Ve table exceeding 100%

[dfarr67]

N/A application, if you didn't want to touch the BPC value, how would you compensate for areas of a VE table that want to go higher than 100% ? BPC should be 127 and are currently set to 135 to scale up table.

[Terminal_Crazy]

N/A application, if you didn't want to touch the BPC value, how would you compensate for areas of a VE table that want to go higher than 100% ? BPC should be 127 and are currently set to 135 to scale up table.

Hi
I don't know what BPC is.

Often scale with Injector Flow Rate or Cylinder size.

HTH
Mitch

[dave w]

N/A application, if you didn't want to touch the BPC value, how would you compensate for areas of a VE table that want to go higher than 100% ? BPC should be 127 and are currently set to 135 to scale up table.

Increasing fuel pressure is an option.

dave w

[1project2many]

N/A application, if you didn't want to touch the BPC value, how would you compensate for areas of a VE table that want to go higher than 100% ? BPC should be 127 and are currently set to 135 to scale up table.

Hmmm...

Just to ask, how do you know BPC is correct at 127? GM's BPC rarely matched injector data.

Increasing fuel pressure does deliver more fuel, which allows one to reduce the BPC and VE table values.

[1project2many]

Hi
I don't know what BPC is.

Often scale with Injector Flow Rate or Cylinder size.

HTH
Mitch


BPC is a value which represents a relationship between cylinder volume and injector flow. It is found primarily in TBI calibrations although $58, the PFI Turbo Sunbird and Syclone application, also uses it.

[dfarr67]

EBL- port version. 385cid with 36pph injectors and 43.5psi fuel.

[steveo]

in rough terms, figure out how far you need to go, say X=10%.

the higher you go the less remaining VE resolution you'll have, but if your ECM uses 16 bit VE it wont matter much.

go ahead and scale whatever constant your calibration uses for base fueling by X%, and subtract X% from your VE table.

then go ahead and modify your XDF add *1.X to the conversion formula for your VE table.

ve table should look exactly like before, but now you have X% of headroom.

this works in theory but in practice it'll twiddle your VE numbers a bit and need some fine tuning.

[dave w]

BPC = 730.75 * (Volume / Injector Flow Rate)

The Injector Flow Rate in grams per second
The Volume of one cylinder in liters

dave w

[dfarr67]

BPC = 730.75 * (Volume / Injector Flow Rate)

The Injector Flow Rate in grams per second
The Volume of one cylinder in liters

dave w

There is a supplied spreadsheet that generates the BPC supplied by DynamicEFI.

[PlayingWithTBI]

in rough terms, figure out how far you need to go, say X=10%.

the higher you go the less remaining VE resolution you'll have, but if your ECM uses 16 bit VE it wont matter much.

go ahead and scale whatever constant your calibration uses for base fueling by X%, and subtract X% from your VE table.

then go ahead and modify your XDF add *1.X to the conversion formula for your VE table.

ve table should look exactly like before, but now you have X% of headroom.

this works in theory but in practice it'll twiddle your VE numbers a bit and need some fine tuning.

I confirmed this with RBob last year when I was getting high VEs on my TBI. It worked quite well and, as mentioned, I continued to VE Learn to get it fine tuned.:thumbsup:

[joecar]

Does BPC require that the FPR be manifold referenced...?

Is there any provision for un-refetenced ("dead head") FPR to handle BPC and IFR...?

[1project2many]

TBI injectors are not "manifold referenced." The regulator can maintain fuel pressure within a narrow window without large swings like you might see in PFI. Since fuel pressure does not change with MAP changes, flow across the injector does not change with MAP changes. Therefore the "Base Pulse Constant" (BPC) is a constant, or fixed, value.