LS7 can only take 7* up top

[Kfred 513]

I'm just getting started on tuning my car after a cam swap. After getting a decent MAF curve (I think) I started to do some WOT runs to work the timing table a bit. The car has pulled timing for knock retard since even before the cam but I never spent time on the tune because I knew it would change and my ECM was toonerlocked.

I am using a Graph to log KR and adjusting the timing table based on that data. I am not finished with the tune by any means, but I know something must not be right and am looking for advice. I finally got a clean pull from first through third but I had to come down to 7* for that to happen. 91 Oct is all I can get here in Vegas until I make the switch to E85, but I still think timing is low for 91 based on the numbers I see people run on 93. Mod list follows

Is the stock timing table too aggressive for 91 with milled heads, would lowering timing below peak TQ help alleviate knock above it? Another thing I want to try is to run 12.0 AFR/Lambda=0.81 to see if it likes that with more timing, any chance that will work? I am also running 60/40 water to coolant and Water Wetter which didn't seem to help.

RPM B3 Cam 24X/25X duration at 0.050"
Halltech Mf103
American Heritage head package, milled 0.020"
cutouts
Using a Ballanger AFR 500 with NTK Wideband sensor

Any help is appreciated, Thanks in advance

[GHuggins]

You'll want to add a few more spark pids into your scanner... I think you'll find iat spark and possibly ect spark pulling timing...

[5FDP]

Word, 140 intake temps was yanking timing and so was the ECT at the time of those pulls.

91 octane may limit you some but it should take more than 7-10 degrees at WOT. I'd disable burst knock with the mods you have and maybe even make the sensors just at tad less sensitive. Haven't tuned any corvettes but the GEN 4 trucks for sure can tend to have overly sensitive knock sensor settings in many cases.

[Kfred 513]

Thanks for the ideas. I'll see what happens with burst knock disabled.

I looked at the ect spark table and it is pulling 3 degrees at these airflow/ect. The problem isn't that it won't command more. The problem is that when does command more, I get knock. After looking at the tune more and reading a bunch of threads I think I need to try a 12.0 AFR given my setup/fuel. Hopefully it will take more timing without knock

[tommytuner]

Khole does a nice set of heads, and that cam should relieve cylinder pressure pretty well. I just did a Z06 for him yesterday that was all stock, heads only, it held 18-19 degrees on the top end, closer to 17 near peak tq, and I did one with a fairly large cam for him last week, same heads, cold air and cam. that car wanted 20 degrees on top, that's on Cali 91 btw. Gas doesn't get much worse than this stuff unless you're in Mexico. A few things come to my attention right off, are you sure your wideband is reporting correctly? Your injector duty cycle seems incredibly low for an LS7 with heads and that much cam. Your narrow bands would seem to agree, you're leaner than rich at wot-not that I'd use them for much more than a reference at wot. Typically I'd want to look at your trims to determine how close you are with your tune, but yours are disabled. Again, your narrow band O2's are trending lean pretty much always, I'd say it's a sure bet you need fuel everywhere. Turn those trims back on, and add the fuel they tell you to. Also, what's your altitude? Your baro/kpa are indicating quite a bit higher than 2000', which is roughly what I thought Vegas was?

[Kfred 513]

Tommy, thanks for some good info. That log I posted was a very early log from when I started to dial in the MAF. Probably too early to be doing WOT, but I couldn't help it. I decided to drop AFR to 12.0:1 or .85 lambda and the difference is amazing. I added 3 degrees just to get a baseline and see if the car would take it. The first WOT run was another 1-2-3 pull, it showed no knock, and took 17 degrees at peak torque (based on log torque) and 20 degrees up above that. I think I was just running the car way too lean.

Im up in the Northwest corner and were at about 2,700 feet. I calibrated the wideband in open air like the manual instructed. The Display on the WB matches HPT when logging. When driving in closed loop the AFR on the wideband is what it should be ~1.00 Lambda. I think everything is working as it should. Keep in mind the heads aren't ported, only milled, so I don't think I'd be getting any extra airflow from that.

As far as the NBO2 trending lean. How should I add fuel globally? My MAF error is minimal now so I would hate to just add to the entire table.

New log attached. I made some changes to the tune file since the log, but its pretty close to the tune from that pull.

[5FDP]

If the wideband is already that close to the commanded at full throttle, no need to add more fuel in. O2 sensors generally can tell you where you are going AFR wise sometimes. The 860-890's yours tends to show it leaner than some but the wideband is showing a nice lambda reading.

[Kfred 513]

thanks FDP. The car does have 60K on it and I am assuming the NBO2s are original to the car. Not sure if they start to go bad or what, but maybe I should replace them in the near future...

[jsllc]

You are lean down low in air volume as previously stated. This log was really too short to tell but here is what it looks like per hertz. WB looks correct but you need to good graph of about a 30 minute drive with the right filtering to get your MAF closer down low. Include Injector Tip Temp in your list of PIDs as well.

11-26-2017 11-14-57 AM.png

[Kfred 513]

thanks for the input jsllc. I believe the injector tip temp influences the "rich after flash" situation people talk about, is that correct? I added it to my channels list, but I'm not entirely sure how to use the data once logged. I plan on dialing in my VE table very soon and running MAF/VVE together as the factory had the car tuned. Do you think ill be able to generate accurate numbers for the MAF down in the 2000HZ range with this size cam?

[Russ K]

As per the owner's manual, 93 octane is recommended for max performance. A .020 mill puts you at ~11.5 cr, 91 octane is not going to allow much timing. Also the 200+ coolant temps are not helping. I would install a 160*F thermostat and switch to a 2 bar OS, but enter your stock map sensor linear & offset values. This will re-scale the cooling fan table to allow lower than 192 ect fan operation.

100 octane is available at the Rebel gas stations. Also a heat range colder spark plug will help.

Russ Kemp

[jsllc]

thanks for the input jsllc. I believe the injector tip temp influences the "rich after flash" situation people talk about, is that correct? I added it to my channels list, but I'm not entirely sure how to use the data once logged. I plan on dialing in my VE table very soon and running MAF/VVE together as the factory had the car tuned. Do you think ill be able to generate accurate numbers for the MAF down in the 2000HZ range with this size cam?

Injector Tip Temp influences ALL fueling. Below idle I usually blend the percent of change of the lowest know good modification down to zero. As for using it You tune the table in the ECM and then only make MAF corrections from about 108F to 138F

[Kfred 513]

As per the owner's manual, 93 octane is recommended for max performance. A .020 mill puts you at ~11.5 cr, 91 octane is not going to allow much timing. Also the 200+ coolant temps are not helping. I would install a 160*F thermostat and switch to a 2 bar OS, but enter your stock map sensor linear & offset values. This will re-scale the cooling fan table to allow lower than 192 ect fan operation.

100 octane is available at the Rebel gas stations. Also a heat range colder spark plug will help.

Russ Kemp

Thanks Russ, I do expect lower timing numbers than what most people are seeing due to all of the factors you mentioned, 7* just seemed too low. The extra fuel seemed to help and I can now run 20* with no knock. I do need a 160* thermostat and ill look into the 2-Bar OS, thanks for that info.

Injector Tip Temp influences ALL fueling. Below idle I usually blend the percent of change of the lowest know good modification down to zero. As for using it You tune the table in the ECM and then only make MAF corrections from about 108F to 138F

Got it, thanks. I kept an eye on it earlier this morning. After every ECM flash it would be up over 200*. I would drive around and not begin a new log until that table was no longer effecting AFR

[jsllc]

Just filter on injector tip temp.