Need Help: Cammed LS3, light load & cruise surge

[n8dogg]

Hello,

I'm looking for some help in dialing in a cammed LS3. The car runs and drives well. Trims look great. Plenty of power, dyno'd strong, 450hp. It's always had a light load/cruise surge. It's felt under 2500 RPMs at light acceleration and cruise, as if the car is moving back and forth with steady throttle application. It's minor, but it is there, some less sensitive people might not feel it.

The build is the following:
Corvette LS3
Stock Heads
G6X3 cam (big street cam)
1 7/8" long tube headers and high flow cats

I've attached the tune and a log if someone could take a look at it and offer some pointers. Thank you!

1783017831

[Tre-Cool]

try zero'ing out B1206. then changing b1205 to 430 across the board. - This will probably richen the idle up as it'll be injecting closer the right valve timing.

Also make sure your minimum idle airflow is not too high, this can cause the bucking feeling.

[n8dogg]

I will give your recommendations a shot.

Could it also be timing related? I'm seeing around 40* advance timing at cruise. Although with some light acceleration/larger load timing drops and the surge is still felt.

[Tre-Cool]

nope, would put money on it being too much air, rather than spark.

Is there a hole in the Throttle blade too?

[n8dogg]

nope, would put money on it being too much air, rather than spark.

Is there a hole in the Throttle blade too?

The throttle is factory untouched, there are no holes.

I checked the minimum idle airflow table (B1829). It looks to be a bit high. Do you think the factory settings will be OK, or do I need to find a happy medium? The modified table looks nothing like the factory stock table.

[joecar]

Try this (what Tre-Cool said above):


try zero'ing out B1206. then changing b1205 to 430 across the board. - This will probably richen the idle up as it'll be injecting closer the right valve timing.

Also make sure your minimum idle airflow is not too high, this can cause the bucking feeling.

[ringram]

Also look at base spark, high octane spark and coast down spark. If the numbers at the load point you get the issue are too different to each other you can get racing and surging as the ECU moves between the tables. (Mainly high octane and coastdown)

Likely your MAP and g/cyl is different from OEM so the delta between the tables at near zero load will be out.