Say I were to design an M42 datalogger...what features would you want to see?

[bmwman91]

Now, let's say that, hypothetically, I was designing a datalogger for the M42.  If I were to do this, I know what I would want it to log.  Things like:
- Air Flow Rate [m^3/hr]
- Intake Air Temperature
- Coolant Temperature
- RPM
- Injector Pulsewidth
- Injector Duty Cycle
- Ignition Advance
- Throttle Position
- Manifold Pressure
- Battery/Alternator Voltage
- A/F Ratio (thanks for reminding me Nick)
- Vehicle Speed (romkasponka & doigal)
- Fuel Level (doigal)

I would also want to have two data display modes: an LCD display to show one variable at a time in real-time (can be changed/selected by pressing a button), and a serial connection so a computer could save the info in a spreadsheet.  But that is me.  What other stuff would someone want to see if they were looking to do some datalogging?

[nickmpower]

A/F ratio?

[bmwman91]

D'oh.  Yeah that was one I was gonna do, thanks for reminding me.

Now, keep in mind, you can only get meaningful O2 readings if you have a wide-band sensor/controller system retrofitted on.  The stock narrow-band type is all but useless, unless you are at 14.7:1.  It only tells you in general whether you are rich or lean, no exact interpretation is possible.  See my attached diagram for clarification.



I guess I am glad I got the wide-band last year.  It was a fun little addition to the car.

[romkasponka]

what about wheel speed (ABS sensors) and shock travel?

[doigal]

Only a few that i can think of:

Car velocity (kph or mph selectable for us ozzies!)
Accleration x and y (using two cheap accelerometers)
Fuel level
Time/date (track work?)

If you did this and sold it as a kit i would buy it. Even if you just sold the PCB and the chip that ran it. Also if it was set up as a generic model that was adaptable to all cars a lot of folks on mp3car.com might be interested as well...

edit: The gear as well. Its possible to work this out by looking at the cars speed and the RPM and comparing the ratio...

[bmwman91]

I could definitely do car velocity, that's a good one.  I would pull that from the VR sensor back in the differential.

Fuel level...could get that from the signal wire going to the gauge.

Acceleration...perhaps on a second revision of the circuit...this would be prettymuch an engine parameter logger.  I am not sure, at the moment, how I would compensate for chassis roll affecting the accelerometer readings.

Shock travel...that's a little beyond what I was envisioning.  Perhaps someday though.  For the moment I am tryign to keep things nice and simple so installation would be as easy as possible.

[sheepdog]

Acceleration...perhaps on a second revision of the circuit...this would be prettymuch an engine parameter logger.  I am not sure, at the moment, how I would compensate for chassis roll affecting the accelerometer readings.

RC helicopter gyros.
With that you could get lateral g's as well.

[D. Clay]

OBDI and OBDII loggers and displays are available for less than $200 that use USB connections. Although it is always nice to develop things yourself, the hard parts and software are all available commercially and cost from $500-$1000 up to $100K plus for over 100 channels. Rousch and Formula 1 even have three infrared tire temp sensors per wheel. I must admit that I know nothing about electronics except buying and using systems. A simple wiring diagram leaves me glassy eyed. Next time you see an Indy Car race, you'll notice a very high antenna that feeds a server in a separate pit cart. There is so much info that they use 10-12 laptops configured for different aspects of the car's performance. There are usually about six guys under a canvas awning monitoring the laptops due to the low visibility in full sunlight. All you can see is their feet.

[bmwman91]

Good lord.  Now, THAT is beyond what I am looking to do!  But man, would I like to get a hand in on that sort of technology!

[Berlin]

could place the outside air temperature sensor behind the rotor instead of in the duct, to get a rough indication of brake temperature

[romkasponka]

speed from ABS sensors is better, because you can log speed from each wheel and solve some brake balance, under/oversteer problems and rear diferential setings..

[bmwman91]

speed from ABS sensors is better, because you can log speed from each wheel and solve some brake balance, under/oversteer problems and rear diferential setings..

Hmmm, that is an interesting idea there.  There are a LOT of things to log on the car...this logger may become one hell of a tool.  The only hard part is getting the initial design working.  Dealing with the VR sensors it not too difficult.  Now, dealing with many at a time could be more challenging...I would definitely not have enough interrupts on the current microcontroller I am looking at to do them all that way...I suppose I could route the conditioned outputs to some digital inputs and do timer counts from when it sees the input go from a '1' to a '0' or something of the like.

Side question for those who have dealt with VR sensors:
Currently, I am using the National Semi LM1815 chip to condition the VR sensor output.  It gives a user-adjustable pulsewidth pulse upon negative-going zero-crossings from the VR sensor.  From a cost & complexity standpoint, it seems a little bit of a pain.  Anyone have any simpler, creative solutions for dealing with VR sensors?  Thanks.

[romkasponka]

I don't know what for you want to create it, but I think what for racing purposes the most significant data is:

Track position (GPS +EGNOS or WAAS)
Speed (from all wheels)
Breaking point
Throtle position
Suspension travel
G load

I don't think what race track is good place for setting up N/A engine (because of you cant affect it so easy), but of course it would be very intresting to see all data what could be logged

[doigal]

Honestly, I think that indiviual wheel speed should be more of an option (or version 2) rather than a standard feature. GPS would be nice, but i'd imagine that would be more of a software thing on a computer rather than part of a standalone datalogger. Perhaps there is a way to 'modulise' this project and have addons, such as GPS, suspension travel, ABS sensors, etc

Also i'd vote for USB connection to a computer if it possible. Would be nice to have but not absolutly neccessary.

How could you measure suspension travel exactly? some sort of variable resistor mounted on a slide?

[D. Clay]

IIRC the two most popular full tilt data systems are Competition Data Systems and Pi. Pi is big bucks but just short of rocket science. Professional teams sometimes have one guy that does nothing but data hardware and software. CDS is scalable from about $5K up. The main thing is that they have the hardware for sale as separate componenets. Sliders for wheel travel, etc. You could buy just what you wanted.
The  first link is to an OBDII system that maybe could be modified for M42's. I think we're OBDI. The second and third are to CDS and Pi.  They have component price sheets.  I think the components are standard items that are sold for more because they are for racing or compatible with their systems. You could probably beat their prices if you knew what the stuff was and where to buy it.

http://www.performancedepot.com/pdadyno.html
http://www.piresearch.com/pihistory.cfm
http://www.competitiondata.com/index.htm