Viperhead on YS91 is it worth it

[Zilly]

I have a YS91 which in all fairness runs really well, what will the Viperhead do for my engine and is it worth the money?

z

[Bert Kammerer]

I personally don't think that the ViperHead adds any more power at all. However, it will smoothen your engine, especially at idle. It will also burn fuel more efficiently and will give you extra redundancy.

[DavidH]

Zilly,
I did the prototype testing for the Viperhead that goes on the YS 91. Yes it does seem to add power to the top end of its range. For me the biggest benefit was it smoothed the engine out in the mid range, so the engine ran smoother when in a hover. Really there is no extra redundancy, usually when one plug dies, the other is going to go also. At least that has been my experience.

David

[Bert Kammerer]

Really there is no extra redundancy, usually when one plug dies, the other is going to go also. At least that has been my experience.


Interesting David. I have burned typically the hot plug before I burn the cold one. I have simply noticed the lack of performance, landed and noticed one plug gone. I have seen this at least 3 times in 6 months. I have never had to do an auto as a result of both plugs going in. At least that is my experience. I can't notice the top end getting stronger, but I am not as good as a pilot as you are. I can definitely notice smoother run in a hover.

[lawrenmd]

I am interested in fitting a Viper Head on my YS 91. Any reccomendations on the proper number head shims required when using cool power 30% at sea level here in Florida?

Thanks

[Bert Kammerer]

I have always used the stock shim that you get with the ViperHead --that is, remove the existing shim and replace it with the one that comes with the ViperHead. I run Cool Power 30% myself. If you are going to run Magnum, you need to shim it differently. Maybe David can confirm the one shim thing :)

Bert

[DavidH]

Yes when we were doing the prototype testing. We found that one .004 shim is what allowed the motor to run the best on CP30% and Powermaster 30%. That is the only two fuels that were tested. The shim that comes with the VH is .004.
Take the stock shim out and install the shim that comes with the head. If your running Magnum 30% fuel, use the stock shim and the shim that comes with the VH for a total of .012 in shims.

David