EFIDynoTuning Forum

I hate to do it, but I must now ask for help. I recently added AFR 165 heads with a Lunati Voodoo cam to my 1995 5.0 HO. Previously had the car tuned for stock except for 95 Cobra GT40 upper/lower, ported and 70mm throttle body. LU47 injectors. Tune was good and I had solved the transition to idle spark sufficiently. No stalls and great drivability.

After the new heads and cam, the engine behaves well as long as I am not in closed throttle under idle spark control. Target idle 800 RPM. Kept in O/L because of a header collector leak I need to address.

My problem is the return to idle spark control. Dashpot is ok. Idle is good and IAC duty is good with IPSIBR close to 0. Set to change to idle spark as I come to a stop at 0.5 mph. RPM hangs around 1000 -1100 RPM until stopping. Then it will either begin the surge and shut down or will just shut down.

I even tried adding some base spark (in the tune for min spark, not at distributor), as the idle really smooths out when idle control advances beyond the base 10 deg. I read through similar issues and write ups, but what am I missing on the return to idle spark control?

Doug

sounds like you have too much spark and when it goes in to idle feedback spark it drops too low and conks out

your dashpot spark needs to be lower than idle spark so when it drops in to feedback idle spark control it has torque reserve

no idea what that means by adding base spark for min spark, id assume your referring to the idle spark min clip? If so no need as that should be lowered for more reserve.

Spk_load_res is idle spark torque reserve. 0 to 100%. Lower it and it will increase idle spark (not what you want) and if you raised it idle spark will reduce (more torque reserve).

for decel spark use the ct dashpot spark modifier function to reduce it so its below the base idle spark before it drops in to feedback idle spark control.

So may need to do something like

16.00 1
0.750 1
0.500 .5
0.250 .5
0.000 1

Thank you! Yes, I meant idle spark min clip.

Many values were from T4M2 base on spark with a few exceptions.
I raised the SPK_LOAD_RES from 0.25 to 1. Will test in a bit.

Which function for decel spark mod?
I see a decel spark table fn2600 reference. Also fn745B.

Doug

.25 to 1 for idle spark reserve will give you no idle spark, you need something, try .8 or so instead.

dashpot ct spark modifier I dont know the FN # OTTOMH. FN839 or something like that comes to mind but I know thats not correct.

yea the decel spark table is your max spark clip at closed throttle. Problem is you only need it retarded during dashpot so you have to use the dashpot spark multiplier function.

Ahhhh! Perhaps FN879, Dashpot Decay? I didn't realize that was a spark modifier. That's the only dashpot CT table that I can find.

Thinking this:
16.00 1
0.750 1
0.500 .5
0.250 .5
0.000 1

Might mean this?
16.00 0.1
0.750 0.1
0.500 .05
0.250 .05
0.000 0.1

Currently:
16.00 0.0500
2.00 0.0500
1.25 0.0200
0.750 0.0100
0.500 0.0061
0.250 0.0020
0.000 0.0007

no not dashpot decay

thats not a table thats a function

fn839 is correct its dashpot ct spark multiplier

if you type in ct spark or dash it should pop up

control f brings up the find box, hope your not using the tree view as none of that is setup

Yes, I've been using the tree view. FN839 never showed up in a search and nothing under CT_ looking like a spark modifier.
Using CBAZA_24016.xdf. T4M2 base bin dated 210514.

What am I doing wrong?
Thank you for your patience and help.

did you try typing in dash?

are you searching titles?

if so then maybe its not in there

Yes sir! Tried them all. Cannot find that name anywhere.
I’ll go look at the T4M0 stock bin and see if it exists there.
I can’t imagine it would show up if not in the CBAZA xdf, though.