C5 Idle suggestions (logged w/ Russ K's config)

[tech]

2001 Z06 w/ LG Pros (catted), G5X1 (228/232 112), VaraRam, Relocated MAF to front of TB

I've tuned VE to 0 to -5 and then added the MAF and adjusted to 0 to -3 (last scan showed about +2% at idle tho).

Before someone comes out and says it... yes... I read the stickies and searched (3 hours just tonight).

At startup, I had the spark advance locked at 26 with the bi-directional controls. When I turned it off, the car idled much smoother. I don't have much experience with ETC vehicles and I'm not sure what I should expect from the IAC. I obviously have no set screw to help get the IAC counts down, so I'm not sure if I should be concerned with my results.

The car doesn't idle or drive all that bad but I have the typical problems of the idle hunting when reversing or on low speed sharp turns.

Also, how do you calibrate the scalar?

TIA

[blownbluez06]

The Scalar is the inverse of the area of the throttle body in sq.mm. multiplied by 100.
For a stock LS1/6, it's .0255. For a 90mm, it's .0192.
I too have read alot and if I understand correctly and am using Russ Kemps Config properly, your values on your base running airflow are off a little. I converted the histogram to g/sec and at 90* show you are at 1.591 and commanding 1.693. All the way to 198* where you're logging 1.109 and commanding 1.177. You might try cleaning up those values a little based on the scan and see if it helps.

The car will idle better with the bi-directional controls as the PCM uses timing to help stabilize the idle. Your LTIT's are at 3.4x% when warm. Get your LTIT & STIT's lower at a given temp and then use the OLFA (open loop EQ ratio under fuel control/OL&CL) table to adjust fueling from startup. Someone taught me to copy those OLFA values and paste them in the PEvs.ECT tables after subtracting 1 from the values. In other words if you get a 1.21, then you'll just put a .21 in the same temp in the PEvs.ECT table.

[tech]

Thanks for taking the time to look through my files (also the explanation of the ETC scalar).

I'm trying to determine how you came up with the numbers you did. The plot value of the histogram is already g/sec, so it appears I've misunderstood what you said. I'm confused as to how you came up with 1.591 and 1.693. Would you mind breaking that down for me?

I noticed that my car generally idles better with spark advance locked around 21*. In all of the reading last night, it seemed like my car might respond well to more timing (hence locking at 26* on startup). Instead, the car idles much rougher until I unlocked the absolute timing value and let it settle. I didn't want to play with it much and potentially skew the cold start log, so I just let the PCM do its thing.

According to Russ's config, I don't even see LTIT % in the scanner. Are you using other histograms than what was included in the config? That might explain alot.

[tech]

Ttt

[MattB]

I have that cam, and I was really surprised with the changes in idle when I set the timing advance a lot higher than I had it at. My latest scan shows I'm running about 28 deg at idle, and it jumps up to 30-33 at 1k rpms.

I'm a little behind you, I think I just got my VE table to what I want. Now for the MAF. But, I'm really liking what I've done with the spark advance.

I was just researching spark advance in general when I saw your post.

I'm going to take a look at your tune and see how it compares to mine, mine is a mess...

[MattB]

Well, it looks like my VE table is a little different, but not a whole lot. The high octane table and the Idle Spark Advance In Drive table are different. Between dialing in the VE table and the changes to these spark tables I've notice a great improvement in the idle and better mid range power.

Do you have issues with the AC causing stalls at Idle? I've tried a couple of the recommended updates to fix my stalling, but I'm afraid that it is messing with my VE logs.

Anyway, here is my tune for reference. Not sure if it will help you out, but I'm interested to see how you fair with your tune as your mods are very similar to mine.

If you or anyone sees something that I'm doing wrong please let me know!!

[tech]

That tune has some idle tables effectively disabled while I work on it. I wouldn't suggest copying over anything related to idle until I get things sorted out.

The car really hasn't idled bad, even with the "pre-cam" tune in it. AC doesn't have much of an affect on my idle however, with the current tune, I'm getting some more hunting/surging. Frankly... it idled better before I started reading and making changes based upon things I've read on this forum. I'm grateful for any help I get from people on the web... but there seems to be many other forums where the willingness to help is greater. Russ seems like a pretty competent guy... but I didn't see any explanation on what his config is supposed to show me... or how to correct issues based upon its data. That being said... I don't think that anybody who contributes to the forum must support everybody asking for help. I just thought (read: hoped) that other people he has helped would repay the favor by passing the information down.

If you need help with the VE or MAF stuff, you're welcome to send me a message or post here. The VE table took 4-5 datalogs (disabled LTFT, disabled DFCO, raised PE threshold, set MAF fail frequency to 0). The MAF only took 2 flashes.

[blownbluez06]

I'm trying to determine how you came up with the numbers you did. The plot value of the histogram is already g/sec, so it appears I've misunderstood what you said. I'm confused as to how you came up with 1.591 and 1.693. Would you mind breaking that down for me?

I noticed that my car generally idles better with spark advance locked around 21*. In all of the reading last night, it seemed like my car might respond well to more timing (hence locking at 26* on startup). Instead, the car idles much rougher until I unlocked the absolute timing value and let it settle. I didn't want to play with it much and potentially skew the cold start log, so I just let the PCM do its thing.

According to Russ's config, I don't even see LTIT % in the scanner. Are you using other histograms than what was included in the config? That might explain alot.

I've got so much stuff loaded in my computer, I don't know where I got the histogram config. I just know that it didn't agree and was measuring lbs/min air or something else when I first opened it, so I converted to the same units that the RAF uses and saw the differences.
Timing not locked in ususally helps idle once you establish a good range in your table.

[MattB]

I think I'm getting the VE table dialed in, still get some wide variations from log to log. I think some of that is the weather, we get some wide temp swings here in CO. I did have all the same stuff turned off, but when I 'double' the AC tables vs pressure and IAC which are under the torque management, I think it impacted my logging. I think it caused more fuel to be added and threw some of my VE updates off. So, I reset those and the logs are looking a little more uniform. That and my technique leaves a lot to be desired, I've been mixing in hand smoothing and programmatic smoothing into my VE updates and I should probably be leaving that until latter

I've had 3 different 'pro's do updates to try and get the idle to be better, so there are some strange things lurking in my tune. That and I converted from A4 to t-56. I think I got everything, but every now and then I wonder if I missed something and is throwing me off. Like TQ management or some shifting tables.

Anyway, I'm much happier with the spark adv settings you can see in my tune. MUCH smoother and I just gave 700 rpm idle a try, I may have to go back up a little but it actually sounds better than 850 on the 'pro' tune. Not to offend real pros, but here in the Denver area I've only been able to find guys that don't put any where enough effort into a tune. No VE table updates, one did mess with the MAF(although just tweaking, no real data collected), and none touched the spark tables. They seem to know what the PE is though...

If you have the VE and MAF going well, I'd really look at the spark. Its a huge factor IMO. What my take is that different cams are designed to work with certain spark adv settings, i.e. the duration and start of a valve event implies a certain spark adv. By not adjusting the spark to match your cam I, in my limited knowledge, could see why rough idling, surging and hunting could result. That is we are seeing the effect of the fuel burning at the wrong times. Getting that timing right may even cause you to go back and re-adjust your VE table, because you could be getting better burn of your fuel which is kind of what the VE and MAF updates are based on. I think I've seen that as well in my logging, I've changed my advance a few times while doing the VE updates and the results then are a little different than what I expected.

The mid range is a lot better as well. The Vette never sounded really 'right' below about 3k rpms. Like it was fighting itself. It would be lackluster below 3k and then take off like a downshift at about 3k. And sounded great above 3k. Now, with the spark adjusted it sounds 'right' at all rpms. Power is smoother from idle all the way up. The better VE table is helping I'm sure, but I did not see that kind of change with any VE table updates.

Of course, I'm NOT an expert I only play one in my garage. So, take my tune and rantings with a grain of salt.