Need help for next article: diagnostic software

[Ian Turgeon]

I've been thinking about this for the longest time, and I'd like to put together a little applied knowlege to the use of datamaster/diacom.

From the basics of what all the readouts mean, how to convert measurements(if needed) and basic relational data to point at where the problem may be.

So I need some intelligent peeps to kinda contribute to this here topic with stuff they'd like to add in.

So heres how im gonna begin:
Fields in Diacom related to fields in datamaster. if someone has the names of datamaster fields, please fill them in next to the diacom fields

diacom name : datamaster name : desciption

Engine Speed : :
Desired Idle Speed : :
Behicle Speed : :
Coolant Temperature : :
Start-up Temperature : :
Manifold Air Temperature : :
Manifold Absolute Pressure : :
Manifold Vacuum : :
Barometric Pressure : :
Throttle Postition : :
Throttle Sensor Voltage : :
Oxygens Sensor Voltage : :
Oxygen Sensor Transistions : :
Air/Fuel Ratio : :
Air Flow rAte : :
Volumetric Efficency : :
Injector Pulse Width : :
Turbo Boost Pressure : :
Wastegate Duty Cycle : :
Idle Air Position : :
Desired IAC Position : :
Spark Advance : :
Knock Retard : :
Spark Control Counts : :
Integrator : :
Block Learn Multiplier : :
EGR Duty Cycle : :
Battery Boltage : :
Engine Running Time : :
Closed Loop Status : :
Fuel Mixture Status : :
Park/Neutral Switch : :
Power Steering Switch : :
Intercooler pump relay : :
learn control : :
clear flood mode : :
battery status : :
tcc shift light : :
colland fan request : :
ac request : :
ac clutch : :

 

[Ian Turgeon]

Re: Need help for next article: diagnostic software

Example

Just grab one and add any info you know or have


Engine Speed : ? : Revolutions per minute, aka rpm

Idle rpm typically bounces 25-50 rpm at a random interval.
This is a good basis to graph upon inorder to compare where and when other sensors are reading and reacting to.

 

[Loeryder]

Since BG is on vacation I will dig out one of his fine posts to the BB.
All this stuff is FREE!
Anyone who wants to can search and find a gem just like this right here in our very on backyard BB. <hiccup>

And since i'm up and sitting here anyways I will do sumptin semi productive.

02 millivolt readings

at startup - should be rich/slightly rich (02 is not warmed up, but warms up quickly, and engine needs to be rich at start/warmup)

at idle/cruise once warmed up, you will see 02 values flicker all over, crosscounting across 450mv.

at WOT/full boost, you should see them in the 900-1000 range. I've seen them in the 800s, but for the *most* part, 900s is safe. You need to watch your truck and apply other tuning skills to find out what works best for your truck

Knock retard - want to see zero, but hardly any trucks see this. A couple degrees during shifts is normal, but ideal is zero, again.

Integrator
128 is neutral (zero), this will change on the fly a lot once the truck is warmed up and in closed loop. I'd say the normal range is 100-140. Datamaster gives you the option of using S terms (short term fueling trim). 128 is zero, 141 is 10% richer, 115 is 10% leaner, for reference. Crosscounts or xcounts is a running counter of the number of times the 02 readings have crossed 450, going lean, or going rich. This number will overflow at 255 and begin again. At closed loop, this value should be moving pretty fast. It is a good indication of how well your closed loop system is working (or not).

BLM - Block Learn Memory
This value is an attempt by the computer to try to adjust for long term fueling adjustments, due to engine wear, or anything that may change the fuel needs of the motor. We have only 2 cells in our trucks, open or closed throttle. So you may see your values change when you open or close your throttle. 128 is neutral, once again. I'd say you have some issues that need looking at if you are outside the window of 115-140.

Timing - you will see 20-30 at idle/cruise, and should see 12-15 at WOT/full boost. Racier chips will push the timing values at WOT to 17-19 possibly.

Wastegate duty cycle -
100% is the solenoid is fully closed, 0% is fully open. Think of it this way, at 100%, the ECM is desiring more boost, at 0% the ECM is desiring less boost.

AFR target is NOT an air fuel reading. It is a programmed value in the ECM for a fueling multiplier. So at start/warmup, you will see richer AFRs until it is warmed up, when you will see it go to 14.7. Once you go into Power Enrichment mode (you floor it), the AFR will go richer, to 11-12:1 ratios, depending on chip programming, and based off of RPM.

IA temp /MAT
20-40 degrees above ambient are typical. You can watch this value increase with heat soak, or if an intercooler pump is dead. EGR will raise air temps as well, usually 40-60 degrees above ambient.

EGR stuff -
EGR duty cycle will kick in during light cruise conditions, unless it is disabled in the chip, or not enabled due to other conditions.

IAC - 10-30 at idle is about normal. Adjusting the throttle stop can manipulate this value, as you are creating a slight vacuum leak.

Battery voltage - 13s are good, at WOT is very important, 13.4+ being very good at WOT. This will have huge effects on performance.

I believe these to be the most important ones.

Watch when trouble spots are occurring, during WOT, during shifts (graph RPM vs MPH), at boost spikes, at knock, at lean spots (02s dip horrendously). Finding correlations is a start for identifying problems, but be sure it is a cause and not a symptom. (I have low 02s because I have lots of knock...) Watch the changes you can make on a datalogger with actual changes to the truck. Make performance logs to document what helped or hurt. Take notes so you learn from your experience and can share, or at least know your truck better.

Vehicle Speed : Speed MPH : It's how fast you are going
Coolant Temperature : ENG ###*F : coolant temp @ Engine Head
Start-up Coolant Temp : Dunno if DM has it : What the coolant temp was when the ECM powered ON
Throttle Postition : TPS % : 100% is all thats important here
Throttle Sensor Voltage : TPS Volts : 3.7V at WOT : debatable importance, as the ECM "Zeros" out the TPS everytime the engine is started.
Turbo Boost Pressure : Boost PSIg : Turbo Boost Pressure. Diacom is in Hg, DM even converts to 3Bar PSI for you.


Adam's getting a funny colored truck.. heh heh heh

 

[InvisiBill]

Would you want anything about making your own DM cable? Using a TechEdge schematic, you can make one with a DB9 plug, DB9 shell, 2 transistors, 3 resistors, a diode, 10' of phone cord, and a cigarette lighter plug. The electronics are all Radio Shack stuff. I got them at work for $6.50, and the lighter plug was $.99 at AutoZone. You can solder it all up free-air (no PCB) right inside the DB9 shell... About the only shortcoming is that it just has a wire with a bare end to stick into the ALDL port, instead of a fancy molded plug. The one I just made turned out quite nicely, if you want me to get some pics of it. If I make another one, I could even take pics as I solder the parts together, and do a whole HowTo...

 

[SY756]

Would you want anything about making your own DM cable? Using a TechEdge schematic, you can make one with a DB9 plug, DB9 shell, 2 transistors, 3 resistors, a diode, 10' of phone cord, and a cigarette lighter plug. The electronics are all Radio Shack stuff. I got them at work for $6.50, and the lighter plug was $.99 at AutoZone. You can solder it all up free-air (no PCB) right inside the DB9 shell... About the only shortcoming is that it just has a wire with a bare end to stick into the ALDL port, instead of a fancy molded plug. The one I just made turned out quite nicely, if you want me to get some pics of it. If I make another one, I could even take pics as I solder the parts together, and do a whole HowTo...

Bill, are you talking about a Data Master or Diacom cable? I made several Diacom cables but if you have a schematic on the Data Master cable I would be interested in looking at it. Thanks.

 

[JSM]

Bill is talking about a datamaster cable. I have made the same style and it works nicely. I did find disabling hardware handshaking helped though. Bill may be able to expand.

I think that right up Bill would be VERY valuable and a good place to point people to.

 

[InvisiBill]

I'm not sure if pics of my current cable would help much, as all the components are just soldered together in one big clump. I literally used only their leads, and put everything as close together as possible. I'll see what I can do. http://www.techedge.com.au/vehicle/aldl8192/8192hw.htm is where I found the schematic, FYI.

http://www.home.aone.net.au/techedge/vehicle/2tran.gif

Like I said, the (expensive!) missing molded plug is about the biggest shortcoming. Sometime I plan to hook it up to the back of the ALDL connector and have it permanently mounted up in the dash (as opposed to leaving it dangling through the interior).

 

[SY756]

Bill, what part numbers for the transistors and diode did you use? I checked out the website but I wanted to make sure. Thanks.

 

[InvisiBill]

I work for a Motorola service center, so they're all Motorola part numbers. But it's standard electronics stuff that you should be able to find at Radio Shack... The resistors are just regular 10k, and the transistors are NPN 9570s (I think 9570 is a generic number for them, but I'm not sure), and a plain old 2.5A 1kV diode.

 

[Coloty]

Not that unit conversions are any big secret or hard, but I could help with that set-up if needed. Just some simple formulas for Kpa to PSI.......centigrade to farenheit.......MPH to feet/sec is a cool one.......... and the reverses...........stuff like that.

 

[danny]

Re: Need help for next article: diagnostic software

you say at idle the iac counts should be between 10 and 30. is this with or without any accesories on(such as a/c or in gear)? mine with nothing on is at 0-2, then with a load it jumps up b/w 10-30..

 

[leroy]

Re: Need help for next article: diagnostic software

you say at idle the iac counts should be between 10 and 30. is this with or without any accesories on(such as a/c or in gear)? mine with nothing on is at 0-2, then with a load it jumps up b/w 10-30..

Low iac counts are usually a sign of a small vacuum leak.

Jim