{B4902} Charge Temperature Filter

[NAH]

Hi,

If I am running MAFless, is this table redundant or does it still hae an effect?

Ta.

[joecar]

NAH,

I believe B4902 is still being used when MAF-less.

Joe

[NAH]

OK, thanks.

I did some logging with DYNCYLAIR_DMA (both the normal one & the Speed Density one) & the value didn't exceed 1.0 grams/cylinder, even at manifold pressure of 125kPa. Does this sound right?

[redhardsupra]

airmass= gmve*MAP/Temp (gmve is the wacky units they store internally, you can make EFILive display your VE in these directly if you want, Temp is a blend between IAT and ECT, in K)

with your MAP being >101kPa i'm assuming this is FI, so at this point you might have a problem with temperatures killing your airmass numbers, that's why intercooling is absolutely crucial.

[SSpdDmon]

I have a spreadsheet I made a while back that I'll upload tonight. It's great for showing VE calculated airmass for two different conditions (ie cool/perfect day* and hot summer day**). The effect the Charge Temp Blending Factor has is quite strong. We can set it anywhere from 0 to 2 in my OS (used a stock 01 M6 F-body file). Depending on what the factor is and using the conditions mentioned above, you can see a 4.7%~10.5% difference in airmass calculations. The more stable 4.7% comes from when the CTB Factor is set to 1, which basicaly equals the engine coolant temp. The down side is, the calculated airmass is considerably less with a higher charge temp. So, do IAT favored CTB Factors work better because they calculate a higher airmass number...even though they have the higher swing in output (10.5%)???

It'll be easier to understand what I'm getting at once I post the SS. I'll try to remember to do so tonight.

*cool/perfect day = IAT of 56* and ECT of 187*
**hot summer day = IAT of 110* and ECT of 217*

[SSpdDmon]

I have a spreadsheet I made a while back that I'll upload tonight. It's great for showing VE calculated airmass for two different conditions (ie cool/perfect day* and hot summer day**). The effect the Charge Temp Blending Factor has is quite strong. We can set it anywhere from 0 to 2 in my OS (used a stock 01 M6 F-body file). Depending on what the factor is and using the conditions mentioned above, you can see a 4.7%~10.5% difference in airmass calculations. The more stable 4.7% comes from when the CTB Factor is set to 1, which basicaly equals the engine coolant temp. The down side is, the calculated airmass is considerably less with a higher charge temp. So, do IAT favored CTB Factors work better because they calculate a higher airmass number...even though they have the higher swing in output (10.5%)???

It'll be easier to understand what I'm getting at once I post the SS. I'll try to remember to do so tonight.

*cool/perfect day = IAT of 56* and ECT of 187*
**hot summer day = IAT of 110* and ECT of 218*

Download VE_Calc_Airmass.xls

[NAH]

Download VE_Calc_Airmass.xls

Cheers mate, I'm having a look now. On a different tack, I noticed from the log file recorded last night that knock was hitting 2.8 & 3.9 on 2 occasions. Need to check the tune for that too.

OK, having had a look at the spreadsheet, from where does the figure 2.436523 in cell B4 derrive?

B4901 & B4902 shows the units for the y-axis as grams/second (B4902 also references GM.DYNCLYAIR_DMA), but MAF is referenced as grams/cylinder in B0104.

What sort of airflow could I expect for a supercharged intercooled setup running approx 5psi? What PIDs should I use to log this (if possible), bearing in mind I have a MAF-less setup?

As you pointed out, it is interesting from your table is that for a hot day, the difference in est charge temp is only 4° higher with the CT @ 2 as oppose to 30° without the factor, which would be right because the major influence is IAT & not ECT (which should remain fairly constant).

So, er what does this mean then? Your point about IAT biased factors sounds logical, I guess the only way to explore would be empirical data collection (unless there are any enginering grads reading this).

[SSpdDmon]

I was hoping someone could use that to help us understand the PCM's calculations better. I'm a fairly smart individual, but this seems to be a little above me.

The VE value comes straight from the tune. In order to see your VE in the default units, you need to click Edit>Properties and use the drop down menu to select the defualt VE units.

(See http://forum.efilive.com/showthread....ighlight=grams)

As for the Charge Temp Factor Table, I says grams/second and calls out a pid that is grams/cyl. The MAF flows grams/second and the numbers in the table are for 0-150. I highly doubt that table is supposed to reference grams/cyl. Those sound like grams/second numbers to me.

[redhardsupra]

you want to log GM.VETABLE_DMA, MAP, RPM, GM.DYNAIRTEP_DMA, the rest you can calculate from these

[NAH]

Thanks for the tips gents. I'll add the GM.VETABLE_DMA & GM.DYNAIRTEP_DMA PIDs tonight & do some logging.

One question though. B5913 refs the y-axis as grams/clinder. B4901 refs the x-axis as grams/second. Both ref the same PIDs. Is this right?