With NN off, is the speed density VE table considered at all when the car is making torque, aircharge, or any other calculation? Does it affect anything other than simply fueling?
2017 charger
Printable View
With NN off, is the speed density VE table considered at all when the car is making torque, aircharge, or any other calculation? Does it affect anything other than simply fueling?
2017 charger
The car will use the VE tables when NN is off, need to setup a proper log/histogram for tuning & editing VE tables
Yes, but use it for what all exactly?
air-mass per cylinder, volumetric efficiency
Not really what I was asking, but thanks anyway.
VE is LTFT + STFT, im not quite sure how to answer your question...using a VE table tells the engine how much fuel to send via air-charge and RPM by logging what the engine wants to see over time.
I believe that the VE combined with MAP and IAT/MAT is used to determine/calculate the aircharge. Thus it would indirectly affect other tables/parameters that use aircharge on their axis.
Hi hoover. Been trying to figure myself where and when the VE tables come into play with NN off. Have not seen any clear definitive explanation yet.Quote:
Originally Posted by hoover
Rockystock, thanks for this info. Not questioning it, but where did you get this, because it is of real significance.
So, will a wideband sensor be required to get the VE table cell inputs, or can the LTFT & STFT log figures be used.
I watched it all happen by logging and tuning, first by adjusting the fuel injector pulsewidths, then trying to tune using the speed density method but with VVT on (which I don't recommend), and finally by using the NNT which takes a while but is by far the best method for VVT.
STFT+LTFT works great for getting your tune close very quickly. I'm starting to think that the last little bit of tuning might be better done with just LTFT though - that's something I've been meaning to put out as a question on here.
You will also need a wideband to get your VE dialed in at WOT. The neat thing is that the wideband can also allow you to see VE error when you're in COT. I think that once the VE is close, a wideband could be used to tune in open loop (by disabling the narrow band O2s) but I haven't tried that in a while. It's also very useful for tuning your FA Cold Enrich table, after the VE tables are done. Other fuel transients like acceleration enrichment and deceleration enleanment will need a wideband to tune because they happen too quickly for the fuel trims to reliably show.
I tried to edit a typo on the other post, but the mobile site keeps glitching and deleted the whole thing. Here's the earlier post:
If your ANN is disabled, the VE tables are used at all times, part throttle, wide open throttle, even immediately after cranking and firing up the engine. That's why it's best to tune everything else (FA Cold Enrich and other transient conditions like deceleration Enleanment / acceleration enrichment) after tuning VE.
If you use ANN, the smaller VE tables that you can see in your tune are ignored.
If you use the Neural Network Trainer (NNT) you will have access to 5 higher-resolution VE tables corresponding to five cam positions from max advance to max phase, as defined in the ANN training values. They are also active at all times (when the ANN is enabled in the tune).
If your cam is locked or VVT is disabled, then disable ANN and tune your smaller VE tables.
If you use VVT and use more than a few degrees of its range, you will be able to get much better results by tuning the neural network with the NNT. Once tuned, the ANN will more optimally estimate airflow for all conditions and cam positions, which will improve power, torque, and drivability.
guys seems there is a disconnect because the original question asked is so very basic, others assumed it couldnt really be the question being asked.
Volumetric efficiency ("VE") is a model of airflow the computer has that is a best guess at how much, by percent, of the air the motor ingests based on its size versus how much it ends up using/burning/making power with. Think of it this way, if a motor is 5.7L in size, thats its mechanical maximum volume it can ingest after 8 cylinders have run their cycle. VE is a measure of how much air it ACTUALLY ingests, which is less than its mechanical size for the most part, until we start talking forced induction, at which point the motor starts to ingest more air than its physical size.
A motor loses efficiency in many many ways, through various intake, throttle body, intake manifold, cylinder heads, cam and valves, combustion chamber design, exhaust setup, but also what are called environmentals, such as air temp, manifold temp, humidity, barometric pressure, etc. This is why you will see most efficiencies are less than 100%. At idle areas its really low, like 30-40%.
The VE table is the starting point of how the computer guesses how much air will be going into the combustion chamber, so it can guess at how much fuel to supply. If the computer knows at a certain rpm (x axis of the VE table) and certain airflow (Y axis of the VE table) entering the engine, only a certain % (values actually in the table) will be used in the combustion process, it knows to supply X amount of fuel. The computer will layer in the adjustments it thinks are needed based on the environmentals I mentioned, which can be tweaked in the various multiplier tables labeled as such. It then measures the burnt fuel and air mixture via the oxygen sensors, and adjusts the fuel supply (viewed by logging fuel trims).
You however, can instead of allowing the computer to just adjust fuel supply, can change the starting point of how much air the motor is using up by changing the VE table. If you see unburnt fuel going out the exhaust, that means the motor isnt actually as efficient as the VE said, and so you should lower the VE table in that RPM and airflow area, so that the computer starts its entire process by supplying less fuel. Car will run better that way, versus letting it adjust afterwards.
Hope that helps.
Quote:
Originally Posted by 06300CSRT8
Good background info.
thanks 06300CSRT8, your explanation confirmed as I expected (and I daresay as hoover also might have), that the present VE table in the tune is the basis from which the ECU will work using the O2 sensor inputs as main input to adjust the fueling.
Your explanation of the environmental inputs are very important, so thanks for helping us.
So, if I consistently have a high value LTFT at specific rpms, then I should increase the VE table at those cells.