can anyone define VE as 100%? is this actually attainable? how does one determine VE %? is it the value in my table after adding in PE? i assume this is my table 1 plus table 2 plus PE add on ? is this close? what does the net PE % tell me? i assume my max VE value will be at my max TQ location as far as rpms. if i am running 12.75/1 A/F at WOT and i look at my VE tables that will tell me my max VE and where the max VE is. again what value is this info?

 

The VE in your ecm is a ratio of the volume of air a cylinder can move to its total volume since the fueling is done on a unit cylinder basis. If a cylinder could move .5 L of air per stroke and it had a volume of 1 L, its volumetric efficency would be 50%. This is needed to do the fueling as it gives teh ecm an idea of what volume of air is being drawn in by the motor.

Its possible to get at or slightly over 100% VE if it was an all out race motor with a killer induction system and exaust. On a street motor, though, its unlikely.

 

You can get over 100% ve with forced induction too.

 

Need too remember that VE% vs a GM ECM is relative. Too high an injector constant or too low an engine displacement and the 'apparent' VE goes up. Same with the apparent BPC.

RBob.

 

And since the cyl volume is not known on a '749, the number is kinda useless in terms of its definition.

-- Joe

 

Not really.
While the 58 doesn't use a gas law calculation, it can still calc an apparent VE.

If one wanted to, they could add a MAF, and then use that as a sanity check for the VE being *real*. Or piggy back say a 8253 to a 749 system and data log that to get a truer VE reading.

 

When you say 8253, do you mean the 3.8 SEFI ECM from the late 80's? I have one of those in my 1989 Olds Touring Sedan (98), what makes it good for data logging, has it been extensively hacked or something I don't know about?

Kurt