Ok, I got all that adjusted. So you're saying that even though 110KPA - 210KPA is on the VE table it's not going to use that part of the table until the boost enrichment number is raised?Originally Posted by MikeOD
Do I need to adjust the MAF to work with the boost?
Thanks for the help by the way!
No, you should not use the VE table to cheat the AFR. You need to log commanded AFR and log actual AFR with the wideband, and you will see a % error. VE and/or MAF tells the PCM how much air is flowing into the engine, not how much fuel to inject. The data in the fueling section tells it how much fuel to inject.
The goal is to get the % error as low as possible, so that when you are tuning the engine trying to find the best AFR for power (or safety, whatever the goal is) you can go into the PE or BE table and say "I want 11.0:1" then command an equivalency ration in that portion of that table of 1.336 (14.7/11.0), or "I want 12.2:1" and then command 1.205 (14.7/12.2)...if the VE table is setup correctly, the PCM will hit very close to, if not dead on, the new AFR you're commanding.
When you simply play with VE and watch the wideband, the PCM might be commanding 13.2:1 and you might be seeing 10.8:1...doing it that way will make it incredibly difficult to tune as there won't be much rhyme or reason to the math that's resulting in your actual AFR, and will make it incredibly difficult to change.
Also, at your low KPA regions, your VE shouldn't look like it does...I've never seen a gasoline engine with a VE table that linear. When you're just barely touching the throttle your commanded AFR is going to be 14.7:1 (or something like 14.68:1) and again, you want to compare that to the wideband, and correct the VE table until commanded matches actual.
You can use the same commanded versus actual AFR logic to calibrate the MAF table too. First I would completely disable the MAF and thoroughly tune the VE, then I would completely disable VE and thoroughly tune the MAF...then I'd re-enable both.
You will need to disable closed loop to tune it like this...disable closed loop fueling, and use the scanner to zero the fuel trims before you start logging.
It might run like total crap at first...but the first few times you log/re-flash not only will you learn a lot, but it'll begin to drive tremendously better and better...then when you're fine tuning (I like to get the % of error in my fueling to less than 2% before I re-enable closed loop) the vehicle will drive a billion times better, and you won't mind how long it takes to really collect enough data to get it tweaked in close.
wow, much appreciated! I would have never done it that way. The ecu I regularly tune only has a MAP sensor, no enhancements available, no BE, so I'm kind of stuck cheating the VE and tweaking the PE and it works pretty well but I can see that would never work here much less well and I would have never figured that out on my own. I'll start doing that today and I'll let you know how it's going. Thanks!
How do I disable the MAF, VE, and closed loop fueling to do the steps you were suggesting?
You can fail the MAF by setting the fail frequency to 0 in the eng. diagnostics tab. You can use only the MAF by setting the "high rpm disable" to something like 1000rpm in the engine >airflow >dynamic tab.
You can disable closed loop by setting the turn on temp to something you will never reach, like 280 degrees in engine > fuel > open and closed loop > enable temp
cool, yeah I was looking at the temp table for closed loop but thought I'd check anyway. Do I also need to set PE enable to 0% throttle?
I'd go lower on the high RPM disable while tuning to make sure it's idling on the MAF too. I usually just take 2 zero's off the ends of the disable and re-enable numbers, then put them back when I want to re-enable it.
The other reason to do it this way, is that the air flow calculations or measurements are also used in determining spark advance. When you cheat the VE/MAF the spark advance gets all messed up too. When you calibrate it correctly it works much better.
If the tune is way off I find it usually idles better on the VE table than the maf, also the low rpm does not offer as smooth of a reading as high rpm. Just my opinion though.
I agree with you, but I still try to get it dialed in as close as I can before switching back to the GM method of blending. A MAF calibration SHOULD fit a 3rd order polynomial, but usually at low airflow it's not able to because of turbulence issues and other problems, and VE/SD helps that tremendously.
Last edited by MikeOD; 03-16-2012 at 12:26 PM.
Ok, so MAF and closed loop are disabled and I'm getting ready to try it out. Do I need to lower the PE enable TPS % to make this tuning process work?
Also, how do I log commanded AFR
You guys are life savers! All of you! So far so good, everything you said is working like charm! Pun intended
Do you guys shoot for 14.7 during normal driving conditions? I'm slowly getting this thing under control and I'm learning a ton but the problem I'm having right now is that no matter how I adjust the VE table I can't get this thing to hit 14.7 consistently. I have a decent map put together and the AFR stays pretty darn stable from idle on up to about 2000 RPM but it won't hit 14.7 (commanded AFR) it wants to hover around (13.4) and I've set every multiplier I can find to 1 so I'm out of ideas
Yes, I do shoot for 14.7 for normal driving conditions...because once I turn closed loop back on, that's what it'll target anyways...if you don't want to run closed loop, there's more MPG to be found in the 16-16.3:1 range. Post the newest version of your file up and I'll take a look and see if I can figure out why it is targeting such a rich AFR.
I'm getting this thing running better and better, the main problem I have now is that the crank case ventilation needs a lot of improvement. Every time we hit boost for more than a split second it starts smoking like crazy! So now I have some more work ahead of me :/
So I've made it this far: It's no longer smoking, we've hit 6psi of boost and it's making some power and starting to be fun. I'm logging commanded afr, actual afr, and percent error. I've learned to copy and paste special (multiply by %), which really helped me dial in the VE table. I've got the 2 bar map sensor and the vcm enhancement working well, and I was starting to feel like I knew what I was doing until I decided to switch over to tune just the MAF. Then it decided to throw me for a loop. Not only was the MAF tuning going bad but when I tried to switch back over to just the MAP so that I could regain my thoughts and send him on his way for the day with a decent running vehicle it started to run like crap again even in just open loop/PE/BE mode :/
I see that my long term fuel trims are at 20% and I don't know how to clear them and I also don't fully understand how to adjust the MAF once I get a percent error table put together. Any help would once again be appreciated.
Here's the editor file
I noticed that there is a section in there under the Main Spark Advance tables that says Min TPS and when hovering over it says that this is the minimum tps required to disable the main spark tables. If those are disabled after 1% throttle then where is the timing values coming from?
Lol starting to be fun. "Yeah my motor home roasts the tires down at a thirty roll and turns 12's in the quarter at 105mph..... No biggie" :P
Gray Ghost- The abomination. 2007 Chevrolet Silverado CCSB. 98mm turbo, nitrous, 428LSX, Rossler 80E with a brake. Finally finished. 23 psi, no numbers, Slow as hell.
PBM G8- Aluminum 364, twin Precision 67/66 turbos, 6L90 trans swap, CTS-V/Vaporworx fuel system, slowly making progress.
Dads 2011 CTS-V- Stock bottom end, stock heads, LS9 cam, pullies, ported blower, ported TB, D3 goodies, and lots of nitrous.
618/618 motor
906/862 spray
Caterpillar 50 Forklift- Duramax swap
I am getting into one of these also.....what injectors are you running? I think the kid put some 60 lb injectors into the one I need to tune. Seems like a big step up for the stock injector size in those motors.
we are running stock injectors and haven't had any problems on 6psi of boost but this thing only turns about 4200 RPM on average.
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