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Old 06-11-2006, 12:46 AM   #1
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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:

Quote:
Computing mileage on an EFI engine is as simple as totalizing the
injector ON time, totalizing distance traveled, multiply in a
conversion factor and display. Hardware needed is a Parallax BASIC
Stamp (about $50) and an LCD display board (about $90.) We use the
PWM input across an injector to grab the pulse widths. We use a bit
line to read the vehicle's VSS to get distance. We write a little
BASIC code to wrap it all together and viola! Mileage/trip meter.

There are several methods of calibrating the fuel injector flow.
The most accurate is to build my fuel injector flow bench and
actually calibrate the injectors.

(http://www.diy-efi.org/diy_efi/projects/inj_flow/inj_flow.html)

The next best way to do this is to hook up a pulse generator (or
even better a PC using my FIT software at the above URL) to the
injector, fire off the fuel pump, discharge 20,000 pulses or so and
catch the fuel in a graduated cylinder. The pulse width should be in
the 2 ms range. This must be done instead of just yanking the
injector open to measure the flow to account for the opening and
closing delays in the injector.

The crudest but still satisfactory method is to hook the Stamp up
with some code that will display the raw injector and VSS totals,
put an accurate amount of gas in the tank, drive until it's used up
(or fill the tank, drive, fill it again and record the amount), then
compute the volume per injector pulse by dividing the fuel used by
the total number of injector firings.

John

--
John De Armond
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:


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

Goal (UFE-III):


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.
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Old 06-11-2006, 04:50 AM   #2
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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!
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Old 06-11-2006, 04:58 AM   #3
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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.
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Old 06-11-2006, 05:46 AM   #4
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Quote:
Originally Posted by krousdb
I'm not sure if it will work on a 2 cylinder but you never know.
It's actually 3 cylinder, btw.


Quote:
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!
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
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Old 06-11-2006, 06:06 AM   #5
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Quote:
Originally Posted by Mighty Mira
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.
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Old 06-11-2006, 10:23 AM   #6
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Quote:
Originally Posted by krousdb
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.
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Old 06-13-2006, 12:22 AM   #7
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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:
Quote:
Behind instrument cluster -bottom screw at speedo head

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.
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Old 06-13-2006, 12:56 AM   #8
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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.
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Old 06-13-2006, 07:21 AM   #9
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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.
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Old 06-13-2006, 10:23 AM   #10
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Quote:
Originally Posted by SVOboy
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.
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