Webra 91AAR

Okay, first the disclaimer. I am not an expert in 2-stroke engines. I have owned, tuned and flown OS, YS, and Webra engines, but I always found their optimum settings by trial and error, just as I did with the new big block Webra 91AAR and YS 91ST. I wanted to see how these two highly lauded, hot-topic engines would perform under the same setup and flight conditions: identical helicopters, same electronics, same fuel, same pilot at the sticks flying both in the same geographic region under the same weather conditions. Because this was not a controlled experiment, my comments amount to anecdotal observations and should not be construed as an endorsement or indictment of any product.

Notwithstanding the ever escalating cost, acquiring a big block engine is relatively simple. Choosing one, however, is extremely difficult. Internet forum topics sing the praises of every engine on the market so that selecting one by popular demand would boil down to flipping a coin. In my case I simply wanted to experience the power of an engine that I might be able to master with enough time, commitment, and spare parts. I purchased the Webra 91 AAR from Cyberheli and the YS .91ST from Ishii Mokei in Japan. Both engines cost the same, $315 shipped, although I spent another few dollars to have Cyberheli break in the Webra for me so I didn't have to hover it through 2 gallons of fuel. I put both engines into Fury Extremes and, after several flights on the Webra, I installed a Perry pump to prevent it from leaning out as the fuel level in the main tank dropped. I used 2-oz header tanks on both Furys just in case I ran the main tanks dry. I flew 30% nitro in both, and over the course of two months I tried Wildcat, Cool Power, and Performance Plus. As far as fuels go, I noticed no difference in performance among the three except that the Wildcat generated noticeably less smoke than the CP and PP. It is noteworthy, however, that the Webra will run well on low or no nitro fuels while the YS works best on high nitro content. This is an economic consideration where the cost of nitromethane is an issue, especially in the overseas markets.

YS 91ST

In December, I took both Furys to southern California to escape New York's snow and wring out both machines under ideal conditions. I flew every day for a week, alternating between the Webra and the YS, pushing them to their limits as much as I was capable. I used identical pitch curves, +11/-11, and regulated throttle inputs with a GV-1 on each Fury. My main blades were MAH 690s, t/r blades were MAH 105s. Both Furys had GY401/9235s, 9253s on cyclic and throttle, and Hatori SB-15 exhausts. My tx is a Futaba 8U system with PCM receivers (I see no advantage to the 9Z's 13-point pitch and throttle curves when I'm using a linear pitch curve and a governor on the throttle). The Webra was geared at 8.18:1, the YS at 8.45:1. On the Webra I used an Enya 3 plug, on the YS an O.S. 8.

Ultimately, my comparison of the performance of the two engines was anticlimactic. Both engines devoured 11 degrees without bogging but would start to bog at 12 degrees when I added cyclic. Their acceleration and vertical penetration was noticeably better than the YS80s that preceded them, but despite claims from their various distributors that each was the most powerful engine on the market, I couldn't claim that either excelled above the other. I had some initial tuning issues with the Webra because its needle settings required more accurate dialing in than the YS, which is essentially a plug-and-play engine that is forgiving over a wide range of settings. Once I got a feel for the Webra, however, slight adjustments for changes in air temperature became second nature. The YS generally ran a bit smoother than the Webra, although when the Webra's mixture was right on it was very smooth too. I always fly in idle up with a head speed of 1,850, so I didn't explore transitioning to lower throttle settings. During rapid descents I assume my governors dropped the throttles to at least 50%, but I observed no leaning or loading up during entire flights. Flight times were very similar for both engines, 10-11 minutes before going onto the header tanks. These engines may behave differently from each other on tuned pipes, but noise constraints on my home turf make mufflers the exhaust of choice. Service and parts availability is better for the YS in the US, or at least will be once YS Performance builds up it inventory on the newly introduced .91. YS performance also offers a domestic warranty with its engines. As far as I know, there is no domestic source of parts for the Webra 91. On the other hand, the Webra runs much cooler than the YS, which may prolong engine life and reduce the need for parts and service. At this point it's too early to tell.

In the end, for me to choose one of these engines over the other would come down more to fuel economics and familiarity with the engine than to performance. If you want to run low nitro fuel without sacrificing performance, the choice is Webra. If you don't want to tinker with needle settings or you want a domestic warranty, the choice is YS. But these issues do not address performance. I suspect that the Youngbloods, Bennetts and Krauses out there might perceive some subtle differences in performance between the Webra and YS .91s. But as a mere mortal having flown both, I can't say that one emerges superior over the other.