FN2300. How is it used?

[DOHCTOR_32V]

Hello, I'd like to ask how FN2300 functions, and what other tables is it associated with? I read that it may be for auto transmission apps only, but I have also read it can affect ignition timing. What is the correct way to use this table in a 5 speed application? Thanks

[decipha]

fn2300 is the mbt spark table

Anything that says mbt is a modifier for it, such as egr, lambe and ect modifiers which adjusts mbt for those conditions.

Its used on manuals too as mbt is how idle feedback spark is calculated but that would be a mostly correct statement as autos use it for torque reduction on shifts (torque modulation) as well as a modifier to tv pressure as torque is based on retard from mbt (torque ratio).

In any case you should always set the table to the most accurate timing for the engine. MBT is the timing where the engine makes the most power so you can think of it as the max timing the engine will ever want.

I just noticed that my timing write up is 11 years old and back in 16' it only had a partial update. I'll put it on my list to update here next.

[DOHCTOR_32V]

Reading through the following, some of my questions are answered, however I would like an explanation of how to dial in the MBT table correctly. Any help appreciated.



"At any given time the actual spark delivered is the lowest spark the ecu calculates.

Idle (feedback) spark is calculated from MBT
using the torque limiting function fn799
from the following scalars
spk_load_res - feedback spark desired torque (setting this to 0 will give you maximum idle spark)
after fbs_entry_tc - feedback spark entry time constant
which is clipped by spk_fbs_min - feedback spark min
and oscillated by spk_fbs_gain - feedback spark gain
not to exceed tr_delta - feedback spark torque ratio max delta (recommend value of 1 in all calibrations)

the MBT Spark table FN2300 is modified
by the Adder for Lambse function FN730
the Adder for EGR function FN731
and the Adder for Vehicle Speed FN743

Its only neccessary to dial in the MBT spark functions when you have an ecu controlled automatic transmission.
However, I highly recommend dialing in the MBT function in all calibrations.

Now you won't get into idle feedback spark unless both the idle flag and the closed throttle flags are set, which is going to be primarily due
to the IDLRPM scalar and its hysteresis. Just make sure your idle air is dialed in and the idlrpm scalar has been adjusted correctly and all should be well"

[decipha]

only way to dial it in is to put it on a dyno and steady state each cell and throw timing around til you find peak torque output


my mbt reference chart on the homepage will get you about 95% of the way there from the get go

[DOHCTOR_32V]

Thanks, I will do some testing to find MBT at specific loads and weigh the info against the logged spark source on a few runs. If I am understanding FN2300 and FN799, I should be able to dial the tables in with that. FN730 and FN731 tables are set to all zeros, stock.

Can you tell me why FN743 and FN766 do not exist in the J4J1 or T4M2 calibration? Your instruction says Fn799 and FN766 should mirror each other, but like I said FN743 and FN766 do not exist. I afraid to mod FN799 if I don't find FN766, or know if those missing tables are of no consequence.

[decipha]

fn743 does exist its null fn766 exists as well but requires no adjustment