having problems on cold start, need some suggestions
12-17-2005, 05:29 PM
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having problems on cold start, need some suggestions my cold starts where fine until i installed a fast 90 intake and nickwilliams throttle body, and it threw it off. when i start the car cold it surges stumbling to find idle and i can take off 50 yards and come to a stop and it will find it and runs fine the rest of the day. my mods are in my sig. what can i look into changing on ls1 edit to help fix this my cold start problem thank you
12-19-2005, 07:20 AM
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Originally Posted by WS6FirebirdTA00
you need to adjust on the effective area and then make sure the idle airflow is inline. the stock effective area wont work will and will cause this on cold starts the most. (BTW your sig isnt there lol)
so should i try adding more air in the airflow table
thanks
12-19-2005, 08:14 AM
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I haven't done as much idle fiddling as some folks
but one thing that's worked to cut surging for me
is to set the running airflow values to slightly under
what your hot idle airflow logs show. This is your
"backstop".
The effective area is different, that represents the
idle air taken in and what the PCM needs to do, to
get its "desired" value. You should set up a config
that logs all of the idle related stuff and go through
a full warmup cycle from start, logging stuff like IAC
counts, desired airflow, the idle trims, RPM, ECT, IAT,
MAP, and dynamic airflow. People seem to recommend
just sliding the table values left or right depending on
whether you have too much or too little air (negative
or positive idle trimming). The aftermarket TBs are
pretty much an unknown at this point, maybe someone
will share up an effective airflow table that's nulled the
trimming on such a piece. But the required / desired
airflow also has a lot to do with low end breathing,
idle efficiency.
With the cam and other breathing mods you are
likely overfueled at the low end, needing the VE table
brought into line (decreased down low, increased up
high). Rich at idle from this, will depress MAP and
this in turn will compound the cold start enrichment
found in the open loop fuel air table (OLFA). Double
the gravy, on your donut.
Last, if you've gon and pushed the main spark up,
you may have forgotten to do similat tweaking to
the idle spark table. This works in lower RPM and has
some pretty punk timing values, more spark will make
the engine respond more crisply to airflow steps and
clean up the idle loop some.
but one thing that's worked to cut surging for me
is to set the running airflow values to slightly under
what your hot idle airflow logs show. This is your
"backstop".
The effective area is different, that represents the
idle air taken in and what the PCM needs to do, to
get its "desired" value. You should set up a config
that logs all of the idle related stuff and go through
a full warmup cycle from start, logging stuff like IAC
counts, desired airflow, the idle trims, RPM, ECT, IAT,
MAP, and dynamic airflow. People seem to recommend
just sliding the table values left or right depending on
whether you have too much or too little air (negative
or positive idle trimming). The aftermarket TBs are
pretty much an unknown at this point, maybe someone
will share up an effective airflow table that's nulled the
trimming on such a piece. But the required / desired
airflow also has a lot to do with low end breathing,
idle efficiency.
With the cam and other breathing mods you are
likely overfueled at the low end, needing the VE table
brought into line (decreased down low, increased up
high). Rich at idle from this, will depress MAP and
this in turn will compound the cold start enrichment
found in the open loop fuel air table (OLFA). Double
the gravy, on your donut.
Last, if you've gon and pushed the main spark up,
you may have forgotten to do similat tweaking to
the idle spark table. This works in lower RPM and has
some pretty punk timing values, more spark will make
the engine respond more crisply to airflow steps and
clean up the idle loop some.