Super MPGuino?

[bestclimb]

Originally Posted by gtkid2002

And I think doing a RPM/Tach sensor would be awesome, but my car has a cable driven tach. Kind of lame for this purpose, but whatever. It works.

How does a mechanic's strobe light get it's signal from a spark plug wire?

[gtkid2002]

I have no clue how it does that. It might have a voltage tap somewhere to let the ECU know, but I'm pretty sure it's cable driven on the cluster. The speedo and the Odometer are, I'm positive of that.

[UK Mini]

Timing strobes are inductive - plenty of volts in plug leads for them to sense. Most programmed ignition setups will output an rpm digital signal somewhere.

I'm certainly interested in an expanded mpguino but I'm a noob to this kind of stuff - I'd be happy to help with/fund some beta testing.

Some ideas:

Vehicle speed by multiplying engine speed by a gear ratio variable, using a few switches on the selector mechanism to sense what gear is selected. You wouldn't need a separate speed transducer; you could gain a gear indicator (7segment led?) & you could build an intelligent shift light, or even a fancy paddle shift/auto selector. A second speed sensor, on an undriven wheel, would give the possibility of traction control. I see people are already using cut switches: which could be automated for TC, and EOC with an additional clutch switch - or those gear selector switches.

A time clock - display default when there's no mpg and/or mileage being counted.

A persistent odometer, in case you do away with the original speedo, so you can still keep an eye on service intervals. You could also count engine hours.

Scrolling display - would make a really cool 'n easier to read electronic speedo.

Analogue inputs used for engine temp, oil pressure, fuel level, manifold pressure etc - user defined labels with a bar graph display. A change in value would put the effected data on the display. You could add a maximum/ minimum reference that triggers a buzzer or warning led. The next level would be to save trip max/min values to revue later

Most AFR sensor kits will put out a 0-5 volt signal too so you could treat that in a similar way. Lambda, manifold pressure (and rpm) are useful as numeric values so a user defined conversion factor would be handy to convert the displayed value in to meaningful units.

Have you also seen Rallyduino? A project ripe for some convergence.

[dcb]

good suggestions I've always wanted a clock. I have padded out the unused pins and am looking at the 328 so there will be room for improvements.

re speed from gears, problem w/that is some (many) of us here do a lot of coasting out of gear, perhaps with the engine off, so you might only be tracking 1/4 of the actual miles.

I like the wii nunchuck idea on the rallyduino But my focus here of course is efficiency and not best ET. I would use the remaining analogs for things like tps or map/maf (or o2 sensor as you suggest), overtemp can be a very simple standalone led circuit however.

I think traction control probably deserves more dedicated hardware (we are at %50 cpu just watching the speed/injector signals and displaying them)

But even something that seems simple, like a clock, you still have to have some sort of "user interface" for it so that you can set the time, and that eats up precious flash space.

[UK Mini]

I take your point on speed when not in any gear - didn't think of that X-). A basic traction control system could be as simple as comparing the driven axle speed with the undriven one and killing the fuel or ignition if the driven one gets too much ahead - it'd be not unlike have a PWM internal combustion engine. Appreciate that's 50% more transducer counting though.

The idea of the over temp (or over/under anything else) would be the warning would be coordinated with the display - the buzzer goes off and the (multifunction) screen shows the related info. It ties in with the idea of the analogues "auto promoting" themselves when they have something new to say. You could have AFR displayed as default, for example, then when the coolant temp notches up another bar on the gauge it automatically replaces AFR on the display for a while, chuck in a blinking backlight so you don't miss it.

A time stamp from a clock could also be useful if you are logging data off your mpg gauge.

Appreciate Rallyduino has a different appeal, just wondered how easy it would be to splice the 2 together to run on the same hardware since so much of it could be the same?

Boy it's easy to dream up these ideas when you haven't got a clue of how to make them happen

[jonoxer]

Since a few people seem to be interested in MPGuino variants based on the Mega, this might be of interest:

www.practicalarduino.com/projects/vehicle-telemetry-platform

It's based on OBDuino but with a bunch of extra stuff to take advantage of the Mega hardware.

[gtkid2002]

Alright, well I was just able to order the Seeeduino Mega last night. Figured it has a few more pins then the Arduino Mega, and it's cheaper. So I have a start, although a late one.


jonoxer - That's a great link idea, but I'm not sure how much good it'll actually be. It says it's based off of OBD-II, while the MPGuino is generally used on pre-OBD-II cars.

To explain what these folks did for the average working Joe, who can't quite afford a car newer than 1995, is just amazing. It still works for just about any car with fuel injection, but for cars built before 1996, there is no OBD-II option.

That's on the workspace thingy. I'm not trying to be a douche or anything, so I apologize for that, I guess we can at least use ideas like coolant monitoring.

Which my car's coolant gauge isn't working right anyways, so that could be of benefit.

UK Mini - Great ideas!
On Honda's pre-1990, I'm pretty sure most of them don't have electric speedometers, which would make things difficult. I suppose you could just do some coding so the mega does the calculations based off of speed and time, but things like spinning tires or locking your brakes (my car doesn't have abs, or alb) could throw that off a bit. Not enough to really matter, but it could make a difference if you're trying to get good readings in snow (Unlikely, yes, but who knows the circumstances).



So far I'm thinking I'll be buying some of the analog temp sensors *I cannot remember their names right now, but they're two wires with a blob of something in-between them. They remind me of ceramic capacitors* so I can do misc stuff like outside air temp, engine bay air temp, intake air temp, and exhaust air temp. I'm still tempted to make a bar graph readout for g-forces and stuff though too, but I'll get to that after I can buy the screens and stuff.

There is a chance I might be ending my participation with this on account of my transmission is going out. I'm not too pleased, but I'm gonna keep driving my car for as long as I can. I like it too much to get rid of it right now.

Another thing I'm going to hopefully get hooked up is going to be a kmh to mph switch for the speed. I'm hopefully going to Canada soon, and being able to push a button and switch from my speed to theirs without having to do loads of mental calculations or even squinting at the little orange digits on my stock speedo (providing it actually worked!) would be incredibly awesome. Something like this would just require a switch to tell the 'duino to switch from one calculation value to another, right?

Since I drive an auto, it would be awesome to figure out how to replace the TCU with a custom one that shifts at different times, or with the paddle switch idea, but that would be incredibly difficult, and vehicle specific, and would probably at most span one make of vehicles. Although there are a lot of Honda's out there, just the difficulty of it wouldn't be pretty.


But yeah. Massive post aside, Things will be getting somewhere! Hopefully. There is always that damned if part.

[bobski]

Originally Posted by gtkid2002

On Honda's pre-1990, I'm pretty sure most of them don't have electric speedometers, which would make things difficult.

I thought I would clarify a few things regarding Honda instrumentation.

First, their tachs have been electronic for a long time... Probably since they switched from points/condenser systems to magnetic pickups. That means the '89 Prelude should have a pulse-driven tach. The ignition control module in the distributor generates a signal pulse every time it fires the ignition coil -- twice per crankshaft rotation.

As far as I know, the cable-driven speedos found in fuel injected cars still have a pulse-type pickup in them so the ECU (and other devices, such as cruise control) can read vehicle speed. The transition period for cable to electric driven speedos was '92-93, depending on the model line. I'm not sure about the '88-91 Prelude since it's sort of a... umm... ******* child of the B-series engine family, but many times the electronic VSS (vehicle speed sensor) units found installed on the transmissions of newer vehicles are drop-in replacements for the cable drive gear found in older cars. The biggest trouble there is getting the old drive gear assembly out, as they tend to bond to the hole in the transmission... 5 mins with a propane blow torch and a good set of channel lock pliers with sharp teeth will often do it. Try to find a decent Honda/Prelude enthusiast forum to find more info.
Once you have the pickup in the car, supply it with power (either 5V from the ECU or 12V from the main relay, both should be available in the engine harness, check your ECU wiring diagram/VSS troubleshooting procedure for which to use), ground (the connection at the engine thermostat housing should do) and run the signal wire to the gauge cluster, splicing into the existing speed sensor wire so the ECU and other devices get the speed signal, as well as whatever you plan to use for the speedometer/odometer.
FYI, I've done this conversion on my CRX and am now running a '94 Integra gauge cluster... It's fully functional except for the warning lights for equipment I don't have, such as ABS, SRS and the low fuel warning light.

For coolant temperature, there should actually be two pickups. A single-wire sender for the gauge, and a two-wire sensor for the ECU.
The gauge sender doesn't respond linearly to changes in temperature. At some point Honda came to the conclusion that the normal variations in engine temperature gave drivers the impression that the cooling system wasn't doing what it's supposed to. So, they replaced the gauge sender with one that responds normally up to the bottom of the normal range of operating temperatures, plateaus for a bit and then continues behaving normally just above that normal range... There is very little change in sender reading within that normal range.
On the other hand, the ECU's two-wire (sensor ground and signal) Engine Coolant Temperature sensor responds in a far more normal manner. I would guess the ECU uses a simple resistor network to read the value of the ECT sensor, so you should be able to just tap into that red/yel wire and read the 0-5V signal.

You should be able to read the Intake Air Temperature sensor the same way as the coolant temp sensor.

MAP (manifold pressure relative to full vacuum) should be another simple to read 0-5V signal, as should the Throttle Position Sensor.

[gtkid2002]

Originally Posted by bobski

I'm not sure about the '88-91 Prelude since it's sort of a... umm... ******* child of the B-series engine family, but many times the electronic VSS (vehicle speed sensor) units found installed on the transmissions of newer vehicles are drop-in replacements for the cable drive gear found in older cars.

The 88-91' Preludes are weird. In between '89 and 90' Honda made a lot of changes to the Preludes on the internals, and some body modifications. The 89' Preludes and prior have mechanical speedometers with a small voltage generator just before the actual part that moves your speedo *which is what fails on a lot of preludes*, and the 90' Preludes have electronic speedos that have the generator in the transmission. Other slight variations like engine type, and what patterns they put at the end of the turn signal/wiper assembly, but most don't really apply.

I'm also not planning on swapping out the VSS unit on my trans. It runs a cable, which is running just fine, and it turns my odometer. Although the ability to have an electronic trip function would be rather nice, I probably won't consider getting parts for such a swap until it comes time for me to pull my transmission out and swap it in.

It is possible to do the conversion on a 89' Prelude to an electronic VSS, but then you'd have to probably do some cluster internal swapping, and things just get sticker from there if you plan on keeping stock cluster settings anyways.

It might be tempting to design an entirely new cluster based with the super-mpguino as its core. More things to fail yes, but that way it could be done perfectly. Only problem for me is that I really like the stock look in these cars, and it would be pretty hard to make it look completely stock.

For coolant temperature, there should actually be two pickups. A single-wire sender for the gauge, and a two-wire sensor for the ECU.

Yep. Well, I can't say that there are only two pickups, because mine might have three if that's the case. It has one single wire sender all right, but it also has two double wire senders right next to it. One of those lost connection and I now have custom splices into it, but it's still not working, which could provide the part of it being the ECU sensor, but they are just smack next to each other. Less than 2" away, on the same piece of coolant pipe so to speak. If they are just single wire senders, I might have to attack mine with a soldering iron, as my temp gauge is flat-lining until it is almost at highest temp. It only started after I messed with the dual wire sensor, but since the single wire send is next to the dual, it could have been damaged as well.

That means the '89 Prelude should have a pulse-driven tach. The ignition control module in the distributor generates a signal pulse every time it fires the ignition coil -- twice per crankshaft rotation.

And after another check under the hood, right again. I looked at the cruise control cable insert and never bothered to follow it. But yeah, there are two pairs of wires that come off the coil and go straight to the harness. So then electronic tachs are possible, and probably fairly easy.

Try to find a decent Honda/Prelude enthusiast forum to find more info.

Preludepower.com - Powered by vBulletin. Massive website, awesome people, and lots of knowledge. I'm over there as well, same user name.

For the TPS sensor, it could come in handy by using that as a factor when it could come to individual cylinder cutoffs. How much further the throttle has to be increased when you have say 2/4 cylinders cut off, how much this effects mpg, etc.

I think the whole MAP sensor got explained to me once before, but it didn't stick long, because I forgot what that thing does again. If somebody wants to refresh my memory on it, that would be awesome.

bobski - You mentioned you had a CRX, but have you ever done any work with Preludes? You sound like you know Honda's in general pretty well.

[bobski]

Originally Posted by gtkid2002

It has one single wire sender all right, but it also has two double wire senders right next to it.

The second one could be the radiator fan thermoswitch. I didn't think about it due to it's location on Civics/CRXs. The coolant temperature sensor and gauge sender are next to each other on the side of the cylinder head under the distributor, while the thermoswitch is on the back of the block or on the thermostat housing (depending on year).

Originally Posted by gtkid2002

For the TPS sensor, it could come in handy by using that as a factor when it could come to individual cylinder cutoffs. How much further the throttle has to be increased when you have say 2/4 cylinders cut off, how much this effects mpg, etc.

Or just to have a readout for the sake of constant-throttle driving.

Originally Posted by gtkid2002

I think the whole MAP sensor got explained to me once before, but it didn't stick long, because I forgot what that thing does again. If somebody wants to refresh my memory on it, that would be awesome.

It's simply a pressure sensor for the air in the intake manifold. The lower the pressure, the less air (and oxygen) gets pulled into the engine with each cylinder stroke. Oxygen is needed to burn fuel, so the ECU injects less fuel when the air pressure is lower.
As far as instrumentation goes, it's not much more useful than measuring throttle position, though it provides a little more information about engine load.

Originally Posted by gtkid2002

bobski - You mentioned you had a CRX, but have you ever done any work with Preludes? You sound like you know Honda's in general pretty well.

Not specifically, though I do tend to familiarize myself with the various models when I get a chance. Hondas go together like lego bricks, so I've used a few '88-91 Prelude parts on my CRX. Power window switches, front brake calipers (well, they're actually Integra calipers, but they're the same part), aluminum wheels and a 3540 brake proportioning valve before I converted to rear disks.
I've got sprinkling of parts from other models as well... Like I said, the '94 Integra gauge cluster, '90-93 Integra power mirrors, a D16Z6 and P28 ECU from a '94 Civic EX, auto->manual conversion using parts from a '90 Civic LX, the driver info center from an '89 Legend... The list goes on, and gradually lengthens (presently working on a '90-93 Accord climate control panel).
Honestly, that's one of the reasons I familiarize myself with other models... To figure out which of the goodies I can conceivably steal from junkyard cars and install in my CRX.


On topic, I started working on my own MPGuino variant a week or two ago. So far I've got '168 and '1280 Seeeduinos, 16x2 and 20x4 character displays, plus a 128x64 graphic LCD to play with. Really my goal is an MPGuino with nicer display capabilities -- a bigger display, maybe an LED bar graph/numerical display (either elevated ala late model Civic, or a HUD projector) and maybe some other stuff thrown in depending on how much I/O that leaves me.
The Arduino platform seems like a decent enough development environment, so I'm also working from scratch as a learning experience.

Originally Posted by dcb

If it were pure arduino then it would probably be portable, but I found myself fighting with the arduino environment early on to get the guino to do what I knew the chip could do but that "pure" arduino couldn't due to space/performance/absent & changing functionality issues.

Old post, but anything specific you could share?

I've been playing with code to measure pulse length, but the output from my first attempt has been pretty jittery. The code just polls an input until it goes high, marks the time (according to millis), waits for the input to go low again and subtracts to get the duration. After trying out a 200Hz square wave, it became perfectly apparent I'm going to need to use micros at very least, and probably use an interrupt pin as the input.
Or is there a more hardware-centric method I should be using?