ProMuffler v2

Mfn. No: PDR0053-2

Availability: In Stock. Ships within 24 hours.


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The ProMuffler hasn't been an easy product to develop.  In fact, it's not really a muffler but more properly, a suppressor. Regardless, muffler is what everyone refers to them as, so we'll play ball, but we mention this so you know that we know there's a difference! Anyway, this is our v2 version, which has been optimized with slightly greater volume for the slightly larger displacement 55-class engines (while still working about as nicely as the original on the 50-class engines).


What makes it really great for you is installing it doesn't make your engine finicky to adjust. Nascially, setting the needle valve is completely uncritical; what we call set-in-and-forget-it easy. Of course this is a slight exageration but nevertheless you're looking at maybe adjusting a couple of clicks of the high speed needle between spring and summer, and once again when winter sets in. Howeevr, it leaves your engine deads nuts simple to tune - especially compared to those tinny-sounding tuned mufflers claiming to make extra power (you know the ones), which often has owners fiddling with the needle setting nearly every day. And all for power differences even experts couldn't discern . . . unless they're, a) paid company-shills, or b) 2-gallon experts yapping on the Internet.


As supplied, PDR0053-2, complete with long silicone exhaust-extension (PDR0062) for cleaner models upon landing.

- As supplied, PDR0053-2, complete with long silicone exhaust-extension (PDR0062) for cleaner models upon landing.


How does it work? Through the use of champbers. Partly it's the result of computer gas-flow software, whihc is useful with respect to flow and timing of the pressure wave returning to the exhaust port as it's uncovered by the piston - this is a tuned-muffler, so this is important. However, partly it's the result of real world experimentation. This is because the real world has such a complex interaction of variables like temperature, atmospheric moisture, engine RPM, fuel composition, glow plug heat, compression ration, e.g. so many variables as to defy accurate computer modeling.  Thus, and quite frankly, absent a NASA budget, plus a time slot on a supercomputer to nail it down with simulation, this means our results owe as much, or more, to art than to science! But it's really, really good art/


In fact, to get to the ProMuffler v2, we've made more than a dozen distinct iterations.  I.e. before pulling the trigger on a production run of what you can buy.  For example, after the first one, we kept making it a little fatter and longer, increasing the internal volume and seeing improvements in responsiveness.  We also varied exhaust stinger ID (inner diameter), which affects the backpressure and idle.  We also varied the size and placement of intermediate chambers, and even the diameter of the interconnecting ports, as we worked to create the best tuned muffler we could.  In fact, to our amazement, seemingly small changes often led to making more horsepower . . . until we went too far on any given step.  Afterward,  it was a matter of figuring out exactly where "too far" was!  I.e. regardless of whether we were configuring the volume of the chambers, or the exhaust stinger ID, or even how much primary volume to allocate.  Anyway, when we tested the first ProMuffler sample, our hopes were modest.  We we intent on making a nice, quiet, variation of the many mufflers offered by our competition because the helicopter engine world had changed with the introdution by OS Max of their powerful 50SX-H to replace the OS 46FX-H.  Simply put, when we began development, existing mufflers were simply too small to allow the engine to breath properly and thus, reduced specific output.  In short, we saw a market opportunity and moved in to capitalize on it.



In fact, our benchmark was the popular Thunder Tiger 50-class muffler, which frankly, is a perfectly serviceable unit for modest power applications like beginners learning to hover.  Compare the original ProMuffler prototype versus the Thunder Tiger muffler (top).  Amazingly, mostly through blind luck, right from the get go we had to open the needle 3-clicks (richer) and increase main rotor pitch 1°, which meant we were making more power.  Hmmm, curious about the why, i.e. about comparative relationship between volume vs. length, we CCed both units and discovered that though ours was shorter, because it was fatter too, it had slightly more volume. Naturally, we couldnt leave well enough alone and promptly hacked theirs apart to learn what we could learn.  Who could have predicted where it would ultimately lead? 


PDR0053 ProMuffler prototype (bottom) versus the Thunder Tiger muffler (top). 

- PDR0053 ProMuffler prototype (bottom) versus the Thunder Tiger muffler.

Interestingly enough, because we'd had to open the needle valve a few clicks, i.e. making the engine's mixture just a tad richer, we theorized it was because the engine was making a tad more power (more fuel=more horsepower every time), which was confirmed emperically by the need to increase pitch. That's because we used an optical tachometer to actually "see" more power happening (via an increase in main rotor blade RPM), which meant we had to increase max pitch to keep rotor RPM constant. Verifying more power was a repeatable process since switching the mufflers back reversed the optimal setting by the same 3-clicks.  Think about it, a helicopter unlike an airplane, can almost infinitely vary the load on the engine by the simple expedient of increasing the pitch of the main rotor blades and thus, a helicopter can essentially be thought of as a flying dynomometer, which is handy for development!



By the way, as mentioned earlier, we started down this road when the OS Max 50SX-H was the top dog amongst 50-class engine.  Since then, OS released the Hyper, so we changed with them because OS Max set the standards for engines in the 50-class helicopter amrket.  Sure, there are 50-class helicopter engines from Evolution, Webra, Thunder Tiger, Align, and YS but the OS product pretty much owns the market and thus, sets the pace for the others to play catch up   Anyway, that first muffler became our internal benchmark and we called it the MM for Muffler Mule.  We kept it for back-to-back testing.  similarly, we kept the same set of main rotor blades (V-Blades), and always used the same fuel (Wildcat 30% standard heli), plus we corrected for temperature and humidity. But the key was having the same set of blades and the orginal prototy to test back-to-back.  Anyway, learning the volume was greater for our prototype than for the Thunder Tiger muffler, and figuring if some is good, more is better, we immediately made a bigger prototype (i2) . . . and promptly lost power!  Thus, back to the drawing board we went to try and "sneak" up on the "right" muffler.  We made many successive units, some a little bigger (until we went too far again, that is), and long story shortened, more volume generally leads to more power, but then we began to play around with chamber volume.


We crash too, and consistent with making lemonade from lemons, testing revealed dents decrease performance!

- We crash too, and consistent with making lemonade from lemons, testing revealed dents decrease performance!

By the time i9 (iteration number 9) rolled around (the one that's not polished in the picture below), we were using the OS Max 50SX-H Hyper. Before someone asks, yes, changing engines seemingly buggered all our previous test result, but by repeating the test runs we were able to extablish the previous results were, fortunately, duplicated right down the line!


Variations on a theme, as we worked to discover the volume, length, and chamber configuration, which works best.

- Variations on a theme, as we worked to discover the volume, length, and chamber configuration, which works best.

With i10 we are pretty close to what would ultimately be the one final product - or so we thought! As it turns out, where the chambers are positioned, and how big the perforations between them are can make a significant difference in power as well as something not so easily described, which we call "user friendliness".


By the time we got to v10 its slimmed back down and a tad longer as compared to v9 - we're on the right track!

- By the time we got to i10, its slimmed back down and a tad longer as compared to i9 . . . we're on the right track!


Folks, in case you haven't figured it out, all along we were in pretty much unproven territory. You see, the computer flow simulation program had already said the mufflers were big enough as of i1, but because we're just a bunch of Southern boys who trust empirical evidence more than a computer, we kept making succeeding iterations, each perhaps a little bigger, or different chamber volume, configuration of ports, etc. What's empirical evidence? That simply means that we tested it to see if the results matched what the computer said, and when it didn't we were on our own!  By then we were developing a feel for what was going on, i.e. intuition and while the theoretical computer results were that it had enough volume, empirically (i.e. by bolting it on and testing it) we kept having to richen the mixture with different versions and whenever that happened, we watched the main rotor RPM increase and thus, knew when we were on the right track - or not!


For what it's worth, 12 iterations doesn't mean there were only 12 protoypes made. Au contraire, there were actually several variations of each iteration. For example, between i9 and i10 - the lost one called i9B existed (as well as i9C, i9D, and i9E) during which we learned you can have too much of a good thing! Anyway, all in the i9-series got sliced and diced (yeah, cut open as if with a sharp knife) as we tried to figure out where we'd gone wrong.


Here's a comparison of i10 in my hand vs. i12, which is the one I finally pulled the trigger on for manufacture.

- Here's a comparison of i10 in my hand vs. i12, which is the first one we first pulled the trigger on for a production run.

By the way, i11 was an abject failure as again we went too far. As with most in each series, those too were lost as we sliced and diced them apart. For example, there was only a 7cc variation between v12 and v11.


Production PDR0053v1 (actually v12B1), which consistently exhibited the best combination of quiet user friendly power.

- Production PDR0053v2 (actually v12B1), which consistently exhibits the best combination of quiet, user friendly, power.


Take a gander at this little sweetheart! There's a lot of intricate aluminum welding going on here folks! What's more, in an attempt to maximize the market, we machined a mount for the pressure tap which can be bolted in to either side, i.e. starboard, or right-hand-side exhaust helicopters as well as port-side mouting. 


Note the smooth welds in the aluminum sections, which are subsequently polished to fine level of detail.

- Note the smooth welds in the aluminum sections, which are subsequently polished to fine level of detail. 


Here's a close up of the aft part of the unit.  Looks pretty sweet, eh?  by the way, the eight ridges are just for looks.  However, the placement of the internal chambers is easy to discern due to changes in OD of the body.


Aft end of the ProMuffler in close up detail - the eight grooves aren't there for anything but beauty and attention to detail.

- Aft end of the ProMuffler in close up detail - the eight grooves are just for show.


So where are we now?  Why did we change the PDR0053 to create the PDR0053v2?  Well, as usual, we gain experience with our product through our customers and thus, we learned a thing or two over time.  For example, the mounting flange of the V2 is more hefty.  Wanna harzard a guess why?  Yup, experience taught us a valuable lesson regarding our initial assumption about how smoothly customer's helicopters are - or more accurately - aren't.  Added to it, when we have absolutely nothing better to do, we continue to fiddle with the design and whip up new prototypes.  Naturally, in addition to putting into place what we've learned with respect to basic strength in the area of the flange, we've been playing with differences in port diameters vs. volume (said results we'll keep to ourselves).  However, the most obvious, i.e. very visible, difference is the mounting flange, which is considerably more meaty in the PDR0053v2 pictured on the right.


Where's the meat? Experience is a harsh teacher because she gives the test before the lesson!

- Where's the meat?  Experience is a harsh teacher because she gives the test before the lesson!  V2 flange on the right.


So there you have it, the development story of the PDR0053-series of 50-class helicopter mufflers from ProModeler. Our product is more quiet, lighter, and far more user friendly than similar competing products - some offered at nearly twice our price.  However, while you can measure some things, i.e. weigh them, or use your ears to determine, which is more quiet, there's something far more difficult to measure.  It's termed "user friendly", and  it's a subjective, which means it's between hard-and-impossible to get a handle on.  In our view, user friendly is the important combination of several factors like a broad power band, plus an easy to adjust needle valve, i.e not finicky about its setting,  Doing it better than Hatori, Muscle Pipe, Century, Thunder Tiger, or Align muffler isn't easy.


In our view, the single most important factor you should consider is a broad adjustment range for the engine's needle-valve because a helicopter pilot absolutely depends on smooth transitions through the power band.  Basically, the constantly changing collective pitch while flying results in near constant excursions through the engine's operating range to maintain constant main rotor disk RPM, which means the engine's throttle is always moving.  Moreover, the engine must 'never' hang at idle as more 'tuned-type' mufflers are prone to behaving, which affects autorotations.  Nor should it ever hesitate through mid-range.  Simply put, it 'must' ensire a smooth power delivery.  These are the two most important factors to consider.  Sure there's weight, and how loud it is, but performance dominates the discussion.


Meanwhile, each manufacturer leans more, or less, toward tuning to make power.  More tuning is shorthand for more fiddling with the needle valve as it becomes finicky, i.e. more affected by changes in the weather like temperature and humidity.  More emphasis on tuning also delivers more power, which is the flip side to finicky.  Striking a balance between tuning for a bit more power vs. an easy and consistent needle valve setting is never easy.  If you insist on the greatest consistent power, you will get it with our product because there's far less frequent need to make needle valve adjustments.  Basically, like the Hatori line of products, our design lean less on tuinng for power than the Muscle Pipe line.  We depend more on chemical supercharging, i.e. the nitro methane in fuel which is there precisely for making more horsepower because nitromethane binds with oxygen molecules and thereby permits more fuel in the mix resulting in more horspower - chemical supercharging!  Conversely, tuned designs are relying on the strength of the pressure wave at the exhaust port, which is more dependent on teperature and humidity leading them to be more finicky.  As in all things, you pays your money and makes your choice!


In short, our design relies on fine tuning the chamber volume and interconnecting port diameters, along with broad measures of length and diameter to create a great muffler.  Added to it, the ProMuffler has a deep, sexy almost, throaty rasp, which portends the power of the engine.  Here's what an experienced 3D-type, i.e. aggressive flying customer recently had to say;


"Had a chance to play with an MP-5 back in the fall. Hung it on a Pantera and it weighs almost 2oz more than the ProMuffler, cost about $50 more than the ProMuffler, and makes the same power (no noticeable increase or decrease)."

- Gus Petraits, Martinsville, IN


In summary, we offer an outstanding suppressor, which is perfect for folks running 15-30% nitro.  It's easier to tune and live with than the somewhat finicky, more-highly tuned-type products, while ensuring great power and a great exhaust tone (though it's pretty darn quiet), and we do it for a reasonable price. In short, it's got practical power and sounds great. What's not to like?


Thank you for considering our product.

John Beech - General Manager (and janitor)

John Beech - General Manager (and janitor)

Audacity Models, Sanford, FL