E-fans and idle trims
09-13-2013, 12:18 PM
#1
E-fans and idle trims I am tuning the BRAF in HP tuners with the fans manually off, when I let them come on, the STIT's rise about 0.3, is this normal and is there a way to tune that out? I have messed with the "Cooling Fan Airflow" and that does not seem to affect the trims.
09-13-2013, 01:14 PM
#2
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This may be due to IAT heat soak bending the air mass
estimate (idle is weighted toward the speed density
air mass in dynamic airflow figuring). Fans will lower the
engine bay temps and the IAT follows.
I run my fans full time low and on high when above 'stat
crackpoint.
Extra electrical load also makes the motor run higher
MAP to make that load-power, so you may just be at
a different place on the VE map. Ditto for when you
engage the A/C. The MAP-dimension of VE may not be
as well fitted as it wants; exhaust mods (including cam)
will change the MAP-axis profile as VE tracks intake-
to-exhaust pressure difference (but there is no data
for exhaust pressure, it is assumed as-was in whatever
hidden calculations go on).
estimate (idle is weighted toward the speed density
air mass in dynamic airflow figuring). Fans will lower the
engine bay temps and the IAT follows.
I run my fans full time low and on high when above 'stat
crackpoint.
Extra electrical load also makes the motor run higher
MAP to make that load-power, so you may just be at
a different place on the VE map. Ditto for when you
engage the A/C. The MAP-dimension of VE may not be
as well fitted as it wants; exhaust mods (including cam)
will change the MAP-axis profile as VE tracks intake-
to-exhaust pressure difference (but there is no data
for exhaust pressure, it is assumed as-was in whatever
hidden calculations go on).
09-13-2013, 03:01 PM
#3
Thanks Jimmy
Questions....
I have read that it's best to tune the RAF with the fans off, I guess so this doesn't happen, so is having the STIT's ~0.5 out when the fans are on worth worrying about?
How close do the short term idle trims need to be? I have the long term turned off.
Questions....
I have read that it's best to tune the RAF with the fans off, I guess so this doesn't happen, so is having the STIT's ~0.5 out when the fans are on worth worrying about?
How close do the short term idle trims need to be? I have the long term turned off.
09-13-2013, 03:56 PM
#4
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I think it's better to tune it like you drive it, and I like
to have it stay tight ECT-wise so that the "envelope"
I have to tune against, is smaller. That's why I run the
low speed fans full time (other than the >MPH cutoff).
I think single digit STFTs are fine, I prefer them to be
negative (slight rich bias) so transient throttle doesn't
ping and I can run decent timing, and let the trims pull
it to stoich in steady state.
to have it stay tight ECT-wise so that the "envelope"
I have to tune against, is smaller. That's why I run the
low speed fans full time (other than the >MPH cutoff).
I think single digit STFTs are fine, I prefer them to be
negative (slight rich bias) so transient throttle doesn't
ping and I can run decent timing, and let the trims pull
it to stoich in steady state.