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2015 Silverado l83 (cam, stall, headers) having an issue where I've been trying to dial in MAF and VVE and my log is showing an avg. of about 8% needing to be pulled so I'm pulling that much across the whole VVE table and upon my next log i get little to no change? is it because I'm adjusting the MAF at the same time and will it equal out eventually or am i missing something?
any help is appreciated!
so i have discovered that STFT VS PR x RPM is showing that its rich and pulling around 10% in some cells, but GMVE math is showing the opposite ? I'm at a loss here and any insight would be much appreciated!
A lot plays into VE corrections such as your base temp setting, at what engine temp you're logging at, at which injector tip temp you're logging at and so on.
I use this to correct the VE. It's Cringer's formula with MAF substituted in. Works great as long as you're making sure to filter out the wrong temperature areas. When done correctly your VE should only show around a 5% change and usually less than that from log to log. You also need to make sure to use a good filter to remove transients and like obstacles.
(([16.71]+([16.71]*([50116.156]/100))-[2311.71])/[2311.71]*100
Then if you're not sure about how you're doing it, you can always fail the MAF and do it the old way. Even then you need to make sure things are being logged right and set right, otherwise it'll still change. For example, just because you failed the MAF and checked it, was a change made? Calibration flashed in which caused heat soaking? Lots of things if not known or accounted for without the knowledge of what they're doing doesn't make for a fair comparison. In the end, MAF airflow and VE airflow should match.
so this is more or less what I'm fighting. by using standard STFT I'm showing extremely rich and by using GMVE STFT I'm showing lean ? i was curious so i took fuel out of the fuel table and it caused the standard STFT to show rich still but the GMVE went further lean, does this mean i need to ignore standard STFTS and just use the GMVE math ? just confused as to why the standard STFTS are showing rich regardless of what changes are made.
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Fuel trims, as long as the MAF is in the picture, will always try to lean on the MAF. So fuel corrections should be getting made to the MAF and then use the math to correct the VE as you go. The stft is needed in the equation to correct the airflow as to make the two airflow values the same.
You just really need to make sure you're using filters to only log data above certain coolant temps and within a range of certain injector tip temps on top of setting your base temp in the cal to the ambient air temp at the time you are flashing the cal into the ecm and then perform a throttle clean after flashing. As long as you do all of that, the VE and MAF should both start coming in line.
On a gen V you can actually get fueling to stay below a 1% error for all temps just not on the VE unless it's a SD only tune. You have to pick one or the other depending on what it's primarily going to be running on. It's an incredible pita and requires a lot of back and forth, but it's possible.
While the MAF is working.. it will be the main driving force for fueling. You could cut the VVE table in half and not see a real difference in fueling while the MAF is active. Its just that tip in, return to idle, etc.. will be messed up.
If you plan on getting a VVE table from dynamic or MAF airflow you should first dial in the MAF airflow as close as you can.
I'm an advocate of purposefully failing the MAF then tuning VVE. That way both can stand on their own. VVE is there to help quick pedal movements, idle, transients, etc. Using the MAF, which isn't good in those areas to tune VVE is not a great strategy.