MSGHUFF

iTrader: (7)

I've done the searches and still nead some guidence...

If the car is spiking lean when you snap the throttle open wich way do I adjust the throttle follower? Do I increase the numbers in the follower airflow table or decrease?

Same thing when the throttle snaps shut if it spikes rich do i add or subtract from the Cracker Airflow?

Is there a way to dial the tables in, everyone always just posts "play with it and see what works"

Billiumss

iTrader: (11)

Those tables have NOTHING to do with fueling, just how it controls the IAC.

Basically, the follower adjusts the rate at which it opens and closes, cracker does just that, it cracks the IAC a tad open over idle to keep the idle a tad higher till you get to a complete stop.

kenkaru

soooo....
What effect does speeding/slowing the follower have?
?????????Slower filters out BS changes and faster gives faster changes (that might be false)???????

TAQuickness

iTrader: (28)

if you speed up the follower, it will decay air faster, if you slow it down, it will decay slower.

kenkaru

can you explain what effect this has? ie why people mess with it and how it helps?

MSGHUFF

iTrader: (7)

I have a C5 and does it matter at all?

YellowToy/A

iTrader: (1)

Here goes I will try. I increase the follower to get more air just off idle. I had to increase the VE to add more fuel. I did this so the car would not die as I let the clutch out. I think that the follower and cracker at air. If u increase them u have to add fuel with ve table. If u make the values to big idle will not drop to 800. To small the car will want to die. If you do not have a cam dont play with them. The idle trims will be affected also.

How much does ur car spick lean or rich??? If it is just a small, dont worry be happy. If you have idle problems that is where to start.

jimmyblue

iTrader: (11)

The lean spikes are most likely telling you your VE
table is too lean. You fall into speed density mode
every time MAP is changing much. MAF is way too
slow to keep up, even the Dynamic Airflow has a
lag to it but when SD mode is out of agreement
with MAF the step can be harsh. You can't get
rid of air surge fidelity problems altogether but I
had reasonable results just fattening up the VE
table wherever I saw a lean drop coming from.

What gives you the "right" VE table for steady
state may give you lean dip problems because
there is really no good compensation for throttle
transients; no accelerator pump I can find. I
went a little to the fat side and tolerate single-
digit negative trims at the low end in the interest
of tip-in happiness. All just by hand, reacting to
KR and O2 sensor dip events.

RedHardSupra

iTrader: (1)

great...now what does that mean? what does it do?

SSpdDmon

iTrader: (10)

Ummm...I think there's a little mis-information in here. My take on these tables are as follows:

Throttle Cracker is a set amount of airflow that references MPH and RPM once activated. If your table says it needs 1.0 grams/second of airflow at 2200RPM and 20MPH, then the IAC will open up a certain number of steps by referencing the IAC Effective Area table, which converts desired airflow into actual IAC steps. The throttle cracker will remain active until it reaches its deactivate speed. Then, it will decay based on its decay rate. This is often the table that causes RPMs to hang while coming to a stop since it usually doesn't reach its deactivate speed until 2mph.

Throttle Follower is airflow added based upon the throttle position percentage and its rate of change. When it exceeds the % change value in a 12.5ms time span, the follower will be activated. If it's increasing, the Throttle Follower values will be added to the desired airflow, which will open the IAC in the same manor as stated above. Once the change in TP% has stopped, the decay delay timer starts. After the timer is done, the follower is then decayed out at the rate listed in the Follower Decay Delay table until it reaches 0 or the TP% reactivates the follower. If TPS% is less than or decreasing by the % change, it will bypass the delay and decay the follower immediately.

The point here is, the decay tables are what controls how fast they IAC closes. Not the actual cracker/follower tables themselves.

MSGHUFF

iTrader: (7)

So if I have a drive by wire throttle with no IAC valve the tables have the same effect right?

I am also still running in OL...no maf and o2's Ve table is dialed in pretty good but when I stab the throttle it spikes lean and when I let off it spikes rich

YellowToy/A

iTrader: (1)

OK How much u open them will make how long to close different. I opened mine more in the throttle follower. The stock decay rate was OK. But it took longer because it was open more.

What r we tring to do here? If it is a spike who cares? Does the car die?

SSpdDmon

iTrader: (10)

Drive by wire will open the throttle body blade in place of the IAC as far as I know.

I'm not 100% sure where your lean spikes are coming from. If your VE is dialed in though, I'd try re-enabling the MAF and getting that squared away. Then if you're still seeing the spikes, do what jimmyblue was suggesting in his post above (fatten up VE where spikes are seen).

True, the more the IAC is open, the longer it will take to close with the stock decay rates. My point was changing the actual airflow numbers in the follower/cracker won't change how fast the IAC moves. That's in the decay rates.

jimmyblue

iTrader: (11)

It might also be possible to play with the dynamic airflow
filtering, in a SD car this is probably the only lag element
left in the system (the MAF is thermally slow in its own
right). When the MAP (real) is changing fast the fuel
needs to follow, but if there is too slow a filter it will lag
reality, lean on open, rich on close.

I see "VE Corr Factor Filt" in the Dynamic Airflow stuff
that says "values closer to 1.0 mean the filtered value
reacts faster to changes at the increased risk of
instability". Basically if you are making a large traversal
across the VE table and the VE value is changing much,
that change will not be applied bickety-bam but will be
rolled on at the filter rate. Someone with a peaky VE
profile (like most big-cam cars leaving / entering low-
RPM areas) might not get the airflow right for about
40-50 "ticks" if I make it out right, as-stock.

There is also a "Dynamic Air Filt" which is applied to
either MAF or SD current airflow value, similarly a lag
factor (but looking like 7 ticks).

My gut says the VE correction filter factor is the
slow pony on the team. Probably OK on a stock motor
where VE changes are not especially pronounced. But
maybe too slow for a motor that can really jump.

02sierraz71_5.3

iTrader: (2)

the easiest fix Ive found for this is to set the PE to engage lower meaning drop the TPS to 40% from 3000 rpms and up, then set the enrichment rate to 4.0, and drop the map enable to 45 this ensure you get your fuel when you need it.
Then tweak the PE divisor quick and easy.
Youd be suprised how much of a difference this makes especially with motors that move alot of air.

Obviously if your having to set your pe divisor to 2.0 to command 13:1 afr or something rediculously high then you know your ve table is very lean and you need a SD tune to fix the VE table.

SSpdDmon

iTrader: (10)

Good point about the PE enabler. On cam'd cars that I tune, I usually start with a 10% across the board drop on that table.

02sierraz71_5.3

iTrader: (2)

Creech should have fixed all that stuff. If I remember right your on horsepowerjunkies Ill be at mooresville tomorrow(baring rain) and the palace on the 22nd if youve got your software bring it out and we'll fix it.

MSGHUFF

iTrader: (7)

I might take you up on the offer thanks

GuitsBoy

iTrader: (4)

Jimmy - If my understanding is correct, I believe the VE correction factor is simply a way to bring dynamic airflow inline with a properly working MAF. For instance, if the MAF reads 3 Lb/Min in steady state as you cruise down the highway, but dynamic airflow calculates out to 2.75 Lb/Min, the VE correction factor will flowly increase to 1.091. Now all dynamic airflow calculations will be multipled by this correction factor in order to match the MAF reading. IE. 2.75 x 1.091 = 3.00 which is what the MAF reads at steady state. The VE Corr Factor Filt would seem to dictate the learning process in which dyn airflow matches up with MAF readings. I dont believe it would have anything to do with how quickly dynamic airflow calculates fueling during a throttle transient.

FWIW, I have effectively disabled my VE correction factor since Im tuning SD and then calibrating the MAF off SD. Ive suspected this playing havoc while tuning since you never know what your last correction factor was. I simply set min to .999 and max to 1.001 in order to take this out of the equation.

02sierraz71_5.3

iTrader: (2)

This is interesting
What results did you see when disabling the VE correction factor and why?