Three most useful gauges?
 

So I've got myself a brand new bone stock Toyota Yaris that I've happily put about 1000 miles on and so far I've been getting in the neighborhood of 40-45 mpg even while driving for break in (varying speed, gear, load, etc.). One of the things that I'm sorely lacking is a tachometer, and the street-racer set makes nifty three gauge pods for this little car that would allow me to install one to my wife's cosmetic satisfaction. Now, I am positive I will be installing a Scangauge, probably above the mirror, but I still want an analog tach for convenience and to help my wife drive stick with the quiet engine. That means I've got two gauge holes to fill!

What would be the best gauges to populate these holes with? The cars computer should be monitoring oil pressure and water temp I'd imagine, so should I rely on it to monitor those for me? Or rely on the scangauge for those? Which two gauges outside of the scangauge would tell me the most about my efficiency, vacuum and voltage?

Just curious what instrumentation besides the scangauge people find most useful or necessary.

- Jason

If it were my car, I'd stick a high resolution engine temp gauge and voltmeter in there. But that's because I have the engine off frequently (need to be careful to avoid drawing the battery down too low), and I run a partial grille block, so want to be able to monitor coolant temps.

40-45mpg? What % of that was highway?

One of the gauges I find invaluable is a wideband AFR gauge. You will have to replace your O2 sensor, but it will tell you what your scangauge can't.

The other gauge I would use is an ammeter. This will let you measure the power draw of various electric devices in your vehicle and can tell you much more than a voltmeter.

As for voltage, vacuum and water temperature, these are things the SG actually does well. I wouldn't bother with an oil pressure gauge unless you plan on running a lighter than recommended viscosity.

Tach, Wideband 02 Sensor, Oil pressure.

Those are the most vital Gauges i beleive for any sort of vehicle (if you dont have a tach then i would say vac/boost gauge). The wideband with ACCURATLEY display your Air to Fuel ratios so you can keep track of what everything is doing @ the moment.

Oil pressure is the gauge that will make sure your engine is running properly. God knows that it has saved me a couple times when i had an oil line blow off of my turbocharger. Otherwise i would have no idea.

If it were my car I'd probably just use a scangauge since it can do pretty much everything... However, since you reeeealy want the tach I'd probably go with the same gauges Metro said if your planning on using pulse and glide and doing aerodynamic modifications. The ammeter is a good choice, but it doesn't really need to be a permanent gauge once you get a feel for what the different accessories pull amp wise. With the scangauge I also wouldn't bother with a vacuum gauge. I'm not sure about the 1NZ-FE (yaris engine), but my 1ZZ-FE (matrix engine) stays in closed loop just about 100% of the time. Wideband is way overkill (and expensive) IMO unless you are tuning an engine.

Scangauge does most everything but will not do A/F ratio or oil pressure. For efficiency the scan gauge is really all you need because it will give you an instantaineous MPG reading, the most important of them all.

95% plus. The car is used entirely as a commuter and I live nearly 50 miles away from my place of work just off major interstates. I'm also fortunate that I commute at a time when there is not much traffic. Because of the break in instructions saying not to keep the engine at a steady RPM for long, or excessive RPMs, I took it as an opportunity to play with a sort of modified P&G with an average speed of about 55 mph. Its the 5 spd hatchback. Note that I haven't had it that long, so I don't have a lot of data to go by yet!

Thanks for the suggestions so far, some good points to think about that I wasn't expecting. I think it would take me some time to actually be able to put the information from a wide band to use though. Without remapping the ECU, how would you apply the feedback its giving you?

Id get a Vacuum Gauge for sure. It shows you how much of load ur putting on the engine when ur accelerating or cruising around. This is the one that i installed on my truck.
http://www.hallspeedshop.com/auto-ga...ge-p-2437.html

It shows you where the needle should be for best Fuel economy. I dont know if the Scanguage can show vacuum. Even if does, I doubt that it is as accurate and instantenous as an old fashioned needle gauge.


With the help of the vacuum gauge I went from 15mpg to 20.5 mpg.

Taco, the SG can show vacuum to a tenth of a PSI.

Using a wideband to lean out your mixture involves setting the gauge or driving unit to produce a 0-5 linear AFR voltage. This voltage must be fed to a switching circuit that produces 0v when the input voltage is above a certain threshold and 0.9v when the input voltage is below a certain threshold. In effect, you're deciding at what ratio you tell the ECU it's running lean or rich. The result is you train the ECU around a ratio of your liking. Though I cruise as lean as 18:1:1, I find that 16.2:1 produces the best economy for my vehicle.

One caveat is that your scanguage cannot tell you which ratio produces the best economy. This is because it measures air, not fuel. When leaning out, it will show your mileage getting worse even though it's getting better, because you're using more air, but less fuel. After a tank of lean-burn, you'll find that your fillup numbers and the SG's estimate are off. It's only after a complete tank of running a certain mixture, that you can halfway trust the SG. A far more accurate way of measuring fuel is an injector based solution. This will tell you the truth for any mixture in any situation.

JohnnyGrey, where can I read more about using a WB02 for KMPL (MPG) increases?

I say a voltmeter and vacuum gauge.

The scangauge can show vacuum but nothing like a mechanical analog gauge though. A vacuum gauge can show a lot more than economy. If there are any engine problems you can usually see them in the vacuum gauge well before they are noticeable from engine vibrations or noises.

And a voltmeter is handy to have in general.

It isn't necessarily what you are looking for, but here is a computerized mpg gauge on an analog tach. It probably won't work out of the box but it might give you some more ideas:
http://www.circuitcellar.com/avr2004...05abstract.pdf

The Innovate Motorsports LC-1 can be calibrated to output a custom 0-1 volt signal, as can other units on the market. It is much easier to buy an inexpensive feature rich wideband and then pointy-clicky the desired output with a computer than it is to build an op-amp circuit and correctly tweak it to work as you wish.


Makes sense, combustion pressures fall way off in the 17:1 or higher range.

Hey, great find! I just recommended this to a friend on another forum who wants to lean out his car. However, there's no pointy-clicky for me because none of my computers run windows. My unit only has one transistor in it, no opamps, and it's more like knobby-turny. :)

SG can do AFR accurately on unaltered o2s signals.

My Elantra have 2 o2s, and the factory pre cat one is a wide band. Your Yaris being a very recent car, it might have one too.

I get the AFR in an XGauge with the following:

TXD:07E00124
RXF:044145240000
RXD:2810
MTH:05BE80120000

SG can do a lot more than we think.

I'm late to the party here...

To fill the pods...

Based on my turbo cars of the past, I had an Oil Temperature Gauge (not sure if there's a sending unit on the Yaris). If you ever affix a grill block or undertray, it might be good info to know the Oil Temp. Oil Pressure is also a good gauge.

Outside Temperature might be a good one...

Otherwise, vacuum, voltmeter, a digital timer, or a custom gauge of sorts could be installed.

I miss the days when the average car came with more than just a tach, speedo, fuel, and temp gauges. I forget the car I drove once, but it had a speedo on one side, and a huge gas gauge on the other. The rest were idiot lights. I like to know what's going on in analog format -- I too crave gauges...

RH77

Joesph Davis quote,
The Innovate Motorsports LC-1 can be calibrated to output a custom 0-1 volt signal, as can other units on the market. It is much easier to buy an inexpensive feature rich wideband and then pointy-clicky the desired output with a computer than it is to build an op-amp circuit and correctly tweak it to work as you wish.


Now i understand this was the missing link in my thinking, i didn't get how the ECU could understand the signal from the Wide band. Thanks, guys

Do any of you gentlemen have any affiliation with the products mentioned so far in this thread?

Anyone else offer opinions on the ammeter vs. volt gauge. I am looking at a boost gauge, and I was wondering if I should go AF and volt, AF and ammeter, or volt and ammeter.

Amps absolutely, and here is why.

Eventually, the battery will start to fail. Often, it will fail by shorting out one cell out of the 6. That means it is now a nominal 10 volt battery instead of a nominal 12 volt battery, BUT the fully charged voltage might be 11.8 or 11.9 so you will not notice it on the voltmeter.

When the battery cell fails, the alternator is going to try REAL hard to charge the battery, and it is going to be doing it ALL the time. The end result, as I have found out in 3 (footnote 1) cars, is that the stator winding in the alternator will overheat, the insulation on it will break down, and it will short. You will then need to get a new stator winding from wai-wetherill and rebuild the alternator.
http://www.wai-wetherill.com/products/ymm.cfm
(They dont have the parts for a yaris alternator yet, too new, but they have all the little itty bitty internal parts for all the older toyota alternators and starters. I look up my part number and then phone my order in to the distributor in Boston Massachusetts :
Boston Auto Electric
103 Clayton St.
Boston, MA 02122
Toll Free: 1-800-225-6650)

Put the ampmeter into the alternator output wire so you will know about this event BEFORE it becomes fatal problem.



(footnote 1: Experience is the second time you make the same mistake. I have no excuse for the third event. :( )

I should add that a low speed accident, or bumping a wall or jersy barrier, or a crackhead at the gas station backing into your car, will make a battery cell fail, I guess the impact breaks off one of the battery plates and it falls off and shorts things out.

I'd say oil pressure and a voltmeter. Ammeter not so much since you have wire the ammeter in series with the cars electrical system requiring the usage of some heavy gauge wire. There is a fire hazard as that cable will be carrying your cars entire electrical load

I'd say oil pressure and a voltmeter. Ammeter not so much since you have wire the ammeter in series with the cars electrical system requiring the usage of some heavy gauge wire. There is a fire hazard as that cable will be carrying your cars entire electrical load

There is no need to cut into the cable. You can use a hall effect amp meter sensor that goes over the alternator cable. Another way that works is to hook a millivolt meter up so that one terminal on the mv meter is connected to the alternator cable at the Alternator end. The other terminal of the mv meter is connected to the alternator cable at the battery end. The flow of current thru the cable to the alternator creates a small voltage difference between the two ends, and you can meausure this and calibrate it for acutal amps.
In other words, the cable from alternator to battery acts as a shunt.
Nice job for an Arduino :thumbup:
Here is an example to show the idea of the hall effect sensor, this one is too big and too expensive, but much smaller and cheaper ones are available
http://www.alliedelec.com/Search/Pro...DESC=RSS-100-A

Are there any off the shelf remote-sender ammeters for auto use?

(although the arduino idea is attractive. I've been looking for an excuse to play with one.)

ttoyoda, what a well reasoned post. I was going to chime in to say "voltmeter" until I read that.

Very nicely explained - thanks.

And this coming from an EV driver. :p

Cool didn't know about that, wonder how well that would work if hooked up to say an IMA cable? ;)

ttoyoda, what a well reasoned post. I was going to chime in to say "voltmeter" until I read that.
Very nicely explained - thanks.
And this coming from an EV driver.

Thank you. Unfortunately for me almost everything I have learned has come from some sort of (usually repeated) near-miss or disaster, large or small. Like the time I touched an electric fence in the dark twice, because I could not believe it had shocked me the first time. :D Only once in a while do I have an opportunity to learn from someone ELSES disaster, e.g. why I don't want power windows.


Are there any off the shelf remote-sender ammeters for auto use?

I have never seen one, (being cheap) I just use the mv meter and the alternator cable as a shunt. If you are going to use a moving coil meter, then a (center zero if you want to read discharges, means different hookup) meter movement that is about a microamp full scale has a reasonable internal resistance to give a reading directly, but if you are going to try that then start off by putting resistors in line with the meter movement to make sure you do not peg the needle right off the bat.
Ideally, the connection to the alternator cable would be to the crimped lug just away from where the threaded stud goes thru the terminal hole, so that changes in the resistance of the contact at the terminals do not have any effect on the results. I am usually lazy and just use big ring terminals, use the threaded stud with the meter ring terminal on last.

Wanted to bring this back up, and see about a fourth gauge. Already have a boost/vac, and I am looking at a water temp and oil pressure. The boost may go on the column, and three in a DIN pod. What should the 4th be?

Meh, if/when that happens your battery completely dies overnight and you get another battery. No ammeter is needed.

I'm really not a big fan of a thousand and one gauges. I tune cars for a living and see an endless procession of cars with pillar pods full of crap information I could do without. Oil pressure so I can verify engine condition (oil pressure switch set to kill ignition if it drops too low at WOT), boost/vac, and maybe wideband AFR. Or maybe not.

Honestly, all of the cars I've tuned that made it on TV or ran notoriously strong, and reliably, have no wideband. It's a great diagnostic or tuning tool, but in the hands of someone less than an experienced technician it's too much information and a distraction.

http://ecomodder.com/forum/member-pt...rs-my-most.jpg

Jason, you can keep your scangauges and tachometers, my most valuable instrument is this bird, mounted on the cowl of my Smart car. All this $4 flowerpot bird has to do to tell me everything I need to know about hypermiling is just to flap its set of spring-loaded wings in a particular way.

This is how it works. When the wings are extended, like they are in this picture, I get the best mileage. At highway speed they fold up into a tight V. In a cross wind, one will fold upwards and the other will lay out flat, pointing in the direction of the wind. In a good tailwind, the wings lay out like in the photo sometimes up to 40 mph. On the highway, I'll get behind a line of trucks or cars and the wings will flap, indicating turbulence and reduced drag. If you dare, pulling up close to a truck will cause the wings to drop down, indicating that you are in the low pressure pocket behind the truck. Naughty bird!

Don't you hate it when you spend hundreds of dollars on instruments and some weirdo goes by you at 65 mpg with a stupid bird on his hood and a speedometer and a couple of idiot lights in his dash? Life ain't fair!

Perfect! After driving 50 miles home in a 25 MPH / Gusting to 40 MPH headwind today, I looked for flags or trees for an indicator. This (or a ribbon) gives you the perfect airspeed and direction. Brilliant!

In all seriousness, I'm worried about the battery. It's 6-7 years old, cranks slowly in cold weather, and could be taxing the alternator. I've often hit hard road bumps or rural/gravel road vibration in typical operation. There's a pull like the A/C engaging, which I'm convinced is the alternator draw.

An Ammeter would be ideal. Installing one seems to be a challenge (and a new batt -- is it too early???). It still starts!

RH77

The question was what are the three most useful gauges. You need a gauge to verify that you need to replace your 7-year-old battery? I use a load tester for that but I keep it in my tool box.

Also, the bird is not a yaw string. It conveys a lot more useful information.

I used to be gauge-happy. I had so many gauges on my XJ12 that I had to buy a dual-needle exhaust temp gauge because I ran out of holes. I'm a big fan of large tachometers and a fanatic for big pyrometers on big diesel engines. But those are all for performance applications. For economy purposes, if I were going to give you just one of all I've used over the years, I'd give you the bird. The bird rocks!

Well, I use a "yaw string" more for severe Weather reporting, but the longevity of a battery is not mutually exclusive. I've had some that have lasted 2 years under normal conditions, and this one, which starts the vehicle at 100F or -10F and is pushing the 7-year mark under severe conditions.

The odd part -- I engine-off coast and run the headlights, ventilation blower, and sometimes the rear window defrost under batt only. So far all I've noticed an A/C-like draw from time-to-time, which I suspect is the alternator. I have a multimeter, but it reads the voltage as 12.5V+ across the terminals when cold, and 14.1V+ when operational.

My fear is a failing batt with an overworked alt, but how do I make that conclusion?

RH77

Use a load tester. It's a metal box with a resistance circuit. You hook it up to your battery terminals and close the circuit. That enables a serious draw across a heater element. The needle on the gauge of the load tester will slowly drop as your battery charge falls off over ten seconds. If your battery cannot deliver a sufficient flow of electrons, the instrument will indicate that your battery is in need of replacement.

A tired battery will register 12.5 volts - the same as a strong battery - but it will fall off more quickly under load. A tired battery will also register 13-15 volts under charge from a healthy alternator but it will make the alternator work harder because as batteries age, sulfate flakes off the plates and creates a growing internal resistance. Older batteries do not stand up to the vibration of mobile applications as well as new batteries. I replace my mobile batteries after 3 years at most and use them for stationary applications if they are still strong.

BTW, when you coast engine off, if you are not on the accessory position but rather return to the ignition position to run accessory electrical systems after the engine quits, you are also energizing your alternator and coil, which is a boo-boo. A bigger boo-boo would be to accidently lock your steering column while futzing around.

I assume the "big box" auto parts places have the load tester device? I've helped replace batts on many other vehicles than my own where they test the load potential and the alternator production. I guess I let stuff like that go until it fails under normal conditions.

To save the alternator, I suppose it would be a good investment to have the test performed -- especially before Winter sets-in. I can say this, however: I let the batt go to slightly under 10V during a long period of drain while at a volunteer event this past summer. It would always start at 10-11V, charge to 14V or better at idle, and then shut it down and drain to 10V or less instead of idling. This occurred about 4-5 times this past year (storm spotting, with windows up and wipers/rear defrost running + ~100 Watt Radio transmission). I guess I'm optimistic that the batt is abnormally resilient...

RH77

That won't hurt it. You've got to run it down to 6-8 volts for permenant damage to set in. But if you do that a lot, and it sounds like you do, you should go to a dual battery system with a cheap solid state controller that isolates your (new) starting battery and runs your accessories off the old one (if it's worth keeping). That way, you never get stuck with a dead battery and you can always charge up the secondary battery. I would consider a small Optima glass mat for my primary battery. They are small, light and powerful and capable of deeper discharge than conventional lead acids. And you can sometimes get two into a space made for a larger battery. They're expensive, though.

After you get the new battery in you can desulfate the old one before you use it as your accessory bat.
Sears and many other stores sell a desulfating charger or you can ask an independent garage if they can/will do it for you. They will probably want 10 or 20 dollars for the job.
S.