TMO Datalogger 101
Since you purchased a TMO Datalogger, you are probably familiar with what it can do for you. Using the TMO Datalogger to "fine tune" your engine is where it really shines.
Using the information from the datalogger you can "tune" your car to run better and run closer to that fine "edge" of performance. This page will only touch base on the functions of the TMO Datalogger, the variables you can select and how to read those variables. For tips on how to "Tune" your car using the TMO Datalogger go to Tuning Tips
Now lets look at some of the data you can select to monitor with the logger.
NOTE: If you have some kind of piggyback fuel computer (VPC, AFC, PMS, MASC etc.) that gives a false signal to the ECU, that false signal will be reported by the Datalogger to you. Keep that in mind when interpreting data.
Under the label "DATA" on the toolbar you have SELECT, TRIGGERS, and QUICK SELECTS.
Select lets you pick all the variables you want to monitor
Triggers lets you select different combinations of variables and conditions (e.g. rpm>4000, TPS>50%) that will trigger the datalogger to start recording.
Quick Selects is a user-defined collection of variables. Instead of the tedious process of selecting each individual variable every time you want to use the TMO Datalogger, you can just choose a Quick select and start logging almost immediately. There are 6 Quick selects you can define, so be creative!
Once you are in the menu Select, you will see a bunch of values to select including FUEL, AIR, SPARK, IDLE, MISC, TMO, and TRIGGER.
FUEL, under fuel you have;
- ACCEL ENRICHMENT (range of 0 to 100%)
This is the amount of fuel that is initially squirted into the engine during quick movements from the throttle. It gets its input from the Throttle Position Sensor. When the TPS voltage increases rapidly it shoots a little extra fuel in to help with the throttle response. Too much or too little will affect drivability.
- COOLANT TEMP (range of 100 to 300 degrees)
This is just what it says, your coolant temp from the temp sensor for the ECU (not the one for the gauge, they are both located in the thermostat housing). The ECU uses this to tell when to go into closed loop after warmup. It also has an affect on timing.
- ENGINE SPEED (range of 0 to 8000 rpms) (may be 8500 on some loggers)
The actual engine rpms the ECU sees from the informantion it gets from the TDC sensor and Cam angle sensor.
- FUEL TRIMS HIGH, LOW, MIDDLE (range of 60 to 140% for 91+ cars, 80 to 120% on 90's)
These are the "long term" memory fuel tables in the ECU. When you drive the car in closed loop (normal to low-boost driving, rpm<4500), the ECU is constantly updating these trim values. The ECU takes the signal from the MAS and calculates how much fuel to add to maintain an a/f ratio of 14.7:1, then compares the O2 readings against the value it calculated and adjusts the fuel trims (adding more fuel or taking away) to try and stay at a constant "stoichiometric" value (14.7:1 air/fuel ratio). A trim value of 100% is stoichiometric, anything greater than 100% and you are running lean so the ECU is adding fuel, anything less than 100% and you are running rich and the ECU is subtracting fuel. The ECU always tries to run at a stoichiometric 14.7:1 ratio under closed loop operation and the values will be reset to 100% when the ECU is cleared.
These values will always be changing up or down a little depending on the air conditions and many other variables. Low, middle, high refer to the amount of airflow that the ECU sees while in closed loop. When the ECU goes into open loop, none of the fuel trims are updated.
- INJECTOR PULSE WIDTH (range of 0 to 25 milliseconds "ms")
This is the actual amount of time that the injectors are open, not duty cycle. Duty cycle is roughly defined as the ratio of the amount of time a signal is "active" to the amount of time available for the signal to be active.
NOTE, once again every car seems to be different. I have personally run my 450cc's to 27+ ms and had a smooth pattern, great flow and no knock.
The one thing I will add is you want a value somewhere around 20ms at WOT. It must be a smooth, straight curve. If the value is jumpy at all your injectors are not squirting a smooth pattern and you will get detonation from this. It is more important that the signal be smooth than the actual number as on 91+ ECUs this number is what the ECU is "trying" to do, not that the injectors are actually open for that amount of time.
- OXY FEEDBACK TRIM (range of 60 to 140%)
Just like the fuel trims, this is also a closed loop value only this is the "short term" value and it determines the adjustments made to the "long term" fuel trims. As you drive along it will switch (cycle up and down) just like the O2 sensor voltage. It should be a nice, smooth and even switching rate, not jittery or jerly up and down. If it is switching from say 80% to 120% then you are right at 100% value, there's that stoichiometric word again. :-) If it's switching above 100% it's showing lean, and if it's switching below 100% you are running rich. Based on this info, under certain conditions the ECU will adjust the appropriate fuel trim until it sees the oxy trim switching closer to stoich.
- OXYGEN SENSOR (range of 0.0 to 1.0 volts)
The oxygen sensor is what the ECU to determine whether the engine is running rich, lean, or just right. 0 volts is lean, 1.0 volts is rich, and stoich is ~0.47v. Once again you want a good smooth pattern of peaks and valleys. At idle you will have a nice and slow switching rate. The higher the rpms and throttle position under a load (driving) the faster the switching rate until it stays constant at a higher reading. Once it stops switching that shows that you are not in closed loop anymore. Most importantly you want a smooth switching rate.
Once you go into open loop, it will show a constant reading. Under WOT you always want as low of O2 voltage reading as you can go WITHOUT any detonation or knock sum on the logger.
- THROTTLE POSITION (range of 0 to 100%)
This just simply shows the position of the Throttle Positino Sensor (TPS) on the throttle body. You can use it to watch the accel enrichment while you open the TB or to tell when your WOT pass starts or watch your shifts when you let off the gas during the shift. You should see a nice and smooth increase with a slow and steady increase from your right foot on the gas pedal. If it's not smooth your TPS could be going bad. The actual lowest the reading will show is somewhere around 10%.
AIR, under air you have;
- AIR FLOW HZ (range of 0 to 1600hz)
This is the actual signal the Karmann Vortex generator in the Mass Air Flow sensor (MAF or MAS) sends to the ECU. This tells the ECU the amount of air moving through the intake. Please note that this is not equal to air mass - the ECU also needs the barometric pressure and intake temperature (also located in the MAS) to determine the actual air mass entering the engine and the corresponding amount of fuel to deliver. Unfortunately, current limitations in the TMO Datalogger limit the reported result to 1606hz. However, the MAS is capable of sending out a signal up to ~2200hz or so to the ECU.
- AIR TEMPERATURE (range of 0 to 200 degrees)
This is the temperature of the air at the MAS. It's great for seeing if your cold air intake or heat shield is working. On a 45 degree day I had temps of 120 degrees at the filter with just a K&N and cut air can. After making a cold air setup and a heat shield I now see 75 to 85 degree temps. This also has an affect on timing.
- AIR VOLUME (range of 0 to 255, actually 0 to 7)
This is the number that the ECU uses internally for air flow. It is derived from Air Flow Hz, air temperature, and barometric pressure. This value has far more precision inside the ECU (11 bits) but due to technical reasons, the logger only sees the top digit of the whole value (technically, the top 3 bits). This gives us a visible range of only 0-7. Because the resolution is so poor, Air flow Hz is usually used instead to monitor air flow.
- BAROMETER (range of .7 to 1.1 bar)
This is also in the MAS . It shows the barometeric pressure of the air to the ECU. This combined with other readings helps the ECU to know how dense the air is therefore to determine total air mass entering the engine.
- ISC STEPS (range of 0 to 130)
This is your Idle Speed Control servo motor on the throttle body (you know, the one that goes bad!). It is a stepper motor that opens or closes the TB plate to control the idle speed due to load changes, i.e. turning on the a/c or using the power steering, brakes etc. It opens up in steps and closes in steps to control the idle. This value is useful to tell if the ISC is working well or not.
SPARK, under spark you have;
- KNOCK SUM (range of 0 to 43)
This is an important value! The knock sum scale is given to represent the signal from the knock sensor to the ECU. The ECU then calculates the amount of detonation present. The higher the knock sum the more the ECU retards timing to get rid of the knock.
With a knock sum of;
- 3 or below, the ECU will advance timing.
- Between 3 and 7, the ECU leaves timing alone.
- Higher than 7, the ECU will begin retarding timing. Higher knock = higher retard, with the possiblity of seeing less than 4deg total advance at the maximum knock sum of 43.
One important note to remember is the knock sensor can detect "false" knock and retard timing. This is most commonly caused from the noisy lifters but anything it can audibly pick up could cause this.
- TIMING ADVANCE (range of 0 to 50 degrees)
This is the real-time spark timing the ECU is using. While at cruise speeds at low throttle settings it can maintain as high as 40 or more. This is a very usefull tool as you can really "see" the timing affect power. The more advance the better up until knock occurs. Ideally you want to maintain around 15degrees advance at WOT high rpms. Any higher advance and you probably can afford to increase boost a little bit, any lower advance and you are knocking and it's being retarded too much. It's very easy to see the relationship between the knock sum and the timing advance.
IDLE, under idle you have;
- A/C SWITCH, (on or off)
This just simply tells you when the a/c switch is on or off. Nice for seeing if your TMO ECU is turning if off under WOT or above 5000rpms.
- IDLE SWITCH, (on or off)
This is the single wire switch on the TB. It tells the ECU when the throttle plate is fully closed. If this switch is faulty it will cause idle problems. This tool is an easy way to tell if it's working correctly.
- PARK/NEUTRAL SWITCH, (on or off)
This is simply the park/neutral switch on auto tranny cars. For the manual tranny cars, it's the clutch switch. This can be used to see how long your shifts take as it will show the switch being made the entire time the clutch is engaged (not counting pedal travel).
- POWER STEERING SWITCH, (on or off)
This shows you when your power steering is being used. Normally off until you move the steering wheel.
MISC, under misc you have;
- A/C CLUTCH RELAY, (on or off)
Indicates whether or not the A/C clutch is engaged (ie the A/C compressor is working).
- BATTERY, (range of 8.0 to 16.0 volts)
Useful to see what your battery is putting out. Also testing the alternator. You monster stereo guys should like this one. The ECU uses this along with other inputs to actually control the fuel injectors.
- EGR TEMPERATURE, ( range of 100 to 400 degrees)
Nice to know info on how hot the air is going through the EGR valve. Not all cars have this sensor, and it certainly won't work if you have a blockoff plate installed.
- TDC SENSOR, (on or off)
The ECU uses this to determine the engine rpms, ignition and fuel injector firing. The ECU assumes that the engine timing is set for 5deg BTDC, and this signal is the only way it knows where the engine is in its rotation.
TMO, under tmo you have;
- TMO ENGINE SPEED, (range of 0 to 10,000rpms)
This is a little more accurate tachometer and you get the added plus of reading up to 10K!! If you try and see if you can get the line graph to reach that high, you're on your own. Don't say I didn't warn you! :-)
Last but not least, TRIGGERS, (user set functions)
These are created by you and are recalled by selecting the trigger you save it as.You can select a value or a group of values that you want to datalog but only under certain parameters. Then have that value(s) only come on when you are in those set parameters.
Now we'll take a look at the DRBII tool and it's useage.
Under the label Tools on the main toolbar you have DRB II.
Once in DRB II you will see all the different data tabs to select from. These tabs are sensors selected into groups that have related functions and info. You can view any error codes that may be stored in the ECU and also disable the fuel injectors one at a time for troubleshooting. Very useful information.
Enjoy the TMO Datalogger and use it wisely, it can be your greatest tool!