B4512 Filtered RPM Airflow Correction - Values??

[bink]

B4512 - anyone know why the HSV GTS has B4512 correction values that are 0.75 g/sec LESS, at deltas of .05 .06 and .07, for the RPM Decreasing table.
2001 Z06, and most other tuns I've checked, the values are equal for RPM Increasing and Decreasing.
See comparison tables below.
Why the difference in Learned Correction AirFlow?

Does the GTS have a much larger cam?? Assuming a greater rate of change in idle airflow. With a bigger cam, does this smooth the rate of change as compared to the larger RPM Increasing values??

Is the GTS a 90mm TB??

Thanks in advance


joel





2001 Z06

Filtered RPM Airflow Correction (Grams/Second)

RPM Rate of Change RPM Increasing RPM Decreasing
0.00 0.000000 0.000000
0.01 0.000000 0.000000
0.03 0.000000 0.000000
0.04 0.000000 0.000000
0.05 1.500000 1.500000
0.06 1.750000 1.750000
0.07 2.000000 2.000000
0.09 2.000000 2.000000
0.10 2.000000 2.000000
0.15 2.000000 2.000000


2004 HSV GTS:

Filtered RPM Airflow Correction (Grams/Second)

RPM Rate of Change RPM Increasing RPM Decreasing
0.00 0.000000 0.000000
0.01 0.000000 0.000000
0.03 0.000000 0.000000
0.04 0.000000 0.000000
0.05 1.500000 0.750000
0.06 1.750000 1.000000
0.07 2.000000 1.250000
0.09 2.000000 2.000000
0.10 2.000000 2.000000
0.15 2.000000 2.000000

[Tordne]

Most of the holden/HSV tunes (all that I checked) have the same table as the 04 GTS. It may be an error in the cal. I noticed a few values that didn'tseem right.

[Tordne]

Sorry, just saw your other questions

GTS does have a larger than stock cam, but it is nothing like what you guys put in your cars. It is very small by all standards!

The TB is also an 78mm piece, so not a larger 90mm or anything.

Cheers,

[Tordne]

Flooding with posts now

Just noticed that the GTS table is the same as an 02 & 02 Camaro. I think Holden way back used the 01 Camaro as a basis. In fact my 2002 Commodore can from factory with PCM OS 12202088 (same as 01 Camaro).

[bink]

Thanks for all the info Tordne!

I might play a little with this table...at the lower rate of change values.
Have you ever changed B4512??

[Tordne]

No worries mate.

LOL, you I just changed this to the same as the 02 Z06 I generally give cal preference to the Chev tunes over the Holden/HSV. I figure there are many more of them on the roads. I doubt I'll notice a difference as a result of this change though, but you eve know.

Cheers,

[GMPX]

Most Aussie tuners will not use a GTS tune, they weren't real good.

Cheers,
Ross

[Tordne]

Most Aussie tuners will not use a GTS tune, they weren't real good.

Cheers,
Ross

What is a good base then (in your or tuners opinions)?

[Highlander]

Dragging back from the grave... How is RPM Rate of change Calculated and is there a way I can "track it" on the scantool? I did try to use the dx() function but nowhere near the results...

[SSpdDmon]

IMO - you shouldn't have to touch B4512 to get a car to idle correctly. Most of this is probably redundant from the idle thread in the Tutorial forum. But, what the hell.

Remember, LS1 cars have a designated idle mode. What I expect to see in a tune to ensure the car goes into idle mode appropriately and isn't fighting itself is:

- IAC & Spark: Idle mode becomes active when the car is below B0107/B0108 thresholds
_____* This is what activates the adaptive spark AND IAC-based airflow trims at idle
_____* In motion, idle is maintained with throttle cracker / follower settings and the normal high/low/base timing tables
- IAC: B4312 should be set equal to or slightly greater than B0107
_____* Because throttle cracker has thresholds, they should play nice with what's going on above
_____* B4311 should be 1mph greater than B4312
- Spark: B5916 threshold should be set similar to B0108
_____* This designates when the base timing table will be used (ideally for very light and off-throttle application)
_____* I prefer B5917 be set to 255mph to ensure B5916 is the only trigger

After all, we're mainly talking air and spark during idle mode (because from the factory, the car is expected to be in closed loop fueling). Once you've looked over the above (values aren't fighting each other, fueling is close, there's enough spark to idle in N, etc.), you should make sure you have enough Desired RPM to idle (B4603). Everyone likes a nice lopey idle. But, sometimes you have to give a little of what you like for drive-ability reasons. 850 or more RPM on a larger cam application isn't a bad thing IMO.

From there, you need to have your Desired Airflow (B4307) in check. This is where the idle trims in the scanner (idle trims - not fuel trims) will help you. Log them vs. your ECT and make changes where necessary to bring the trims closer to 0. It doesn't have to be perfect. That's why the trims are there.

On cam'd apps, you need to keep the car from fighting itself with the idle trims. This means adjusting the Learned Airflow Correction table (B4514). Why? As you sit there at a nice (steady - yet lopey) idle, the RPM is making bigger swings than it used to with the stock cam. So, you need to zero out the first couple of rows in the LAC table and reduce the 3rd row to almost nothing.

Now, if you're still fighting big idle swings (RPMs ranging from 1300, then to 400, back to 1300, then down to 550, etc.), I say tackle it in the Direct Airflow Correction table. The DAC is basically the big influence on the IAC valve. Problem is, the valve is a tad slow to react. When it finally does, the correction in correlation with the timing adjustments is too much...pushing you past the desired RPM & causing the swing. So, what I tend to do here is drasticly reduce the high RPM corrections under the pretense that we'll let the trims and the timing controls help keep the idle from running too high. This then turns this table into an idle stall saver of sorts. On my car, I zero'd out the first 3 rows, reduced the high columns, and smoothed out the lows. Big difference here.

As for air, I think those are the main tables I tend to hit. For spark, obviously you need the right timing at idle. But just like the IAC tables, spark is making adjustments too (B5935/B5936). I think one of the reasons we have big swings in idle is B5936. In my factory file, it looks like it tries to make a correction in timing to save a low idle speed for only the first 200~300rpm. If idle falls more than 300rpm below desired, it just gives up. So, I like to taylor this along with my base timing tables to make sure that doesn't happen. In the same regards, the other table (B5935) tends to get a little trigger happy and pull tons of timing if RPM is too high. I perfer to level it off at the 200 RPM mark to keep from overshooting desired RPM on the way back down.

After these adjustments have been made, the engine will become a much easier beast to tame....and that is why you don't need to touch B4512...IMO of course.