i know little of timing. i notice the timing curves of different gereration GM SB engines vary greatly.

i believe i run a conservative timing table. it was given to me by another forum member that runs a similar vehicle.

max timing is at 3600 *** 33 deg plus PE spark of 5.6 = 38.60 total

at 5800 rpms i see ***20 plus PE of 5.6 = 25.60 total

i will assume that to be conservative.

i recall removing 2 deg at around 3600 rpms as i saw KC's a couple years past. KC was with 93 octane. switched to 89 oct and KC did not reappear.


real Q is my idle. i idle at 21 deg and i have in all low rpm cells from 400-1200 rpms and 30-50 map @ 21 deg. i am thinking of changing those cells up and down 5 deg to see what effect it has on idle. i am a bit dissapointed in my lack of idle quality. my buddy has same cam in 327 carbed 750 cfm and his car idles fantastic. rock solid.

EBL is coming soon so will not spend much time working on the occassional surge. seems it occurs due to an assortment of potential influences.

like:

1. cam has some overlap that may be causing nb02 to dump in fuel. trying to catch that event on WB but cannot see it. seems i see enleanment as iac opens. seems the surge starts at a reasonable A/F of 12.5/1. yet rpms drop to 500 BEFORE the iac opens? something is causing the rpms to drop?
2. idle is OL at 12.5/1. some times it is smooth(50%) and sometimes surges. impossible to predict. TC will be adding the "throttle follower" constants to reduce IAC values during stall save. that may not prevent the rpms to drop however. blms are 124 in all possible idle cells. and again idle is OL.
3.synch/asynch may be occuring. i see on winaldl but i do not log every day. seems idle fueling may be on edge causing asynch occasionally. not a smooth transition?. does this cause the rpms to drop causing the iac to open to catch stall. does asynch cause interruption of fuel delivery?
4. timing... i will move 5 deg each way to see what happens to idle qualiity.

thanks for comments...

 

Unless your running some old large chamber heads, IMO, the 38d is ALOT.

Try it.

Wait til you're done before passing judgment. Some things take time to work out.

 

TY.

i have logged last night this AM and have confirmed the events that precede the surge. i logged BLMs as well but have not yet looked at them.

the A/F seems to be around 12.5-13.00/1 at idle before surge. i am idleing in CL per flag in winaldl. yet A/F is showing 12.5/1? is that not kind of impossible? i thought my .bin was set for OL idle? will reapproach that later. what i am seeing is the ECU flipping fueling to asynch and back again. a cycle. that event occurring is apparently cutting off fuel momentarily. causing a stall.

so i think the problem is too large an injector(80) and or too high FP(20) for idle. the inj/fp is necessary to fuel WOT however. so that package is correct. i will look at tunercat and determine what constats are available and where i have them set. maybe someone can lead me to disable CL at idle?