Hello, I just deleted DOD and VVT from my 13 Sierra 5.3 LC9. I replaced the factory DOD cam with summit racing SUM-8712R1 stage 1 truck cam. 210 intake 218 Exhaust 112 LSA 1 degree advance .294 lift at .500 intake and exhaust. I'm fairly new to tuning but I'm working on getting it dialed in. When coming to a stop I'm getting a little bit of surge from the engine as the trans downshifts. It's almost as if the engine is hunting for the proper RPM wile it shifting into the lower gear. Any help would be greatly appreciated.

 

Sounds kinda like intake gasket leeeeeeeek.

 

Throttle body cracker settings?

 

It does not appear that my E38 ECM has a throttle cracker setting, only throttle follower. I'm assuming the idle airflow table has to be adjusted to have the same effect as the throttle cracker settings on the older ECMs. However, Im not sure of the best way to tune the idle airflow table.

 

Silly question… did you disable DOD and VVT in the tune?

 

Go to idle--throttle follower--torque and change the numbers to what I have in my tune. i have a larger cam and no surging.
Your VVE table needs some work also. It is "not smooth" in the idle and off idle areas. Also, Both open and closed tables should be the same. Also do a little work on your MAF table. Be sure and make a copy of your tune before you make the Throttle changes, so you can revert back if it doesn't help.

 

I will give this a shot but I think I found the main culprit. When I put the original tune in after the cam swap and DOD delete I added about 3g/s to the idle airflow table in the Idle areas. This I believe was too much for the profile of this cam. I reviewed one of my log files and found when returning to idle the engine should be at about 18 degrees of advance. When letting off the spark timing is "oscillating" to keep the RPM in check as low as -6 degrees. Ill play with the idle airflow table and give an update.

 

It's very important to have your air/fuel correct everywhere, both MAF and VVE. That will help a lot. The Throttle torque chart that I sent will help with the oscillations. Your Final air has a lot of 9's in it in the low rpm areas and shouldn't be that far off. Reducing won't hurt though. At idle, look at dynamic air in your channel chart. That should give you an idea on where you need to be.

 

So I played with the torque follower table with no noticeable change. I also disabled the CT downshifting in case this was caused by transmission tuning. This also did not change much of anything. I'm really starting to wonder if this is caused by the rich condition (about -25% according to my wideband) I have at low RPMs and idle on decel. I have not really done any MAF or speed density tuning at this point because I just assumed this was an idle issue. What is the correct order to tune idle, MAF and speed density tuning? Should you get the idle good enough to drive then do MAF and speed density and return to perfect the idle after?

 

Q "What is the correct order to tune idle, MAF and speed density tuning?"
Answer Establish ANY kind of idle, ANY idle stable enough to start, warm up and get in gear will do. THAN: "Tune VE Table first "
. EVERYTHING hinges on the VE table(s).
Later, when getting the idle stable, and consistent through cold start, warm-up, rolling to stop, etc work on the Base Running Airflow, idle spark, throttle cracker/follower and a dozen other tables but DO NOT **** with all the fine tuning of idle parameters UNTIL your VE is "Nuts ON"

I'll say it again: A smooth, well tuned VE is the KEY, the base upon which the rest of your tune is built.

 

I have come to realise this now. I left the idle alone and started to do some other tuning ie VE and spark. After some changes the surging has started to subside. Downshift are still a little "clunky" but i think that's in the trans tune.

 

Yes man, when you have an aftermarket camshaft, getting the afr on its point becomes critial, especially on idle. And it becomes more notorious the bigger the camshaft is. There is also a parameter you want to modify that determines how open your throttle body can get in order to maintain a good idle control.

 

That cam is very small for a 5.3L engine, it should literally drive like stock once it's all dialed in. Without a log or a tune posted it's just guessing on everybody's part.

 

Finally got it figured out! Got everything dialed in the best I could but still had the surging coming to a stop. The only thing I didn't touch was the virtual torque table. And of course the one thing I didn't touch was the exact problem. These newer gen 4 trucks must rely on the torque side of things a lot more than the older ones. Obviously since the cam is less efficient at idle the torque needs to be adjusted accordingly. I pulled about 25% of torque out of all virtual torque tables below 1000 rpm. Now when coming to a stop there is virtually no surging anymore. I feels just as good as stock now.