tweaking idle air base and iac table
tweaking idle air base and iac table Ive opened my throttle set screw about two turns and set the base idle air table to stock, shifted the iac effective area table to the right about 5 spots and reduced it by 15 percent. I have problems with spuradic surging if Im not easy on the go pedal.
For example in reverse if I mash on the gas with the wheel turned over then let off the pedal it will tend to surge and die.
Ive tried several variations of throttle set screw and base air/iac tables but cant seem to get rid of its tendancy to dip below the set idle of 750, thus causing surging. If Im just sitting there it revs and sets into the idle nicely.
What am I missing? My STIT is around .20, iac count around 20.
For example in reverse if I mash on the gas with the wheel turned over then let off the pedal it will tend to surge and die.
Ive tried several variations of throttle set screw and base air/iac tables but cant seem to get rid of its tendancy to dip below the set idle of 750, thus causing surging. If Im just sitting there it revs and sets into the idle nicely.
What am I missing? My STIT is around .20, iac count around 20.
First off...put it back and do it right....
If you have a stock TB...leave the IAC effective area alone
If its a 90mm multiply the table by 1.44
if its an 85mm multiply by 1.29
second..to do Idle air.....
start with your stock table.....
use the idle command on your Tuning program to hold it at a high enough Idle to not dip and waiver too much..
do a RAF calculation using ECT, LTIT, and STIT's
Make a table that plots your RAF ECT table.
Log
ECT
LTIT Gear AC Off
LTIT P/N Ac off
STIT Adapt
then do Idle Adapt + LTIT for the appropriate thing...
M6 Gear only... (Idle Adapt + LTIT Gear)
A4 Once in P/N once in Gear with foot on brake (Idle Adapt + LTIT Gear) and (Idle Adapt + LTIT P/N)
you can do all of this without moving the Idle set screw usually...
IF you still need to move the set screw a little...then do it and relog..
this will fix 95% of your issues..and it will be done correctly
do this from a cold start and let it idle up to full operating temperature...
If you have a stock TB...leave the IAC effective area alone
If its a 90mm multiply the table by 1.44
if its an 85mm multiply by 1.29
second..to do Idle air.....
start with your stock table.....
use the idle command on your Tuning program to hold it at a high enough Idle to not dip and waiver too much..
do a RAF calculation using ECT, LTIT, and STIT's
Make a table that plots your RAF ECT table.
Log
ECT
LTIT Gear AC Off
LTIT P/N Ac off
STIT Adapt
then do Idle Adapt + LTIT for the appropriate thing...
M6 Gear only... (Idle Adapt + LTIT Gear)
A4 Once in P/N once in Gear with foot on brake (Idle Adapt + LTIT Gear) and (Idle Adapt + LTIT P/N)
you can do all of this without moving the Idle set screw usually...
IF you still need to move the set screw a little...then do it and relog..
this will fix 95% of your issues..and it will be done correctly
do this from a cold start and let it idle up to full operating temperature...
can you point me in the direction of a complete write up on this method of tuning. Ive never read one on tuning idle air and a way to log/correct and what tables. I havent had time to properly research.
http://redhardsupra.blogspot.com/
try lokingthere...MArcin has a great write up on it....
Its exactly what I described above
try lokingthere...MArcin has a great write up on it....
Its exactly what I described above
Ok I set all tables back to stock and adjusted the throttle set screw to .67 V when closed. Put the iac and other associated tables back to stock I used the spreadsheet from supras' site and I still have issues with it dipping below the idle and surging under quick throttle variations at low speed.
I can get rid of the surging but I run into higher idle and cruise effect.
I can get rid of the surging but I run into higher idle and cruise effect.
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if it still dips then you need to change the throttle cracker/follower settings next...
try moving the follower 2 or 3 cells to the left and try multiplying the cracker by .8
seems to work good for me...even on the larger cams
try moving the follower 2 or 3 cells to the left and try multiplying the cracker by .8
seems to work good for me...even on the larger cams
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Scott:
Is there a reasonable range for the RAF end up? My hot idle (176*) has a RAF table value of 7.9 based upon one pass through through the RAF Spreadsheet which was a reduction of my previous values. It made things worse in terms of surging at most temps. When I look at the scanner, my LTIT is -3.00 and the Desired Idle Air is showing 4.9 (7.9 less 3.0). My STIT are bouncing around. Should I try cutting the RAF by 3 or is there something else going on?
Is there a reasonable range for the RAF end up? My hot idle (176*) has a RAF table value of 7.9 based upon one pass through through the RAF Spreadsheet which was a reduction of my previous values. It made things worse in terms of surging at most temps. When I look at the scanner, my LTIT is -3.00 and the Desired Idle Air is showing 4.9 (7.9 less 3.0). My STIT are bouncing around. Should I try cutting the RAF by 3 or is there something else going on?
