Auto Enginuity and ZVW30 Prius
 

Hi,

Auto Enginuity is a 'good news' 'bad news' system:

• reports NHW11 codes
• reports byte size engineering data OK
• mixed results on 16 bit sized metrics
• terrible results on longer data values
• ZVW30 is still in 'generic' mode

However, I found the 'generic' ZVW30 data appears to be useful but their "Speed Tracer" seems to have a problem when calculating MPG:
http://hiwaay.net/~bzwilson/prius/zvw30MPG_010.jpgThese were two runs, same route, opposite directions. The obvious problem is it shows MPG going down, not up, when the Prius decelerates. The Prius shuts down the gas engine so there should be a brief peak of MPG when coming to a stop. So I decided to work from the raw engineering data:
http://hiwaay.net/~bzwilson/prius/zvw30MPG_020.jpg
The data elements are:

• Coolant temperature - values on the right axis
• Engine rpm - values on the left axis
• Vehicle speed - values on the right axis
• MAF airflow - values on the right axis. By using the 14 to 1 ratio, the fuel consumption can be calculated.
• Commanded EGR settings - the values are on the right axis
• Catalytic converter temperature - values are on the left axis. However, the 'cold' temperature' before the engine ran were abnormally high. I had to substitute the ICE coolant temperature for the first seconds of data.

These data points look right and match how we know the Prius works. But there were details not seen before:
http://hiwaay.net/~bzwilson/prius/zvw30MPG_030.jpg
Key elements are:

• engine runs at a flat-line speed - until the engine coolant reaches at least 60C, the engine runs at a steady speed. Not tested, yet, is whether or not shifting into "N" reduces ICE fuel consumption.
• Exhaust Gas Recirculation - unexpected, it runs any time the ICE is generating traction power and the coolant is over 70C. I was under the impression this happened only at high power settings but obviously it is diluting the fuel-air charge even at low power settings.

One thing is it looks like I can use Auto Enginuity to remap MPG vs MPH. Unlike my earlier benchmarks, the Auto Enginuity data significantly reduces the duration of each test. Combined with GPS tracking data, a total energy picture should develop.

Bob Wilson

That looks like a pretty nifty datalogger. I have to wonder if the mpg versus time plot is intentionally dumbed down. The real picture would have the mpg hit infinity every time you DFCO, and then slam back down to zero when you come to a stop. What if this is some sort of moving average?

In any case, a plot of gpm versus distance would be the easiest thing to look at and make good sense of. Area under that curve is obviously fuel consumption.

As always, I would love to see a breakdown of aero, rolling, braking, and accessory load.



Somewhat off topic, how hard are you accelerating when your catalyst temperature shoots up to 3000°C? Does this represent a leaner fuel/air mixture than you'd see in a high-speed hill climb?

3000°C! That's higher than the glass point of glass or the melting point of steel. That seems unsustainably hot. It makes me think I should be careful about adding insulation to my cat. Fiberglass batt would be too much; I'll just wrap it in a few layers of aluminium foil to replace the rattling heat shield.

I'd expect this. It reduces pumping losses.

Opps, left axis on the catalytic converter temperatures. Closer to 600-700 C.

I'll post the data later. In the meanwhile, here is Google link of the test route I used.

Bob Wilson

Actually it allows them to run a leaner mixture because the exhaust gasses don't 'burn'. This cools the exhaust temperature so it won't burn out the catalytic converter.

You can kinda of see it in the catalytic converter temperatures just after the ICE coolant reaches 70C. The catalytic converter peak temperature plateaus and even goes down when the car is in a sustained cruise.

Without it, they'd have to run a slightly richer mixture to moderate the exhaust temperatures especially at higher power settings.

Bob Wilson