Say hello to the Mighty Mira!
 

Hi,

Looks like I found my niche here. I have long been interested in fuel economy, however few people were as obsessed or actually knew as much about it as I did, and now I found a forum where people not only know more but have implemented what they know! Very impressive!

And what a torturous path to get here...googling undertray, to these articles on autospeed about how to DIY a very partial undertray, to phil knox, to gassavers.

I am an engineer (EE) and as nearly all engineers do, I love efficiency. And as such, I can't stand most of the automotive world. We are in a stupid arms race for height and weight, with no one better off in the end. But fortunately rising oil prices are waking people up in a big way. It is very possible to get Cds of 0.20-0.25 (or lower!) and we are stuck with 0.35.

Only a few more years before we get cheap commuting cars for the masses. We aren't there yet, but at least those who are in the know can insulate themselves from fuel dependence.

CAR

On to my car. have a 1993 Daihatsu Mira that I purchased recently. I spent quite a bit of time looking and researching before I purchased it. My goal was to minimize both the expense of the car and the fuel costs, with an eye to make a daily driver that was as fuel efficient as possible.

I bought it mainly for the engine. It has a 660cc, EFI engine. I figure it would beat a 1 litre carburetted daihatsu charade (which was the main alternative at the same price point). The 660cc combined with the EFI should set me up with the best base possible.

Cursory tests reveal that I get about 6.5l/100km in city with normal driving (no engine off or anything). Not that bad.

I would prefer a more bubble shape, something that would lower the height and width at the top (e.g. lower seats, less van-like looking), however, this was the only thing on the market at the price range, especially with the EFI engine.

It also has a 5 speed gearbox, better than the 4 speed van version you can also buy (although heavier).

Surprisingly enough the manual says that it should weigh 1000kg, which I am very skeptical of. But maybe so. I might remove the back seats since I have no need for them (or their weight).

MODS

The very first thing I need to do is have some way of estimating instantaneous fuel economy. This sucks because I am in Australia, my car came out before OBD-II. That means I will either need to measure fuel consumption directly (not sure how), or I will have to figure out how to measure injector pulse width, etc etc.

I'm more a programmer than an electronics guy, so it will be interesting to get my hands dirty with this. I do have a rough idea what to do, based on a newsgroup search:

So unfortunately that seems to be what I have to do first, and since there is no one here who seems to have gone this route, looks like it's up to me. (correct me if anyone has, I'd love to see a DIY of this).

After I have a base I can compare to and a means to compare with, I can then set about actually doing the various mods that actually improve the fuel economy.

So, I am starting with this:
https://i5.tinypic.com/1412wdz.jpg

Roughly 6.5l/100km city. Kerb weight 1000kg? At least 750kg, for sure. Cd 0.35?

Goal (UFE-III):
https://www.diseno-art.com/images/Daihatsu_UFE-III.jpg

The UFE-III gets 1.3l/100km, has a Cd of 0.19, kerb weight of 440kg, engine size 660cc. Notice especially the design of the undertray right in front of the front tires - this should be relatively easy to copy.

I will proceed to make modifications on the order of price/increase FE %.

In the pipeline are:
-corflute undertray (you call this "coroplast")
-corflute deflectors in front of front wheel and rear wheel (side skirts)
-reversal camera and removal of external mirrors
-rear wheel skirts
-smooth wheel covers
-blocked grille
-either raised bonnet or some sort of deflector over the wiper blades.
-LRR tires (+40psi)
-possibly larger tires
-aftermarket cruise control

Possible
-antenna removal
-front wheel bubble faring
-caulked gaps
-shaved door handles (no clue how to do this)

I hadn't planned on doing all this stuff when I got it, especially the stuff that won't be reversable. However, seeing as the car was cheap and chances are that the mods will improve the value, I suppose I shouldn't worry. It's just that I would have liked to have bought a beater since then it wouldn't matter what it looked like and I could have done a half assed job on the asthetics.

Please give feedback and any suggestions etc. certainly wouldn't go astray.

Hey MM, welcome to Gassavers. It sounds like lots of work to build your own mileage computer, but certainly doable with your credentials. But before you go through all that work, you should look into the OzTrip mileage computer, made in Austrailia. Just google oztrip and you will find some articles about it. I emailed the manufacturer in February to order one and got this reply:

Hi Dan

sorry but we are no longer stocking this kit, the kit will be replaced with a new computer towards the end of this year...hopefully...

my appologies.

regards
Robert

You can contacto Robert at: rob@oztechnics.biz

I'm not sure if it will work on a 2 cylinder but you never know.

There is another option called a SuperMID. They will work on the Prius and many 4 cyl Hondas. Depending on the size of your injectors, it may work on your car. As long as they are larger than 115 cc the SuperMID should work to measure fuel consumed down to 0.001 Liters. If you car has an electronic VSS (vehicle speed signal) the SuperMID will also measure distance and calculate average fuel economy. It will also show instantaneous injector pulse width. What will not read correctly would be th instantaneous fuel economy because you have a two cylinder. For more details, just search this site for SuperMID, Super Mid or just MID as it has been referred to on this site.

Good luck!

Welcome to the site! There really is a great deal to learn from everything that's posted. Hmm, I've been noticing something for the past few years. There are a bunch of people from Oz and Canada that are very interested and very knowledgable about FE. I have figured out why yet.:) Again, welcome.

It's actually 3 cylinder, btw.


Thanks, that looks interesting. Whatever I do, I want to get it up and working soon because I am anxious to start the other modifications.

Any links to buy it?

MM

I think that Matt Timion is working on some distribution agreement with Yoshi. Why don't you PM Matt for details on cost. Just be aware that it wasn't made specifically for your car so it may not work properly. You won't know for sure until you try it. Kinda risky. I would be happy to help you with setup and calibration if you do decide to buy one.

I'd still like to iron out a few things before we bite the bullet and try to distribute it. I should email Yoshi about this. Perhaps it would be good to get a wish-list from the people already using it.

Well, I'm slowly figuring out where to go for what. Apparently service manuals are rare as hen's teeth, I've called pretty much EVERYWHERE. The UK site doesn't stock them either. But maybe I can figure it out by myself.

I checked the first injector, it has two wires connected to it, a black wire with yellow stripe, and a white wire with green stripe.

Also, a google of "vss ecu mira" led to this page. Apparently google's cache of it is still good, though the original is nowhere to be found. The page is titled "Vehicle Speed Pulse Locator", which I suppose is what we want. According to that page, the 92-95 Mira (my car), has the Vehicle Speed Pulse:

That's probably all I will need, then. Of course, I will need to check that it actually exists, and to remove the dash.

"Bother", said Pooh.

I suppose that's what I get for buying what is probably the smallest car with the smallest engine for the cheapest price in Australia.

I also tried my first FAS (Forced Auto Stop), or CODFISH, or whatever it is. Basically turning off the car, letting it coast down a hill in neutral, then turning the car on again, putting the car in gear, releasing the clutching and feeding some fuel via the accelerator again.

It works, how about that.

Well, at least you know where everything is, w00t w00t.

You could also check for the vss itself, should be coming off the differential area.

Hey, thanks for the advice!!! I need all the help I can get.

I think in theory you should be able to remove the cluster without removing the dash.

Oh, and that was a good link. I saved the info for future use if we ever start selling MPG computers here.

Yes... if the theory assumes that I am either 5 years old or have plastic arms 2 inches in diameter.

Actually Matt, you are right.

I just went down to buy an automotive multimeter (about $60 Aus, or $50 USD).

I unscrewed 2 screws on the cluster and 3 behind to access the cluster. There were two connectors in back. One which I assume is some sort of mechanical speed signal. I'm not sure what it was exactly, it had quite a bit of grease on it. I figured it was something mechanical and not electrical, as otherwise, why the grease? I managed to get that out. There was also a 16 pin (from memory) connector that plugged into the back that I managed to get out with a bit of work.

And so, with trepidation, I had a look at the screws on the back.
Hmmm. Speedo... bottom screw... Was there a ground to attach in order to get a proper signal? There was! I hooked the black alligator clip to the GND signal, and the red alligator clip to the mysterious bottom screw. Dangling the wires through the back down near the peddles, I hooked it up to the multimeter.

Then I hooked the other stuff back up. The mechanical grease connector didn't feel right, and wasn't. When I started it up, I saw no increase in kph.

Stopping, I jammed it back in and it seemed like it seated properly. I was rather worried, because I thought it might have some mechanism whereby if you screwed with it, it wouldn't work again to prevent winding back the odomoter.

However, as I went faster this time, the speedometer appeared to be functional.

And what's more, as I turned the multimeter to "RPM", I got a signal that went higher as I went faster, went slower as I went slower, and did the same independent of gear.

I HAD FOUND THE VSS AND VERIFIED IT!!!!!

So now it's only a matter of finding a convenient injector signal. I can either buy a stamp myself to program, or buy the Supermid.

But no matter what, this sure beats having to mess around with mechanical vss signals. I can do several things now, measure l/100km on the fly and also attach a cruise control unit, both of which I have wanted to do.

Anyway, I am happy, that gives me a feeling of accomplishment.

welcome, how are your bump starts? i'm curious to hear your results. Although if your stats are correct then that's crappy power to weight ratio :p but i bet its easy to park around town!

I can bump start almost every time (take it to mean clutch starts). However, still sometimes it starts with a bump, and it's a little less predictable than I'd like.

Is it better to change to a high gear for the rpms, or a low gear? I started off using a low gear, but now I think it's working better with a high gear.

I should probably stop it, because just reading the manual it says "Caution: A large amount of unburned gas introduced into the catalytic converter may overheat the converter, which may cause a fire. To prevent this and other damages, observe the followings; ... Do not turn off the engine while vehicle is moving. Do not push or pull start your vehicle."

So far no problems though.

BTW, here are the vehicle stats:
Length: 3.295m
Width: 1.395m
Height: 1.415m
Wheelbase: 2.28m
Fuel tank capacity: 32l
Gross Vehicle Weight: 1040kg.

Now, GVW is usually 300-400kg more than Kerb Weight (just figured out through googling). So kerb weight should be 640-740kg, which is right around what I want.

From what I find, it's not underpowered at all. (Of course, it will be even better when I have shaved off 50% of the drag.)

A bit more about the VSS:

It looks like however the rpm is configured, it measures the vehicle's speed perfectly. I am using the digitor q 1585 multimeter, rpmx10 setting. It shows a speed of 25kph as 250, and keeps going. This means that according to the manual, if it were measuring rpm, a 250 signal means 2500rpm.

Hmmm. since 1kph is obviously 10 on the guage, or 100rpm, what signal is actually being sent? Well, since the rpm meter is designed to be connected via an inductive pickup to a spark plug lead, that means that at 1kph the metre will be sending 100 pulses per minute. Or 1.6667 pulses per second.

There are a bunch of other screws at the back of the instrument cluster. I have a mind to attach wires to all of them and see if I can reverse engineer them. Perhaps I will get lucky and find an RPM signal, an INJ signal, or a fuel guage signal (very likely).

Anyway, I'm very lucky that the VSS signal was so easy to interpret, not requiring any fancy calibration.

Good job with the VSS!

I bump start in the highest gear I can for the speed, makes it smoother.

Anyway, mehbe you'll whip something up in terms of instrumentation, I wish I had the know-how!

something to helkp with your bump starts ^ higher gear the smoother, i go as low as 2nd when my speeds are low but i try to make it a high gear.

Well, I had another look at my instrument cluster, this time in more detail. And got some pictures...

As you can see, there is a 22 pin connector in addition to the mechanical odometer cable (or whatever it is). I reverse engineered the pins as best I could with the new multimeter and some educated guesswork judging by which conductors lead to which lights or went to connectors behind which guages.

https://i6.tinypic.com/14kxqav.jpg

https://i6.tinypic.com/14kxqmd.jpg

https://i6.tinypic.com/14kxt8i.jpg

Another great bonus - I was tracing the route that the injector wires take, traced them through the firewall, and lo and behold, I found the ECU! It sits right under the passenger side of dash, and is trivial to access (although I need to get a proper socket set to get the bolts off; my socket screwdriver won't cut it.).

This means that no longer do I have to remove the whole dashboard to get at what I need to.

At the moment I'm a bit awestruck at all the things I get to play with: a VSS, INJ signal, and hopefully an RPM signal (which I can get inductively from the spark plug anyway).

That means I can make:
-l/100km guage (Need VSS, INJ)
-digital speedometer (Need VSS)
-digital tachometer (Need RPM)
-digital temperature signal (useful for grille testing) (Need Temp signal)
-digital tank guage (also how many km left to travel, worst case). (INJ)

All of which should be relatively easy once I understand how to setup the basic stamp and the LCD screens. This looks helpful.

So, my basic plan of attack is now:
1) Get basic stamp, LCD, board, etc, everything needed for final project.
2) Pry off ECU to get a good look at it, see if there is any schematic on the back, and see how to easily detach the various wire bundles for splicing. (Need socket set).
3) Find RPM signal for tachometer.
4) Use a PC oscilloscope through soundcard setup to analyze the various signals, such as this one.
5) Splice various wires such that I have easy access to every signal I need.
6) Start programming the stamp and testing out the basics of the device, troubleshooting until finished.

I think that's it.

All my quick replies get lost...

Anyway, this is worth retyping...

Good job with the cluster, I had to do a bit of that and it was a pain in the side.

Also, you should have a tach signal coming off your distributor and going to the ecu to control the function of the engine wrt timing/fuel, so you shouldn't need to use a spark wire.

Hey, thanks!

I got the basic stamp, will see if I can find the wire you are talking about tomorrow.

Hint: Before posting, hit CTRL A, CTRL C.

I dunno if this is the industry standard...but try solid blue, :p

Well done Mighty Mira. I wish I could do something so productive.

Try putting a teggy cluster in your car, it's as much fun, :p

I took some pictures of the ECU. Here is one (after I opened it:

https://i6.tinypic.com/14y0kfb.jpg

The various i/o pins are as follows (with my guesses for what they signify in brackets):
Top 12 pin plug:
IG (ignition)
E02
#10
FC
ISC
VSV1
E03
E01
AMP
W
VF
BAT (battery)

+B1
SPD (speed)
IDL
N+
THW
PIM
VC
E1
+B2
A/T
AC
PSW
N-
T
THA
OX (With an overbar over the "O" - could this be an oxygen sensor?)
E2

I also note that there is a group of three sequentially numbered labels - E01, E02, E03. I'm guessing that these correspond to individual cylinders.

If any of you have any idea as to what these may portend, let me know. I think I will need to get an oscilloscope, hook it up to individual outputs, and play with the car in order to get a feel for how the outputs change and what those changes may signify.

p.s. The outputs I'm most interested in are as follows:
Speed
Injector (any injector)
Tachometer
Also, a BAP sensor would be invaluable (or if there is another way of figuring out the Barometric Absolute Pressure), because I want to be able to measure altitude on the fly, hopefully.

Does the ECU have a BAP sensor on it? I know honda put the BAP in the ecu, if that helps.

EDIT:

AC could be the a/c clutch control, that's something you couldnt try disconnecting or checking for power/ground by toggling the ac switch.
A/T could be the lockupsolenoid control, depending on what kind of lockup you had, but since this is in AUS and it's a 95 it's very possible you only would have the one pin controlling lock-up.
AMP Part of the alternator test circuit perhaps?
PSW Does power steering need some sort of electrical crap?
FC Possibly fan control based on ECTs
IDL Mehbe controlling the idle air control valve?

I'm guessing the e01 stuff are injector things. You could always try following the wires/checking for continuity in the coloration.

Thanks for the help,

I'm not sure if the ECU has a BAP sensor in it. Any idea where/what to look for?

AC - you mean Air Conditioning? If so, this car doesn't have A/C.

I wonder if AMP = MAP. If so, that's not going to really help me here because the car will never be at WOT hardly, and it needs the BAP sampled as much as it is sampling speed etc.

I'm just heading out to the car now to check up on the wiring continuity.

Most of the things you can test by looking at the signal that goes through them. I should take a picture of my BAP...but I'm a little tired at the moment and I think my batteries are dead, but anyway, it looks like a plastic brick with a little hole in the side, :p Anyway, even if the car doesn't have a/c if any of the cars did (or any of the cars that shared a similar ecu) did the ecu will have a space for the a/c, regardless of whether or not it is used, *shrug* Unless they were really picky about that.

The following is a pic of my ECU. Let me know if anything resembles a BAP sensor, otherwise I will have to wait until I get an oscope to have a proper look at stuff.

(BTW car was actually manufactured in Sept 92.)

https://i5.tinypic.com/14y5zz9.jpg

BTW, I just went and copied down all the colors of the wires and the pinouts they correspond to. I will get that up shortly.

However, I did have a look at the distributor like you told me to. I am fairly new to engines, but I found the spark plug leads and followed them from the cylinders to a cylindrical thing on the end of the motor, with three heads pointed off at 60 degrees spacing. I figured that this is the distributor.

So, this has 4 wires coming off it - two come off the end and are white/cream, and black/red, both with two silver bars. They are larger wires, and furthest from the engine.

Now closer to the engine are two smaller wires, signal wires obviously. They are blue/yellow and blue/green. I traced them to the N+ and N- in the ECU. I'm guessing that these are going to give rpm. I can probably test that with my multimeter now.

ALso, my injectors are hard to get at. I can look at the first one, which has white/green and black/yellow coloring. The next one is impossible to get at properly, and the only thing I can do is to lift up the shielding slightly. They too look white/green black/yellow. ????

But when I have a look at the ECU wires, there is +B1 and +B2 showing black/yellow, both are thick wires. Also, there is a white/green wire, that is marked #10. Or if I am mistaken, there is also E01 and E02 which are both white, black and thick.

I have a feeling that I may need to install an aftermarket BAP sensor on the car. I'll have to do some research to figure out how much resolution these devices have.

My basic purpose with this is to enable the FE meter to track changes in elevation.

Damn that ECU is bare as hell! Anyway, no BAP, what do you need it for?

Only 4 wires on the dizzy! Geez.

Black/yellow is the power the the injectors, you'll want the other wire, which is a switched ground, for injector pulse signal.

The rpm wire should only be one wire, hmm, odd. I wonder what sensors are in the dizzy, if any. I wonder if you even have these sensors? They didn't seem to be on the ecu side of things.

Perplexing.

I've finally been able to figure out my highway mpg. Highway is 50mpg (4.7l/100km or 21.3km/l), City is 31.3mpg (7.5l/100km or 13km/l).

Note that the highway wasn't completely highway, but maybe 65-70%. I wouldn't really consider it to be a true highway run. Which means that perhaps unmodified, I might be able to get what?

Let's see, if I travel 45km at city and use 3.46l... and I travel 128km and use a total of 6l, then the highway section I used 2.54l and travelled 83km, giving me 3.06l/100km!

While I don't think it is quite that good, I would certainly be pleased if it was! That would be 70mpg.

I did pump the tyres up to 50psi though. :)

I just found myself an old oscilloscope that should do the trick. Now I will be able to examine the signals first hand, which should prove interesting. I may need someone else to drive the car though. :)

Well, at least for the VSS.

Ok, I have set up my oscilloscope to run off an inverter powered by the cigarette lighter. I did some cursory testing - the scope measures 12 volts coming off the battery, so that seems to be fine.

I looked at the VSS. The VSS triggers a pulse every time the wheels turn a certain amount. That pulse is about 4 Volts. The waveform looks like so (it returns to the same level as it started, excuse my hasty drawing) :

https://i1.tinypic.com/1zp6zyr.jpg

I had a brief look at some of the ECU pins. There is one that varies the pulse width compared to how hard I mash the throttle. It obviously has to be either the rpm, the TPS, or the INJ signal. I suppose the best way to test that is to get on the highway in 5th gear and mash the throttle. If it doesn't change, then obviously it's got to be RPM. If it does change, then it's either the INJ or the TPS.

I'm not sure how to distinguish the TPS from the INJ. Well, I imagine that the INJ will vary according to the RPM, it's just that the pulse width will change. Whereas I'd imagine that the TPS will not depend on RPM at all. Thus if we know a signal is either the TPS or RPM, then a change in RPM should tell the difference.

e.g.:
1. Go to highway speed in fifth gear. Step on the gas. If no change, signal is RPM. If signal changes, go to 2.

2. Go to second gear. Put the throttle down a reasonable amount. As the rpms climb, note the signal. Does something increase frequency? Then it's INJ. If not, then it's TPS.

My car's ECU / sensors stay active if I stall the engine and leave the key in the "run" position. If your car is the same, you could stall it intentionally (while stopped) and then observe sensor inputs with the engine off. IE. INJ / RPM will drop to 0, but TPS will continue to vary depending on pedal position.

Thanks for the hint!

I made some more progress. I tested a few more pins at random, and got some interesting ones.

I think I found an injector signal. It pulses when I put my foot on the gas, frequency in proportion to rpm, and the pulse width gets longer when I floor it. When I take the foot off the gas, the pulses stop until the engine slows down to the point where the accelerator is, and then resume. That one is labeled "#10".

I think I found the rpm signal, or at least, something that measures rpm. It is labelled "IG".

And I think I found the TPS, which rises up and down when I pump the gas. It looks to be a straight voltage signal, although there appears to be some noise in that one. It is labelled "PIM".

If it's truly the case that these measure all those things, I have all the inputs that I need.

Nice detective work, Mira...

Rises & falls with the engine on, or off? The MAP is also a straight voltage signal on my car which varies (with noise) with throttle position - but only with the engine on. Engine off, it's a constant voltage.

Happy hunting...