break up / how is battery voltage measured?

[drifteddreams]

Hey all,

Im running a microsquirt v3 to tune a 2017 ninja 650, the car was built before me and has some less then idea wiring. Anyways we finally got a chance to dyno the car last weekend, i set the limiter for 10K and start doing some pulls, right away we realize past 6k the car starts to break up hard, it sounds like its hitting limiter but bouncing around at 6-8k while continuing to climb slowly. AFR for the pull was stoichiometric until the car started to break up at that point it started to go lean towards 18:1 with each break up. What i noticed was that our battery voltage on the gauge(in Tunerstudio) was very unstable during the entire time the car was running, when shut off it read about 12.5V but when running it was bouncing around 10 and only got worse during the pull even going down to as low as 7 for a brief second when the car got into the higher RPMs. We presumed it was the battery but even with a verified new battery and jumppack hooked up the voltage was doing the same thing. I unfortunately do not have logs for any of the pull, however i do have a video the gauges for each run if needed. I was wondering how a micro-squirt reads voltage and what can cause that issue? what wires should i specifically probe? Attached is a good tune from the day

[jsmcortina]

We really need to see a datalog.

James

[bobxyz]

MS measures +12v using the BOOT wire when it's not jumpered to ground. If that wire is bare and shorting to something else, it could cause erratic +12v readings and bad MS behavior. On the prebuilt microsquirt harnesses, I think the wire is purple.

[drifteddreams]

Ill get a data log today, were just firing up the car and revving it but it still breaks up even with no load on the car, could it possibly be something with the dwell settings? (the car has no charging circuit)

[drifteddreams]

We really need to see a datalog.

James

As promised heres the log from today, it seems like were loosing tach sink hence the 0rpm at points at the 13K at others, towards the end of the log i turned on a 5k RPM rev limit which it seemed to actually run pretty happy at

[drifteddreams]

Also wiring schematic if needed

[jsmcortina]

I'm not following the wiring diagram - which pin are you using for the signal wire from the Hall crank sensor.

Does it have a built-in pullup? See the Microsquirt Hardware Manual for wiring directions.

With a (Vauxhall as it happens) Hall sensor, I have physically tested a Microsquirt to 9600RPM with a 60-2 wheel.

James

[drifteddreams]

I'm not following the wiring diagram - which pin are you using for the signal wire from the Hall crank sensor.

Does it have a built-in pullup? See the Microsquirt Hardware Manual for wiring directions.

With a (Vauxhall as it happens) Hall sensor, I have physically tested a Microsquirt to 9600RPM with a 60-2 wheel.

James

I didnt realize but that was the default microsqurit wiring diagram from the hardware manual lol, were using a VR (magnetic) sensor input So Vr + and Vr - are being used the manual also notes "Some installs may find it necessary to install a "shunt" resistor between VR+ and VR- to reduce the signal voltage at higher RPMs. A 1/4W resistor is sufficient and values in the range of 1k to 10k". I think were gonna put a oscilloscope on the VR pins next time we run the car and see how noisy it is up top. And check if we have that resistor between + & - since that would explain why its breaking up in the higher rpms and loosing tach signal

[dontz125]

MS measures +12v using the BOOT wire when it's not jumpered to ground. If that wire is bare and shorting to something else, it could cause erratic +12v readings and bad MS behavior. On the prebuilt microsquirt harnesses, I think the wire is purple.

You don't want 12v anywhere NEAR the BOOT wire on a MicroSquirt - it goes right to the processor pin! You're crossing up the MS which shorts the BTTY ADC to ground. The uS shorts a processor pin to ground!

[bobxyz]

dontz125 - oops, you're right, I must have brought up both sets of schematics and then looked at the MegaSquirt set.

drifteddreams, sorry, the MicroSquirt measures 12v internally using a voltage divider to feed an ADC input on the CPU. It has nothing to do with boot. Maybe you have a loose +12v connection to the microsquirt and it is still good enough to barely keep the microsquirt running? There is some voltage filtering within the MicroSquirt but it seems doubtful that it would be enough to work with a loose connection.

[drifteddreams]

dontz125 - oops, you're right, I must have brought up both sets of schematics and then looked at the MegaSquirt set.

drifteddreams, sorry, the MicroSquirt measures 12v internally using a voltage divider to feed an ADC input on the CPU. It has nothing to do with boot. Maybe you have a loose +12v connection to the microsquirt and it is still good enough to barely keep the microsquirt running? There is some voltage filtering within the MicroSquirt but it seems doubtful that it would be enough to work with a loose connection.

a little bit of a update, our battery was super super super dead (someone put a lawnmower batter with less then 150 CCA in it) i also did learn the car does indeed have a functioning charging circuit, im assuming this is why the voltage was so sporatic, we have a new battery and it definitely seems like our break up was related to not having the shunt resistor between VR- and VR+, ill get the new battery and resistor setup and test the car over the weekend