what to adjust: throttle cracker
12-05-2015, 03:23 PM
#1
what to adjust: throttle cracker i have a bolt on ls1 and im having a stumble/recover issue at very low speeds when im in gear.
if im taking off from a light and begin to hit the gas, and then I have to brake quickly from some reason, the car will stumble and bog down to like 400rpms. it sound like it will stall, but never does.
sinces the motor is stock internally, im thinking this is because of my 4k stall. its caused other tune issues which I have resolved. I believe this issue is due to the throttle cracker tables. mine are still stock, and I think I need to change something. but what exactly?
the decay rate and delay are zeroed out. enable speed is 2mph. maybe up that? this only happens at very low speeds in gear.
any theories or assistance is much appreciated.
if im taking off from a light and begin to hit the gas, and then I have to brake quickly from some reason, the car will stumble and bog down to like 400rpms. it sound like it will stall, but never does.
sinces the motor is stock internally, im thinking this is because of my 4k stall. its caused other tune issues which I have resolved. I believe this issue is due to the throttle cracker tables. mine are still stock, and I think I need to change something. but what exactly?
the decay rate and delay are zeroed out. enable speed is 2mph. maybe up that? this only happens at very low speeds in gear.
any theories or assistance is much appreciated.
12-07-2015, 09:42 AM
#2
Anything that affects airflow has the potential to cause the RPM to dip and the engine to hunt. First you need to make sure your VE, timing and base airflow are spot on. Then you can look into the follower and cracker. The follower is very sensitive to changes.
You can use rolling idle but I think it's more suited for bigger cams to keep the vacuum up for the brakes. For a bolt-on it would be a bandaid and the idle "hanging" while slowing down I just find annoying.
http://www.hptuners.com/forum/showth...de-(w-pictures)
Check this read out....VERY helpful.
One note, having changed out your torque converter will affect how fast your car returns to idle. You need to have the follower and cracker decay to zero at or JUST before the engine gets to your target idle RPM. If they are not at zero by this point the adaptive idle does not kick in.
You can use rolling idle but I think it's more suited for bigger cams to keep the vacuum up for the brakes. For a bolt-on it would be a bandaid and the idle "hanging" while slowing down I just find annoying.
http://www.hptuners.com/forum/showth...de-(w-pictures)
Check this read out....VERY helpful.
One note, having changed out your torque converter will affect how fast your car returns to idle. You need to have the follower and cracker decay to zero at or JUST before the engine gets to your target idle RPM. If they are not at zero by this point the adaptive idle does not kick in.
Last edited by Exidous; 12-07-2015 at 09:49 AM.
12-07-2015, 11:30 AM
#3
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First look at your particular table, cracker, for whether
it has a clean soft landing or has spikes / divots as you
slide across the map from higher pedal positions & speeds.
Such features can be a destabilizing "kick".
But look too, to your idle-range air mass accuracy, which
often suffers silently as you mod up. Soggy mixture is the
most destabilizing thing. Unfortunately you can't really get
data at 400RPM to feather in the VE table using the "easy"
(AFR error paste-histo) way, but if you can get the rest of
it clean, I've found it's possible to "eyeball the lines" and
set the response surface to something sensible looking by
hand (just follow the trend from 1600, 1200, 800, ...).
it has a clean soft landing or has spikes / divots as you
slide across the map from higher pedal positions & speeds.
Such features can be a destabilizing "kick".
But look too, to your idle-range air mass accuracy, which
often suffers silently as you mod up. Soggy mixture is the
most destabilizing thing. Unfortunately you can't really get
data at 400RPM to feather in the VE table using the "easy"
(AFR error paste-histo) way, but if you can get the rest of
it clean, I've found it's possible to "eyeball the lines" and
set the response surface to something sensible looking by
hand (just follow the trend from 1600, 1200, 800, ...).