Throttle Follower Airflow Decay - Throttle Cracker Airflow
03-06-2004, 07:12 PM
#1
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Throttle Follower Airflow Decay - Throttle Cracker Airflow I just love how ls1-edit gives you no F'n clue what the tables are.
what do these values represent?
air flow? fuel? other?
what should I see if I raise or lower the values?
TIA
what do these values represent?
air flow? fuel? other?
what should I see if I raise or lower the values?
TIA
03-06-2004, 09:17 PM
#2
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Throttle follower decay is how much air flow (grams/sec? grams/cyl?) is allowed to decrease per each 12.5 milliseconds. This comes into play when you let off the throttle - the PCM gradually closes the blade (for electronic throttles anyway) instead of slamming it shut. Throttle cracker is something like a minimum commanded airflow (grams/cyl) to keep the engine idling...
03-06-2004, 11:05 PM
#3
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Thread Starter
that makes good sense. so I guess that table is exposed more for the vettes than the f-bods.
just trying to track down this weird issue where if I coast down in gear a/f goes rich as in high 11's low 12's then as I get back on the throttle it goes way lean as in 16' 17's for a brief moment and recovers.
extremely bad for me seeing the car is blown. so any sudden slamming on the gas or rapid gear changes equate to a super lean condition for a short period of time and is the only time I experience audible knock.
if there are any idea's on how to fix that I am all ears.
car did this pre-blower too.
just trying to track down this weird issue where if I coast down in gear a/f goes rich as in high 11's low 12's then as I get back on the throttle it goes way lean as in 16' 17's for a brief moment and recovers.
extremely bad for me seeing the car is blown. so any sudden slamming on the gas or rapid gear changes equate to a super lean condition for a short period of time and is the only time I experience audible knock.
if there are any idea's on how to fix that I am all ears.
car did this pre-blower too.
03-07-2004, 08:36 AM
#4
I'll take a stab at this....if anyone would care to help or correct please jump in.
On throttle transitions the PCM uses the VE table to calculate an injector pulsewidth as it isn't able to instantaneously determine airflow via the MAF sensor. Sort of acting like an accelerator pump on "Tip In". Since you are FI and your VE is increased I would try increasing your VE table at those sites effected - actually it might be better to calculate a new VE table for your MAP range.
What part of the VE table do you use - I would guess a narrow upper MAP range???
Your MAF is still seeing boost pressure at run-down/coast so it's adding too much fuel and your getting rich AFR? Too much fuel for a nonload condition. Sounds right to me- if I have this wrong someone correct me. In Edit V1.4 there is a "Decel Fuel Cut-Off" section on the fuel tab. You can set "Enable RPM", "Disable RPM", "Speed"- MPH vs 65,75,85,95,105 kPa, and "Delay" - appears to allow delay of "Cat OverTemp ( COT)" by milliseconds. All of this allows you to fine tune Decel Fuel Cut-Off (DFCO) - would this table help by allowing you to cut off the fuel at coast??? FWIW.
NoGo and ChrisB would have great insight on this
joel
On throttle transitions the PCM uses the VE table to calculate an injector pulsewidth as it isn't able to instantaneously determine airflow via the MAF sensor. Sort of acting like an accelerator pump on "Tip In". Since you are FI and your VE is increased I would try increasing your VE table at those sites effected - actually it might be better to calculate a new VE table for your MAP range.
What part of the VE table do you use - I would guess a narrow upper MAP range???
Your MAF is still seeing boost pressure at run-down/coast so it's adding too much fuel and your getting rich AFR? Too much fuel for a nonload condition. Sounds right to me- if I have this wrong someone correct me. In Edit V1.4 there is a "Decel Fuel Cut-Off" section on the fuel tab. You can set "Enable RPM", "Disable RPM", "Speed"- MPH vs 65,75,85,95,105 kPa, and "Delay" - appears to allow delay of "Cat OverTemp ( COT)" by milliseconds. All of this allows you to fine tune Decel Fuel Cut-Off (DFCO) - would this table help by allowing you to cut off the fuel at coast??? FWIW.
NoGo and ChrisB would have great insight on this
joel
