fun fly in Spokane Washington last fall and Perry Pike was the CD (a really nice guy)
He also works at one of their local hobby shops. He asked me for some tuning tip he could pass on at their hobby shop to help some of the new guys.They were having problems tuning their motors and some were smoking them some were blubbering rich. I suggested using a temp gauge as a tuning tool to help tune the top end until they could get some more tuning experience to keep them from burning them down.

It’s simple if on a summer day say 70 to 85 degrees your safe target depending on a 50 or 90 size
50 are 160 to 180. 90’s YS 110 to 160 OS 140 to 190.
If you’re an experienced pilot some like to run them hotter I personally don’t.
Keep in mind this won’t help to much on the bottom or mid.
The temp will spike 40 or 50 degrees after you shut down not to worry.

This is not the way to fine tune them but it will help you get them close with out smoking them and they will be lean enough to make enough power to have fun!

I have more tuning tips on the low and mid needle settings. I’m getting tired of typing!!

I don’t usually like giving out information like this on these forums because it just opens things up for criticism. Perry and his friends were grateful and thought it would really help them so that’s why I threw this out there

Bill.

[DavidH]

Not criticising anyone. But the person bkervaski has helping him ( Don Wade) has no problem tuning motors by ear. He has been doing this for 20 years plus.

Personally I prefer a Hatori over the MP2 on a YS 91. The YS 91's I have seen running the best were using Hatori mufflers. SB 16 or 17 will work.

David

[Rodney]

8:45 and MP2 with YS works for me.

[Ray Fernandez]

My Tempest, running a YS .91, using the 8.45 gearing, CY MPII and using CP 30% works well for me also. Plenty of power when I am flying. :D

[bkervaski]

It just runs really rough compared to my Evo 90 with Hatori pipe which runs smooth as silk.

It has been a bit cold down here, 40-50 degrees. I didn't think the cold would affect it that much ??

I ordered a viperhead but I think I'll swap the MP2 for the hatori as well.

Thanks!

[3DME]

Yellowjacket,

Your post has some very good info in it for the newer guys or guys having trouble with engines. Alot of people ask lots of questions on the temp subject. The only problem is it is a little off topic. I think there is good info in your post and Will should move it to its own thread if you agree. I feel the same way about the critisism issue, but the guys here on the freak are able to have an intelligent conversation without all the bashing that you will find on the other sites. We just dont put up with that stuff here. So what do you say about moving this post to its own thread?

Mike

[3DME]

bkervaski,

Please let us know what your results are with the Hatori.

Mike

[bkervaski]

I'm going to install the viperhead and run it to see if it smooths out a bit. I really like the MP2 from a audio and visual standpoint :)

If that fails I'm going to give up and put the hatori on.

I'll post the results. Thanks again all!

[bkervaski]

Got the viperhead installed. Man, I hope that shim is in there straight!! :)

Of course, the weather is freakin awful and I can't test it.

I have a new theory on weather. I personally think ronlund.com controls the weather and they have a grudge against me. Whenever I order something NEW and COOL, the day I get it, the weather sucks for 3 days. heh

[DavidH]

You did use the .004 shim that came with the Viperhead only? The stock shim that is in the motor would need to be removed. With PM 30% the .004 shim is all that is needed.

David

[bkervaski]

Yep, removed the stock shim - put in the .004 shim. I also went ahead and put on the hatori sb16fh while I was at it.

Of course it's cold as hell today! :)

[Gary O]

You will like the Hatori pipe better. I'm not knocking the MP2 at all, it's a great pipe, but you have to remember that Curtis designed it around the C-Spec. That's not to say that it won't work on a YS but from my expreience the YS likes the Hatori better for overall performance from low to top.I've got all my YS 91's on Hatori pipes now. I had MP2's on a few but the powere band just seemed to have some flat spots in it where with the Hatori it's smoother. I'm also just running the stock head and have gear ranges from 7:91 to 8:45 and they are great running engines.