Low Timing due to IAT Modifier table
07-21-2007, 11:33 PM
#1
Teching In
Thread Starter
Join Date: May 2007
Posts: 4
Likes: 0
Received 0 Likes
on
0 Posts
Low Timing due to IAT Modifier table Hi,
Specs:
2004 CTS-V LS6
Slight mod to intake (K&N panel filter)
Otherwise stock
Outside temp = 79 deg F (26 deg C)
I noticed that my overall ignition timing is running between 18 and 20 degrees when the primary commanded is ~25-27 degrees (depending on the exact cell at the time). I found that because my IAT is running at about 50 deg C at the beginning of the run (standstill) and comes down to about 42 deg C by the end of 3rd gear, the IAT table's timing modifiers has the ECU subtracting at least 5 degrees of timing (and sometimes 7) at the beginning and about 2-3 degrees of timing at the end. Taking those modifiers into account it would be right at the primary table's commanded timing (25-27deg) if the IAT were below 40 degrees C. Assuming 2hp per degree, I am losing at least 10-15hp. I know it doesn't sound like much, but I would still like to not lose it.
The main fix for this is to somehow make the IAT so that it doesn't get so hot. In this car, the IAT is part of the MAF and is located in the snorkel just in front of the air box and just to the drivers of the edge of the radiator. I admit it isn't in a good place, but there is not an easy way of relocating it without cutting metal and a fair about of fab. Any ideas?
The "patch" to this is to slowly reduce the values in the IAT modifier table and continue to scan until I can get it down to zero, or I start seeing KR. Does anyone have any experience with the results of lowering the IAT modifiers? I'm wondering if the LS6 inherently has a lot of room to increase timing (reduce the negative modifiers), without bumping into knock. Is the LS6 prone to knock? Anyone play with timing?
Thanks for your help.
- Bill Hooper
Specs:
2004 CTS-V LS6
Slight mod to intake (K&N panel filter)
Otherwise stock
Outside temp = 79 deg F (26 deg C)
I noticed that my overall ignition timing is running between 18 and 20 degrees when the primary commanded is ~25-27 degrees (depending on the exact cell at the time). I found that because my IAT is running at about 50 deg C at the beginning of the run (standstill) and comes down to about 42 deg C by the end of 3rd gear, the IAT table's timing modifiers has the ECU subtracting at least 5 degrees of timing (and sometimes 7) at the beginning and about 2-3 degrees of timing at the end. Taking those modifiers into account it would be right at the primary table's commanded timing (25-27deg) if the IAT were below 40 degrees C. Assuming 2hp per degree, I am losing at least 10-15hp. I know it doesn't sound like much, but I would still like to not lose it.
The main fix for this is to somehow make the IAT so that it doesn't get so hot. In this car, the IAT is part of the MAF and is located in the snorkel just in front of the air box and just to the drivers of the edge of the radiator. I admit it isn't in a good place, but there is not an easy way of relocating it without cutting metal and a fair about of fab. Any ideas?
The "patch" to this is to slowly reduce the values in the IAT modifier table and continue to scan until I can get it down to zero, or I start seeing KR. Does anyone have any experience with the results of lowering the IAT modifiers? I'm wondering if the LS6 inherently has a lot of room to increase timing (reduce the negative modifiers), without bumping into knock. Is the LS6 prone to knock? Anyone play with timing?
Thanks for your help.
- Bill Hooper
07-22-2007, 09:45 AM
#2
You can reduce the IAT table a bit, I do it all the time.
Last week our club had a dyno day and I did a few tweaks on a car just like yours (100% Stock). It wasn't getting full timing due to the IAT being too hot. I modified the IAT table and took a little fuel out and it picked up 7RWHP. Could've gotten more but it wasn't a real tuning session, just making 4 pulls.
Last week our club had a dyno day and I did a few tweaks on a car just like yours (100% Stock). It wasn't getting full timing due to the IAT being too hot. I modified the IAT table and took a little fuel out and it picked up 7RWHP. Could've gotten more but it wasn't a real tuning session, just making 4 pulls.
