2009 Corvette LS3 First Tune Attempt

[s3an78]

Between forum posts and the book from Greg Banish I thought I would have enough knowledge to start tuning. I might be wrong. I had a 09 Corvette with an LS3 and a manual trans. The car is stock besides my recent mod of adding Speed Engineering Headers, X-Pipe without cats, all attached to the stock NPP exhaust with the fuse pulled. I bought an AEM AFR gauge and got it to log and finally had a chance to do a pull. Attached is the log. I noticed it sightly rich throughout the RPM's at WOT and also 1.5 and 1 degree or KR at 3 areas. Nothing else seemed too far off. Tune is stock from the factory besides the downstream O2 CEL's being turned off.

I plan on doing the following.
1. in the EQ ratio, try and lean out the whole curve slightly maybe 2% and maybe 3% in the 4000-5500 RPM area.
2. Retard the timing 2 degrees in the 2 spots that I saw KR.

If i am anywhere in the ball park let me know. If I am totally off, I'd love an explanation as to why I'm wrong.

[5FDP]

Don't forget to disable the Post 02 sensor test and cat test as well as turning COT off.

Try smoothing the whole power enrichment EQ ratio out. Pick an AFR/Lambda value(s) and see of it responds.

Aim for something safe, like an EQ of 1.190-1.210 for right now. The knock you see right now could be from too much fuel so see what it's like after this minor change to commanded fueling.

[s3an78]

Don't forget to disable the Post 02 sensor test and cat test as well as turning COT off.

Try smoothing the whole power enrichment EQ ratio out. Pick an AFR/Lambda value(s) and see of it responds.

Aim for something safe, like an EQ of 1.190-1.210 for right now. The knock you see right now could be from too much fuel so see what it's like after this minor change to commanded fueling.

Yup I got all that disabled also just forgot to mention it. Driven probably 100 miles without any CEL's. I will work on what you suggested for sure though I appreciate the advice!

[Carbon]

S3an78
Interested in some feedback on the Greg Banish book and which one did you buy?

[s3an78]

Carbon,
I bought the "Engine Management - Advanced Tuning" book. Worth the 25 bucks to be able to understand what everything on the car does. I've read it twice now, its not necessarily tuning guide though. I still am doing a ton of research on this forum and youtube videos.

[s3an78]

Hi 5FDP,
I got the PE set to 1.174 across the board. The EQ was about 0.85 across the RPM's at WOT which I think is a good point for me to be at. I noticed that my Commanded EQ was slightly off though, should I go ahead and do some MAF tuning now? I also keep getting some KR (2-3*) at around 4-4500RPM, I was going to pull timing there but a friend at a reputable shop told me it cuold be because my exhaust is all clamped together and that spot welding a few areas might help? IS that true?

[s3an78]

Hi 5FDP,
I got the PE set to 1.174 across the board. The EQ was about 0.85 across the RPM's at WOT which I think is a good point for me to be at. I noticed that my Commanded EQ was slightly off though, should I go ahead and do some MAF tuning now? I also keep getting some KR (2-3*) at around 4-4500RPM, I was going to pull timing there but a friend at a reputable shop told me it cuold be because my exhaust is all clamped together and that spot welding a few areas might help? IS that true?

[s3an78]

Has anyone ever desensitized the Knock Sensors? I gave it a try and went up 25mV on the minimum threshold and 30 mV on the initial threshold tables. Is that a huge change or is it playing it pretty safe? My KR is basically gone now and I was able to go back to my stock levels of spark advance where as before I had 3-4 degrees taken out of a few areas to see if I could get rid of KR.

[07GTS]

if u know its not actual knock u can log each cylinder and see which one is causing it then just desenstize that one or couple if a few are doing it, i usually only go high enough to remove the noise so then if u get actual knock it still picks it quick

[Gpargament]

I have actually gone through exactly what you are facing, and would like to help. Because the knock is so early in the WOT and trends downward, most would expect that to be burst knock. Go into your vcm scanner, and add burst knock to the channels you monitor, this will help you find out if its pre programmed burst knock, based on large movement in torque and spark, or if you are actually pre detonating. Also GM sets the cars to run rich, my stock ls7 2007 z06 ran at high 11's when i first pulled its AFR, I was like WTF, and then i read my wife's ls3 2008 and she was rich too. GM does this to protect the motor, while this does not max out hp it does allow for 100k miles, if gm really tuned the car to 12.8 and pushed the spark to 26 or 28, they would max out the motor, add hp to the motor and have them blowing up in under 40k miles. But you can do it lol. from here you can adjust your maf airflow ve output frequency, bigger numbers add gas, smaller numbers remove gas( dont go crazy start with small adjustments) the other thing you can do is raise spark, if spark goes higher with no knock pulling it down, your afr will also go higher(leaner). because you are scared of knock, i would actually back the WOT spark down 2 degrees just to start, start monitoring burst knock, and dial in the maf to reach just below your targeted afr. i would shoot for 12.3-12.5(remember go extreme lean, motor goes boom, so leave it a little rich) once my afr is close i would try pushing the spark forward, while monitoring knock per cylinder in addition to burst knock. in the end i like to tune NA cars to 12.5 with about 2 degrees beneath max spark(generally 24-26) Yes I leave 20-30 hp on the table but I prefer the safer tune. I tune forced induction to 11.6(I know not very aggressive) with methanol or e85 to reduce knock. I hope this helps.

[s3an78]

So i basically tuned WOT to 12.5 afr and its almost dead on throughout the pulls I have logged. I didn't think to monitor burst knock but I will definitely add the channel and give that a shot. I'm only at stock timing like 19 degrees at WOT so I def have some power but I wanted to figure out this KR issue first. I appreciate the advice and I'll reply back in a few days after I get some time to log.

[s3an78]

Okay so, I added burst knock and individual knock channels to my logs. I logged twice, no burst knock but got KR at both partial throttle and WOT. I checked my whole exhaust today. Its not hitting the frame and I made sure all the clamps are as tight as can be before all of this. Attaching the the log, I'm hoping someone can help me. Also, I know I forgot to plug my AFR gauge in so that didn't log but its pretty spot of 12.5/0.85 at WOT.

[s3an78]

Another log, no change from my last few logs but the car is now richer?? VCM didnt record RPM for some odd reason but I got a TONNN of knock retard....Worst I have ever seen it. Just filled up with 93 two days ago. Does anything in the log look concerning?

[???]

have you checked the timing in different driving modes?

my 08 sure looks like it pulls timing different based on what driving mode it's in

[s3an78]

have you checked the timing in different driving modes?

my 08 sure looks like it pulls timing different based on what driving mode it's in

Honestly, I haven't thought about it. I will have to try a pull in competitive driving mode to see if there's a difference.

[s3an78]

Pretty sure i finally figured it out, the driver side header touches the bellhousing and the passenger side taps the heat shield in one area. Opinions on whether i should take them out and dent them or just make the knock sensors less sensitive now??

[Ben Charles]

Fix where it’s touching, it will drive you nuts if you don’t

[03worthy4link]

Unrelated, but review on the speed engineering headers aside from hitting? Fuel smell with no cats? Looking to do the exact same as you in the coming days stock w/ headers/no cats.

[s3an78]

Unrelated, but review on the speed engineering headers aside from hitting? Fuel smell with no cats? Looking to do the exact same as you in the coming days stock w/ headers/no cats.

Besides the 2 spots they hit on the torque tube for the price they are good headers. Quality looks good and even after beating on them to dent in those 2 areas they held up no problem. With any header/xpipe without cats you will get a fuel smell though so if you don't want that get cats.

[eficalibrator]

If your exhaust is hitting ANYTHING, fix that before you touch the knock sensor calibrations. Any noise or vibration that is transmitted back to the engine has potential to be binned as "knock" by the sensors which are really just microphones. Don't waste your time tuning around a mechanical issue.