Ok I was wondering about the Main Ve table in tuning if someone can explain in simple dummy terms, it seems to me I am getting different info form multiple people that sounds like they aren't sure because they are confused with all the detailed explanations. so here is the question.

What happens when you increase or decrease a number in the cell?

I know its part of the Fuel/ air mixture, but when you increase the number in a cell , is it adding fuel or taking it away?

 

VE table is an estimate of how much cylinder fill you have or air that is going to be combusted. When you increase the number in the cell it thinks there is more air being consumed for a given rpm and map, and will proportionately add more fuel.

 

cool that is what i thought, i jst needed confirmation that. now i have to figure ot what i have set wrong on my afr error table that keeps reading backwards

 

are you adding the error % from your histogram or multiplying it? when I first got started I was adding it

 

I am multiplying % or -% . So when i do that what is showing rich on the histogram and i multiply by % it just makes the numbers increase on the ve table , so if thats the case then its putting more fuel in and not taking away

 

do you have your cells and rows matched in your histogram vs your VE table?

 

i do have the axis's all set the same, I think my problem is in the math perameter equation

 

VE table put simply is. either in combinations with or individually used for fueling.

the numbers in there relate to a pulsewidth commanded of the injector solenoid.

bigger the number the more pulsewidth is commanded and the more fuel you have
smaller the number the less pulsewidth is commanded and the less fuel you have.

the VE numbers don't relate directly to anything theyre just a number. make it bigger youre adding fuel. make it smaller youre removing fuel

 

Don't mix up air and fuel...

The VE table is the cylinder air fill (regardless of fueling) at each cell.

The various fueling tables (Stoich AFR, OLFA, PE, PPM, COTP) specify the ratio of fuel to air that the PCM applies to the cylinder air fill.

Keep air and fuel separate.


Same with MAF table... it gives you the mass of air per second, PCM calculates cylinder air fill from this, then applies fueling on top of this.

 

The VE table is an airflow table.

However, it uses back calculation to add fuel (which you don't see). So you tune with a wideband... when you're too rich (compared to Stoich or your PE desired EQ ratio), you don't have enough air in the VE table and you increase it by the delta between Stoich or your PE desired ratio. Lean is opposite. This is why Lambda works well, it converts the stoich A/F to a number... 1 is Lambda. And everything is a ratio based off that. So your PE should be EQ ratio of 1.18 or so and etc.

But that's getting too deep. If you measure dynamic airflow in the VCM scanner, you can see your airflow in g/sec. Which is just reading from the VE table. So once it's tuned, you know about how much airflow your engine is ingesting. For an SBE LS1 with H/C/I anything in the 400g/sec and over mark is making very good power.

Note: EFI Live allows you to view the VE table in g/sec vs. the somewhat useless percentage in HPT.

 

Actually, if your fuel pressure, injector size, and engine size are accurate, VE numbers absolutely do relate to something.

 

what's your theory here?

in all the GM, AU ford and aftermarket VE or "main fuel" tables i've seen the values vary dramatically.

 

The tables vary from fbody to fbody by year because GM changed things like cams, exhaust manifold, and they introduced the lat intake. Certainly different makes models will vary because the efficiency and c.i. of the motors vary.

 

You can also calculate airmass from the VE table...