After-Throttle low Idle issue
Ls3 tables are way different. And are already biased with more underspeed air and less overspeed. Main thing is get your timing down, so you can crank spark correction, and get your scalar right for the TB
darth v8r/justinfusion im going to make the changes to my tune for idling issues u recommended have some questions. idle integral low is it in g/sec or lb/h? what about proportional and integral rpm error? what about iac park position airflow? my setup is a ls3 with vengeance racing kaotic cam,holley high ram intake with 102mm throttle body. car has a th350 trans and im on a sd tune
g/sec. Metric units are not fun for most americans, but the tunes are actually easier in metric units (except injector flow, I still use lb/hr for injectors). My earlier post pretty much put everything out there. I just don't feel like retyping the whole thing. In that idle rpm screen, set the proportional, integral, and derivative the way I described.
Having looked at your tune another change I'd make is in the idle-airflow screen, all your min's in the adaptive idle airflow are -3. I would personally set those to -0.5 to avoid it saving a persistent -3 g/sec and undershooting on return to idle.
The best test is to sit in your garage, stab the throttle without the car moving. if it undershoots when it comes back down, you need more proportional low airflow. Car not moving keeps the cracker out of the equation. You can crank the cracker way up to avoid it while moving, but it's a bandaid
Having looked at your tune another change I'd make is in the idle-airflow screen, all your min's in the adaptive idle airflow are -3. I would personally set those to -0.5 to avoid it saving a persistent -3 g/sec and undershooting on return to idle.
The best test is to sit in your garage, stab the throttle without the car moving. if it undershoots when it comes back down, you need more proportional low airflow. Car not moving keeps the cracker out of the equation. You can crank the cracker way up to avoid it while moving, but it's a bandaid
thank u darth v8r I have started to change the tune to your recommendations just wasn't sure on a few thing also I cant find anything u recommended for the derivative tables. again thanks for the quick replay
Last edited by JHZ28; Feb 11, 2019 at 06:04 PM.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo darthv8r tried your recommendation for my tune today idles pretty good until u give it throttle, then returning to idle it starts to surge and afr goes really fat,rpm lower than desired, this is undershoot correct? u said I need to play with proportional low air flow. my guess is I need more airflow do to the fat afr reading is makin the numbers in proportional airflow bigger add or take away airflow?
@JHZ -- would you be willing to poast up your current tune? I was looking through the earlier posted tune, and realized there should be quite a lot changed since then.
this is the lastest tune and scan log. still surges but its way better ran out of time sunday but im trying to get iac counts down to around 40 when warm at idle. I believe the correct way of doing this is to open throttle body blade and then adjust base running airflow
OK, a few things...
1. you are persistently lean. It looks like your O2 sensors are unplugged, because they just sit at 440 mV. your wideband is showing 16:1 up to 18:1 in places. If you had tuned the car previously with the min fuel mg at stock, then that setting was keeping you from leaning out the mixture. Now that it's lower, you are lean. Getting some fuel in there will help.
2. You went a little too high on your proportional airflow low tables. Try these values: 0 0 0 0 0.03125 0.328125 1.203125 1.6015625 2 2.3984375 2.796875 3.203125. Hold 3.2 out to the end of the table.
3. Under Engine - idle - RPM, set the "Update RPM Err Max" setting to 80 rpm.
4. I noticed in the log that your spark is not going into adaptive idle. It was just holding at 20 degrees. Had you commanded the spark to 20?
5. Your IAC is holding right at 30-50 counts at warm idle. Your idle trims are persistently high. Two possibilities, but would need to see dynamic air on the log to know for sure which is the case. You may have pasted your IAC values too far to the right.
6. Base Airflow - Set your 100C column to 14.3 g/s and interpolate back to your 40 C column.
7. Engine - idle - Airflow. Set your max InGear / AC Off field to 5.00 g/s
8. Engine - Spark - Afvance. Set your overspeed spark table to mirror your underspeed table. Where there is a "10" in the underspeed table, put a "-10" in the overspeed table for example.
The mystery for me is why your spark was holding a steady 20 at idle. If it was doing what it should do, it would likely correct 80% of the remaining surge.
1. you are persistently lean. It looks like your O2 sensors are unplugged, because they just sit at 440 mV. your wideband is showing 16:1 up to 18:1 in places. If you had tuned the car previously with the min fuel mg at stock, then that setting was keeping you from leaning out the mixture. Now that it's lower, you are lean. Getting some fuel in there will help.
2. You went a little too high on your proportional airflow low tables. Try these values: 0 0 0 0 0.03125 0.328125 1.203125 1.6015625 2 2.3984375 2.796875 3.203125. Hold 3.2 out to the end of the table.
3. Under Engine - idle - RPM, set the "Update RPM Err Max" setting to 80 rpm.
4. I noticed in the log that your spark is not going into adaptive idle. It was just holding at 20 degrees. Had you commanded the spark to 20?
5. Your IAC is holding right at 30-50 counts at warm idle. Your idle trims are persistently high. Two possibilities, but would need to see dynamic air on the log to know for sure which is the case. You may have pasted your IAC values too far to the right.
6. Base Airflow - Set your 100C column to 14.3 g/s and interpolate back to your 40 C column.
7. Engine - idle - Airflow. Set your max InGear / AC Off field to 5.00 g/s
8. Engine - Spark - Afvance. Set your overspeed spark table to mirror your underspeed table. Where there is a "10" in the underspeed table, put a "-10" in the overspeed table for example.
The mystery for me is why your spark was holding a steady 20 at idle. If it was doing what it should do, it would likely correct 80% of the remaining surge.
Every time i tried that it made things worse. my theory is the engine does not like 40 degree or timing at 400 rpm. 40 degrees makes less power than whatever the ideal spark advance is for your engine. If your engine likes that, then great, but all the engines ive tuned didnt like that.
dartv8r im in olsd so my h02s are not being used. at that scan I believe I forgot to change my in park and drive spark tables to 18 from 20. my trims I never really look at I thought those are a reading from my h02s? which im not using. I will make these changes and log some more and post them up. u have been a great help and the car has gotten way better this is the tune with the changes u suggested
Last edited by JHZ28; Mar 5, 2019 at 07:22 PM.
glad the changes helped. What I meant by the 20 degree timing was that it was not using adaptive spark in that last log. It was just holding 20 degrees like it was commanded in the scanner.to do so. If it settles into adaptive spark, it should pretty much be stable.
Originally Posted by JHZ28
Darth v8r u want me to change my adaptive idle max in gear/ac off valve to 5.00gs. do I change the other max values in adaptive idle to match?
darthv8r this is the latest idle scan and tune. im not sure why my timming is not acting right it get stuck at whatever is in my main spark table doesn't move. this is kind of a long scan u can see I turned off the car and started it backup to see if it would help timming. sometimes it did not sure what is going on. it also seams to idle higher than before