Question about Injector Pump Timing

[idagon]

I put a long block in my 96 . New timing chain, 5521 pump ,FSD.

Fired right up.

Now, the desired and pump timing was off. 11.7deg cold

I back it down and now its at 8.7deg desired and 8.7deg actual.
Should it be 8.5deg


the tdc offset is at -1.2

I relearned the TDC Offset by the KO KO method.

it resets to -1.2 after warm up.



Do you guys agree that I should advance the pump?

if I move the pump to get to -1.5 or -1.94, will the desired and actual increase as well?



pump actual timing goes from 10.9 cold to 8.7 at 180deg.

[gmctd]

Timing operations should not be attempted until ECT is above 180deg, so PCM is not demanding cold advance.

I'd leave it at -1.2deg for a month or so, observing operation as engine 'wears-in' - those numbers are not bad, as is.

-1.94deg is within reach merely by increasing rpm in TDCO LEARN, observe numbers fluctuating, exiting TDCO LEARN when you see your number - ko-ko will recalculate the actual position of the IP, tho, so leave that alone during the testing period.

-1.2deg to -1.94deg is less than 1mm rotation of IP for repeatable ko-ko recal.

Remember - 180deg ECT minimum..................

[idagon]

thanks for the reply gmctd,

I will make sure it is above 180deg.

Since I dont see a TDCO learn on my Genisys, I will use carcode.

when using carcode to adjust the learn, (while in the TDCO adjust screen)after hitting the enable button,do I use the round dial on the upper right or the two arrows on the upper right to adjust the learn. when moving the dial, the numbers in the box on the left side of the dial change from 8.8 to ~20.x something.(those numbers dont make sense to me)

Also there are 2 disable buttons, it seems only the right disable button will keep settings.( I used the up arrow button and it seems to learn)

I assume that if I moved the TDCO to 1.94, the ECM would move it back in 50 starts or so, is this correct?

That is probably why you mentioned a testing period.

[idagon]

My Genisys has a Time Set function. Will this permanently move the timing, as if I rotated the pump?

[gmctd]

Start the engine cold, watch Desired and Measured IP timing numbers as PCM retards timing as ECT rises to 180degF - that temp should result in no further retard, so the numbers should represent actual IP timing

The only way to change IP timing is to physically rotate it, altering it's positional relationship to crankshaft Top Dead Center - the scantool allows PCM to recognize that position.

TIME SET function causes PCM to rotate Optic Sensor\Camring between full retard and full advance, as limited
by IP at any set postion - IP housing limits OS\Camring travel to 22deg on IP shaft, or 11deg crankshaft

PCM then compares those limits to Crank Position Sensor output at TDC to determine IP's rotational position in degrees BTDC.

TIME SET functions are incorporated in the ko-ko routine and TDCO LEARN in the OBD2 systems, so TIME SET is not necessary - TS can be used to verify Timing Stepper Motor action when necessary.

TDCO is a number which PCM calculates based on IP rotational position relative to crank TDC - any IP position will result in a 'spread' of TDCO numbers which can be selected in TDCO LEARN as crank rpm is increased to ~1700rpm - any higher rpm will DTC for TDCO.

Ko-ko will determine real TDCO based on actual IP setting - scantool TDCO LEARN function can have several variables which can result in a lower or higher number - if scantool displays -1.94deg after TDCO LEARN, then ko-ko displays -1.5deg, the ko-ko value is correct for that IP position.

If IP position is at low-end of TDCO range of values, but the hi-end number is selected by increasing rpm while in TDCO LEARN, then it is likely that TDCO will recalculate to the lower number within 50 starts - all the GM manuals state that it will do so.

Also, if the FSD resistor has been removed or is out of range, that automatic TDCO recalculation will be the most likely event of FSD resistor DTC.

And, BTW, that is why the 'variable fuel rate can be selected on-the-fly by installing our variable FSD potentiometer' scam is not even functional - who wants to wait 50 cycles to get the increase for power or decrease for economy.

[Slim shady]

And, BTW, that is why the 'variable fuel rate can be selected on-the-fly by installing our variable FSD potentiometer' scam is not even functional - who wants to wait 50 cycles to get the increase for power or decrease for economy.


Ok GMCTD, what resistor range are we looking at for the variable FSD resistor? Are the resister amounts specific for the different fuel tables? Examples like the number seven FSD is 1000 ohm, and the number nine FSD resistor is 5000 ohm. i just threw those numbers out as examples.

[gmctd]

That's the point, Slim - we are not looking at any 'variable' value - it's a one-man scam - PCM looks at that value every 50 starts, or when timing functions are commanded

That resistor is used to calibrate the Fuel Solenoid characteristics to the FSD module to get injection pulsewidth in spec - run the factory calibrated resistor and the FSD and FS will run cooler.

[idagon]

gmctd,
Is fuel economy any better with a -1.94 vs a -1.2?
Have you noticed an increasing power increase the higher you go?

[Shikaroka]

There is some talk here that alludes to something I have been wondering.

I have a new #9 resistor to put it. Is it worth it?
Should I do it before I start screwing with my TDCO?

Will doing the KO-KO routine make the PCM look for the resistor?

[gmctd]

A 6.5 dyno chart indicated the torque band raised and flattened and a slight increase in horsepower with the -1.94deg setting - fuel economy is usually dependent on driving habits, and so that setting has usually resulted in poorer economy for a while, accompanied by a silly grin on the driver's face!

PCM will check the value of the FSD resistor during the ko-ko routine - a #9 resistor would effect the greatest difference if the oem value is #1, much less if the oem value is a #8.

Bill Heath recommends a #5.