I take it that the second fuel table essentially just ads more percentage to the RPM rows in the main fuel table? What is the purpose of this when the values could just be included in the main table anyway?

Since the numbers are percentages, or multipliers, I assume it is not necessary to mess with the second table when adjusting the VE based on BLM readings?

What is the purpose of the 0 RPM entry in FL2, since there is no corresponding RPM entry in FL1?

 

Generally, it extends the RPM range of the table, and it does it with a 2D table instead of a 3D.

 

Hmm. Now that you mention it, I see that the high end RPM is much higher on FL2. Does the computer just use the highest value in FL1 (for the measured MAP?) as the baseline then?

For example, a table I'm looking at goes up to 3200 in FL1 and 6400 in FL2. The VE's in FL2 don't take a jump at 3200 though, so if the computer didn't pick something from FL1 also, then the VE would really drop off after 3200.

I hope my question makes sense.

 

Best I can tell is having the VE adder table allows them to skimp on a few bytes (literally) by not needing a full sized table and save what little rom/prom space there is. Same thing with the spark table. The VE adder table allows for control of the fuel after the limit on the main table has been reached. The last row on the main VE table is used along with whatever is in the VE adder table and the two values are added together. The 0 rpm entry is jsut due to the fact that the rpm value used can be less then 400 rpm. If you can jsut leave the VE adder table alone while your doing part throttle tuning. Make the changes to the main VE table when your tuning below 3200 rpm.

 

Generally the VE2 table entries get smaller at the higher RPM. That prevents the engine from going too rich at the higher RPM levels.

If you were to 0 out the VE2 table then the ecm would use the last entry in the VE1.

 

Thanks guys, good stuff.

A slight tangent, but in real life, how is the VE tuning done by way of BLM? Specifically, do you really try to drive around and get good BLM readings in every single cell, or do you normally just get as many as you reasonably can and then interpolate/extrapolate to get adjustments to the rest?

I don't want to get arrested trying to fill in some of the more extreme cells.

 

Once you have *enough* points you can try and interpolate them, or if you have an ecm bench, do less guessing, since you can actually see what the entries generate as the ecm processes the interpolated data.

Much safer, to do some of your high speed runs in the kitchen/lab., then in the car. Well except for a couple incidents, Doc's had. The local Fire Dept., way over reacted when Sleepy called about a 747 crashing here......... Well, they weren't alone on that one, those FBI guys can get really carried away....

 

I've been waiting for that....
I guessed that might be what you've been talking about.
Never quite sure though.
Now to make that bench earn it's keep...No more boneyard fresh ecm testing....Well maybe a few more 749's if I can find them.
Feel sorry for whomever follows me at that yard looking for 730's