B4512 Filtered RPM Airflow Correction - Values??

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.:nixweiss:
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 :D

:cheers:
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

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.

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,

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).

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??

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,

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

Cheers,
Ross

Quote:

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Originally Posted by GMPX

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

Cheers,
Ross

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

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...

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. :D

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. :)

One more thing. All of that is for when the car is stopped or barely moving (again - based on the thresholds mentioned early on in the post). To tackle idle swings outside of Idle Mode, you're dealing with the base timing tables, throttle cracker, and throttle follower for the most part. So, get it to idle while sitting still first. Then, worry about rolling idle. :)

The main issue here with my car is stalling. I have a 92mm super ported tb that is not that linear. I need the rpms to come back down slowly in order for it to not stall.

I do not zero out the first cells of the DAC and it idles fine. It will stall on some occasions and it usually is after revving from 3krpm or over. Even on my stock z06 i do notice aome under rpms after revving but since its factory it will recover nicely as a stock car. Given that this tb is huge and a little too close means zero airflow i get this issue!

This happens more often with the a/c.

Next step is to try a stock 90mm

Quote:

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Originally Posted by Highlander

The main issue here with my car is stalling. I have a 92mm super ported tb that is not that linear. I need the rpms to come back down slowly in order for it to not stall.

I do not zero out the first cells of the DAC and it idles fine. It will stall on some occasions and it usually is after revving from 3krpm or over. Even on my stock z06 i do notice aome under rpms after revving but since its factory it will recover nicely as a stock car. Given that this tb is huge and a little too close means zero airflow i get this issue!

This happens more often with the a/c.

Next step is to try a stock 90mm

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You just ID'd the place you need to fix this. You said "after revving". The first thing that says to me is, adjust the throttle follower. You can do this 2 ways. Increase follower airflow or reduce the decay rates. :)

Another option would be to slightly increase the throttle cracker some incase it's happening in a situation similar to:

- I was driving down the road at 3K RPM, took my foot off the gas & coasted for 10 seconds down to 2500 RPM, pushed the clutch in and it stalled on me.

Throttle follower is based on throttle movement. It's there to "cushion the blow" of changes made with your right foot.

Throttle cracker is based purely on MPH & RPM. If the car is at "X" MPH and "Y" RPM, the IAC allows "Z" more grams/second of airflow to pass. So, this is like the idle screw on a carb...but only for when the vehicle is in motion above the thresholds I previously mentioned.

See edit above.

've had that happen to me from time to time. Coast down, dump clutch and stall. But only with this tb.

I have drop al decay rates to .01 for the most part and i still get the issue, hence why i was looking at other tables. Specially this one that deals with rate of
change.

One other important thing to remember about B4512 - it works off of a delay. The delay description reads: "... (B4512) is enabled this many seconds after the engine speed drops below the PCM's desired engine speed." On the f-bodies, that delay is usually set between 1 and 2 seconds. So essentially, that means that this table isn't going to work as a stall-saver....assuming the descriptions are accurate.

If you want Highlander, post up a copy of the tune and I'll see if there's something I can do to help.

SS, I have also noticed, but not verified, that even with the TC activated, it will get into an idle mode if the RPMs get into the range of desired idle. Now, I have disabled TC completely because either you would need too little airflow as the rpms hang a lot and on the next day you would need a lot more airflow or it stalls. Then you have a "rolling idle" that varies from time to time from stalling to 1100-1400rpms... It gets annoying.

I disabled TC and let the idle do it's thing... Now, I have only done this with this car as it has been a REAL pain because of the stalling issue. As of now, it doesn't stall... or at least it hasn't in the past couple of days.

The best results where to adjust b4504-6 to make Filtered RPM airflow come on first and then DAC and LASTLY the learned values. I did this because with the filtered RPM airflow, the way I see it... It will control the rate of deceleration of the engine when you dump the clutch or whatever. Then the DAC will have "different" values if you have the A/C and then the learned values will do it's thing to bring the idle nice down and safely...

THus far this is the combination I have used to make it work.

Quote:

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Originally Posted by Highlander

SS, I have also noticed, but not verified, that even with the TC activated, it will get into an idle mode if the RPMs get into the range of desired idle. Now, I have disabled TC completely because either you would need too little airflow as the rpms hang a lot and on the next day you would need a lot more airflow or it stalls. Then you have a "rolling idle" that varies from time to time from stalling to 1100-1400rpms... It gets annoying.

I disabled TC and let the idle do it's thing... Now, I have only done this with this car as it has been a REAL pain because of the stalling issue. As of now, it doesn't stall... or at least it hasn't in the past couple of days.

The best results where to adjust b4504-6 to make Filtered RPM airflow come on first and then DAC and LASTLY the learned values. I did this because with the filtered RPM airflow, the way I see it... It will control the rate of deceleration of the engine when you dump the clutch or whatever. Then the DAC will have "different" values if you have the A/C and then the learned values will do it's thing to bring the idle nice down and safely...

THus far this is the combination I have used to make it work.

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That's what I get confused on though. If that table works off of a delay as the description indicates, it won't do anything for you until a second or so has passed after the RPM drops below desired.

Either way, I'd be happy to take a look at your tune...and if I get a minute, show you how I would have set it up. Up to you...

The delay is set on: B4503

I am going to send you my last tune, which has thus far worked.

Here it is... Check it out...

Quote:

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Originally Posted by Highlander

Here it is... Check it out...

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Here is a bit different spin. It's the direction I would have taken to set things up.

Undriveable... but I don't blame you... my setup is barely driveable... I will change that throttle body... i am tired of dealing with it.

SS.... just so you get an idea... I kept fiddling with this.... the problem lied in the OS...I changed the OS and everything went fine. I ran the COS5 and had NO issues. That was my previous setup. I wanted to go back to a regular OS. I enabled the MAF on the custom OS. Maybe I have a problem with the maf, which honestly didn't bother for WOT fueling. I do feel the car was a lot more responsive with the MAF on than TPS/VE and SD.

Hmmm...I'd be curious to try and play with this one-off. But, that's not going to happen. Best of luck! :)

Thank you SS, this tune is DONE.

Curious when I change to the corresponding OS with the same calibration (both are maf enabled) the idle gets all screwy.