My tune is basically a hacked together version of several tunes I've found, plus some tweeking. A bit rich at WOT, but okay otherwise.

I had a couple bad O2 sensors, so I bypassed those in the PCM. The car ran great like this; no cam surge, pretty smoothly, etc.

Now that I put 2 new GM O2 sensors in, reactivate them, and the car just doesn't run as smoothly at very light throttle. At freeway speeds it seems alright. W/ light throttle, it almost bucks/stutters ever so slightly. Doesn't really feel like cam surge, almost like a very slight miss. Open loop and power enrichment modes are still fine, as is decent throttle application in closed loop.

I haven't taken the time yet to run Datamaster on her and log any around town driving. What should I look for when I tune it for light throttle?? Any places I should focus on. I have LT1_Edit and Tunercat, but tend to just use my LT1_Edit. Important mods are ported heads, LT's w/ true duals, CC306 cam, Mallory ignition, TR6 plugs gapped .040, 6-speed car.

 

I would guess its going lean. See what the o2s do when you barely touch the throttle. You can adjust that by tweaking the MAF table at the appropriate airflow reading when the leanness occurs.

 

Joe, let me know if this works. I experience the same problem in my Z. I am just going to delete the rear 02's unless someone thinks I shoudl keep them on for my cats.
By the way, how did you run lastnight (wednesday)? I was at NTR on my street tires and could only manage a 13.3.

 

Ran a new best, 11.29 @ 121.52, 1.61 60'. Track prep sucked, and I pulled that 60' spinning on my ET Streets. That wasn't a fully clean run either, so it definately had more in her, but I busted a bolt off on my tranny dust shield ending my night early, as I didn't feel like racing it w/ a zip-tie holding it on, and just drove it home. W/ any luck I should hit the high 10's this year w/ another mod I have yet to install.

 

nice times, wish i could have seen you run! your new "mod" wouldn't happen to be a set of front mounted nozzles spraying VHT (the sticky stuff if my abbreviation is wrong) on the track in front of you?

Friend, "Dude, I just seen him purge the nitrous!"

Me, "no, that was a VHT purge, you have to run it at this track."

I've only been to NTR once when it was actually prepped okay. It's sad when we have hondas chirping the tires when they shift at thet 1000' mark.

 

Nope; got a set of 4.10 gears for the car that needs installed. 4.10's are really the appropriate gear for my setup, but I went 3.73's back when I was internally stock and 4.10's wouldn't have worked.

 

no 02's = rich which = no cam surge more down low power.

You could mess with the maf table and short term/long term itegrators to run richer in closed loop, reason you have to do this is so the 02's can't compensate to 14.7:1, you need a wide band and play with the maf/itegrators to get lower then 14.7:1 A/F, where you get cam surge.


The good thing about doing it in closed loop is after 2300 rpm, those areas you don't need to change in the MAF table so you'll be at 14.7:1 there where the cam makes enough DCR and doesn't surge, but down low like idle you want super lean but driving below 1800rpm for cc306 you want richer then 14.7:1 to run smooth.

Its time consuming but if you don't care about gas milage and your cc's getting a little dirty just unplug the o2s and run pig rich at all rpms then just tune for WOT and you won't surge but also gas milage will go out.