carcode questions

[derekja]

I'd like to start a carcode thread. Now that my truck has made it's first post-new-engine test run, I'm starting to watch what is going on with carcode and finding that I don't really know how to interpret everything. Here is some of the enhanced data from the middle of my drive, and corresponding questions:

These are when I was going 29 mph at 2367 rpm. Load percent read 60.8 (although I'm not entirely sure what that means) and ECT was 161.

1) boost pressure: 19.6 psi
barometric pressure: 14.77 psi
wastgate solenoid command percent: 82.4

I take it this means that the wastgate is closed 82.4 percent of the time with a boost pressure of 4.83 pounds (which is about what my boost guage read)

2) fuel rate calculate millimeters: 45.3
Injection pump solenoid command milliseconds: 1.57
injection pump timing signal degrees: 16.4
injection pump timing desired: 16.4
top dead center offset: -0.6
injection pump cam reference signal missed counts: 60

a) is there any way of calculating an instantaneous fuel mileage from the fuel rate? mostly just curious...
b) tdc offset seems perhaps less than optimal given that people are talking about advancing that to -1.9 and such. Is this something that I want to do? Is this timing value way out of whack or just not as performant as it could be? (GM service manual says to leave it between -0.25 and -0.75, btw)
c) not sure how to interpret the timing signal degrees or solenoid times, are these significant?
d) by the end of the drive the ip cam missed counts were up in the 200 range. Missing something seems bad, is it?

3) transmission stuff

trans fluid temp - tft 111
output shaft speed - toss 1328.4
torque converter clutch slip speed - tccss 421.9
torque converter clutch duty cycle - tccdc 0.0
transmission actuation pressure current cell - tctc 0
transmission actuation pressure current memory - tctm -16
trans latest shift - tls 0
t12st .5
t23st .4
t34st .6
t12se -0.2
t23se -0.1
t34se -0.4
trans mode number - tccm 2

a) I never saw tccdc read anything but zero. Does that mean the torque converter was always locked up? never locked up?
b) what's the trans mode number? I see it read 1 or 2. Is that related to up shifting and downshifting?
c) I wonder this with my trans temp guage as well, what's a reasonable maximum trans temperature on a 4L80E?

Thanks!

--Derek

[More Power]

a) I never saw tccdc read anything but zero. Does that mean the torque converter was always locked up? never locked up?


Gotta be above 45-50 mph and below a certain throttle percent to get the TC to lock.

Jim

[rjwest]

you got most of it figured, just keep playing with it,

too much info at once for my old tired brain,

there was a post that explained how to do the instant calculation of mpg,

I will try to find my old data, you have to enter a formula and
turn on MPH and fuel rate ( leave rest off ) and use the data in a formula format to get a output,

[joed]

Your numbers seem reasonable to what I've seen. I don't have an auto trans, so can't offer any input there.

As for the cam ref. signal missed counts, I seem to recall there is a duplicate value listed (~255) that is bogus. Just ignore that one. The other one should read zero - if you're seeing it change you may have an issue.

As for the TDC offset, I've set mine to -1.94 and it did seem to boost performance. The downside is more injection "rattle", especially on cold starts. Since you're at -0.6, you could change it to -1.4 or -1.5 at first. I think you'll notice some difference and have some room for further adjustment, if desired.

As for instant MPG, I wrote a formula for this. I'll have to see if I can find it, as I haven't used it in a while. It won't be entirely accurate as I believe it is based on 'desired' fuel rate which may not actually be reality.

Hope that helps.

Thanks. Joe.

[rjwest]

Instant MPG in carcode...

Found old data:

GPM = rpm x 4 x FR Divide by 3785411 = gal per minute
set this as a function, A

Than VSS divide by 60 = miles per minute set function b

than divide by Function a by Function b above..

I think above is how I did it...

You need to have the RPM, VSS & FR active for the calculation to work...

Info from sep 2000 forum

gmctd, I see you posted in this thread:

[DA BIG ONE]

As for the cam ref. signal missed counts, I seem to recall there is a duplicate value listed (~255) that is bogus. Just ignore that one. The other one should read zero - if you're seeing it change you may have an issue.
Joe.

I've knocked this around for awhile now as my truck has missed counts always. That famous skip, or what seems to be a miss that everyone who has an electronic pump seems to have is when the missed count occurs. Mine varies greatly w/new pump (latest version) changing out PCM (have spare) did nothing to get rid of the missed count.

When I encountered failure of cam ring was after I had some random pump driver issues, Bill Heath told me it would not be long before I needed a new IP he was right.......................

[rjwest]

I believe there were to data fields for missed counts
1 was to be ignored , (info from car code,)
the other was valid,