Ok prom geniuses I need some educating! If the answer is, it doesn't matter give it what it needs, then that's fine!

I'm tuning my 93 Buick that came with the L05 motor. I'm currently programming the chips using Tunerpro, using the $62 mask.

I'm trying to understand what the VE tables represent. The factory tune (downloaded from the original chip) had a few spots where it was 96 or so. I changed the fuel pressure spring to a 14lb (from the factory 9-12lb) and leaned out the BPW until the BLM's started looking better. I figured factory fueling once adjusted it should be fine. BPW went from 135, to 120. Looked pretty nice except that I had a few places where the map was showing 96 and then another 40 something in the adder table (VE#2)

I found the formula to calculate BPW, and have adjusted accordingly the rate to 127 (61# injectors running at 14psi gives around 65# flow) I then leaned out everything by a similar percentage (around 6%) BLMs again look fine 128 +-6, but the VE table is still really close to 100 once you add the VE2 table.

From what I've read I'm supposed to run the injectors at around an 80% duty cycle, which if the BPW is correct, I'm running them close to static which isn't good. But the factory tune ran the injectors at near static (or at static) and they run for 100k's of miles.

If I adjust the BPW back to 135 or 140 I can change the VE table to only reach 80-ish % but that won't really be helping would it? The computer uses the BPW + VE to give the injection amount so as long as the BLM is fine then I'm fine (I think?) it'd be nice to know exactly what's going on in there though. It's hard to know if I'm static without the tables being able to show it properly.

 

Lots to cover here. To get/know the injector duty cycle (DC%), need to use the injector PW and the engine RPM along with some math. No other way to do it. To get the injector PW need to modify the ALDL data stream to include it.

As for the relation between the BPW and the VE table, they are both multipliers for the PW calculation. Think of the BPW (also called the BPC), as a centering device for the VE table values. Hitting 95%+ in the VE, increase the BPW by 10% and reduce the VE by 10%, and continue tuning.

The VE is the volumetric inefficiency of the engine relative to intake manifold pressure. But since we can move the VE around by changing the BPC, it can be a relative value.

Hit the tuning guide book sticky. There is a section on the '8756/8063/7747 ECMs. Tons of information in the links.

RBob.

 

Thanks! I'll start doing some reading!

I suppose the wideband will let me know if I'm out of injector so I'll just adjust until the map looks close to right and continue tuning from there.

I shouldn't be having so much fun adjusting a car but I can't seem to help myself at this point!

 

Playing w the BPC to affect the VE isn’t going to change the amount of fuel flow from the injectors unless u change the fuel pressure. What u want to know is if ur injectors are flowing enough fuel at current pressure. For that, u need to do what RBob suggests and derive the duty cycle, most likely at WOT in particular.
And at WOT, you’ll want to be somewhere ~ 80-85% DC to provide headroom.

 

Ah, ok, now further understand the "math" part.

Time to do some reading before I mess with the tune more. I might be fine, I might not, won't know until the duty cycle is known.

Thanks!

 

As Grumpy would say, set the BPW where it should be and let the numbers fall where they may.

 

Thanks for the help fellas!

I made the adjustments and the car seems to be running fine (maybe a little better at steady state throttle). VE#1 table is down to a maximum 91 at one spot. I'll be logging for a couple days to get a good reading (love that 160 baud) and will continue adjusting from there.

Still doing the reading on patching the bin so I can get PW in the PROMID field, but if I can't get it, at least the car's happy.

Thanks for the advice about the guide book sticky, so much to read, so freaking much to learn. Thanks to RBob and Grumpy I've got a lot of bedtime reading. It hasn't really clicked yet, but I'm seeing a lot of places I can make improvements to this stock code.