LV8???- Please explain

[JHensberry]

Can someone please explain to me what LV8 is on the scan tools and exactly what it means to the performance/tuning of the engine? The scan master shows it as grams of air per cylinder and the turbolink shows it as filter load variable. TIA, Joseph.

[kenmosher]

From the TurboLink Help file (How to ... Interpret the data section)


Load Filtered Variable

This field indicates a calculated scaled value that corresponds to engine load. LV8 is calculated from many factors and is used in determining engine operating parameters. The higher the number, the higher the load on the engine, and the lower the number, the lower the load on the engine. It is calculated by (air flow/engine speed ) * K where K is a constant. The LV8 should max out at 255 on a WOT run in a good running turbo Regal running 17-18 psi of boost (or more).

[JHensberry]

Thank you, that makes alittle more sense now. My L8 is quite a bit higher in the idle than the quick reference. Will keep plugging away

[JHensberry]

OK, so I guess my new question is if your L8 is higher per say in idle. Does that mean it is a bad thing because there is more of a load on the engine or good because more air is going through it???? TIA, Joseph.

[kenmosher]

LV8 is actually more complicated than the HELP file would indicates (it's actually a couple of scalars, the MAF table and RPM all in a formula ... *digs around* ...)

I think this is right for 86/87 stock programs...

LV8 = (MAF cell value/256) X RPM X LV8 Constant X (MAF Table Constant/256)

From looking at the code over in the ECM section, RPM is actually the crank reference, so it's converted, but essentially it's an RPM type value.

Basically, if you look at it, it's almost like manifold pressure ... kind of a way to compute air charge and load on the engine. It looks to be kind of a speed density number using MAF and engine RPM to drive it. It'd work pretty good at low loads... it looks as if it is used to determine "gross timing and fueling" before the various trims/PEs and such kick in.

From notes I found:

LV8 is used in for determining EGR duty cycle (and I believe charcoal canister purge too?)
In conjunction with coolant temp and open loop, it enriches cold start conditions
It is a primary driver for determining Power Enrichment (PE) in conjunction with TPS
LV8 <25 will disable "Learn" mode
LV8 is a main parameter for timing
It is used for decel fueling (reduces fueling) and for DFCO (decel fuel cut off) in conjunction with TPS
LV8 may play into idle trims as well (can't find my notes on it). I know on some of the later ECUs they use LV16 (16 bit number vs the GN's 8 bit number) and I think that may only apply to them.
In the end, the higher the load the higher the number. I wonder if there's a difference in the chip you are using?