Here a couple of things I’d like to understand:
During PE (and assuming COT is disabled) the PCM will inject a certain amount of fuel ON TOP of what it would need if it was in closed loop.
Example: 1.2 PE means 20% more fuel than stoichiometric = 14.7/1.2 = 12.25
This should be the AFR I see on my wideband.
Correct?
IFR: I have installed a new set of flow matched Bosch injectors. They are built same as the stockers: they are rated at the same pressure and just flow a little more.
I also installed an additional fuel pump in line with original one.
Old injectors: 28.4 lbs/h
New injectors: 36 lbs/h
Old pressure: 55 PSI
New pressure: 64 PSI
The factor to calculate the new IFR is SQR(64/55)x36/28.4 = 1.3674
So I should multiply the old IFR values by this factor.
Correct?
VE: I drove around for a while in SD (MAF fail freq = 0, low octane table = high octane table). Result: all cells between 0 and 15 were +/-2% LTFT.
Can I assume that the stock VE table is correct? In this case I think the new IFR table is fine.
Don’t look at my signature: right now the engine is NA; it only has a K&N FIPK filter and has stock internals. That’s why I assume the stock VE is correct.
MAF table: after putting back the program to work with the MAF I logged Raw Frequency and LTFT. This allows me to make a pivot table in Excel and I can see for what frequency I need to change the G/sec value of the MAF table.
The result is fine, the method works: in closed loop all LTFT are pretty close to zero.
I had to change the stock MAF curve just a little (2-3%) and smooth it down so that it still looks like a curve.
Now the problem: In PE and commanding an AFR of 12.8:1 (see above how) I can measure values in the region of 13.5!
12.8 is about 14.8% more fuel, but 13.5 are only 8.9%!
Where is the mistake?
Is the stock VE table wrong and makes me believe the IFR table is correct?
Should I change the MAF curve in the high frequency range?
This of the commanded AFR is a BS? Should I just add/reduce fuel until is fine and don’t bother about the theoretical numbers?
OK, this was a long post, but how tell those things in a simpler way?
Thanks - Stefano