Update on my misfiring/stalling 910 project - MVAgusta.net
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post #1 of 34 (permalink) Old 11-11-2007, 06:28 PM Thread Starter
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Update on my misfiring/stalling 910 project

i mentioned in another thread that i have spent about 50 hours reverse-engineering my 910S electrical system in an effort to diagnose why my engine skips/misfires occasionally (it used to stall before i put in iridium plugs). a couple of other members of this forum mentioned it happening to them when they pull the clutch in, which gave me an idea to investigate the sub-circuit that controls the "OK-to-crank" condition along with the "kill-engine-when-not-neutral-and-sidestand-down" condition. these two conditions are part of one (pretty simple) sub-circuit.

one of the key lines in this circuit is pin #7 of the CPU. the CPU holds this pin at 12V through a pull-up resistor. it is the responsibility of the neutral-switch, relay-box, and sidestand-switch to GROUND this pin, otherwise the CPU will forcefully kill the engine.

so i hooked up my scope to CPU pin 7 and got the waveform below. EEE-GADS there are random giant noise spikes that recur over and over! the larger noise spikes seem to happen every few tenths of a second. i mean WTF i could not believe what i was looking at-- my jaw must have literally dropped in amazement. note that the noise lasts only about 2 microseconds, but this kind of noise floating around in a circuit can WREAK HAVOC on things. it is indicative of bad design-- there is no good reason why this particular circuit should have this kind of noise present-- it absolutely should be filtered with a bypass capacitor (inside the CPU). as is, it is very possible that the CPU thinks (for 1 microsecond at least) that it should kill the engine because pin 7 is not at ground, instead is bouncing all over the place with positive voltage up to 6 volts!

more testing is required to determine if this is really what is causing my engine to misfire, and other owner's engines to stall. it's simply impossible to know anything for certain at this point, but this trail looks pretty promising.


Two '01 Suzuki SV650 race bikes; '06 Brutale 910 street
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post #2 of 34 (permalink) Old 11-11-2007, 06:38 PM
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Damn. That sound amazing. I don't understand, but I'm impressed that you do.
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post #3 of 34 (permalink) Old 11-11-2007, 08:24 PM
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Kinda hard to be certain, isn't it?

Quote:
Originally Posted by ridesideways
... it is the responsibility of the neutral-switch, relay-box, and sidestand-switch to GROUND this pin, otherwise the CPU will forcefully kill the engine.
I'm impressed with your attempts at analysis, but wonder if there's not more going on than you've been able to see with your o-scope. Is an examination of pin-out waveforms enough to really have an idea of what's going on inside the ECU?

'08 910R
'11 Husaberg FS570
'05 Lotus Elise

Bike History: '64 CL72 Scrambler, '65 Bonneville, '69 TR6, Yamaha 360 RT1, '72 Rickman Weslake 500, '82 Yamaha 550 Vision, '83 Eddie Lawson Replica, '85 900 Ninja, '86 GSXR1100, '91 GSXR750, '95 CBR900, Triumph TR595, TL1000S, Ducati 748 Mono, '95 KTM Duke, CBR929, '01 Aprilia RSVR, '01 KTM Duke II, Monster S4R, Husqvarna 450SMR, Brutale 750, Ducati 999 Mono, Husaberg FS650e
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post #4 of 34 (permalink) Old 11-11-2007, 08:30 PM
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This reminded me of the time my Gixxer kept cutting out when ever I hit a bump on the highway. It turned out to be weak kickstand spring that allowed the kickstand to dip down and trip the kickstand switch….
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post #5 of 34 (permalink) Old 11-12-2007, 04:08 AM
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Very impressive analysis!

The noises you are talking about must be happening on all MV ECUs then. Your CPU must be one of those that have more noise than others which don't stall or misfire...

Once you've finished your analysis, it'd be interesting to push it over to the R&D guys at MV Agusta. I have just the right contact ;-)
I don't know if it's too late, but if it turns out to be a manufacturing defect, MV will definitely be on MagnetiMarelli's ass to get this fixed.

One thought though, is there anyway you can fool pin#7 by placing an emulator or something that'd constantly tell the ECU that its pin#7 is OK and gets whatever ground signal it needs to get ????
As for the lambda sensor for instance, once can suppress it by placing a lambda emulator that tells the ECU it's getting A/F values (that are actually bogus because not really coming from actual A/F ananlysis).

Last edited by khameron; 11-12-2007 at 04:11 AM.
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post #6 of 34 (permalink) Old 11-12-2007, 05:38 AM
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post #7 of 34 (permalink) Old 11-12-2007, 08:19 AM Thread Starter
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Quote:
Originally Posted by asg21
I'm impressed with your attempts at analysis, but wonder if there's not more going on than you've been able to see with your o-scope. Is an examination of pin-out waveforms enough to really have an idea of what's going on inside the ECU?
you are correct, i am certain of nothing. but "certainty" is for lazy people, not engineers. if i needed to be certain of the outcome of every first step i've taken, i'd still be living with mommy in a crib.

when my bike stops misfiring because i've bypassed the noise (or corrected whatever other electrical gremlin that's causing the problem), then you can decide for yourself if you want to keep owning a bike that stalls and misfires, or if you want to make the same change to your bike.

caveat emptor, it is always possible that the problem may turn out to be something that is impossible to correct without major changes to the CPU. i'll risk my time to find out though.

Two '01 Suzuki SV650 race bikes; '06 Brutale 910 street
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post #8 of 34 (permalink) Old 11-12-2007, 09:21 AM
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Quote:
Originally Posted by gio8856
+1. Where is JamesC on this important technical matter

However, sounds like a credible explanation. My uninformed view is that the skip could easily be an electrical issue. Thx for all the effort and report out Ridesideways

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post #9 of 34 (permalink) Old 11-12-2007, 09:40 AM
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Very interesting sideways, keep up the investigation.

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'88 Ninja 250 > '92 GSXR-600 > '01 YZF-R1 > '06 Brutale + '07 Customized VTX-1300
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post #10 of 34 (permalink) Old 11-12-2007, 10:17 PM
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Certain?

Quote:
Originally Posted by ridesideways
you are correct, i am certain of nothing. but "certainty" is for lazy people, not engineers. if i needed to be certain of the outcome of every first step i've taken, i'd still be living with mommy in a crib.

when my bike stops misfiring because i've bypassed the noise (or corrected whatever other electrical gremlin that's causing the problem), then you can decide for yourself if you want to keep owning a bike that stalls and misfires, or if you want to make the same change to your bike.

caveat emptor, it is always possible that the problem may turn out to be something that is impossible to correct without major changes to the CPU. i'll risk my time to find out though.
I've re-read my email, but can't find the word "certain" - maybe you confused me with someone else. I was just wondering if a problem that's internal to a chip can be understood by looking at output waveforms, that's all. Good luck, though - I hope you're successful. I just think problems with modern engine management systems aren't really amenable to your approach, but I'll be glad to hear your report when you prove me wrong. I'm just glad your problem's not universal - my 910 doesn't exhibit the behavior you describe.

Btw - I'm an electrical engineer, and I'm certain sometimes.

'08 910R
'11 Husaberg FS570
'05 Lotus Elise

Bike History: '64 CL72 Scrambler, '65 Bonneville, '69 TR6, Yamaha 360 RT1, '72 Rickman Weslake 500, '82 Yamaha 550 Vision, '83 Eddie Lawson Replica, '85 900 Ninja, '86 GSXR1100, '91 GSXR750, '95 CBR900, Triumph TR595, TL1000S, Ducati 748 Mono, '95 KTM Duke, CBR929, '01 Aprilia RSVR, '01 KTM Duke II, Monster S4R, Husqvarna 450SMR, Brutale 750, Ducati 999 Mono, Husaberg FS650e
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