Can the timing tables 'x' axis be changed

[Jason S.]

I am in speed density mode, os5, and am wondering if there is anyway to get the timing maps to lable the 'x' axis from mass air (oz/cylinder) to Speed density (Kpa). I did a search but didn't come up with anything.

Thanks

Jason.

[SSpdDmon]

Timing in our cars is based on grams or ounces per cylinder. You can't change it to represent RPM vs kPa (like the VE table) because grams/ounces per cylinder can and will vary within the same kPa range. Fueling depends on kPa because manifold vacuum affects the performance of the fuel injectors. That's why we either use a vacuum referenced fuel pressure regulator or slope the injector curve to correct for manifold vacuum. I'm sure I'm leaving a lot on the table with what I don't know. Maybe someone else will chime in with a little more reasoning....

Now, if you wanted to invert a table's x-axis and y-axis (to make it look like HPT), there's a tool in the last tab of the Calibration Window (pops up when tune is opened) that will do that for you.

[Jason S.]

Timing in our cars is based on grams or ounces per cylinder. You can't change it to represent RPM vs kPa (like the VE table) because grams/ounces per cylinder can and will vary within the same kPa range. Fueling depends on kPa because manifold vacuum affects the performance of the fuel injectors. That's why we either use a vacuum referenced fuel pressure regulator or slope the injector curve to correct for manifold vacuum. I'm sure I'm leaving a lot on the table with what I don't know. Maybe someone else will chime in with a little more reasoning....

Now, if you wanted to invert a table's x-axis and y-axis (to make it look like HPT), there's a tool in the last tab of the Calibration Window (pops up when tune is opened) that will do that for you.

How is it determing oz/cylinder or grams/sec without the maf? Seems to me there is some default somewhere when the maf is defaulted to calculate it off of the map sensor. So, there should be some way to do that.

[SSpdDmon]

MAF measures grams/second or lbs/minute. With the MAF enabled, GM.CYLAIR_DMA represents the grams per or ounces per cylinder value the PCM is using for timing based on airflow reported by the MAF.

If you're in SD because the MAF has failed or been disconnected, then the PCM calculates airflow based on air/coolant temps, MAP readings, current RPMs, and the values in the VE table. The GM.DYNAIR pid shows this value in the same grams/second or lbs/minute as the MAF would. The grams per or ounces per cylinder value is shown with the GM.DYNCYLAIR_DMA pid, which is also calculated in with the variables listed above.

Don't get them confused though...
grams/second or lbs/minute
SAE.MAF
GM.DYNAIR

grams/cylinder or ounces/cylinder
GM.CYLAIR_DMA
GM.DYNCYLAIR_DMA

[dfe1]

How is it determing oz/cylinder or grams/sec without the maf? Seems to me there is some default somewhere when the maf is defaulted to calculate it off of the map sensor. So, there should be some way to do that.

Keep in mind that these are "hybrid" systems, meaning that when unmolested, they operate in both mass air and speed density modes. The system continually references measured air flow against calculated air flow as a rationality test and uses data from the MAF sensor, the speed density calculation or a combination thereof to determine fuel requirements. (See the explanation accompanying B0120.) Internally, the PCM processes gram/cyl data, which is actually a more precise measurement of engine load than manifold pressure. Next time you're looking at a data log, reference grams/cyl to kPa, and you'll notice that grams/cyl values vary significantly for the same kPa readings, depending on rpm.

[joecar]

I am in speed density mode, os5, and am wondering if there is anyway to get the timing maps to lable the 'x' axis from mass air (oz/cylinder) to Speed density (Kpa). I did a search but didn't come up with anything.

Thanks

Jason.Jason,

No the each table's labels are fixed (unchangeable) in tune tool.

But, in the scantool you can create a map using anything you want for the axis's.