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TDCO -1.5 or -1.94?

Matt Bachand

Matt Bachand

Depends on the 6.5
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Location
Worcester, MA
What are the pro's and cons of each?

I am looking mainly for economy, but increased efficency and power to boot.

Obviously I live in cold climate.

I am thinking of trying to get a tad over -1.50. Maybe around -1.75.

For anyone else around me, if you want to swing by I am thinking of doing this the day after thanksgiving. I'm flexible on the date if anyone close wants to modify the date. Good chance to get your truck done too.

Borrowing 540s10's modified wrench, and have the scanner all set up and ready for OBD2 trucks. (Thanks to 96TD (Brian))
 
I have mine at -1.94 even started at -30 pretty rattly for a while but it sure does perform better. I don't know how much better than 1.5 cause I went from way off to 1.94
 
Matt,
Mine was way too noisy in the cold. I cut it back to -1.50 and it was much beter and I noticed no difference in performance or MPG. Being that you live in the same climate as me I would cut it back.
 
Well I'm at -1.06 now, so I'm going to move it a touch to drivers side and see where my carcode can set me. I want a tad more than -1.5.

FWIW, I have noticed that sometimes when turning off and restarting the engine after a stop, it feels better than previous. I think this is because the computer often changes its TDCO? Not sure. I look forward to a little adjustment either way. Been a long time waiting.
 
It has been between -10 and -20 the last week here in AK. My truck would NOT start in that crap. I installed new batteries and a new starter. It cranks over way better now, but is still a bitch when cold. Could my tdco be off enough to cause the hard starts? All glows were replaced with 60g this summer and I have the glow plug override. Thanks.

Steve
 
STEVE53 said:
It has been between -10 and -20 the last week here in AK. My truck would NOT start in that crap. I installed new batteries and a new starter. It cranks over way better now, but is still a bitch when cold. Could my tdco be off enough to cause the hard starts? All glows were replaced with 60g this summer and I have the glow plug override. Thanks.

Steve
Click to expand...

Hmm, should start a new thread here, but try unplugging your ECT so the computer goes to max cold advance. Perhaps its bad, and the PCM doesn't know its cold out, thus not using cold advance?

:hijacked::85:
 
Here's another trick, if your close to your offset, then rev it up, sometimes it will change, if it does change, then hold the rpm and set your TDCO, :thumbsup:

Turbine Doc told me that, works great, :D
 
turbovanman said:
Here's another trick, if your close to your offset, then rev it up, sometimes it will change, if it does change, then hold the rpm and set your TDCO, :thumbsup:

Turbine Doc told me that, works great, :D
Click to expand...

What exactly is happening when you change RPM's? Is the stepper motor adjusting timing? There must be a physical limitation somehow, that forces mechanical move of pump.
 
Matt Bachand said:
What exactly is happening when you change RPM's? Is the stepper motor adjusting timing? There must be a physical limitation somehow, that forces mechanical move of pump.
Click to expand...

It could be the timing chain slop or ?, I don't know but it works, and there isn't a drawback, timing is timing, :thumbsup:
 
Planning on Friday Guy, you're welcome to come by. I'm going to attempt my truck first thing, I have no A/C so I can't imagine it taking more than a couple hours, another vehicle afterwards would have to be alot faster being done already??

When you move the IP does it have 'click' type movement, or does it freely rotate?

Or is it so tough to move that its always snug?

And to double clarify, just loosen the 3 bolts a few turns before attempting to 'bump' it 1mm or so to the D.S. ?

Does it move easily with the prybar? Is it easy to not overturn it?

Or because its been sitting there for 95k miles, its probably gonna be tough to break free like everything else in my truck?
 
I moved mine by hand and no it doesn't click or ratchet. Also don't loosen those bolts too much when you tighten them down it will affect the position.
 
I made a scribe line (or reference mark) on my pump so I could tell how much I moved it....


.
 
scribe it before you move it. No "clicks" It can be a little difficult to move by hand because you are twisting the injector lines as well. I guess in theory the proper way to do it would be take the intake off, loosen all the inj lines then turn it, Tighten them back up then reinstall and check. Of course that would be RIDICOULOUS to do. There is enough flex in them to move it the little bit you'll need but that is why you need a tool or some sort of prybar and the bolts i described. I guess if you got a really good grip you could move it by hand. Actually I can usually move the 6.2 ones by hand but there is more room to grab it. You need not make the nuts super loose IMHO because you don't want it to pull itself back, also another advantage of using the tool or bols and prybar is you can keep tension on it while you tighten a nut down. Some will say you need to tighten all 3 before starting and checking. That is the proper way although myself, I have never had a problem just tightening the two easy ones and then checking. Just don't forget the 3rd when you have it where you want it.
Just remember -1.94 i spoken like Gospel but most people won't notice the difference. There is a wide window that is considered acceptable by the manual. UNless you are pushing max performance and have it "tuned" I think anywhere within GM spec is fine but that's just one man's opinion...
 
I tried -1.94 but it was scary in the cold. I am running -1.6 and don't notice any difference other than it's not so rattly on the cold mornings.
 
Well, its probably in my head but I got -1.32 from -1.06 just by playing with the carcode software for an hour.... When I moved it back out in the street, it felt more responsive :)...

I'm aiming for -1.7. By bumping it towards the DS, I should be able to cycle through -1.94 - -1.3 or so, as now I can go all the way down to -.60 and up to -1.32.

Showing IP Timing at around 12.2 degrees, so one degree to DS should get me around 13, giving me the option to adjust TDCO to where I want it.
 
Matt Bachand said:
Planning on Friday Guy, you're welcome to come by. I'm going to attempt my truck first thing, I have no A/C so I can't imagine it taking more than a couple hours, another vehicle afterwards would have to be alot faster being done already??

When you move the IP does it have 'click' type movement, or does it freely rotate?

Or is it so tough to move that its always snug?

And to double clarify, just loosen the 3 bolts a few turns before attempting to 'bump' it 1mm or so to the D.S. ?

Does it move easily with the prybar? Is it easy to not overturn it?

Or because its been sitting there for 95k miles, its probably gonna be tough to break free like everything else in my truck?
Click to expand...

They don't stick but as mentioned, are hard to turn once past a certain point because of the lines.

Loosen all 3 nuts.

They don't click.

Best thing is to use the prybar/turning tool and then tighten the top bolt, check it, then scribe, adjust as necessary then finish tightening the nuts.
 
I have no A/C, so this may be pretty easy, with the bent wrench most peeps don't even remove the upper intake to do this?
 
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