surging in reverse

[steve40]

i've been scratching my head on this one. the car starts up fine and idle decently. what i find is when the car is put into reverse and starts to roll after lifting the brake, the rpm will start to swing/surge. i don't think the swings in rpm has caused it to stall yet.

i have a 6.0L with LS3 top end and a 4l80e with a 3200 rpm stall

[joecar]

Does it ever happen in Drive...?

[steve40]

Does it ever happen in Drive...?

if it does, its not very noticeable.

i do see a idle swing of 50 to 60 rpm while in gear stopped....the cam isn't huge
227 / 238 .613 / .586

114+5

[LastCall]

Looks like the surging is coming from timing. I would take about 15 degrees of timing out of all of your idle spark tables. 35 degrees is way too much timing and does not leave enough capacity to control idle with spark. Maybe start with 22 degrees if timing and see how it feels. Also consider adding a few grams of air into your desired airflow table, unless you have a hole in your TB. Have you done a RAFIG/RAFPN to correct your desired airflow? Also correct your VE table. Lower MAP values have larger VE values. Should be the other way around. I would also correct your LTFT RPM boundaries to get more trim resolution at idle.

Hope this helps.

[joecar]

Hi Jason,

I agree with what you said, 35* is way too much, but I don't see where you're looking (I did not have enough coffee)...




EDIT: Ah, I see it now, base spark IG/PN 400/800 rpm below 0.24 g/cyl.

[steve40]

do these tables make more sense?

i think i see what you meant in the ve tables, the 400 thru 1200 rpm and 15 to 30 kpa shouldn't be a spike?

also, should i change the high and low octane tables in those regions to be closer to the base in-gear map?

[LastCall]

Yes the VE should trend down at lower KPA values.

Timing looks better. I usually make all tables the same from 400-1200 up to .24 g/cyl. It will help in timing swings when transitioning from park to drive/reverse.