I was given an MVVS 49 for Christmas, however when the person that gave this gift got it from Morris Hobbies, the Mini-tuned silencer that was supposed to be with it had been replaced by Morris Hobbies with a full sized tuned pipe. I would really prefer to have the mini-tuned type silencer for the plane I will be using this engine on. As I read threads in this forum it is apparent that there is more than one mini-tuned silencer that is used with this engine. I will be using it on a CA Models Funky 40, if anyone has got any recommendations for the silencer & a source for it, since Morris Hobbies has told me that they do NOT have any.

Thanks for the help.

Anaconda

Anaconda,


The MVVS #3248 tuned silencer gives a bit less RPM boost than a full length tuned pipe (200-300 RPM), but it has a very wide operating RPM band, without a need to re-adjust. It gets on-the-pipe at part throttle with it.

It is recommended that you use at least an 11x6 APC, or a prop of equal load (10.5x7, 10x8, 11.5x5, 12x4...).

This exhaust system is not very expensive, for a 1,500 RPM boost over a standard silencer.


MVVS engines are designed for running with tuned exhaust systems, no less than 20% oil (a lot of Castor) and up to 5% nitro, unless the head is shimmed up with one extra shim. Then you can use up to 15% nitro.

I also have purchased the .49 with tuned pipe. I will be using this for a patriot and want the additional rpm that the pipe offers. The versioin that Morris Hobbies sent does not have a pressure tap. Without the tap nor crankcase tap can anyone help me out with the best option to make this work.

Thanks for your help,

morewatts

Morewatts,


If an exhaust system does not have a pressure nipple, it must either use a pump (Perry VP-30...), or a pressure nipple must be installed in the pipe/header.
This is the cheapest solution, but the full length tuned pipe is peaky and needs tuning (cutting the header) for optimum length.

This is not something I would expect a beginner to do properly.
If shortened by too much, it can damage the engine.

The crankcase pressure cannot reliably be used on any RC engine.


Or, you can get the MVVS .40-.49 tuned silencer #3248 (or the #3249, if you want your engine converted to rear-exhaust - YOU CANNOT DO THIS AFTER RUNNING THE ENGINE).

This system is fit-and-forget.

For your Patriot, I would suggest a 9x8, 9x9, 10x6, or 10x7 prop.
the 9" sizes will be faster and the 10x6 with the best vertical performance.