Ahrmike

Just finished datalogging a diablosport intune with a WOT run, from 0-100ish, there are absolutely no knocks except for shift knock (not real knock, from what I have read), and from about 100-120, i am getting ~ 6 degrees of KR. Is this normal?

Just learning how these things work and i am in over my head... I just read all 30 pages of:

https://forum.diablosport.com//viewt...=917&start=315

and while informative, it gives no good "rule of thumb" that tuners with experience have...

Also, I am getting ~-7% LTFT bank 2 and ~+4 to -4% LTFT on bank 1. i am fairly certain I have a small exhaust leak (exhaust tick noise) post manifold on bank 1 - that means i am probably getting ~-7% LTFT on both banks? Should I be leaning out the mixture?

What else should I look for? Also, I turned down my rev limiter for reliability/longevity by 200rpm or so but im still redlining at 6400... is the stock LS3 engine a 6600 redline?

2L8LUZ

LS Motors LOVE to rev.... no need for reduced limiter

Unreal

No reason to turn down RPM.

And 6 degrees, is a lot of knock and should be tuned out, assuming it is real knock.

Ragtop 99

In my experience with moderate cams, LTrims should not consistently be outside +/- 5%. -7% across a wide operating range indicates a problem. Likewise, an exhaust leak would not result result in swings form -4% to the 4%.

What mods are on the car?

Ahrmike

Thanks for the insight: Would the -7 possibly be to my tune not yet settling in? I just installed the 91 octane diablo tune. What kind of ltft difference should be expected from a header to x pipe leak?

Mods: No breathing mods, no exhaust mods (NPP open), no cam. I do have a catch can.

Ragtop 99

It should only take one good drive for the tune to settle in. Once the car is warm, the LTRIMs start learning. Weather can have a small effect, so it doesn't hurt to take a second look since it has been a few days.

I've seen header leaks near or before the O2 sensors cause it to read lean. A leak well afterwards is less likely to have a big impact.

Joe_G

You'll have fits trying to tune a car with an exhaust leak, that's likely the cause of your LTFT's. Get the exhaust leak fixed before trying to tune it.

Any knock is bad knock in my book, I don't like to rely on the knock sensors. if I'm getting any KR (particularly around torque peak, 4800 or so) I reduce timing.

If you reduce timing and it still knocks at the same rpm there it might be exhaust hitting something. Look at the floor pinch weld on the right side, it's often close to the headers, I had to massage my pinch weld with some big channel locks for clearance. I could hear it hitting when I lit into it and the engine moved over to the right a little.

Ahrmike

thanks guys. i know im leaking somewhere on the left bank cuz of the sound, and it seems to be trying to richen bank 1. ill chase down the leak this weekend and datalog again.

Joe_G

If your headers have a welded on strap that ties to the torque tube look there. I've seen cracks where the strap is welded on.

Modern header gaskets are great but of course the black carbon trail may show where your leak is.

If that doesn't work to find it if you can have someone break torque the car a little in a completely dark garage you might see fire from where it's ticking. Be careful you don't get run over.