How clean is 12V normally?

I'm seeing a decent amount of noise on my 12V... about 1.8V of noise, with 13.7V being the peak where the regulator seems to obviously be limiting. This is around 4000 RPM. Wondering if anyone had measured A/C noise on their 12V, or used an o'scope on their 12V supply.

 

...and, now that I went back and measured it again, I'm seeing about 50mV of noise on the 12v. This doesn't seem unreasonable to me at all.

 

Ive never considered noise on DC. Are you concerned it would cause problems?

 

For my system it could. I converted mine to fuel injection.

 

I can make a comparison later today and post it. As far as the system you are using I suspect they don't give you a schematic on it, but it may be designed somewhat like the TCI. You often read here that the TCI will not operate below about 10V, but truth be told it has an on board zener regulator that lowers the operating voltage down to 8V. Consequently, the main issue with low voltage and weak spark on the stock setup is more to do with the ignition coils and the lower secondary output with lower primary input voltage. I guess one could speculate on FI that at some point a lower or poor quality supply voltage might have an adverse affect on the injectors as well as the ignition coils.

 

Provided the input ac is above the 12.8VDC needed for output I would expect little ripple. But of course this is 1980s electronics, and nearly the only electronics on the bike, so maybe they weren't that fussy? 50mV? Wouldn't surprise me.

 

at the battery
key off motor off 12.7
2200rpm 38mv
1100rpm 50-60mv
is there a filter cap in your future?

 

50mV is what I was seeing at 5500 RPM or so. With a meter. But, from the ECU, in an earlier log, I was seeing a LOT more noise.

 

So I am seeing about 250 mV with a slightly discharged battery at 3000 RPM. You mentioned earlier "log." Is that a capability of the system software to monitor B+?

 

Filter cap won't help much without a series element before it, choke or resistor?

 

I am guessing Yamaha didn't worry too much about "hash" with their electrical systems since there are so few electronics on my XJ550. Newer electronics also tend to be more sensitive to noise and needs more regulated power. As long as the bike isn't sending out RF above legal limits, Yamaha probably thought "why bother?"

 

"Is that a capability of the system software to monitor B+?"

Yes. The 12V supply (vBatt) is one of the inputs to the ECU, as other things, like dwell time and the amount of time a fuel injector takes to open, vary with battery voltage.

This is what I'm seeing now, which looks pretty good, except for the noise in the baro signal.

 

is there foam over the barometer like they did in quads. they could be doing some software magic to ignore spikes

 

The barometer is the same MPX4250AP as the MAP sensor, but, instead of being connected to the manifold, it's in free air under the seat. My local ambient is about 78KPa. Spikes before I added some local and internal capacitance were to 105Kpa. Now they're only hitting about 84KPa. Both are ridiculous. Adding a tube, filled with polyester fiber, to the inlet of the sensor made no difference at all.

I think the spikes are probably noise generated internally in the Microsquirt - maybe from ignition drivers, or maybe from injector drivers. No spikes at low RPM, but they are not that clearly linked to high RPM.