A few days ago we started receiving e-mail from readers concerning the rev limit of Yamaha’s 2006 R6. I’m sure by now most of our readers have seen our review of the bike, as well as those of other web media and print mags. All of these reviews emphasized that the new R6 revved to an incredible 17,500 RPM redline – by FAR the highest-revving production bike in memory. We were so impressed by this claim, we wrote an article on September 28, 2005 asking whether valve springs could control valves at this RPM level — approaching the 19,000 RPM achieved by F1 race cars.
R6s have already begun arriving in dealers, and a few early buyers have had a chance to take them to the dyno. Anyone who has dyno’d a bike knows that the dyno can take its own RPM readout by means of a sensor clipped to one of the bike’s spark plug wires. It seems that “unbelievable” might have been a better term to describe the 17,500 RPM limit – the tach may say 17,500, but the dyno’s RPM plot tells the real truth, and that is that the R6 is revving to somewhere around 16,200 RPM before hitting the programmed-in rev limiter.
When we first heard about this on the message boards at r6messagenet.com, we found it somewhat hard to believe. After all, the 17,500 redline was a centerpiece of Yamaha’s pre-release promotional campaign, and our own tester rode a bike whose tachometer spun far enough to touch the edge of the 17,500 RPM “red zone”. That would mean that not only did Yamaha promote the R6 (heavily) as having something that it didn’t, but that the tachometer actually deceives the rider by telling him that the bike is revving much higher than it actually is.
To confirm the truth of these claims, we turned to Yamaha Media Relations Manager Brad Banister. In a phone call yesterday afternoon, Banister confirmed that the 2006 R6 is definitely not revving anywhere close to the claimed redline – admitting that the tachometer is “over 1,000 RPM off”.
We later spoke to another, more senior Yamaha representative, who told us that Yamaha Japan blames the issue on tachometer error. He stated that all bikes have some margin of error in the instruments, but because the tachometer on the R6 is reading so far off from the engine’s actual RPM, Yamaha will no longer be advertising the R6 as having a 17,500 RPM redline. Yamaha has already modified their web site to remove all traces of the 17,500 RPM claim.
This still doesn’t explain why Yamaha claimed that the bike revved so much higher than it actually does. Whether or not the tachometer reads accurately, the ECU certainly knows exactly how many RPM the engine is turning – it has to, since it sends the signals that tell the spark plugs to spark and the fuel injectors to open and close. Most ECUs determine engine RPM based on signals from a sensor that monitors the rotation of either the crank or the camshaft, and these sensors are typically extremely accurate. If they weren’t, the ECU wouldn’t know where each cylinder was in its cycle, and thus wouldn’t know when to open the injectors or send a spark to the plug.
The rev limiter is programmed to take effect at a certain RPM, and it gets its cue from the ECU, not the tachometer. This means that the actual RPM that cues the rev limiter (we’ve heard 16,200 RPM, but Yamaha won’t say exactly and we haven’t had the opportunity to test it for ourselves) was programmed into the ECU by the engineers who designed and developed the bike. If the development team KNEW that the bike didn’t rev to 17,500 RPM, why would Yamaha promote it as doing so? We’re not sure, and company representatives did not say anything beyond the statements we quoted above.
We’d like to apologize to our readers for the fact that we included this incorrect information in both our technical preview, and our ride review of the R6.
Keep your eyes on Motorcycle Daily for more information on this situation as it develops.