Oil pressure too high isn't much of a problem. Oil pressure too low, on the other hand, can be a severe problem.
As for making it cheap, I imagine a custom PCB will be the way to go. You may want to have a footprint on the board for a 14point7 SLC OEM module, or perhaps several. Since they can be accessed via i2c, you just need to have various address pins pulled high/grounded, and hook it up to the same i2c lines as the eeprom.
This is an info-dump post for anyone curious. Reading the above reply made me go digging for more info.
Here is a narrow-band O2 sensor graph. By this graph, it is theoretically possible to get an exact AFR from a narrow-band, but I suspect even minor electrical interference would make it impossible to get a reliable signal (with a high-resolution ADC). http://en.wikipedia.org/wiki/File:02-sensor-vs-Voltage.jpg
I don't like how expensive these wideband readers are. Everyone will already be looking at ~$60 for the sensor itself.... I don't want to add another $60 for electronics just to read that sensor. I will definitely look into creating our own reader. Doing some searching though, I found a few low-res graphs that showed what the current looks like, but never an equation or high-res graph. If someone found me the equation for current & lambda, that'd be hugely helpful. Otherwise, I'll further into myself later
The wideband sensor is a feedback-based device. It has a narrowband O2 sensor and an ion pump in one piece. Basically, you bias the ion pump in order to keep the O2 sensor balanced. You read the O2 level by how hard you have to drive the ion pump to keep it balanced, so there's a feedback loop, and it's not going to be instantaneous, so you need to have a PID control loop.
More challenging is that lambda sensors have heaters in them that aren't thermostatically controlled, so the controller needs to manage the heater and keep it hot enough without overheating as well. I have no idea how that's done.
You don't need to put the SLC oem on your board, but leave a footprint to add one for people who do want one.
Get an engine from CraigsList. A used one, especially a low-miles one, will be just fine for your project. If it's <100k, then it may as well be new. If you prefer eBay, there's this one for $700 +s/h.
Getting AFR right will be one thing. Adjusting turbo and timing is where you'll really get power gains out of it.
None of us have money to buy an engine... we're college students remember? lol
Anyway, worst-case scenario, I'll probably end up using my car. It sits in the garage most of the these days anyway since I bike to school every day.
I'll sell you my '96 900se 2.0t convertible. $300 for the car, $500 for the (factory, turbo-back) exhaust I haven't yet installed. Head is fresh from recent head work, head gasket is new, turbo newly rebuilt, cylinder compression is Smile; I think piston rings. It is perfectly drivable, but gets horrible gas mileage. Maybe you can see if your school has a Formula-SAE team with sponsors that could help.
Maybe you can see if your school has a Formula-SAE team with sponsors that could help.
Missouri S&T has an FSAE team alright! One of the best in the nation! I helped them for a few weeks when I first transferred here but it was just toooo much of a time commitment. Those guys are crazy!
I'd probably buy the '96 from you if we weren't hundreds of miles apart. But, once shipping, towing, or driving cost is added to it, I could buy a beat up rust bucket Honda here with a great engine.
Also, thanks for the tip about eeuroparts! I thought I'd already posted that saying thank you but apparently not... weird. Anyway, I emailed them this morning but have yet to hear back. TheSaabSite.com has already agreed to some kind of sponsorship, but they have not responded to any of my specific requests, just "Sure we are. Let me know". I'm very hopeful... from what I can tell, they're a cool bunch of guys that eeuro.
Threads for this project exist on multiple different forums and I'm tired of it. Its a waste of forum space, it's unorganized, and it's a waste of my time trying to post to all of them.
So, I have created a public forum via Google. If you're sick of signing up for more and more forums, I understand, but if it's cool with you go sign up for some notifications and post your comments here! If you don't have a Google account, messages can be sent to stefi-mst@googlegroups.com
I thought all injectors were pintle-style, and some just had the pintle inside. My mistake. My EFI system involves a motor driving the pin on the bottom of a Bosch CIS (K-Jetronic) fuel distributor with mechanical fuel injectors.
Interesting. Regardless, I wouldn't think injector type would matter. Surely it will change the timing, but that's going to change for each engine anyway.
It may be more comparable to throttle-body injection. Look up K-jetronic on google. Here's a picture of a fuel distributor on an air meter. Air flows up on the right, and the plate in the middle of the bowl lifts up as air moves past it. It's on a lever that pushes on a button that sticks out of the bottom of the fuel distributor on the left, so fuel flow depends on how far that button is pressed. I'll be driving that button with a servo motor rather than the air flapper.
Just finished building a tachometer on the propeller - we are getting well on our way here. It works wonderfully... sort of. If my scope probe is connected. If I disconnect the probe, displayed RPM becomes sporadic and about 30% high. I connect the probe... PERFECT! Exactly the right RPM. I specify "probe" not "scope" because the probe doesn't have to be connected to the scope. When connected in this fashion:
it works great. It's as though the probe is clamping down on the connection and solidifying it, but the connection feels very tight and solid already.
Also, when I switch the probe from 1x to 10x, it raises the displayed RPM. It is not as sporadic as when unconnected, but it does increase.
I'm open to any ideas you have!
I took another picture just to show more clearly what the connection looks like. The unconnected wire is simply there to give an unobstructed view of the wire:
That looks like a nice clean signal. Does your prop circuitry share a good logic ground with the ECU? Vehicles are notorious for all kinds of nasty offsets, ground loops, noisy grounds, etc. Logic level items are very susceptible so it's usually a really good idea to have a single point ground for your logic signals. Using the ECU logic ground usually works well. The extra capacitance of the probe wire could potentially minimize a noisy signal. I've mitigated similar situations by either pullups, pulldowns or, in the case of taking signal off the coil negative, which you are not doing, lots of series resistance. It can get difficult to diagnose without a high impedance scope which I don't think yours is. The problem is that the very system you're looking at is modified by the means you're examining it with, i.e., your probe. I'd put a 2-5K in series with that anyway just to protect both your ECU and the prop input pins from accidental misadventures. A Prop is cheap, the ECU and ign module is most certainly not. Keep posting your progress, this is an interesting issue!
It's from Seed Studio - DSO Quad 203. *Wonderful* little pocket scope for $200. My friend showed me his DSO Nano v2 (http://www.seeedstudio.com/depot/dso-nano-v2-p-681.html) and I liked it, but didn't think it was quite functional enough to justify buying. Then my professor bought a DSO 203 (http://www.seeedstudio.com/depot/dso-quad-4-channel-digital-storage-oscilloscope-p-736.html?cPath=174) and I figured if it was good enough for him, it was good enough for me. It's *perfect* for working on my car or on the move because it's so small and stand-alone. Even something as small as the PicoTech USB scopes would be significantly more cumbersome.
There's a way to calibrate the voltage, but I haven't figured out how to do that correctly I guess. I tried once and apparently failed. The two digital input ports are useless out of the box - somewhere on the interwebs is a guide that shows you a couple components to replace (a couple capacitors I think?) that fixes them to work as well as the analog ports.
Try putting a capacitor (0.01uF or so) across the input to the prop. The fact that switching the probe from 1X to 10X changes it makes me think capacitance, as 1X will probably have a higher capacitive load than 10X (which includes a voltage divider in the probe).
capacitor sounds like a very easy fix. I'm still getting a decent supply of random parts together - all I have is 0.1 uF. I'll try that tonight and get back to you.
* In piggyback configuration * If this arduino can do it, I would imagine the parallax + appropriate shield will have an easy time as well, and not have the ignition issue he posted about, requiring some coding to prioritize the ignition events over the injector events as the parallax has the cores to handle all of that multitasking- if I have all this read right.
I saw a youtube vid of an arduino in a standalone EMS fashion, but can't find it now.
Comments
I might do something like:
Check oil pressure
if oil pressure too high {
if oil pressure too high { shutdown() }
As for making it cheap, I imagine a custom PCB will be the way to go. You may want to have a footprint on the board for a 14point7 SLC OEM module, or perhaps several. Since they can be accessed via i2c, you just need to have various address pins pulled high/grounded, and hook it up to the same i2c lines as the eeprom.
What do you mean SLC OEM module? OBDII? This is definitely something I'll look into adding. Just have to figure out what signals mean what.
Here is a narrow-band O2 sensor graph. By this graph, it is theoretically possible to get an exact AFR from a narrow-band, but I suspect even minor electrical interference would make it impossible to get a reliable signal (with a high-resolution ADC).
http://en.wikipedia.org/wiki/File:02-sensor-vs-Voltage.jpg
I don't like how expensive these wideband readers are. Everyone will already be looking at ~$60 for the sensor itself.... I don't want to add another $60 for electronics just to read that sensor. I will definitely look into creating our own reader. Doing some searching though, I found a few low-res graphs that showed what the current looks like, but never an equation or high-res graph. If someone found me the equation for current & lambda, that'd be hugely helpful. Otherwise, I'll further into myself later
More challenging is that lambda sensors have heaters in them that aren't thermostatically controlled, so the controller needs to manage the heater and keep it hot enough without overheating as well. I have no idea how that's done.
You don't need to put the SLC oem on your board, but leave a footprint to add one for people who do want one.
I've also made all project documents publicly viewable via Google Drive.
https://docs.google.com/folder/d/0Bzb72JUPBLSnSWpUb1VIRkt5N1k/edit
Getting AFR right will be one thing. Adjusting turbo and timing is where you'll really get power gains out of it.
Anyway, worst-case scenario, I'll probably end up using my car. It sits in the garage most of the these days anyway since I bike to school every day.
Missouri S&T has an FSAE team alright! One of the best in the nation! I helped them for a few weeks when I first transferred here but it was just toooo much of a time commitment. Those guys are crazy!
I'd probably buy the '96 from you if we weren't hundreds of miles apart. But, once shipping, towing, or driving cost is added to it, I could buy a beat up rust bucket Honda here with a great engine.
Also, thanks for the tip about eeuroparts! I thought I'd already posted that saying thank you but apparently not... weird. Anyway, I emailed them this morning but have yet to hear back. TheSaabSite.com has already agreed to some kind of sponsorship, but they have not responded to any of my specific requests, just "Sure we are. Let me know". I'm very hopeful... from what I can tell, they're a cool bunch of guys that eeuro.
So, I have created a public forum via Google. If you're sick of signing up for more and more forums, I understand, but if it's cool with you go sign up for some notifications and post your comments here! If you don't have a Google account, messages can be sent to stefi-mst@googlegroups.com
Also, when I switch the probe from 1x to 10x, it raises the displayed RPM. It is not as sporadic as when unconnected, but it does increase.
I'm open to any ideas you have!
I took another picture just to show more clearly what the connection looks like. The unconnected wire is simply there to give an unobstructed view of the wire:
The scope sees this when plugged in with the 1x probe:
Voltage is not very accurate (I think it usually reads low? can't remember). Time is very reliable.
-Mike
Unrelated to the Thread, just wondering what brand of scope you are using?
There's a way to calibrate the voltage, but I haven't figured out how to do that correctly I guess. I tried once and apparently failed. The two digital input ports are useless out of the box - somewhere on the interwebs is a guide that shows you a couple components to replace (a couple capacitors I think?) that fixes them to work as well as the analog ports.
I saw a youtube vid of an arduino in a standalone EMS fashion, but can't find it now.