4th gear low rpm KR
09-11-2013, 02:13 PM
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4th gear low rpm KR I have a 2000 trans am with a lid, ls6 intake, ported TB, ls6 cam/springs, 7.425 pushrods, long tube headers and a catback. It also has stock 3.23 gears and a stock 4L60E with stock converter.
For normal and cruise conditions I'm using the stock spark advance table, stock lock up and shift tables.
When I go uphill The trans shifts into 4th and locks the converter at around 35mph according to the stock tables, but the rpm drops to around 800-1000rpm and I see up to 8* of KR.
I've dropped up to 5* (down to 18*) on the spark advance table in these cells, but I still see 1* or 2* of KR. Actually I've had to drop timing across the whole table in overall, at wot it will only take as much as 26* with 13.2 AFR and at this altitude it only goes up to .52-.56 g/cyl in the cylinder airmass cells at WOT.
I also just changed to all polyurethane mounts, but this didn't affect the KR conditions at all.
My questions:
I was wondering if it's supposed to shift this soon into 4th and drop the RPM that much, it does seem to be a lot of load for the engine for stock settings.
Also, am I having to drop this much timing because of the LS6 cam? I thought it was the LS6 heads (which I don't have) with better flow and higher compression that called for lower spark advance.
For normal and cruise conditions I'm using the stock spark advance table, stock lock up and shift tables.
When I go uphill The trans shifts into 4th and locks the converter at around 35mph according to the stock tables, but the rpm drops to around 800-1000rpm and I see up to 8* of KR.
I've dropped up to 5* (down to 18*) on the spark advance table in these cells, but I still see 1* or 2* of KR. Actually I've had to drop timing across the whole table in overall, at wot it will only take as much as 26* with 13.2 AFR and at this altitude it only goes up to .52-.56 g/cyl in the cylinder airmass cells at WOT.
I also just changed to all polyurethane mounts, but this didn't affect the KR conditions at all.
My questions:
I was wondering if it's supposed to shift this soon into 4th and drop the RPM that much, it does seem to be a lot of load for the engine for stock settings.
Also, am I having to drop this much timing because of the LS6 cam? I thought it was the LS6 heads (which I don't have) with better flow and higher compression that called for lower spark advance.
