Something puzzles me here, when I have seen a MVVS 51 on a factory supplied (quarter wave) mini pipe the model sounds like it goes into a slightly higher pitched break in the overheads and at about the top 20 degrees of any loop - now is this classed as a type of 4/2/4 break (which I doubt because it was never four stroking in the first place) or simply coming onto pipe a bit harder, or is it something else coming into play here?

Fuel is 20% castor, 5% nitro and 75% methanol, tank is uniflow and the prop I believe is an 11x5.5.

The model has stacks of power everywhere and a beautifully consistent airspeed so there is nothing wrong here, its just that I have the same engine waiting for model and was wondering about how it runs and how to describe it.

Thanks.

Sounds like a "rich-2  run", a lot like a MACS Muffler setup, which is also a 1/4 wave pipe. I've used these, and like the setup. Easy to run, but finding the right prop to get into the correct rpm range does take some doing. For the .40/.46 size, 10,200 rpm at launch is about right. Larger engines may launch slower, and smaller engines might launch higher, but I've run only the .46LA. Sweet!  http://www.macspro.com/onepiece.asp

You should still be able to tune the amount of break with 1) nitro content 2) venturi size  3) muffler outlet size and 4) compression, in no particular order.    Steve

Thanks for the info Steve, but are the Mac's pipes in the supplied link really 1/4 wave resonant pipes?

I mean, I can't see them labeled as such on the site and they do look different to the MVVS and the old pylon racer pipes so I was just wondering if they give a power boost.

And a LA 46 on a pipe? Sounds like a winner there!

Well...I was going to ask what the MVVS 1/4 wave pipe looks like, because few folks over here have seen them. I sure have not. 

I would expect that the overall length would be longer for lower rpm/bigger engine. And that avoiding leaks would be important. The MACS Muffler has a pressure tap, so I am guessing that as long as the "leak" is steady and consistent, it wouldn't matter. But then, like any muffler pressure setup, if a leak develops in flight (muffler loosens, fuel hose pinhole, etc.), the engine goes lean at best.  Steve

Steve,
check out item 3254 on this link -
http://www.mvvs.cz/prislusenstvi_e.html

The long since out of production MVVS 51 has virtually that same pipe but minus any header length (so it is very short, much shorter than one expect - just think Stalker muffler length and you would be close) and is supposed to give a 30% power increase over the stock canister muffler.

The 'magic muffler' design has the header pipe length running about 3/4 of the way into the canister and you can see a cut away pic in this link (4th pic from the bottom)-
http://www.rconline.net/magazin-2001/variationen/variationen.shtml

Leaks in a quarter wave tuned pipe also show as a lean run and although little harm should result to the engine, you will be rubbing your shoulders and arms after one due to the massive increase in line tension.

Cheers mate.