VE Table Help

[vc81]

Can somebody please explain what the ve table actually does? I have read the tuning guide but I still don't grasp the subject. This is my first time playing with efi. I have tuned carby engines for years. I have a VN v6 running on 12p. What do the numbers in the table mean?
Thanks,
Vc81

[Jayme]

the VE table represents how full of air the cylinder is, in % at that particular MAP and RPM. say the VE is 80%, the ECU knows now the cylinder is 80% full of air, and it knows the volume of the cylinder (thanks to the injector rate) and it also knows what AFR you are trying to target in the target AFR table. it does some maths and detemrines how long it needs to open the injectors for. this all assumes the VE table is correct, which it might not be.

to tune the VE (fuel) map you need to adjust your VE table until the Real AFR (read off the wideband) matches your target AFR table. once it matches then your VE table is correct. if your VE table says 80% and the wideband is reading 10 % leaner than the target AFR then you need to add 10% to the VE table at that spot. once the VE table is done, then you can type in your desired numbers into your target AFR table to get your engine to run how you want it.

[The1]

Have a read of the basics
http://pcmhacking.net/forums/viewtopic.php?f=7&t=1396

Q. What is VE or Volumetric Efficiency?
A. This is the measurment of how well the combustion chamber has been filled with air during intake, 100% VE means 100% fill of air, if we add the right amount of fuel and right spark timing then max torque will be achieved.

In the real world this near impossible with inlet losses, fueling and timing and exhaust back pressure all having effects on VE. Real world 75% - 90% can be achieved.

[delcowizzid]

a good cam intake and headers will see over 100% if done right but it takes a well matched combo of parts

[charlay86]

a good cam intake and headers will see over 100% if done right but it takes a well matched combo of parts

especially on engines with 4 valve / cylinder heads

[Charlescrown]

Nothing like force feeding some VE with BOOST.
Just a point don't think you have an engine problem if your VE figures are set low because the injector flow rate comes into it. It's all maths and I agree you can only get it right by using a wideband O2 sensor.
There are some very clever people here and they will help you a lot.

[vc81]

Thanks for the replies everyone. Its starting to sink in now.

[vc81]

the VE table represents how full of air the cylinder is, in % at that particular MAP and RPM. say the VE is 80%, the ECU knows now the cylinder is 80% full of air, and it knows the volume of the cylinder (thanks to the injector rate) and it also knows what AFR you are trying to target in the target AFR table. it does some maths and detemrines how long it needs to open the injectors for. this all assumes the VE table is correct, which it might not be.

to tune the VE (fuel) map you need to adjust your VE table until the Real AFR (read off the wideband) matches your target AFR table. once it matches then your VE table is correct. if your VE table says 80% and the wideband is reading 10 % leaner than the target AFR then you need to add 10% to the VE table at that spot. once the VE table is done, then you can type in your desired numbers into your target AFR table to get your engine to run how you want it.

Thanks for your reply Jayme. When you say target AFR table, is that the one called - MAP A A/F ratio 20-100kpa air fuel ratio vs RPM & MAP ?
If so do I need to have the MAP A - A/F ratio 20-100kpa air fuel ratio vs RPM & MAP table open as well as the VE 20-100kpa volumetric efficiency (VE) as a function of MAP & RPM table open at the same time and also have the wideband readings showing as well?

On a stock tune wouldn't the VE table be correct from factory?

[Jayme]

yes the VE should be correct for a stock motor. but something as simple as an exhaust upgrade will change VE. go and open a stock VR V8 tune and a VR HSV 185 tune and look at their VE maps. both are the same motor, the only difference is the 4 into 1 headers and exhaust system, yet the VE table is verrry different.

yes you have the correct AFR table, but you dont need it open. Target AFR is in the ADX and you can monitor it, and Current VE and Wideband, and only need to have the VE table open to alter it.

[Holden202T]

I guess it all depends on how your tuning.

for me for something like yours where the VE table should be pretty close only needing minor adjustments i'll usually just log while driving to work etc .... then use the log to plot the wideband readings or blms, or whatever you choose to work with into a histogram that can then be put into the wideband converter spreadsheet etc to convert the numbers into percentage offsets or you can even use the adx VL400 made which will use wideband input, target AFR and current VE and make an adjusted "calculated VE" which is just about able to be pasted directly into the VE table.

theres plenty of different methods and some people prefer one over the other, but at the end of the day the results are usually all the same. Get some logs of your setup to get familiar with what your seeing and use them along with the tuning guides to see if you can make some changes, if you have issues or questions post them up and we'll be able to help.