max timing advance
This is a discussion on max timing advance within the Computer & Tuning forums, part of the LSx Technical Help Section category; a friend and have been looking at a number of factory and tuned timing tables and have been wondering why ...
11-19-2008, 03:58 AM #1
max timing advance
a friend and have been looking at a number of factory and tuned timing tables and have been wondering why max advance timing on all the tables are so low compared to the older small blocks. anyone know if its just for emmissions or what the max safe timing advance is? also should the knock sensor sensitivity be turned down with long tube headers, and how much.
thanks for any input
11-19-2008, 04:05 AM #2
if it makes a difference, the car we are tuning is my 04 a4 gto, with lt's, and true duals, p&p tb, cai/ram air, SDtune, 2,800 stall, torque management deleted, with hptuners programing and some weight reduction
11-19-2008, 06:11 AM #3
Our engines are much more efficient than the SBCs (which were designed 50 years prior!).
11-19-2008, 07:21 AM #4
The heart shaped combustion chambers are much more efficient,,,so more ignition lead isn't necessary to get a complete burn.
Alot of things will affect how much timing an engine likes. Changing the cam timing alone plays a huge roll.
I personally have found what little I have tinkered with stock LS1 engines that about 22-24 degrees is pretty close for what I have with the 241 heads, that was closer to sea level. I believe the older LS1's with older cast heads like even more ignition lead but not certain. Frost has tuned enough variety to know the differences. But there are too many variables to nail down an exact timing table to recommend for your particular car over the internet. Even altitude plays a role.
It would be best to log it and see whats going on.
11-19-2008, 08:33 AM #5
I run 93 octane only. so far copied and pasted the high octane table to the low table, data logged with no knock. bumped the table up 2 degrees across the board and ended up getting 1 degree knock retard at just one point through the second data log right at the 1-2 shift (rear subframe bangs against body)......thats as far as we have gotten sofar.
is there any way to tell true knock from false knock coming from somewhere else?
11-19-2008, 10:58 AM #6
1 degree isn't bad though, hardly worth worrying about. Knock retard is pretty common though on shift points where you are loading the motor the most. But you'll have to fix the banging issue for sure.
I get knock on shift points as well when it's real hot outside. Cooler temps say below 80 degrees it goes away. It's usually only 1 or 2 degrees,,,and generally only on the 1-2 shift where the engine has that huge drop due to the gear ratio's in the auto tranny,,,it's fine on the 2-3 shift. So I don't even worry about it. Now that I have a loose converter installed that keeps the rpms up I'm willing to bet the 1-2 shift knock has went away all together,,,I just haven't logged since the converter install.
One little tip that Frost gave me was to add 1-2 degrees of timing up top,,,,above 5,000 rpms or so. That seemed to help my car quite a bit since I couldn't really run much down low around the shift points.
11-19-2008, 06:21 PM #7
If your AFR is correct; let your tank get low and throw some 100 octane in there. Ride around and try to create knock in methods where you have previously repeatedly seen it. The AFR must be right though so that you know that the knock is not coming from a lean spot.
If the car has a stock stall, as noted, the 1-2 shift spread is a lot of load and is a common knock point. If you are having this issue you can add back 10-15% of the the tq mngmnt to get rid of it (assuming you have already ditched it).
The stock cammed LS1s from 01-up, in general, don't like as much timing at WOT as the earlier years.
11-19-2008, 07:07 PM #8
hey guys thanks for the inout and info. I'm hoping to get back in the programing over the long thanksgiving weekend.
sofar running the stock stall, but putting the 2,800 stall in this friday so all that we have to do for 4 days is tune next weekend.
anything I have to look at changing to accomidate the new stall when I put it in as far as up/down shift rpm or mph?
11-19-2008, 07:13 PM #9
You may also find you'll have to lower the engine misfire tables a bit. Seems a loose converter sets those off.
11-19-2008, 07:27 PM #10
11-20-2008, 05:07 AM #11
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