Tuning WOT on an LS3 with Knock
I have just gotten done recalibrating my MAF sensor for the RotoFab intake I have and also just installed my Kooks 1 7/8" headers. I have my AEM wideband installed and am tuning based on Lambda for E10 so I have Stoich AFR set at 14.137. I tuned the MAF in Open Loop and have the Lambda Error at +/-2% across the full range of the MAF Sensor. I did all the MAF tuning at Partial throttle never going over 4500 rpms since I had PE disabled. After all the partial throttle work, I put the new MAF mapping into my main tune, extrapolated out past 6000hz to extend the correction trend out into the WOT range and then did a single WOT run to try and see where I was at. The good news is, it looks like the MAF is +/-2% all the way through to redline but there are two things I need to address. The Commanded fuel is a flat line at 0.80 Lambda (11.31 AFR for E10) and I would like to get the car to command 0.85 so I have to richen up the PE Ratio but during the WOT run I noticed a lot of knock throughout the run. It started to knock a little bit at the beginning of the run, maybe 1 degree, and it pulled a bit of timing, then again 1.1 KR at 3700rpms and it pulled a few more degrees but then at 4600rpms the knock sensor read roughly 4 through the end of the pull.
So the question is, where do I go from here, I know I have to pull some fuel to get to 0.85 commanded lambda but if I pull fuel I am assuming it will knock even more. So is it best practice to get rid of the knock first or get the commanded lambda in line first. Thanks in advance... |
Get your fueling in line. If you still have your low octane table intact and haven't desensitized your knock sensors, then you have nothing to worry about. Go ahead and put 1.176 in your PE table. I run leaner until about 2000rpm, and by 2500rpm I reach the 1.176 PE ratio. From there, start eliminating the knock by playing with your timing tables. Remember to keep your tables smooth.
|
I agree completely with DSteck but I recomend paying for some dyno time to more accurately tune these two tables. . . (I'm assuming you are doing this on the road)
A load dyno will allow you to tune your MAF transfer a little more accurately, you could hit each cell in the table with the dyno set to replicate road load, and you can easily do a long 4th gear WOT sweep to get the upper end of the table in line. When it comes to timing its even more important to use a load dyno. When making changes to the timing you should be watching torque output. . . tuning until the knock sensors read knock then backing it off a little is not a good idea lol Just my oppinion, hope it helps. |
While I agree about using a dyno, he'll be fine on the street to do fueling although it can take longer. Dynos make everything so much easier, but they are so damn expensive. Buy a dyno... or twin turbo my Z06... hmm.... :bellyroll:
|
Quote:
Around here there are a few dynos that let you rent time. . . I just do this now and its probally cheaper than the gas I wasted trying to tune on the street! |
Thanks guys for the input, I'm glad you folks are willing to help work through this. I would love to be able to do this on a dyno and will probably look into some of the local shops to see if they rent dyno time but have no idea what kind of bill I would be in for. As for tuning on the street, I had a lot of success filling all of my cells during the partial throttle MAF calibration as I have a lot of quiet roads to be able to hit each cell and I also have plenty of room to do 2nd gear WOT runs although I would prefer to be able to do maybe a 3rd gear run on the street and ultimately a 4th gear on on a dyno but I'll have to take what I can get for now.
As for not advancing until I see knock and then backing off a few degrees, I really have no other choice on the street, I know on a dyno I could really hone in on MBT, do some spark hook tests and avoid knock at the same time but the street is all I have right now so if I can tweak out all the knock I will be happy for now while getting my 0.85 Lambda at WOT. Maybe when I go back to Tune Time in Toms River, NJ to see how much I have improved from my baseline, Matt who owns the shop will have mercy on me and let me rent some dyno time, not sure if he does that though so it looks like I'll be giving him a call. |
Just curious, are you going to tune the VE or just leave it MAF only? Right now I'm running MAF only and am very happy with it.
|
Quote:
|
Your correct, but the exhaust also changes the pumping efficiency, this is where the extra power comes from.
|
Quote:
|
Running around yesterday in MAF only, the one thing I noticed is idle is a bit flakey when coming up to a stop light and the car settling down, looking at my Airflow vs frequency it looks like I have to smooth out the bottom end around where idle occurs
|
All times are GMT -5. The time now is 06:50 AM. |
Powered by vBulletin® Version 3.8.9 Beta 4
Copyright ©2000 - 2024, vBulletin Solutions, Inc.