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Now that my MicroSquirted Yamaha is ride-able, I've been riding it. I've been seeing an intermittant failure, though, that has me puzzled. Occasionally, the tach will suddenly drop to about half of what it should be and I lose power. This is while moving at speed, so the engine is being driven by the bike's inertia, but uS is clearly firing ignition at less than the rotational speed of the engine. My tach picks up from one of the coil inputs, not from the uS tach output, so it's measuring the actual firing of the coil.
Rarely, uS will recover if I jiggle the throttle a bit or downshift, but usually this does not help and the engine will die if left like this. However, if I turn the ignition off and back on, while still rolling at speed, uS will pick back up and run normally again. To give and idea of frequency of this, it happened twice during one nine mile stretch yesterday.
Any ideas?
Thanks,
Paul
Last edited by SQLGUY on Wed Jun 04, 2008 6:19 pm, edited 1 time in total.
Data log attached. I have found that, in top gear on the highway, this behavior happens almost exactly at 4500RPM (per my tach, which seems to agree well with Megatune at lower RPMs). The attached data log was done in neutral by starting the bike (cold - which took three tries), letting it idle-ish for a few seconds, then slowly opening the throttle. Though the data log shows peak RPM's in the 8K range, the engine actually sputtered and near-died each time I got just over 5K, I never got anywhere near 8K. When it hit the problem point, the RPM's dropped down to idle, but, unlike what I'm seeing when on the road, the engine recovered and could be revved again without having to restart Microsquirt.
I see this behavior regardless of engine temperature or load, though one or the other of these does seem to affect the trigger point a bit, since I never got over 4600 on the highway.
The "events" occurred first at 4906.689, second at 4921.006, and third (less severe) at 4927.124.
I should also mention that my ignition system is a pair of GM Saturn coils from a '95 or so SC. They are being directly driven by uS (not through an EDIS base). They are connected to Microsquirt with about three feet each of coax. There are no capacitors currently in place. The coax shield is grounded to frame and coils at the coils.The HT side is four lengths of about 14" of 7mm solid copper Accel silicone with 5K NGK resistor boots. The plugs are non-resistor type (NGK BP7ES).
Power to Microsquirt comes from a relay that also provides power to the fuel pump relay, injectors, coils, IAC, and HEGO. The supply side of the relay is about 8" of 14ga to the battery (through a 20A fuse). Power grounds run about a foot to an eye bolted to the crankcase. Battery ground is bolted to the crankcase about 8" from there. Nearly all connections are soldered (there are a few insulated terminals where it wasn't practical to solder). My CLT is a one-wire sensor, all others use sensor ground.
From the rpm jumps, this looks like a tach input noise issue. The lack of recovery (which should be very quick at high rpm) and the fact that there is no indication on the trigger +/- may mean that the pulse tolerance is too high, so the processor is accepting anything as valid, but is then not working properly - kind of like a timing chain skipping a few teeth off the sprocket. However, when I look st the mapdot - it makes no sense and is way too high. The map/baro column is also a bit fishy. This leads me to think there may be some code corruption or a bad ini file. If you post the msq you are currently using I will try to run it tonight or tomorrow night. I will use a high rpm. When you psot this msq, do it by doing a save and post the saved msq, which should represent what is in the processor, which may not be what you originally loaded.
I ran your saved (last) msq exactly as it was with a dual tach input that ran from 3500 to 6000 rpm, back and forth. I looked at each ign output on the scope against the corresponding tach input and everything looked very consistent, with no missed outputs or change in dwell as the rpm crossed the rpm range. The only change I noticed was the 12 deg retard in timing between 5500 and 6000 rpm due to the rev limiter. From what I can see if it runs ok at 3500 rpm, it should run ok up to at least 6000 rpm, the limit of the test.
I didn't realize I had a rev limiter in place. I had recreated this msq from scratch back when troubleshooting the rising-edge/falling-egde offset issue. Either I set this by utter accident, or it's just the default. I'm going to try taking it out, or at least changing it to what it should be (9500RPM).
OK. Just tried it with the Rev Limiter disabled. No change in behavior.
So, it's not the msq, and doesn't seem to be ignition or power supply noise. What else could it be? Could this be the same issue that other people have been seeing as far as overdriving the VR inputs? Now should I try resistors?
Yes I would try increasing the resistance since it is a fairly easy thing to do and the fact that the rpm is affected on the data log does point to a tach problem.
