Base pulse width vs Time between reference pulses

[J Ludwig]

I noticed that under high power conditions, the base pulse width can be a higher value than the time between reference pulses. Can I assume that once BPW is higher than TBRP that the injector is on all the time?

[robertisaar]

depends on the application.

for what i mess with the most (MPFI 60V6), there are 3 reference pulses for every revolution of the engine. the injectors are fired once every revolution.

so if i saw the BPW rise above the reference period (X3), then the injectors would be on at all times.

TBI is different, since i believe they fire with every ref pulse.



it's easier just to make a variable in the datastream for injector duty cycle.

[J Ludwig]

Robert,
That appears to be correct about the injectors firing every reference pulse. At a steady state 55 mph, I see 7.3 msec time between ref pulses (2050 rpm)and on level ground approximately 3.7 msec base pulse width. As the vehicle starts to go uphill, the BPW increases to around 5 before the torque converter clutch unlocks and, shortly after, the downshift occurs. (rpm around 2800, ref pulse 5.4 msec) The throttle position on cruise maximum is 76%. If I manually push the accelerator to the floor to get 100% TPS, I see the BPW increase to a value greater than the ref pulse time but no increase in performance.

My performance issue with this system is that as the TPS increases past 62%, the timing retards about 10-12 degrees and the power output drops. The target fuel ratio remains at 14.7 for about 20 seconds, then ramps down to 12 at which time I can feel the power increase somewhat. The instant the TPS gets less than 62%, the AFR goes back to 14.7 and the timing jumps back up. (I'm rolling down the road at about 20,000 pounds GVW and that power drop sometimes causes a loss in momentum that results in another downshift to 2nd.)

I can understand the need for retarding the timing with respect to MAP but can't figure out why the delay in lowering the AFR.

Any ideas?

Thanks,
J L

16147060, $85, 138.adx 7.4 Liter in a motorhome.

[robertisaar]

that's referred to as the PE Delay.

i hate it, and they seem to be almost entirely limited to being used in TBI applications.

if you have hardware to burn your own PROM, then it's something that you can remove so that PE is instantly in effect whenever you give above whatever level of throttle you deem necessary to enter PE.

[robertisaar]

if you know how to modify an ADX, this equation will create a usable injector duty cycle value for you.

(X*y)/300

X is RPM
Y is BPW

and the 300(which i THINK is the correct value for a 8 cylinder TBI application) is used to convert the other two into a %.

[J Ludwig]

Robert,
Thanks for the formula. I couldn't figure out how to add an ADX using two input values but I plugged that formula into the microcontroller I'm using to monitor the engine and it came out that at steady 55 mph on level ground it had an injector duty cycle of 25%, just half of what I originally thought. Using that as a basis, it appears that the time between reference pulses is every other cylinder (twice per rev) instead of every firing like I originally thought. That makes the numbers I'm seeing make sense. All values I'm getting with my program agree with those using TunerPro RT.
Thank you,
J L

[J Ludwig]

Robert,
That's an answer to what I've been trying to find for a long time. I do have the equipment to burn an EPROM but it's at home and I'll be on the road for another month. Also, my software is only good for hex machine code level programming so I will be at a disadvantage there. If I knew the exact hex address on the chip where that value sits that would help. Or, a recommendation for suitable software.

Is there someone who could modify that PE delay? I can pull the chip and read it, then send that as a hex file.

Other than that delay, I'm happy with the way the old beast runs. As I like to rationalize, I'm getting "80 ton miles per gallon".

Thank you,
J L

[EagleMark]

Your on the right site for the right software to make it easy on yourself. You could fine the PE delay and look for address, change setting and get corrected hex.

You then need to UV erase your chip and a chip burner but it much better to go to Moates and get an adapter and newer EEPROM to just click erase and then write to burn new chip with Burn 2 .