Surging Throttle and eventual stall

[JakeFusion]

Hi all,

I just purchased HPT and got it today. I had my car street tuned a few weeks ago and the idle has been wonky ever since. I decided to grab HPT and see if I could begin modifying the tune to clean up the idle. I've been reading furiously the past couple of days, but wanted to get the current tune and log out there to see if you had any ideas on where I need to focus. I used Russ K's config file for idle and started the car and let it run in park until it stalled out. IAC counts dropped pretty low and timing looked high (27-30 degrees).

Here is my Tune File and the results of that logged run.

My specs are as follows:

02 Trans Am
EPS 234/242 111+3 Cam
TEA Stage 2 LS6 Heads
FAST 102 Manifold and FAST 102 TB
TSP 100mm MAF with the LS3 Cartridge (disabled - only using the IAT)
Kooks 1-7/8" LT Headers and 3" True Duals
Bosch EV14 52lbs Injectors with data from FIC
Racetronix Pump & new WIX Fuel Filter
FLT Level 6 4L60E
CircleD 2E 4200 Stall Converter
BeCool Aluminum Radiator with 160 T-Stat
New Delphi MAP relocated to front of FAST
New IAC Motor
OLSD Tune at present

Thanks!

[JakeFusion]

I just realized I saved the log, but not the data. Sigh. I guess I'll have to wait until it cools off to log it again. Also, I noticed the STITs were like -50 cold and damn near -80 when warm, so my RAF is way too high?

[JakeFusion]

I let it cool to 108 degrees on the coolant. Not enough for a cold start. But it is in the upper 80s today so this is what I have. I'll log it cold tomorrow.

[JakeFusion]

I've been playing with the tune some... the 102mm TB I know brings the Base Idle Airflow down... but numbers of like .4g (3g/sec) can't be right. I put them at 10.7g/sec in the tune and plan to try it tomorrow morning. That cam with that overlap should like that.

Is the histogram showing .4 (where it died and stalled out btw) because of what? The STIT are like around -70 so the Base Idle Airflow is off quite a bit (I think I had it around 10/g sec before).

Also, the IAC counts are hitting 0 which means the TB is too open? But there is no airflow? Should I be looking at fueling?

[david_viny]

Also, the IAC counts are hitting 0 which means the TB is too open?

I would start there, closing the throttle body some will raise the IAC counts.

[JakeFusion]

Had some time and updated the tune. Put things back to stock that didn't make sense and changed the VE table back to stock, then altered idle between 60-90% of stock values. Then smoothed. Then I added 10% above 1600 to make sure it doesn't run lean.

Changed a lot of little things based on the HPT idle tuning guide. Set OLSD to 1 across the board and configured PE for 1 for the idle RPMs and 1.14 for a 12.8:1 AFR. This will hopefully get the car idling decently and allow me to do some data logging with the wideband to see what my AF actually is so I can adjust.

Then I'll go back and adjust the timing around idle and the idle RPM until it lopes good and doesn't shake like crazy.

How does the file look? Plan to upload it to the car in the morning and test it out...

[JakeFusion]

So I used the tune file I posted. It fired right up and didn't surge (it didn't crank over like 8-10 times like it used to - one crack of the started and BLARP). It settled into a 950 ish idle with 22 degrees of timing. But my IAC counts were like 10-20 and my STITs were -60 still. So, turn of the TB screw, adjust the Idle Airflow (which it's calling for like 3g/sec... I'm thinking there is no way that's right... but it is). And playing with the TB made it start surging again.

So I kept playing with timing. I'd add 4-5 degrees in the scanner and lean it out from 14.7 to 16.1 and it would smooth out a little and chop more (though still not enough). I put that in the tune (added 4 degrees across the 800-1600 cells for Idle Spark Advance in Park) and it didn't seem to do anything. So, I played with the TB like 4 different times closing it. My IAC is still in the 20-30 range hot. And it idles pretty good when hot. But at like 172 degrees it still surges (though smaller). When I command my fans off and the temp gets over 180 the surging quiets down quite a bit and it starts to chop and hold idle pretty well. I'm guessing without it coming up to full temp of around 195 it's not able to idle like it needs to.

What should I be looking to tune during the transient temp ranges?

I also got my STITs to -5 and then played with the TB screw again. It's hard to get Desired Idle Airflow spot on when the car is hot. So I'm guesstimating based on what I see in the real-time scanner. I'm thinking of bumping up the fans 10 degrees and seeing if that helps. But I'm going to be doing idle tuning in gear this weekend and the added load should help get the temps up. But I was in the sun, it was 88, and it still idled at 172 degrees. Go BeCool Radiator? STITs are -14 in the current tune as the constant TB adjustment is throwing any log of the Desired Airflow out the window.

I've also reduced the sensitivity of the overspeed/underspeed so wild swings of timing don't surge out a cam with lots of overlap. The one thing I'm not happy about is the throttle hanging at 1200rpm after a blip of the throttle. I am going to play with the decay a bit tonight.

Anyway, here is my last data log (using Russ K's cfg) and the tune file. In gear, it won't idle. I need more Desired Idle Airflow, but I wasn't logging. I was trying to get it back in the garage. The VE Table is a reduction from the stock table and may need more adjustment. I believe I reduced 60-80-90% respectively across the 400-800-1200 cells. I then removed another 10% with smoothing to further lean it out. Wideband is coming early next week so I might be able to adjust that a bit more.

[JakeFusion]

I have it running better now... my IAC counts are in the 30s with TPS voltage set at .45. Car is still surging in idle after getting the Desired Airflow inputted - but not all the time, so I guess my VE table and Spark advance are closer to being right at certain temps. I'm playing around with spark and A/F now using the bi-directional controls. I turned off adaptive spark and find the sweet spot for timing and am trying to lean it out so it idles well. I'd like it it idle around 900-925 but if I can get it to idle at 750 without much surge I think I'll have it. I did just upgrade to the 1-Bar OS for RTT. I think that will help me find the right settings in a hurry.

Here is my latest base tune if anyone has any input/suggestions? I plan to upload it in the morning and see how she behaves. I'll be honing the VE table with my wideband later this week. Current VE is based off what a tuner did for me logging with a wideband, so it should be close.

Also, would this be easier to tune with a NW 102 vs the FAST 102?

[edcmat-l1]

Your over and under speed spark tables weren't aggressive enough. Once you have everything dialed in a little better, you may be able to soften them up a bit. You'll know when you've gone too far, the idle will become unstable again.

Also your adaptive idle airflow was kind of extreme.

[JakeFusion]

Thanks, Ed! I'll give that file a try today and see how she does.

Btw, the adaptive idle, I thought, was set in g/sec. I thought I had changed it. But this is what happens when you start tinkering with stuff late at night.

[JakeFusion]

Woohoo, seems to be idling pretty good now using Ed's file.

Here are the logs. It died out after a while for no reason. I don't know why. It might be running a bit rich; the fuel smell is a bit worse than it has been. So I'm going to lean it out and see what it does. But the timing seems good. My kPA readings are right around 70 kPa now, which was down from the 75 I had before, so I know the timing is close.

My desired airflow the last couple of days have been very high. After the restart, everything was back to being within like -5lbs off in the Rev Log. It does take a little effort to start cold, so I may add 10-15% on the Desired Airflow, but 3lbs/min seems a bit much. What could be causing that? I did close down the TB to .45-.47 V to get the IAC counts up from 5-10 to the 40s.

I'd rather not raise the desired airflow too much as I am having a bit of a cruise control effect tho when I rev. I took a second log after it just died on me so you can see what it does.