cracker/follower equiv?

[ringram]

Has anyone played with anything that acts like the old cracker/follower tables?
Im after some cracker action to smooth gear shifts, then stock tune in SD mode drops rpm too fast causing some jerk action unless I keep some throttle on.
Ive noticed some idle correction tables in the latest calz and have done some messing with the "coastdown" Idle proportional values when above idle target speed, but need to spend some more time on them to see if its the right area or not.
So if anyone else has had any joy on this please do tell :fluffy:

[ringram]

Ok gents, when coming to a stop at certain speeds if I push in the clutch the RPM rises about 1000rpm so Im assuming some extra airflow is going in there from somewhere.
Since there are no cracker or follower tables does anyone know what else I can change to sort this out?
Or are we missing some tables that would deal with this?
Thanks.

[ringram]

Good.
Lots of experimentation and now I have hanging Idles etc, so Im on the right track. The Proportional and Integral idle airflow correction tables are helping..

[hymey]

Use max. idle area as I wrote about in idle tuning to act as a follower, this will control the rate rpms drop in neutral. I would imagine with your engine being big cube with a big cam max idle area will need to be much higher then stock. Start at 2.20 and work up. Once you get close to what you want trim the area 0.01 at a time.
As far as a cracker. There is none there. There is no IAC as such, basically if max idle area is correct and VE is right it should drive smoothly at low rpms. If max idle area is to high it can surge a little. If too low revs will dip fast and it will tend to hunt.

[ringram]

Thanks mate, Its all good except during some conditions slowing to a near stop she drops too low. Not enough to stall, but enough to overshoot idle target.
max idle area was too low, Its higher, but will add some more. IIRC Stock LS7 is 2.3 so I probably need a little more than that.

[swingtan]

Another point about the cracker/follower in the E38. B1604 indicates that it is controlled to some degree by the MAF airflow and if going MAFless, you may find you get throttle follower under all conditions. In my OS the default setting for this is 25gm/sec, so any airflow over this would disable the follower. If you go MAFless, the MAF airflow will never go over this level and the follower will always be active. I tried setting this low and found the car felt sluggish off the line so put it back to 25.

For the hang on deceleration, I've also been looking at the correction factors in addition to the max/min idle air flow. I look at where the hang occurs and work out how far off the target it is hanging. Then I increase the corresponding correction factor in the "transition" table to help pull the idle down. It seems to be working fairly well.

Simon.

[hymey]

That will work simon. I have my follower table set at -30 g/s so its disabled??Anyway it drives nicely.

If you rev the engine with it will maintain the max limit until it reaches idle speed or thereabouts. Ringram your engine will definately need more max idle airflow and I would say then min idle airflow would be over 12g/s. Raise the min idle air flow to close the gap. The idle should settle even at the max idle setting. Once it gets close to desired idle speed the airflow will trim slightly. I have idle timing correction dulled down and let airflow do most of the work. If the timing does all the work it wont let the PI controller do its job.

I run a linear table for integral although the stock settings will over correct as its far from linear. So any miscorrection and the idle speed will hunt.

Once you get airflow settings close, reduce idle correction(timing) and work on the correction tables, so they should be doing 50% work each.

[ringram]

Hmm, I tried max over 3 and it didnt help, but left it just over anyway.. The LS7 is just over 8 at idle for min idle air, mine seems to run best at around 9.5
My problem is under some circumtances, not all, it drops too far, so Im guessing either coastdown or transition decay rates are too high. I tried min airflow higher like 10.x but it didnt seem as nice and was chewing more fuel. Its only when you clutch in,
and only under about 1500rpm and only on decel. Otherwise it drops to idle speed with almost no overshoot. Ill get there, eventually. I think Im going to go radical like you guys and start zero'ing tables out instead of just changing a few odd values here and there each day :)

Im going to zero some tables out to see what makes it worse.. or better.
I did whack idle timing up a little, but I think only to 15*so only 2*

[hymey]

Also remember the LS7 doesnt have a big duration cam either. I would not look at instaneous fuel usage, but injector pulse. Zero ur tables and experiment. Increase idle airlflow to at least 11 for starters. You have the keep the max and min within 2 percent and it will fall in place everytime and idle much smoother, Idling smoother means less overlap and fuel wasted. I have pulled 10% out of VE at idle since I got the airflow correct. And save 1.5L/100km around town. 3 is fairly high but I would jack up min idle airflow and zero tables first, get familiar with the airflow tables, Mine works with 1.5% upper and lower limits.

Also note anything above 2km/h and the idle tables arent used as far as timing goes. Look at coast down timing correction, that will help with clutch in stuff with the car rolling.

[swingtan]

Hey Ringram, I would have thought that your idle timing would be a bit higher than that. Maybe around 19' for anything with a cam. The way I usually do it is to let the car idle for a while, and then average the commanded timing as a guide. that being said, these do handle lower timing very well and in testing I've had mine idling well on -8.5' ( even if I didn't actually mean it ).

Simon

[ringram]

Yeah I logged timing and it seems to like it around 15* so I didnt argue. Maybe less airflow is required.

Anyway something Hymey said in a PM around coastdown timing made me recheck things like fuel and spark instead of mainly just airflow. Just disabled cfco last night and it seems to have made a big difference, still a little overshoot, but maybe thats normal. Anyway almost good enough to say its done now. I just need a few more days of monitoring to confirm.

My static is only 11:1 so cam eats a fair amount of part throttle timing ok on 95 RON octane.

There is an Australia day meet in London on Sunday, so Ill post up some pics for you blokes. Loads of Holdens, also some Chrysler Valiants, usually a couple of old Hx Kingswood's, Falcon's etc. Check the Lounge out :)

[hymey]

sounds good mate. When the car is rolling and clutch in it is using coast down spark and the under and over speed coast down spark correction will correct timing until it reaches its desired idle speed.