Hi Dar,

Does MVVS carry a straight venturi for the .21, like the ones I got for the little .15?

And if they do, what's the diameter of the inlet bore? I would like to try one of these .21's in Club 20 racing, and the rules state that the inlet diameter is restricted to maximum 4.5 millimeters...

Winibald,


We will have to see about that.

The 3.5 uses the same carburettor (#3216) as the larger engines (13 mm spigot size).
The .49 Acrobat venturi should fit, but is it legal size...

I will ask for you.

Any updates...?

Winibald,


The diameter of the venturi for the #3077A engine is 5 mm, which I believe is too large for your needs.
Or you will have to add a choke plate/insert, which cannot be obtained from MVVS.

Winnibald,
This weekend I turned a 4.5mm venturi for the .15 engine. It is a peculiar construction using 6 fuel spray jets, but can be made quite easily.

OK guys, thanks for the input.

Dar, that is correct, the rules in this racing class limit the venturi diameter to 4.5 millimeters. And since we are racing, and running the engine above 20.000 rpm (hopefully), a properly shaped venturi is important. So no choke plates...

Another question: does the needle valve of the .49 Akrobat fit the .21 engine? The one of the .15 is slightly too short...

PĂ©, why aren't you using the MVVS venturi on your .15? Just experimenting a little?

Winibald,


There are three MVVS venturi needle types available for MVVS engines:

1. The .15 type.
2. The GFRT type (for racing .40-.44).
3. The .49A type.

They don't interchange.


I am afraid you will either have to make your own venturi and needle, or to find suitable products elsewhere.