Hi, Steve - One was given to me for evaluation so I tried it on the prototype ARF Cardinal.

Being an RC engine, I had to machine a venturi and install an OS NVA.

The run was satisfactory - smooth and steady, virtually no vibration.

But, the engine was quite thirsty - requiring around one ounce more fuel for the pattern than an LA .46. This may improve as the engine gets more time on it.

Also, as I recall, it was quite a bit heavier.

That's about all I can offer.

Bob Z.

I used Google, and I found three basic types of VMAX, but none were model airplane engines. It's probably safe to assume that these are a Chinese engine? It seems like they will make the same engine with any name on it. Apparently, they're all reasonably decent engines. I'm pretty happy with Magnums, but also have an ASP. They come out of the same door of the same factory. If you can provide a link to a VMAX website, please do. Curious in rainy Washington.  Steve