7000 RPM 'soft' rev limiter?

Today was a great day. 60 degrees, plants turning green everywhere around, and a road to the top of a mountain almost entirely to myself.

BUT

I had something strange happen. I found myself on a long, straight road with no other human beings in sight, and since this was really the first proper fun ride I've been on this year, I couldn't resist the urge to twist the throttle to the stop in 5th and hold it there for a bit. All was well until exactly 7000RPM, when the GRiSO suddenly stopped accelerating and the engine changed in tone as if maybe timing advance was being taken away?

Thinking it was a fluke, I tried again in 5th, then in 4th and 3rd gear. Wide open throttle at exactly 7k, it suddenly falls off. Not like a traditional 2-step limiter that it bounces of off, but like some sort of "soft" limiter is the best way I can describe it.

Other than that, all is well with the bike. Fresh tune up in the last 300 miles, and as I said in my other thread about Beetle's roller map, it runs faultlessly. Better than it ever has.

Any ideas? Is that normal? Something in the map? There's no fault codes or check engine light or anything of that sort.

Roller maps are set 8750 RPM. Spark issue?

What would should I look for? Plug caps I assume? Anything else?

Are you sure the ECU rev limiter isn't set to 7000?? This is a settable value.

The shift light thing is set to 7700, but that has no affect that I'm aware of in terms of an actual limiter. It's just a light.

Yes, it's just a light. An annoying one at that.

Check plug caps and maybe pull the wings to check the coils. Check ECU ground and connections.

beetle wrote:

Yes, it's just a light. An annoying one at that.

Check plug caps and maybe pull the wings to check the coils. Check ECU ground and connections.

Sad, but true it is that what I know about automotive electricity weighs about a gram ... but would any of those possibilities you mention cause the reported effect, i.e., "All was well until exactly 7000RPM?"

Surely "plug caps, coils, ECU ground, and connections" would be issues throughout the wind-up, no?

Going to fetch my dunce cap in anticipation of my failing grade ...

Bill

Think 'frequency', Bill. Throw in a smidge of inductance. Then think like Tesla.

Should I add 'hysteresis'?

Okay, so after at least visually confirming the plug caps, leads, plugs themselves, and coils appear normal, I went for a quick fling around the block. I tried every gear except 6th, and a variety of throttle positions, (ie, half, 3/4, and wfo) and the issue persists under all the conditions and gears I tried. There's a distinct change in sound and the bike noticeably drops off in acceleration at 7k. I pulled my phone out of my pocket and tried to capture it on video. Unfortunately the sound isn't as distinctive as I'd like in the video, but hopefully you'll be able to recognize it:

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The low fuel light came on shortly after I left home, I don't suppose that has anything to do with it??

Phase sensor or injector? Guzzidiag has some tests that may help.

My guzzidiag cables are at work. I'll have to wait until tomorrow to take a look there.

beetle wrote:

Phase sensor or injector? Guzzidiag has some tests that may help.

Went ahead and went in to the shop, so I have guzzidiag in front of me right now hooked up to the bike. Under the actors page I see that under "engine off" I can do "ignition L" and "ignition R" but it doesn't seem to do anything when I select one of those, other than blank out the other options... What tests should I be running?

Thanks!

Also, brimmed the tank with my usual 90 octane no-enthanol on the way, that didn't change anything. But I just wanted to rule it out. And I found that the bike revs freely to the limiter in neutral, it's only under load that it has the issue.

beetle wrote:

Think 'frequency', Bill.  Throw in a smidge of inductance. Then think like Tesla.

beetle wrote:

Should I add 'hysteresis'?

Thanks, but, as you likely well know, my thinking like Tesla is out of reach.

I had to look up hysteresis as I had no clue and, actually, just figured you were (understandably) insulting me.  

Good luck, Kevin; interested to hear the cause.

Bill

Sorry Kevin, I'm at work. Can't really help you the moment

Heaven forfend, Bill, just a good natured jibe.

Kevin, I tried the ignition tests. I think it just resets the 'ignition on' signal. Sorry.

No worries, I appreciate the attempt,

So, to recap, thus far I have visually confirmed that the caps, leads, and coils are in good condition, pulled the plugs themselves and they look fine, re-uploaded the map in the bike, and played around on guzzidiag, running all the tests and such available. There are no fault codes, stored or active.

What should my next test be? I don't remember experiencing this issue previously, should I try one of the older maps, like the non-roller mistral map, just to rule out something goofy in the programming? (Not in any way trying to blame you, Mark, just trying to think what has changed lately on the bike..)

I was going to suggest reflashing the map anyway. Try another map, weirder things have happened.

Does the pipe you are running have a cat? If so it may be clogged, especially if your bike had had arcing plug caps at some point.

Pete

It's the mistrial hi-pipe. No cat to the Best of my knowledge. My knowledge these things is nowhere near yours Pete, but the fact that it's an instant thing, like, flip a light switch at 7k makes me think it's something electrical, as opposed to a restriction somewhere?

Success!

I loaded up the non-roller Mistral hi-pipe no-dbk map that I had been using previously and sure enough she sings all the way to the redline now no problem. But isn't as smooth around town as it was with the roller map, haha.

So, there's something about the roller mistral map that doesn't jive well with my bike at 7k rpm.

Well, load the roller map again and see what happens.

What are the main differences with the roller vs. non? My roller runs great with the non-roller HMndBK, I've never tried the roller version. The non roller version may be more compatible with our US fuels and northern hemisphere airs.

Different fuel maps, different engine-temp correction tables and higher rev limit.


There could be any number of factors. Since I've never mapped the Arrow can, it's all conjecture. In Kevin's case, I'd suggest some sort of software corruption?