Coasting and a.f.r

[smslyguy]

Which setting adjusts a.f.r. while coasting on manual trans? Does b4307's nuatral section affect this area?

I am trying to adjust a.f.r to be around stoich(or leaner) while i am coasting to a stop light instead of it fluctating down to 12.8. I have played with d.f.c.o as well with not much luck with coasting.

[WeathermanShawn]

sms:

A lot of that is related to transient fueling in a low MAP area. It is very common in cammed cars. The Table you referred to would have a very minimal effect on fueling..which is being controlled by your Injectors. Desired Airflow only effects the IAC control.

In closed-loop fueling it is very difficult if not impossible to tune. The good news is that is may not hurt your tune to be a little rich on a coast or decel. Prevents that lean bucking or surge many get with bigger cams.

There is a very good read here:http://forum.efilive.com/showthread.php?13684-How-much-the-A-F-should-be-when-releasing-throttle-after-hard-acceleration. (http://forum.efilive.com/showthread.php?13684-How-much-the-A-F-should-be-when-releasing-throttle-after-hard-acceleration)

While it mainly discusses decel, it is very applicable to coasting also. The bottom line is that if it eventually goes back to stoich..so no worries. Thats life with a cam..:)

[smslyguy]

sms:

A lot of that is related to transient fueling in a low MAP area. It is very common in cammed cars. The Table you referred to would have a very minimal effect on fueling..which is being controlled by your Injectors. Desired Airflow only effects the IAC control.

In closed-loop fueling it is very difficult if not impossible to tune. The good news is that is may not hurt your tune to be a little rich on a coast or decel. Prevents that lean bucking or surge many get with bigger cams.

There is a very good read here:http://forum.efilive.com/showthread.php?13684-How-much-the-A-F-should-be-when-releasing-throttle-after-hard-acceleration. (http://forum.efilive.com/showthread.php?13684-How-much-the-A-F-should-be-when-releasing-throttle-after-hard-acceleration)

While it mainly discusses decel, it is very applicable to coasting also. The bottom line is that if it eventually goes back to stoich..so no worries. Thats life with a cam..:)


Thanks for the Reply. Why does it say in table b4307 "Although listed in the "Idle" section, this calibration also controls the base airflow for non-idle conditions".

What is it meaning "base airflow for non-idle conditions"?

[WeathermanShawn]

B4307 is definitely used for Non-Idle conditions. It is essentially used as your 'base' airflow..which is ironically also used at Idle.

If you log B4307 you will see it is always active. Throttle Cracker and Throttle Follower are additive (subtractive) modifiers to it.

The question is how would that affect fueling? Injector flow is computed by the PCM independently of the IAC. So any affect of B4307 on fueling would probably only occur tangentially. If you put enough air into B4307 and obtained 'cruise control'..it would be the same as keeping your foot on the throttle. You might keep your AFR up artificially by that method.

Thats my take on it. Very few have actually studied it extensively enough to really come up with any rock-solid data..:)