Negative Duty Cycle - What??
 

Howdy folks,

Went for a drive today, happened to glance down at the Commander and noticed a negative 25.3% duty cycle in the peak-hold box. This is odd for obvious reasons (but think of the gas mileage!) and strikes me as just a glitch (some sort of wrap-around error perhaps), as nothing eventful happened during the drive and the engine remains not blown-up. Anyone else ever notice such a thing?


https://cimg3.ibsrv.net/gimg/www.rx7...c196896004.jpg

Maybe a neutrino hit the circuit for that reading.

Reference issue - loose ground maybe?

The only reason I sort of doubt that is that as I understand it, duty cycle is not really a 'reading' with a reference to ground but a digital value, representative of a pulse-width sent to the injectors by the PowerFC itself. I imagine then that a poor ground in this case would be an 'it works or it doesn't at all' kind of scenario. Could be wrong though.

In any case I was just wondering if this kind of thing was ever seen by anyone else, as the PowerFC is still fairly new to me (guess I've had it for a bit over a year now). The drive during which it happened was just going home from work in traffic, so in vacuum really just about all the way. I do wonder what exactly was going on at the injectors themselves, or if maybe damage could have been done if the manifold was in boost. But, unless anyone thinks its critical I'll stop worrying about it and just keep an eye out if it happens again.

Thanks!

It's definitely not like an analog input but ignition noise could potentially corrupt stored values. I'd be tempted to pull the maps and check over things very carefully, and clean the harness earth on the engine as poor earthing may make things more suceptible to noise.

^ Aha, good call. I'll do so. Thanks!