Timing VS. TDCOffset

[buddy]

???? Now i'm lost and haven't a clue what you are getting at

Sorry to confuse you.

Its the point I have been trying to make from the get go, that PCM makes injection timing whatever it wants regardless of base timing. But then someone again comes in saying Im completely wrong, I dont understand, and then ends up saying it himself.

The PCM sets injection timing to desired programmed timing with the stepper motor regardless of base timing. So to get this extra performance at the top end you need to see actual 8.5* when the desired is 0* in time set.

The parallel with the vacuum advance unplugged is what I was paralleling to stepper motor being disabled, to where it can't change the timing. Its not entirely accurate, I apologize for saying it that way.

You had stated you can get -1.94 TDCO when at 3.8* base timing by revving engine a little and thats what you would do, but that is not the same as -1.94 TDCO at 8.5* base timing. So I wanted someone to explain the difference, which is the max advance ceiling.

So I asked the questions to have it come from gmctd instead of me saying it and someone poking holes in the wording.

 

[ak diesel driver]

So my ? is how do you read base timing my scanner won't let me do that? It will read adjusted timing and TDCO.

 

[Turbine Doc]

So my ? is how do you read base timing my scanner won't let me do that? It will read adjusted timing and TDCO.

What scan tool are you using maybe someone else who has it can tell you how to do it if yours has capability to do time set?

Time set is a bi-directional test function, your scanner has to be able to command it or you won't see it, in time set you remove computer timing adustments, and you are just reading feedback of IP position in relation to TDC of crank/cam

 

[ak diesel driver]

I'm using Carcode. Quomack has been helping me and he said Gmctd helped him. He said he has the same ?

 

[Turbine Doc]

Sorry to confuse you.

Its the point I have been trying to make from the get go, that PCM makes injection timing whatever it wants regardless of base timing. But then someone again comes in saying Im completely wrong, I dont understand, and then ends up saying it himself.

The PCM sets injection timing to desired programmed timing with the stepper motor regardless of base timing. So to get this extra performance at the top end you need to see actual 8.5* when the desired is 0* in time set.
The parallel with the vacuum advance unplugged is what I was paralleling to stepper motor being disabled, to where it can't change the timing. Its not entirely accurate, I apologize for saying it that way.

You had stated you can get -1.94 TDCO when at 3.8* base timing by revving engine a little and thats what you would do, but that is not the same as -1.94 TDCO at 8.5* base timing. So I wanted someone to explain the difference, which is the max advance ceiling.

So I asked the questions to have it come from gmctd instead of me saying it and someone poking holes in the wording.

This is where confusion is coming from to me it looks like you don't have it quite right here or a least it reads that way to me that you don't have it quite right, base timing of 3.5 does have an impact along the entire operating range.

I'll try to splain it as I see it, JD correct where I get too far off base.

Let go back to my orignal gasser analogy, piston engine basics, step 1 cam and crank have to be positioned via chain/gears so that they match at TDC, distributor rotor in a gasser has to be positioned so that at TDC rotor is pointing at plug number one, if too far BTDC or ATDC vehicle fire will not happen corrctly.

Same thing with the 6.5 EFI Diesel IP has to be positioned in a way so that the injection for injector 1 is at TDC or pretty close to it, in time set you disable the timing control feature if the PCM so it does not try to correct a too far off TDC timing event, and you are only reading the position feedback of the IP,

If too far retarded in time set the engine will stumble and die, if too far advanced truck may also die but usually runs smoky & rough. Base time has to be established 1st so that when in PCM control the full timing window of operation is there.

So for the IP in normal control may be electronically commanding a actual/desired of 8.5, physically IP timing will be offset by mis-adjustement by mechanical position from TDC, PCM has no idea of mechanically where the IP is sitting on the engine in relation to cam/crank, that has to be established by setting that relationship by moving the IP. Think of a optic bump moved too far away inside the IP, IP cam ring vs optic sensor out of whak and truck timing gets jacked up.

So similar again to the distributored gasser, where you unplug the PCM spark advance, or vac advance so there is no spark advance that will add extra spark to try keep the engine running if the engine tries to cut out. The 6.5 EFIs PCM will also try to adjust timing to keep a laboring engine running smoothly.

When setting base timing you don't want that input, you want just base timing so that distributor or IP are calibrated to basic running at TDC squirting or firing the #1 cylinder, once that mechanical position is established/satisfied you can come out of time set for the 6.5 or enable vac advance/PCM spark advance in the gasser, then let the computer take over timing.

With the 6.5 control you are regulating a pump (IP) that sucks, squeezes, holds. releases as a "timed" event, if mechanical base timing is wrong performance suffers, or emissions suffers so TDC without PCM bias has to be correct 1st, PCM can not correct for far out of adjustment, yes engine can run, but further up in rpm one goes further out of whack it goes with timing vs fuel vs rpm schedule, resulting in stumble-or overfuel general or general driveability suffers.

 

[Turbine Doc]

I'm using Carcode. Quomack has been helping me and he said Gmctd helped him. He said he has the same ?

I've got Qwomack's cable and program with me, I'll play with it tomorrow depending on weather and work schedule and may be able to share some insight once I better understand it.

 

[Matt Bachand]

Does the PCM actively adjust the timing bias depending on pedal position, engine load, gear, etc. to maximize power and efficiency?

 

[buddy]

This is where confusion is coming from to me it looks like you don't have it quite right here or a least it reads that way to me that you don't have it quite right, base timing of 3.5 does have an impact along the entire operating range.

No disagreement, and of course you must be within tolerances for everything to work correctly. That was an assumption, and why I suggest setting TDCO each time you do an IP change or PCM change. Rather than the set it and hope its good.

 

[Turbine Doc]

Does the PCM actively adjust the timing bias depending on pedal position, engine load, gear, etc. to maximize power and efficiency?

Basically yes, takes all sensor inputs on engine vs program algorythm to schedule fuel/timing, this is why driveability, economy and emissions wise DS4 is superior to the DB2. DB2 is dumb in this regard, but can be reliable as it not sensor dependent, it just pumps out the fuel.

 

[buddy]

Does the PCM actively adjust the timing bias depending on pedal position, engine load, gear, etc. to maximize power and efficiency?

Yes, Ive seen mine top out at 100MPH at 15.1*, which is why I advanced base timing further, havent been on a 100MPH run since last weekend though after I set it. Might try it tomorrow.

 

[Turbine Doc]

Yes, Ive seen mine top out at 100MPH at 15.1*, which is why I advanced base timing further, havent been on a 100MPH run since last weekend though after I set it. Might try it tomorrow.

Last weekend on MS to Ga run 107 mph WOT/100% load, no more go fast(needs FTB) in the burb 19 act/19 desired timing, 3104 rpm, 3:42 final, will make similar test jaunt with ATT installed next weekend Ga, to Ms.

 

[ak diesel driver]

I've got Qwomack's cable and program with me, I'll play with it tomorrow depending on weather and work schedule and may be able to share some insight once I better understand it.

I found a feature that was called Timing Set and when I first turned it on the numbers started at 2.8 and then increased from there. Couldn't ever get it to do it again. Was wondering if that initial number is the Base Timing.

 

[ak diesel driver]

Also it would be interesting to know how much deviation there is from this scanner to the others you've talked about.

 

[buddy]

Does your timing set screen show desired and actual timing?

 

[buddy]

Last weekend on MS to Ga run 107 mph WOT/100% load, no more go fast(needs FTB) in the burb 19 act/19 desired timing, 3104 rpm, 3:42 final, will make similar test jaunt with ATT installed next weekend Ga, to Ms.

8* base timing?

 

[ak diesel driver]

Does your timing set screen show desired and actual timing?

It shows IPT which I believe is base. And IPTD which I believe is desired. And TDCO. The problem is that I can't get it to show Base in and of itself, only shows it after being altered.

 

[Turbine Doc]

8* base timing?

I'll double check, but base timing is checked in time set, should be around 3.5 deg, idle timing fully warmed up may be 8.5, I haven't checked in a while what that is.

 

[buddy]

IPT would be the actual, which would be the base only when in the time set procedure. Otherwise it will show the PCM adjusted actual timing (which was why seeing 8.5/8.5/-1.94 isnt telling you youre timed for top end performance). So when running time set you want IPTD to say 0, and what does IPT say?

Actual injection timing is also known as measured injection timing.

And injection pump timing is something else other than injection timing, more like 30* at idle. So IPT, which I guess stands for injection pump timing is a little misleading but understandable that it is supposed to be the injection timing measured.

 

[ak diesel driver]

IPT would be the actual, which would be the base only when in the time set procedure. Otherwise it will show the PCM adjusted actual timing (which was why seeing 8.5/8.5/-1.94 isnt telling you youre timed for top end performance). So when running time set you want IPTD to say 0, and what does IPT say?

Actual injection timing is also known as measured injection timing.

And injection pump timing is something else other than injection timing, more like 30* at idle. So IPT, which I guess stands for injection pump timing is a little misleading but understandable that it is supposed to be the injection timing measured.

When I'm in timeing set the numbers are the same as when viewing TDCO. The only time it is different is upon intial reading it start at a low number like 2.8 and quickly goes up to about 10.5.

 

[buddy]

I'll double check, but base timing is checked in time set, should be around 3.5 deg, idle timing fully warmed up may be 8.5, I haven't checked in a while what that is.

Obviously you haven't been reading gmctd's posts ):h

Or youre one of the masses that didnt understand what he meant and how to set this timing, and havent fully grasped the truth. Playing with you.

He clearly said max of 11* stepping from base, so to reach 19* you must be at 8* base. And he repeated it a couple times because Im dyslexic.

And thats where you see the PCM is setting it to 8.5* at idle, and it will step to 8.5* regardless of what base is, so at 3.5* youve lost 5* of possible advance stepping after idle of 8.5*.

Will be good to see what you get for base timing, prove out the theories, everyone is learning, this thread is the best explanation I have read on the timing.