M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => General Topics => Topic started by: bmwman91 on June 02, 2006, 11:15:18 PM
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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?
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A/F ratio?
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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.
(http://www.e30tuner.com/other2/o2sensors.gif)
I guess I am glad I got the wide-band last year. It was a fun little addition to the car.
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what about wheel speed (ABS sensors) and shock travel?
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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...
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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.
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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.
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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.
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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!
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could place the outside air temperature sensor behind the rotor instead of in the duct, to get a rough indication of brake temperature
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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..
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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.
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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 ;)
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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?
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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.performancedepot.com/pdadyno.html)
http://www.piresearch.com/pihistory.cfm (http://www.piresearch.com/pihistory.cfm)
http://www.competitiondata.com/index.htm (http://www.competitiondata.com/index.htm)
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For GPS you could probably use one of the Microsoft or Delorme usb GPS as they are pretty cheap.
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For GPS you could probably use one of the Microsoft or Delorme usb GPS as they are pretty cheap.
for big accuracy you need DGPS (GPS with differential corrections) WAAS in USA, or EGNOS in EU
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One thing I recall is that track maps are drawn by driving a lap @ about 90% and following the racing line. The map is then drawn by the software from speed, time and steering input.
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Well, not to sound confused but are you trying to piece together an inexpensive unit? Troubleshooting these things in a car specific mode is a PITA. One of my buddies has the AIM MXL unit from http://www.aimsports.com and it's almost like it's worth the price when you look into it being a package with support. His unit had some issues and they had to send it to Italy to get fixed.
I am not trying to shut you down,I am just trying to see your approach to this as we all know what's often deemed to be a simple get-me-by-kit get's influnced by "might as well" do this elements and then you're better off with an off the shelf kit.
For GPS readouts on the units it seems there's still a degree of error with regards to "accuracy" with the concept and method used. I forget what the scale was but it converted to a few feet or metres of error or so. I think even the high end ones are susceptible to this as well. Any comments on this?
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for big accuracy you need DGPS (GPS with differential corrections) WAAS in USA, or EGNOS in EU
Accuracy costs money.
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I think this has escalated waaay out of the context it was originally in .
My first impression before even opening this thread , was that this was a datalogger for parameters used or produced by the engine or computer.
Stuff like throttle position , fuel injector pulse width , accurate miles per gallon .... not shock travel , shock tower deflection , or frame twist.
It seems like this has escalated to something the original poster didnt want it to , and now hes streched thin trying to appease the masses.
I could be wrong tho
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In response to jonboy318is's post, I know that I mentioned megabuck systems. However I meant to do so only in the context of showing the hardware used and the possibility that someone that was pretty sharp with electronics would know where to source sensors, etc. at lower cost. If we had OBDII we could buy a unit that interfaced via USB for a few hundred. Perhaps the OBDII logger could be easily adapted to a pre-1996 M42. One folows:
If you want to know the horsepower and torque of your engine, or the 0 to 60 time of your car, or even the 1/4 mile time and speed, the answer can be in the palm of your hand. The PDA-Dyno™ turns your PDA into a Data Logger, a Data Acquisition System, and OBD II Scan Tool.
(http://www.performancedepot.com/ART/featuredprod/pdadynoL.gif)
Record several 1/4 mile runs and compare them later, record all data during a road-race, or record your car's gas mileage (mpg) for a specific trip. Do all this and more, by simply connecting your own PDA (Palm, Handspring Visor, Sony Clié) to your car's OBD II connector under the dash, using the supplied OBD II compliant cable (supports all car model years 1996 and newer). A standard 8 MB PDA can hold hours of driving data (depending on free memory space).
The PDA-Dyno™ can also be used as an OBD II scan tool and supports all Generic OBD II Data such as: SAE J1850 (VPW, PWM); ISO 9141 2 (ISO); ISO 14230 (KWP 2000). Use it to check and clear the Diagnostic Trouble Codes (DTC), or to turn off the “Check Engine” light. Yes! the one that comes on right after you do all those cool engine mods. Perfect for when you have to get the car smogged.
DISPLAY:- General Engine and Vehicle Information
- Diagnostic Trouble Codes (DTC)
- Displays real time sensor data. Up to two sensors can be monitored and graphed simultaneously
- Up to 5 sensors can be displayed in bar-graph and analog
- Display the following sensors types:
- Load Value
- Vehicle Speed
- Coolant Temperature
- Ignition Timing
- Engine RPM
- Fuel Trim
- Mass Air Flow
- Intake Air Temperature
- Throttle Position
- Fuel Pressure
- Intake Manifold Pressure
- Oxygen Sensors
[/LIST]Of course this would depend on the sensors available on the E30 M42.
Now here's a part we could use and I am sure would sell. One end plugs into our E30 diagnostic plug (with maybe a few loose wires for the extra sensors) and the other into an OBDII socket.
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I think this has escalated waaay out of the context it was originally in .
My first impression before even opening this thread , was that this was a datalogger for parameters used or produced by the engine or computer.
Stuff like throttle position , fuel injector pulse width , accurate miles per gallon .... not shock travel , shock tower deflection , or frame twist.
It seems like this has escalated to something the original poster didnt want it to , and now hes streched thin trying to appease the masses.
I could be wrong tho
Yeah, you are prettymuch right on. I am doing this as a sort of after-work fun project. Maybe someday I would try to sell logging units (more generalized ones for MANY models of cars), but for now it is an enthusiast project.
Yes, accuracy is not cheap or easy. It takes copious amounts of time to get good sensor calibration curves, and $ to get good components. Then not half-assing the MCU coding takes even more time. I have a little time while I am on my engineering internship (well, a few hours after work anyway). I just want to play around with making my own, NICE, data acquisition system.
And yes, originally it was going to be an engine-parameter only setup, that could be used to understand how the engine was tuned from the factory, or by whoever's chip you have in there. Then from there one could perhaps decide to further fine-tune their motor. For me, this is an intermediate step of sorts...once I get a fully working DAQ system going, I plan to make a stand-alone ECU. Rag all you want, I am WELL WELL WELL aware of what cost effective, widely supported/used units are out there. I built a Megasquirt & used it on the last car, and have lots of respect for the TEC-3 unit. However, I will not start my own business someday selling Megasquirts, I will need my own products. Hell, even if it is a side-job, I will at least enjoy what I do, and that is what counts to me. I just happen to be a part of the BMW enthusiast community, and am a little perturbed that there are not enough cool goodies for the M42. Poo on the M20.
As far as wheel speeds, that is fine. It is just interfacing 4 more VR sensors, and they do not even have to deal with counting missing teeth like the crank damper wheel does. Shock travel & GPS...hmmm, yeah definitely not gonna lose any sleep over figuring those out. Perhaps someday, but I feel that engine parameters and wheel speed are a LOT more useful. There are not that many people out there with coil over suspension (even the ones that DO have it, cmon I know you are not gonna go adjusting the springs every week based upon datalogger readings). And GPS, well, useful or not, go buy a TomTom or something. Not that many people track their cars, or care enough to get anything meaningful from the GPS reading. Lap times are more than sufficient for the enthusiast.
Haha, and no I am not ragging on anyone here. I just like to be to the point, and I AM The Godfatherer...I can voice my opinion freely. Don't like it? I'll have ya whacked by my coisin Little Tito.
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little tito FTW
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Lol, oh Lord.....what have I started?