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Discussion Starter #1
I don't know if anyone else here is interested besides me and GMCTD, but just to try and clarify a few points I thought it best to start a new thread than to continue piggybacking on others.

Just to get everyone up to speed, the topic is Closure Time vs Pulse Width.

Closure Time is just what it sounds like. The length of time it takes for the Fuel Solenoid to Close, in milliseconds.

Pulse Width is how long the Solenoid stays closed so that the pump will deliver the desired quantity of fuel.

First point is that scanners commonly (and incorrectly) report CTIME as Pulse Width. So no matter what it says, its really Closure Time in ms.

Second part of this discussion is determining the window that the pump has to deliver fuel to each cylinder. So first we should convert RPM to injections per second.

We'll use 3400 RPM as redline, since thats peak on the test bench and I think thats as high as you can get max fuel.
3400 engine is 1700 pump.
1700RPM = ~28.33 Revs per second.
X 8 injections per rotation is ~227 injections per second @ 3400 RPM engine.
1 second / 227 inj/s = 0.0044 seconds (4.4ms) duration for each injection (45 deg).
From that 4.4ms window, you have to subtract the closure time because the pump won't start pumping until the FSOL closes, so for argument sake will use a CTIME at the upper limit of 2.1ms, which leaves a 2.3ms window for the PCM to pump to each cylinder.

Now of course you can't use quite ALL of the window otherwise you would be pumping past port closure, but the 'window' on the rotor of the hydraulic head is quite long due to the trailing port, which is timed to give maximum range to pump fuel across the RPM range, so its pretty close. I'm not sure how close the Lo Res pulse is to port opening, but I know the window is QUITE large and you can have the optic sensor WAY outta whack without losing fuel quantinty, so missing port opening is never a problem unless you have LONG CTIME.

I'll have to double check on that hi res count, I think 512 is too high, and I've heard the number before, but I might actually have to count it for myself now. I've recently recieved some inside information that the PCM actually controls fuel on a table of cells from 0-255, which would be multiples more resolution than the hi res is capable of... I'll get back to you on that.

I have to get back to this thread later too, I'm trying to chase my infant son around and figure out how to explain CTIME/PW and its wearing me out! ;) I'll come back to add more later...
 

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Good job, TDG - thanks, again.

BTW - think outloud, so that little rascal can pick up on it, as well.
Like father like son, apple and the tree, chip off the ole block, and etc.;)

FYI the Tech-II does display "Injector Pulse Width in ms" which 'appears' to be FS closed duration.
2000 OBD-II sets DTC's at 0.75 min PW and 2.5 max PW, attm

Optic encoder\timing disk data -

0-255 is 256 x 2 = 512 is binary computer numbers
(not hexadecimal)

0,1,2,4,8,16,32,64,128,256,512,etc

512 / 8cyl = 64 hi-res slots per cylinder

Any hi-res slot could represent one 0-255 cell

512 hi-res slots / 360deg = 1.422 slots\deg

#1 lo-res TDC slot is 10 hi-res slots wide
10/1.422 = 7.03deg x2 for crank angle

#2 thru #8 lo-res TDC slots are 4 hi-res slots wide
4/1.422 = 2.817deg x2 etc

tbc.............
 

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Thanks for the explantion(s).
Very imformative and interesting as always.
 

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Discussion Starter #4
...If only the boss wouldnt think I was up to something if I took my digital camera to work and took pictures of IP internals...

Not to mention I could make a video of a diesel timing light being used to time a 6.5 (mech).

Can anyone count the little slots on this picture?

No affiliation at all with 'Real Diesel', just like the handy pics they have.
 

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I did it with a lab microscope..................

Whoever they got to file all them little slots straight sure was a smooth hand.
 
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