LBZ Pump in LB7

NOTE: This information is for learning purposes only. We do not take responsibility for anything that happens to your vehicle as a result. Please use at your own risk!

To have the LBZ pump/regulator work and idle properly with no lope on the LB7, table B1010, Rail Pressure Valve Current, must be re-scaled. Start by first looking at table B1015, Desired Flow Vs Current(ma), in the LBZ file. B1015 is found underneath Fuel Pressure or you can simply just type B1015 in EFILive's handy Navigator at the top left.

B1010 has to be re-scaled because the replacement LBZ pump delivers different amounts of fuel for the same ma setting. If you leave the table alone and just swap the pump the significantly different Flow/ma settings will cause your perfect tune to go all to heck.

Here you can see the differences between the LBZ table on the left and the LB7 table on the right:

So you need to fill in the 19 spots on the LB7 table using the 9 useful spots on the LBZ table.

We used LB7(OS 15186006) and LBZ(OS 12606128) for this example.

Start with the easy cell.  Both tables have a 0 mm/sec so you can just copy that value over. Now you'll have 1550 in the zero slot in the LB7 table.

To properly determine the rest of the numbers you will need to use math. Start by assuming that there is a straight line between each pair of adjacent numbers on the LBZ table.  So the next number you need on the LB7 table is 1000 and the cells on the LBZ table we have to work with are 0 and 2230. 0 contains 1550 and 2230 contains 1450 so those cells are 100 apart. If you divide 100 by 2230 you find that each number on the mm/sec axis is worth .0484 ma so 1000 numbers is worth 44.84 ma and since the chart uses whole numbers you must round that to 45ma. If you look at the chart you'll see that each ma number is smaller than the last so you'll need to subtract to get the next number.  So, if 0 is 1550, then 1000 is 1550-45 or 1505, then let's put 1505 in the 1000 cell.

Next is the 2000 cell and it would seem like you could just subtract 45x2 or 90. But, to avoid rounding errors you should run the numbers for each cell. For the 2000 cell, it's still 100/2230 = .0484, which we then multiply by 2000 giving us 89.68, which rounds up to 90.  So, our guess would have been correct in this case, but it could have just as well been 89 or 91, so it's worth running the numbers. So, cell 2000 is 1550-90, which is 1460, so we'll put that in our table now.

The next cell is 3000 and now the math seems just a tiny bit trickier.

In the LBZ table you will now be considering cells 2230(1450) and 3570(1400).

The difference between the cells is 3570-2230 = 1340
The difference in the ma is 1450-1400 = 50
so, the ma per cell number is 50/1340 = .0373

The next cell you need a number for is 3000, which is 3000-2230 = 770 numbers away from 2230.
Now multiply the result, 770, by the ma/number, which is .0373, and come up with 28.7, which rounds up to 29.
Subtract 29 from the contents of the 2230 cell and you get 1421. Put that in the 3000 cell on the LB7 table.

After you add each value to the LB7 table, look at the table and make sure it appears to be following the same general line as the LBZ table.

Now that you understand that, let's define the general solution for each cell:

For the purposes of this discussion, the numbers for the LBZs 9000 mm3/second cell calculation is in parenthesis.

We want LBZma

We have:

        LBZFlow (9000)
        LB7FlowLarger (11390)
        LB7FlowSmaller (3570)
        LB7maLarger (1300)   // The ma matching the Larger flow
        LB7maSmaller (1400)  // The ma matching the Smaller flow

We need:

        LB7FlowPerMa = (LB7maSmaller - LB7maLarger) /
                                   (LB7FlowLarger -LB7FlowSmaller)
        0.01279 = (1400 - 1300) / (11390 - 3570 )

        FlowDifference = LBZFlow - LB7FlowSmaller
        5430 = 9000 - 3570

And the answer is:

        LBZma = LB7maSmaller -
                          (FlowDifference * LB7FlowPerMa)
        1331 = 1400 - (5430 * 0.01279)

Remember this concept, because any time you need to move a table from one tune to another where the axis are similar in units but different in cell spacing this same general formula will work.

Also, when calculating the last entry, 60,000, you can get numbers between 414 and -967. We didn't like the big negative number so we figured it would be safe to assume the slope from 44000 to 52000 would continue. Using that assumption you get 414 for the 60000 cell.  It turns out the distance between 44000 and 52000 is the same 8000 as the distance between 52000 and 60000. So to keep the slope going the same you just need to subtract the difference between the 44000 value and the 52000 value from the 52000 value. In our calculations, those numbers were 874 and 644, different by 230, and 644 - 230 is 414, so let's put 414 in the 60000 cell.

All that is well and good, we've come up with numbers that seem to make sense. The table looks almost perfect so it's likely safe to put it in the truck and see what happens. But please pay attention, especially up past 52000. We've made the assumption that the change is linear up there, but there is an excellent chance that is also wrong. It's likely that you'll end up changing the number to something a lot closer to zero but until you've logged what happens up there we feel a lot safer suggesting conservative numbers.

Thanks, and we hope you learned a thing or two!

-Kory@ Power Performance Enterprises
www.latuning.com

With a little bit of help from Ira (and editing from Robyn :) )