Found an interesting event at idle....

with my current cam (lt4hotcam) i am playing with 24-26 degrees of timing at idle 40-60kpa range (idles in 50=55kpa). I found in the stock prom that the closed tps spark advance vs rpm that itn is 25 deg at idle and the base timing at idle in the MSA is 20 deg.

Using this i adjusted the closed TPS SA to 30 deg to make the difference in my prom to the same number as the stock prom (5 deg additional). Made quite a noticeable differnece in idle quality and i have began experimenting at dropping the idle MSA even further just to see what other gains are to be had in smoothness.

Just sharing some info i've managed to piece together and if u think it will help u out give it a whirl

Later
Jeremy

 

I have one question, you mention something called MSA. What does that stand for? Thanks...

 

Then,

Did you move two tables (2d & 3d), O.K.?.

1.- Main Spark Advance Table (MSA).

2.- Closed Throtle Spark Advance vs RPM.

Did you (in table 2) : º @ idle = º @ idle in table 1 + 5º?.


It's O.K.?

 

My base idle in the MSA (main spark table) was at 26 degree..


like i said earlier in the strock bin idle is roughly 20deg in the msa with a 25 deg in the closed tps vs rpm.....

in the 0 , 400, 800 rpm ranges i increased it by 5 degrees to keep the same relation that the stock closed tps vs rpm did when compared to the stock msa?

understand?

pain to type cut the heck out of my index finger on my right hand
later
JEremy

 

O.K, it's clear. I'll try the same.

Thanks,

Denis V.

 

Currently have my idle when hot down to 675 in gear with some slight surging present.. trying to see if i can push it all the way down to 600 rpm in gear and make it smooth if possible. Surging appears to be stemming from the fact that its is now a little bit richer as i have been playing with lowering the idle speed , so more work yet to be done..

Will keep informed as i make progress or go backwards
Later
Jeremy

 

Too, low and you'll have the alternator dropping in and out. You might look at the min alt speed and see what your pulley ratios are if you want 600. That's really low.
I forget the v steps on the PW vs voltage on the 8D, but you might first look and make sure one step lower then your normal charging voltage is the same, so that if the alter does drop out for a sec., the engine doesn't hit the stall saver, or surge too much becuase of that.

 

is there a relationship in idle speed vs timing? doesyour post infer that? I have idle set at 750rpms in closed loop in eprom. throttle blades are set to minimal setting, no vac leaks. and IAC "s fully seated. Idles 800-900. usually 900. if i change my timing at idle will that drop my rpms? It seems if i blip the throttle once at stop sign after exiting xway after long steady cruise. i can drop it from 900 to 800 rpms and idles smootly. TB's were bored 2.00 and at that time the throttle shaft/TB seemed to be OK and not needed bushings. The blip tens to suggest that the linkage is hanging up or spring is sacked or the cable is worn(90,000 mi.). or does the blip add fuel (PE) and that helps the idle temporarily. any thoughts?

 

The only thing I can say about that is when I adjust my base timing while its warm idling, the rpm will change some as I either advance or retard it. If my base timing is set to low, it will idle very low. I like my idle RPM about 900 in park. So in drive it is about 750-800...

 

i have a stick. i am running 10 deg adv base timing. and that is also in my tunercat constants. idle in TC is set at 750. i dont think setting it to 650 will make any difference? will it? is that contributiung to high idle? that is 10 deg adv? no vac leak!