Yamaha Power Information

[NoWingsAttached]

Mohawk Aero has purchased the complete set of dyno data sheets and informative articles for the Yamaha snowmobile 4-cycle series of engines, including 2-cylinder, 3-cylinder and 4-cylinder (what I call the YG2, YG3, and YG4, respectively), from 2003 through the 2017 model years.

We also purchased the official data (as required per racing regulations) for each manufacturer's sled raced in each year, starting in 2003, for the AMSNOW and Adirondack shootouts held in December in the northeast. This set of data included some very interesting information about the first year the YG4 was introduced.

The racing teams demanded that the YG4 be completely broken in prior to the race so that there would be no advantage to Yamaha for racing a brand new engine. I understand the meat of the article from my conversation with the technician who did the testing, but will wait until I read it thoroughly before telling you about it so that I don't make any mistakes in the re-telling of the story. For the moment, suffice it say that the dyno shop owner told me that choosing the YG4 engine for an aircraft conversion kit is/was the most excellent choice of all engines he's ever tested, bar none, in his professional opinion.

We now also have the technical data you would want before spending your valuable time and money on any mods such as turbos, intake plenums (silencers), tuning, exhaust, mufflers, different boost setups, cams and cam timing, fuel injection tweaks, etc.

As I pour through this impressive tome of definitive information I will be happy to post some highlights and basic information. Stay tuned, I may be back-pedaling on prior YG4 claims, and I may be posting some stuff you hadn't expected concerning the YG3's etc.

Meanwhile, feel free to ask anything you like and I'll try to dig up an answer for you.

 

[NoWingsAttached]

As promised, here is the first reproduction of the new set of dyno stats. After speaking with the shop I found an error in my original iteration of the "Corrected HP" data published here on RF previously, extrapolated from the original dyno run which proved to be faulty in a second trial run on the following day - data I never had until now, and was "guesstimating" from the info I had available.

The original test fault turned out to be a sticking carb slide. If the choke is not fully disengaged (cable not adjusted properly etc.), it will cause pressures to be too low to offset the spring pressures on the carb vacuum slides - which are put there to prevent leaning out the engine with low venturi pressures caused by opening the throat valve too far for the engine manifold pressure.

Here is my revised chart of the official results straight from the horse's mouth so to speak. Although the two charts appear to be the same at first glance, the second one indicates output shaft RPM, while the first graph is for crankshaft ("engine") RPM.

In any event, the original RX1 engine introduced for model year 2003 easily clears 140 HP over a broad range from ~9500 RPM to 10,500 RPM. That, alone, is truly impressive no matter how you slice the cake. My own redrive testing has been 2.58:1 ans 2.72:1. Both have been able to hit over 9600 RPM with impressive results at the 68" Warp Drive prop. (My next project is scheduled to be a 3.01:1 Air Trikes.)

The results were established over ten dyno pulls done 10/31/2002 on a stock RX1 model 2003 using pump mogas. In other reports I've glanced over today from the techs they have reported a loss of HP in some of their other tests when using higher octane fuel, like a few HP higher for 87. Huh.

Other reports include changes to the intake plenum resulting in loss of power, etc. No surprises there, and I have been passing that info along to you guys here for several years now. Yet I continue to see builders eliminating the intake plenum (silencers). Oh, well. You can lead a horse to water...

 

[NoWingsAttached]

More to come: HP gains in the EFI version introduced in 2006 are attributed by the dyno techs in their reports to changes in cam timing, not the fuel delivery itself - injection vs carbs. (May sound vaguely familiar if you've been following my posts on RF for the past few years.)

Vector and Nytro Dyno results.

Stock vs Turbo Vs Supercharging, with stock engines blown or boosted as well as totally reworked w/ lowered compression ratios for higher boost capability.

Muffler and exhaust mods.

Tuning mods.

Other sled engines, including Rotax (Ski Doo) and Suzuki (Arctic Cat).

 

[Lee Scatt]

something still is not right, These curves look more realistic than the ones posted before, but, shouldn't the countershaft torque value be 1.35 X (or whatever ratio it is) the crankshaft value?

 

[N962GT]

Bueller. Bueller. Bueller...