Timing VS. TDCOffset

[buddy]

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.

What does IPTD say when this is happening?

 

[ak diesel driver]

One of the things I don't understand is the increase in rpms to 1000rpm. If I read it correctly. It does this automatically when you do a timeset after moving the physical location of the pump. I moved my pump twice in 1mm increments and it never went into this fast idle mode. Was wondering if that is part of the scanner program or the pcm program.

 

[ak diesel driver]

What does IPTD say when this is happening?

Stays pretty much fixed at about 10.5.

 

[buddy]

Stays pretty much fixed at about 10.5.

1. What is coolant temp in scanner?
2. Are there any DTCs?
3. What does TDCO say?

 

[ak diesel driver]

1. What is coolant temp in scanner?
2. Are there any DTCs?
3. What does TDCO say?

1. 180+
2. none
3. -1.85

 

[Turbine Doc]

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.

.

Actually I think he and I are saying same thing but different terminology, I would not consider the timing that it idles at as base timing, unless I'm way off base, (and I could be), IMO base timing would be the timing that the engine operates at without the assistance of the computer, and as I see it in time set the IP feedback in time set is akin to the strobe one sees in a gasser from nr 1 plug in relation to TDC marks on crankshaft.

Since we have no ignition stobe to pulse off of like the gasser, the IP "talks" to us from it's feedback loop, so we go into time set, the PCM backs out of it's authority to control timing and we read base timing on scan tool that communicates with the IP which then says I am here in relation to TDC with a 0 desired timing we check actual and if necessary we adjust IP to meet a 3.5 deg average.

Hopefully when that is completed you are at or are near the desired TDCO when out of time set and the computer is fully controlling timing. Again the times that I've done it, I've had to make less TDCO adjustments if I go with 3.6/3.8 average when setting base time.

 

[buddy]

1. 180+
2. none
3. -1.85

Not sure then, must not perform like GMTDScan, where desired shows 0* during time set. Might be normal for your software. 10* is a bit high for idle, especially if base is at 2.8*, and no way you can get -1.85 TDCO off of 2.8*, unless the revving method really goes far, because that would actually be somewhere around -.25 TDCO.

 

[Turbine Doc]

I'll check with MT2500 & car code tomorrow, wait it is tomorrow, gotta hit the pit guys or I'll be falling asleep at church later this morning I'm EST this week it's 02:25

 

[ak diesel driver]

Sucks getting older doesn't it. I used to be able to do some marathon drives not anymore.

 

[buddy]

Actually I think he and I are saying same thing but differnt terminology, I would not consider the timing that it idles at as base timing, unless I'm way off base, (and I could be), IMO base timing would be the timing that the engine operates at without the assistance of the computer, and as I see it in time set the IP feedback in time set is akin to the strobe one sees in a gasser from nr 1 plug in relation to TDC marks on crankshaft.

Totally agree there, idle timing is not base.

I think the forum needs a procedure with some pictures for factory vs performance time set. That would clear things up.

 

[ak diesel driver]

I think we need a procedure for time set using all the different scanners along with their deviations from each other. Then we could have a more uniform timing setup.

 

[buddy]

I think we need a procedure for time set using all the different scanners along with their deviations from each other. Then we could have a more uniform timing setup.

Maybe scanner workshop at 6.5 dyno event. People would pay for this class!!

 

[buddy]

It appears that by 8.5* base timing, what is really meant is -1.94 TDCO, and base timing as shown in timeset is still between 3.5* and 4.0*. And then with TDCO it makes an effective timing perhaps. So still at base timing screen of timeset should show desired/actual/TDCO of 0/3.8ish/-1.94. When I set my timing to 4* it was on the hairy edge of out of TDCO tolerance -2.02, then popped into -1.94, so 3.8 average is a good recommendation.

I'll try setting the timing to 8* without resetting TDCO and see what DTCs I get when driving. It would absolutely be out of TDCO range if I tried setting it, but I did that successfully this weekend in idle with no DTCs.

 

[gmctd]

Still not getting it, Buddy:

- very important in your case, aftermarket tunes are not always totally compatible with oem versions - reinstall your oem chip, run your tests for base comparison - that's the only way you'll get a handle on what's actually happening in these timing procedures

- TIMESET will always show ~3.5* at any IP position - it is illegal to alter timing on a federally-mandated EPA-compliant engine - GM is liable for compliancy - if TIMESET reflected actual advanced Base timing, the resultant lawsuits would be unimaginable as MrGoodwrench turned out hi-perf 6.5 tunings - which is why

- fsm does not clearly state that TDCO absolutely reflects Base timing in OBD1 and OBD2, and why TDCO does not change after TIMESET

- TIMESET is required in OBD1 to allow determination of IP position, required to allow resultant TDCO calculation

- rotate IP, command TIMESET, scan DES\ACT IP TIMING - command TDCO LEARN, scan - resultant value should confirm IP position and Base timing

- +8.5* Actual timing at idle is result of programmed matrices - it does not reflect +8.5* advance from Base timing - it is the result of and does reflect the quantity of advance from Base:

+3.5* BASE + 5* DESIRED (advance) = +8.5* ACTUAL at TDCO -0.5* at idle

+8.5* BASE + 0* DESIRED (advance) = +8.5* ACTUAL at TDCO -1.5* at idle

Aftermarket tunes may skew the numbers, fe those that idle at +10.5* DES\ACT, all else normal

 

[buddy]

GMTDScan will show you other than 3.5* base timing, I can see it show 4*, 6*, 8* as I turn the IP the timing changes in timeset. But I guess thats not accurate is what youre getting at. I've had it show 10* in timeset, and then while idling I had 8.5 desired with a measured of 10*, because it couldnt go below the base. I didnt have any DTCs, since I didnt run TDCO relearn yet. I imagine if I tried driving away it would code and not function correctly, I'll test that sometime.

And I'll throw in a stock chip to see if it does anything different. Maybe then it will cause 1000 rpms because I never got that.

If revving the engine can net you a higher TDCO value, then it must not be entirely 3 bolts of the IP position dependent.

 

[NVW]

Whenever I use time set I get 3.5* Act and 0 des. or vice versa, can't remember. When I leave time set it goes to 8.8* for both des. and act. I never get anything but 3.5* while in timeset.

Leo

 

[gmctd]

It is 3.5* ACTUAL, and 0* DESIRED, Leo - PCM disables DESIRED under the timing commands altho the DESIRED numbers are still there

TDCO LEARN or KOKO is entirely "3 bolts of the IP dependent" at idle - read the sticky TDCO thread again(?) for enlightenment - I've even explained the explanations................

Far as GMTDScan Tech, I don't remember having this much trouble with it, but then I was using it with oem and Heath's chips - I would have to have some up-close and personal hands-on with each am chip in order to give explicit details for each one - other than that, you'll have to punt -

Engine will run at idle after TIMESET without doing TDCO LEARN - try to make any changes B4 50 starts, or PCM will self-learn - if you're moving the IP with engine running, that is ok, too, long as you don't do TDCO LEARN until TIMESET timing procedures are completed

 

[buddy]

Does OBD2 do a relearn every 50 key turns? Or is that just OBD1 fuel calibration value?

make sure to update the TDCO value limit to +/-2.02

No trouble using GMTDScan, its just a different experience than youve had, possibly due to aftermaket tune, will try OEM.

 

[NVW]

Does OBD2 do a relearn every 50 key turns? Or is that just OBD1 fuel calibration value?

make sure to update the TDCO value limit to +/-2.02

No trouble using GMTDScan, its just a different experience than youve had, possibly due to aftermaket tune, will try OEM.

Pretty sure OBD-1 only, relearns resistor value every 50 key cycles.

Leo

 

[NVW]

It is 3.5* ACTUAL, and 0* DESIRED, Leo - PCM disables DESIRED under the timing commands altho the DESIRED numbers are still there

Thanks JD, couldn't remember off hand, haven't used it for quite some time. If it ain't broke sort of thing.

Leo