Rev limiter?

[semimojo]

I never notice this when I'm on an excursion away from home, whether riding spirited or leisurely (the latter more common when traveling two-up), but it gets me all the time on my commute to or from work, or on short jaunts through town.

 

I'm accelerating smartly, as usual, still in first because the bike is pulling nicely, feels like it could wind out forever, when all of a sudden, CHOKE, RUMBLE, SPUTTER, SHUDDER, and DIVE ...

 

It's very disconcerting when that happens. It makes me feel like I'm riding a bucking bronco, especially if I happen to be leaned over. The problem is that it happens well before red line, and well before I think I need to shift. Is it a rev limiter kicking in? It seems a very conservative limiter, if so. I think it kicks in easily 1000 RPM under red line, right around 8K. Is that normal?

 

I guess I could just shift sooner. I could paint a red line at 8k on my tachometer to help me remember, but it's going to feel funny shifting that soon, like leaving power on the table. If it's possible to adjust the point at which the rev limiter (assuming that's what it is) kicks in, I'd like to consider that option. If it's not a rev limiter, then I'll take it in to the shop.

 

[Tri750]

Yea,

If you're riding at that rpm in 1st, leaned over, uh...shift.

They rev very quickly so by the time you "see" 8k and are maybe thinking about shifting once in a while, the engine is still revving.

 

No, the limiter is not adjustable, the rider is. Keep riding and you'll be fine as you get used to the bike.

 

Oh, get ready to buy a new rear tire before "you think" you need to with that type of riding. It's going up in smoke without you knowing it.

 

On my Z1 Racebike, I have a label cut like an arrow pointing at the 10,500 mark on the tach and the label says "shift, already!"

 

Shift .

 

 

[mneblett]

You're not leaving much on the table -- the torque curve drops off at the top end.

 

As to the rev limiter, it may be "smarter" than previous "fixed" limiters. It's a pretty simple calculation to determine from the current crankshaft acceleration rate at what point the limiter needs to kick in to avoid overspeed. In other words, we think of a conventional rev limiter as "kill the ignition at X rpm," but I would not be surprised to learn that BMW has added a variable limiter, one that permits you to slowly build engine speed up to the redline, but also looks at the acceleration rate and says "whoa, he's hammering it so I need to kill the ignition sooner to ensure rpm doesn't overshoot the limit."

[realshelby]

Well, I cannot run full throttle in first gear as the front wheel thinks it is attached to an airplane. It could be that the tachometer is not keeping up with actual engine rpm and it is indeed the rev limiter kicking in. But reading 8k when that happens seems wrong. What happens in second gear? I don't know that I have hit the rev limiter in the new RT now that I think about it. I did it about every ride on the old one. They usually kick in somewhere around 250-500 rpm beyond red line.

[lkchris]

Are you in rain mode?

[semimojo]

Thanks for the replies, folks.

 

Answering questions:

 

"Are you in rain mode?" For around town driving, I'm always in Road mode with Normal damping, so those are the conditions that apply when I hit the limiter. I don't recall ever hitting the limiter in Dynamic mode, but I only use that when I'm sprinting around the back roads. I find Dynamic mode a bit too responsive for in-town driving (e.g., front wheel often wants to lift when I'm rolling on the throttle ... not something I feel safe doing in traffic, not to mention looking like a clown). I've never tried rain mode.

 

"What happens in second gear?" Beautiful, hard pulling power happens. Same for third. By forth, I am backing off to stay safe. I've never hit redline or the limiter in any gear but first.

 

"You're not leaving much on the table -- the torque curve drops off at the top end." Yes, that is what I need to keep in mind. Today I tried shifting sooner than it felt like I should, and the bike stayed happy. So did I. Plus, I got to the power band sooner.

 

"No, the limiter is not adjustable, the rider is." I'm really enjoying my RT, but I need to adjust my riding habits to become more comfortable with it. This is my first big twin, and it is nothing like the inline four-cylinder sport bikes I rode in the past. I definitely need a different approach for the RT.