The last two questions I asked about tuning here were answered quickly and accurately -- man, it's great to have an awesome forum to go to in order to learn more about LSx tuning!

I got my AutoVE in line using the EFI tutorial, got my MAF in line based on a map I found on their site using BEN factors, and I got my PE *real* close just based on past experience (I had tinkered with fueling in PE in the past on another car I had).

So everything is starting to work real great, except for those first few hundred RPMs Specifically, even with VE and MAF dialed in, my car wants to die when I let off the throttle (even if I'm parked and stab it up to 1500 rpm and let off, about 1/2 the time it won't recover and dies). Sometimes it WILL find idle and it sits there comfortably but not all the time, and rarely when I'm actually driving. I find I have to baby the throttle down usually to make it work, even though my wideband is saying air/fuel is in line.

Where should I start? This is a baby turbo cam and mild heads car (with TTs for the power) so I shouldn't need any real radical changes. The slight changes I made to IAC park position and IAC max steps didn't seem to help, rather they seemed to hurt. I have heard reference to changing running airflow, and I changed my park/neutral air flow to 1 across the board which seemed to help, but I feel like I'm just stabbing in the dark here.

I read the sticky on idle tuning but didn't find that it helped too much (I'm not drilling my TB, and I don't have a set screw on my fly by wire).

Can anyone give me a sentence or two on which table to edit and what approximate values/percentages I should be aiming for? I am using Flashscan and some of the table names seem to be slightly different than the names in LS1Edit that I think many people reference. Or maybe I just haven't found the tables in Flashscan yet

Thanks!

 

I would start with the desired airflow. Increase the values and see how it does and go from there.

 

Which OS is in question here ??? 97-98 or 99-03 or 04 ??? THey have screwed around a bit with idle stragtegy reuqiring modified tactics for each generation succesively. For the record 97-98 is the worst..

 

Check that your IAC valve isn't sticking.

 

2003 Z06.

 

Base running airflow is the starting guess for all
the adaptive idle junk. When in doubt, aim high
and let it learn itself down.

But realize too that the airflow it targets, is the
product of your speed density tune (dominant at
idle & low range RPM). So if this is inaccurate you
may have a compound problem - less air taken in
than estimated, and more required than stock -
and when you fix it you will have to re-tweak the
idle again.

Airflow errors also bring in fueling error behind them
and bad fueling makes the engine slower to respond
to air steps and can destabilize the idle RPM seeking
loop.

So you can see it's kind of a circular deal. Begin with
a high RPM target and a high airflow target, and at
least it will stay lit long enough to log the data you
need, to trim it down methodically.

If you have a modified TB there is some chance that
the airflow (effective area) vs throttle position is no
longer accurate, this back-drives the electric throttle
control position based on the desired airflow. But a
stock TB should be accurately-enough represented.

 

Psst...do a search on EFI Live's site for RFAIG or running airflow in gear. More maps to learn.

 

1st - I don't think ETC's have IAC valves.

2nd - It sounds like this is an easy fix with the Throttle Follower Decay and/or multiplier. The Z06 tune I have shows a flat multiplier of 1 for the throttle follower {B4316}. My stock tune shows a multiplier of 2 for the 0-800rpm rows, 2.5 for 1200rpm, 3 for the 1600-2800rpm rows, 2 for 3200rpm and 1 for the remaining rows. The main trend to notice is the multiplier is higher for lower rpms. This essentially doubles/triples the follower airflow applied for that region. That's why I believe adjusting this would help to solve your problem (not enough airflow down low).

The decay rate {B4317}/{B4319} may also be set too high. These tables are referenced by MPH. However, I don't think it should matter how fast you're going when it comes to the rate the follower backs off. I'd pick something between .005 and .010 and set it there across the board for {B4317}. I'm not 100% sure about {B4319} though. It has me confused because many of the P/N tables are ignored in an M6. I'd look to see how the PCM reads whether you're in gear or P/N and when it reads each of those. Then, you'll know if you need to adjust this table.

That's my $0.02...

 

Can you post up some table data ??? and do you have acess to the Throttle area factor In Iadle constants ?? sounds like the TB apature sizing needs to be adjusted. I find alot of times you can;t get enough Idle air without adjusting the apeature size for the throttle body first.

 

sure, just tell me which tables to post up. I'm using Efi Flashscan Commercial, so I'm pretty sure I can get access to the aperture size, but I've never looked for it.

This is a stock TB, btw. No porting or polishing. I've found that stuff doesn't make much of a difference when you're cramming air down the motor's throat at 15psi

 

Forgive me if I am wrong but when you say "aparature" size you are talking about IAC effective area? I don't know what else it could be?

 

when i go in tommorowo i will try to remmber to grab the names of tables you will need to modify.

 

Ditto, but make the search for RAFACIG or RAFIG. Idle air flow correction.

Look for "Idle Airflow Correction" group under Calculated PIDs. Pay attention to More information windows, not all PIDs will be supported by your Z. Several PIDs will need to be selected to get results for the calculated PIDs. Log from cold start to fully warm idle.