fiery

My Feedback: (2)

As per the Barton VTR Rules:

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Quote:

Note: Schnuerle porting is defined as two or more directionally shaped ports, symmetrical about, and adjacent to, the exhaust port, normally in conjunction with, but not limited to, a flat topped piston.

Unquote.

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A boost port directly opposite the exhaust port is commonly also seen. It is not however a necessary feature for an engine to be considered Schnuerle ported.

Mr Cox

I got curious and took mine appart to check for assymetric ports, and this one doesn't have it (black-backplate version). Seems to have been a problem with the earlier ones then.

To me the porting is schneurle, perhaps with a little twist as the ports are inclined to open ealier near the exhaust port and later where the boost port would have been positioned (if they had made one). The piston is domed like on a PAW engine with radial porting (don't know the proper word for that one...).

fiery

My Feedback: (2)

Here is one of my "alloy backplate" "C" series MVVS 1.5. It feels and more importantly runs very well. It was obtained from Jiri Kalina. He said it was one of his "fast" examples.

The casting passages look very like Schnuerle porting. However the liner governs entry of mixture. The liner ports are not opposite each other. They are opposite the exhaust port. Therefore it is not Schnuerle porting. It is "Vortex" porting. Designed to clash streams and increase swirl. That is why these engines are allowed in competition events banning Schnuerle ported engines.

My engine had some carbon build up on the piston crown. A backplate pressure take-off riser is machined in.

Mr Cox

I'm just glad I don't have to be a judge at any of those competitions...

My runs/ran strong too, but I didn't have a tach the time. I'll have to run it again when the weather permits. Do you have any tach numbers from yours?

fiery

My Feedback: (2)

The diagrams in this link are illustrative.

http://en.wikipedia.org/wiki/Schnuerle_porting

Mr Cox

The wiki one barely looks like any real engine though with that exhaust outlet. The only thing that differs for the MVVS, as I see it, is that the two channels are very close together, had there been a little more space between them, then surely it would have been a schneurle porting.

What do you call this one then, schneurle with PDP and three boost ports ?

Mr Cox

Here is a better picture then the wiki one. Perhaps the best definition of schneurle is then that the two ports are right next to the exhaust port.

fiery

My Feedback: (2)

Well spotted.

The moving diagram in the "wiki" article is not clear in its description of the viewer perspective. It says from the side. That is generally correct, but the diagram shows the engine with the viewer looking at the "side" of the engine from the front.

Now, is that a factory set up on the liner in post #31? The engine is?

Recycled Flyer

The key descriptor with Schnuerle ports seems to be 'transfers entry adjacent to the exhaust exit' and the MVVS is the exact opposite - you couldn't get the tranfer entry point into the combustion chamber any further away from the exhaust exit point except by taking out the bridge between them.
(The look of the channels in the case is quite deceptive when considering it really is the ports angled entry not how it is fed.)

Mr Cox

The liner with multiple ports above is a typical high performance liner, you can get them with up to 7-8 ports...

Here is another picture of a standard novarossi/rex engine;

fiery

My Feedback: (2)

Impressive, for buggy application? I see the brand "Rex" is increasingly used for buggy engines by the NovaRossi concern.

Mr Cox

They do airplane engines too, .12,.15, .21 etc. I have one of their .12 engines but it is only a 3 port engine and setup for a regular muffler. The quality and attention to details look great though, here is a peak into the exhaust;

greggles47

The speed flyers in OZ say the 3 port motors are the way to go (for speed). Probably the extra ports give the car uses additional torque in the mid ranges. That's certainly not required in speed.

Greg

Recycled Flyer

RC Pylon racers use more transfer ports than Ican count.

greggles47

Chris,

I'm very tempted to respond to this.

G

Recycled Flyer

Sorry Greg, its just that once having seen inside Ranjit Phelans engine, the amount of ports and cut aways astounded me.

It seemed that on face value that so much of the liner was machined away that it couldn't possibly have any strength left in it!