Explain throttle cracker and follower..again!

The hardest part of tuning is just understanding what each table is doing. I find that some of the descriptions in EFI Live don't really answer what the table is doing but rather what that table ties into. The throttle cracker and follower are two that I keep getting mixed up and I'm not afraid to admit it!:bash:

Growing up with tuning carb's I can see some of the similarities. If I am not mistaken, the TC is what controls the return to idle once the throttle is lifted. If you have a car that the rpms hang after pushing in the clutch I assume you reduce the grams/sec of air that the IAC allows into the motor. One question I have is how much of a change is significant?

I see that this is also based upon MPH. I again assume that those MPH limits control the window in which the TC is active and adding air to the motor.

Are these values added to the desired air flow table? Is this the base table? This now leads to the proper way to dial in the desired air. I have done maps to log grams/sec vs. coolant from a cold start. Once these values are logged I assume this is the actual grams/sec that the motor is ingesting at that rpm and coolant temp. Should these value match the B4307 table? What if the throttle blade has been cracked?? Doesn't this skew the numbers? I am on a big rant with this but know that all these tables interact. I just need a better explaination of the overall big picture.

Oh yeah.............how does the throttle follower work?

I am having some issues with a 02 A4 F-body with a H/C setup that is pushing me to throughly comprehend this.

One last thing is what table controls air on cranking/startup? Airflow Parked?

All this after a couple glass's of Grey Goose!

Howard

Start up airflow: B4303, B4343.

Airflow parked I believe to be a reference value for the PCM. I have not found a way to tune this table that I'm comfortable with.

TC engages after the car is rolling and disengauges just before the car comes to a stop - mostly effects your rolling idle and transitions from rolling idle to stationary idle.

TF is always working and I've found it to have more of an effect on stationary idle.

What is the difference between "adding" air by raising the IAC effective area vs. desired airflow? If I understand it correctly, the IAC des air is internal PCM conversion to change the grams/sec values into steps. Seems to me we should leave IAC effective area alone and only change the desired. I am also trying to confirm that the desired is the root base air flow that is leaked into the TB and that many other tables contribute to that value. If the the throttle blade is not touched from the factory, then the ONLY place more air can come from is through the IAC. Now the trick is to add, or delete air for the variety of conditions the engine sees. Another question I have is; once the IAC moves off the seat,at some point it has to be at its limit. I know as a rule of thumb that 60-90 IAC counts at idle gives the IAC enough range to have the ability to shut air off and add more air quickly. I noticed on this A4 car that it idles at 56 in P/N but as soon as it goes in gear it jumps to 160's. This is clearly too much air as the car wants to pull. I played with the bidi controls and the car feels real good in gear at 100-115 counts. What is the proper way to calculate the air requirements to reduce the counts in gear by 50 counts? Desired airflow in gear? I am also trying to smooth the transition from in gear to out of gear.

Finally, I got the car idling decent and starts up great cold. Warm startup is rough for the first 10 seconds and then stabilizes. Could this be from the start up friction airflow? Seems to be the car needs more air on warm start.

Thanks

Howard

IACEA is another reference value used to conver airflow to steps. At one point I liked this method to dial in the idle, but have since found it better to leave this table alone (for cable driven TB's anyway, can't speak for ETC).

Desired airflow, B4307, is the base air flow and all other tables will add or subtract from this value. RAFIG and RAFPN will give you the data you need to adjust B4307.

will get back to you with more info later.

Is there a way to accurately monitor all the tables that add/subtract. It would be cool to see the PCM going threw its motions to see when air is being added to the DAF. Can FS derive a total?

Thanks

Howard

Quote:

---

Originally Posted by Redline Motorsports

Is there a way to accurately monitor all the tables that add/subtract. It would be cool to see the PCM going threw its motions to see when air is being added to the DAF. Can FS derive a total?

Thanks

Howard

---

Log the IAC - xxx (airflow) DMAs - especially the short and long term corrections. You can watch the PCM go through it's routines from startup via the Data (F9) Tab.
You will need to separate them into groups due to the their "Channel" consumption. I separated them into Startup, Sitting and Running. That way you can select the unique PIDS for each group along with RPM, MAP, IAT, ECT , VSS etc.
FWIW.
:cheers:
joel

Quote:

---

Originally Posted by Redline Motorsports

. Warm startup is rough for the first 10 seconds and then stabilizes. Could this be from the start up friction airflow? Seems to be the car needs more air on warm start.

Thanks

Howard

---

Mine needed LESS fuel at warm startup (cold startup was very good). I scaled the cranking VE to match the Percentage reduction of my EFILive Main VE versus my Stock Main VE table in the Idle RPM range. Big help.

FWIW.
:cheers:
joel

Joel,

Good pointers! I only assumed that it wanted more air as when I crack the TB a bit a try to start it, it starts decent.

When you say to separate them are you logging these "groups" one at a time?

Noticed a pid named IAC Final Airflow Sum................hmmmmm. Actually I found all kinds of neat pids!:bash:

I just went and reviewed a log from this car.

Based on a coolant temp of 90 degrees F;

DAF 1.456
Startup Friction Airflow Correction 2.500
Engine Speed Compensation 6.666 with a .50 multiplier so its 3.333

All other air adder tables where 0.

Based upon a coolant temp of 131 degrees F;

DAF 1.029
Startup Friction Airflow Correction 2.500
Engine Speed Compensation 6.666 with a .50 multiplier so its 3.333


Since the TC and TF are speed based air adders, I don't see how they effect startup and idle in and out of gear.

I can see once you break the mph values that those parameters will add additional air. How much air is a significant amount?
Howard

Yes, I logged them separately so I could correlate with the other non-IAC parameters.

I think TF is applied to all throttle Deltas (non idle).

0.2 g/sec TC deficiency will cause my car to surge at 2000 RPM - and slightly below 2000. It's "significant"
to a passenger -> "WTF was that?!!".
:D

The bitch about idle is, it seems like every car is different. For example, my '01 H/C M6 SS idles fairly well with the stock tables and only needed a few adjustments. On the other hand, my friend's cam-only '00 A4 WS6 needed a little more tweaking.

Usually, spark is a major contributor to idle issues. So, keep that in mind while working on idle. Bi-directional controls will be a lifesaver for spark. What I usually do first (after some initial spark adjustments) is set the desired airflow table using the RAFIG and RAFPN (for autos) by logging from several cold starts. One trend I notice here is the curve tends to smooth out a bit (kinda looks more like a hockey stick). Once that is done, you have your base. Throttle cracker will be added to this base and the throttle follower will be either added or subtracted from this depending on changes in RPM. **On a side note, I usually adjust B4308 based on the changes I made to the desired airflow. Just be aware of the different coolant temp scales between the 2 tables.**

The next thing I do is take about 50% out of the cracker & follower airflow tables (B4309 & B4315). My theory in doing this is, there's more of a cam now so less compensation is needed. The same theory can be applied to the 3 airflow tables (B4512, B4514, & B4515) that control the IAC. Their overcompensation can be the cause of some surging too (mainly on A4's). Tweaking the throttle cracker further is best done by logging the idle pid for it. Then you can see when it's being applied and whether or not it's jumping between cells (up...down...up...down) causing surging.

IAC effective area should be left alone assuming airflow to the IAC valve is still unobstructed. Epoxied TB's can be the cause for some problems with idle airflow. In that case, you can try tweaking this table. But, chances are it's just easier to get rid of the epoxy.

The tricky part is doing all of this while keeping an eye on spark. Jumping between the high/low tables and the base tables can be the source of surging as well. Usually, cam'd cars like 42~45 degrees of timing during decel under 2400 RPM. The trick is to figure out where your grams/cyl are at for 0% throttle decel and set the cells around there to a single number (ie all cells .08~.24 and 1200~2400RPM to 43 degrees). Generally, you want to do this until just before idle (or when the TCC is going to unlock) in the high/low and BSIG tables.

Playing with those tables is the best way I've found to tackle the real issue...surging. To answer your original question though...the TC is always added to the desired airflow (when enabled) for the given MPH/RPM cell. Too little can choke the motor down and too much can cause a cruise control effect. The TF is subtracted from the base (desired airflow) during increasing changes in RPM and added during decreasing changes in RPM. This essentially softens the blow of changes made by your right foot for both more or less throttle.

Well...that's my $0.02 on the matter. Hopefully it helps someone. :)

I am trying to get my Nova to Idle. I am not using o2 sensors, running open loop all the time. Can you still do the Rafig without 02's?

also is this what you were talking about sspdemon on spark?
I only changed it in high octane timing untill some one confirms this is what it should look like. it looks excessive to me.

Wow - thread from the dead! LOL

If I get a chance later, I'll take a look.

It just shows I am searching:grin:

One last thing is what table controls air on cranking/startup? Airflow Parked?


The other guys have answered the TC TF stuff spot on. All I have to add here is that I tend to set the TF by travelling at 100km/hr then throttling off and logging the decell right down to 5km/hr or so. The car should decel at a constant rate, depending on your personal preference really. If certain speed zones exhibit a cruze effect or too much decal make the alteration on the TC table in the logged zones. Most of the TC table is never actually "used" ....
Also another critical spot is say at 100km/hr and you approach a small to medium downhill stretch you throttle off, you want the car to mantain speed downhill and not race away or slow down excessively making you break the DCFO benefits to maintain speed by touching the throttle.....

With airflow parked I have found this useful in fixing the warm start/instant stall with a cammed engine. Simply bumping up these numbers slightly say 1g/s at 60 to 80deg centigrade opens the IAC a bit more at startup and makes starting more consistent.
Cheers,
Mike

Quote:

---

Originally Posted by The Alchemist

One last thing is what table controls air on cranking/startup? Airflow Parked?


The other guys have answered the TC TF stuff spot on. All I have to add here is that I tend to set the TF by travelling at 100km/hr then throttling off and logging the decell right down to 5km/hr or so. The car should decel at a constant rate, depending on your personal preference really. If certain speed zones exhibit a cruze effect or too much decal make the alteration on the TC table in the logged zones. Most of the TC table is never actually "used" ....
Also another critical spot is say at 100km/hr and you approach a small to medium downhill stretch you throttle off, you want the car to mantain speed downhill and not race away or slow down excessively making you break the DCFO benefits to maintain speed by touching the throttle.....

With airflow parked I have found this useful in fixing the warm start/instant stall with a cammed engine. Simply bumping up these numbers slightly say 1g/s at 60 to 80deg centigrade opens the IAC a bit more at startup and makes starting more consistent.
Cheers,
Mike

---

I prefer the startup friction airflow correction table. B4343 IIRC.

The reason why is you can adjust the decay rates based on ECT where as the other table you mentioned has one decay rate. Also, B4343 doesn't decay as fast. :)

Good info!!!