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Author Topic: Voltage or amp-meter?  (Read 12575 times)
krede
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« on: January 01, 2007, 01:47:31 pm »

At the extreme risk of sounding foolish, I ask the question... is it a volt ot amp meter thats fitted to the dash of the murena?
I havent had the chance to mess with mine yet(mine isnt working like it should), so Id have to use what written material I have on the issue.
On the wireing plans I have its listed as a voltmeter, but in simons spare catalogue its an amp meter!.. so... wich one is it?  Huh
From the top of my head id guess voltmeter.. but its really just a guess
« Last Edit: January 01, 2007, 05:29:49 pm by Lennart Sorth » Logged
Anders Dinsen
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« Reply #1 on: January 01, 2007, 05:17:08 pm »

It is a voltmeter... or as I posted previously a combination of an interior thermometer and voltmeter Wink

In fact it consists of a bimetallic strip with a coil of resistor wire around - when heated, the strip bends. The amount of heat the coil produces depends on the voltage.

DO NOT rely on it to claim either generator or battery to be defective, always measure on it with a real voltmeter.

- anders
« Last Edit: January 01, 2007, 05:23:07 pm by Anders Dinsen » Logged

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Lennart Sorth
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« Reply #2 on: January 01, 2007, 05:33:40 pm »

DO NOT rely on it to claim either generator or battery to be defective, always measure on it with a real voltmeter.
And I will add: DO NOT rely on an external voltmeter either, unless you fit a fresh battery in it :-)

I just almost condemned my battery/alternator/regulator, as my digital voltmeter measured 16 Volts (!).  The dash voltmeter was fine, - and in this case it was actually the most accurate!  A new battery in my digivoltmeter at the voltage read 14.5 on the battery while charging :-)

/Lennart
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Lennart.Sorth@matrasport.dk
Murena 1983 1.9i silver // Alfa Romeo Giulietta 2.0d 2012 white // Smart 4two cdi 2010 blue //
krede
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« Reply #3 on: January 01, 2007, 05:56:59 pm »

Im fitting digital instrumentation to my murena when i get home... I know some might not approve of this as its a "classic " car, but I think they will suit a wired french car like the murena quite well.  Smiley.
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Anders Dinsen
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« Reply #4 on: January 01, 2007, 06:27:25 pm »

DO NOT rely on it to claim either generator or battery to be defective, always measure on it with a real voltmeter.
And I will add: DO NOT rely on an external voltmeter either, unless you fit a fresh battery in it :-)

I just almost condemned my battery/alternator/regulator, as my digital voltmeter measured 16 Volts (!).  The dash voltmeter was fine, - and in this case it was actually the most accurate!  A new battery in my digivoltmeter at the voltage read 14.5 on the battery while charging :-)

/Lennart

And while we are in the DO NOT section, I'd like to add that you should never rely on a cheap 100 kr (10£) multimeter either!

Quote
Im fitting digital instrumentation to my murena when i get home... I know some might not approve of this as its a "classic " car, but I think they will suit a wired french car like the murena quite well.

NOOOOOOOOOOOOOOOOO WHAT'S HAPPENING TO YOU MAN!!!!?Huh (banging head hard into the wall, think it will need fixing - wall and head)
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krede
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« Reply #5 on: January 01, 2007, 06:40:44 pm »

I guess its a matter of taste.
I think it goes well with the style of it... I was considering using the panel from the citroen bx digital.. but those were just plain awfull
I will make a complete dash to fit in place of the original, and thus not make any "irreversible" changes to my car.
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« Reply #6 on: January 01, 2007, 06:47:17 pm »

I guess its a matter of taste.
I think it goes well with the style of it... I was considering using the panel from the citroen bx digital.. but those were just plain awfull
I will make a complete dash to fit in place of the original, and thus not make any "irreversible" changes to my car.

Hey, you're a nice guy, so I guess we can forgive you.... Grin
Is it a modern racer style panel or something you rip off a used car?
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krede
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« Reply #7 on: January 01, 2007, 06:54:50 pm »

My first  thought was, to piece something togeather from what is availeble on ebay. Various vdo porsche 911 and 944 gauges are nice, but I finally came across some from a manufacturer called "Nordskog".
They are digital, with red numbers that completely blacks out when not in use.
it will be ok.. I promise..... I wont "go german" on the poor eel... I just want some fancy gauges....I CAN TRUST!!  Wink
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Lennart Sorth
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« Reply #8 on: January 01, 2007, 08:46:42 pm »

Owning a car with digital instruments (Espace JE) I must say it is NOT my favourite. I really dislike it when I get distracted to look at the dashboard just because the amount of light emitted by showing "109" is much more than "111" (km/h that is)

However, I think having a more or less hidden digital readout of a number of nifty parameters would be excellent. Maybe one could fit a fold-up LCD display in the ashtray - sort of like the Blaupunkt GPS system. Pull it out, and you have a multifunction "telemetry" readout of everything your heart desire.

Possibly also with the ability of showing just one of the readouts in huge, (friendly?) digits, so you can see them while driving.

Now what would we like such a system to show us?
  *  Coolant-temp near engine
  *  Coolant-temp near radiator
  *  Coolant-temp near heater matrix (?)
  *  Inlet air temp
  *  engine oil temperature
  *  engine oil pressure
  *  gearbox oil temp (?)
  *  Voltages - several places
  *  fuel-gauge
  *  speed
  *  engine revs
 
And how about using a lambda sensor to tell about the amount of oxygene in the exhaust ? - just for the measurements sake.  Could also be nice to know, when adjusting carbs.

Personaly I'd love to also include support for some webcams, - as I really would like to see how much the engine moves about while accellerating, or parts of the suspension. Does anyone e.g. know how much the trailing arms flex while driving through a curve ?

Maybe what I'm looking after is a full-scale telemetry system, with and interface to a laptop, rather than a little multifunction display.


/Lennart
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« Reply #9 on: January 01, 2007, 09:58:40 pm »

My first  thought was, to piece something togeather from what is availeble on ebay. Various vdo porsche 911 and 944 gauges are nice, but I finally came across some from a manufacturer called "Nordskog".
They are digital, with red numbers that completely blacks out when not in use.
it will be ok.. I promise..... I wont "go german" on the poor eel... I just want some fancy gauges....I CAN TRUST!!  Wink

The Murena gauges are qute reliable and trustworthy. Except for the voltmeter, that is, but this was obviously never intended to display anything but a rough indication of the voltage. The speedometer is in fact very precise, and far more than most other cars that has a mis-display of about 5-10% (usually to the high side). The rev counter could be better, but when you think about it you don't really need an exact readout of the engine rpm.

The same applies to water temperature and oil pressure, in fact: You cannot really use the exact numbers for anything. Coolant temperature is dependent on the water pressure at the pick up point, and the exact number will tell you nothing about whether the coolant is close to boiling or not (or even whether it does local boiling inside the cylinder head). As for oil pressure, what you will be looking for are pressure drops that could indicate problems - whether the oil pressure is 3.0 or 3.5 bars will tell you nothing. By the way, oil pressure will also be dependent on engine temperature (since the viscosity of the oil is). This is why your gauge shows a higher number when cold than when hot.

If you want something reliable, why not stick with what has worked in the car for the last 25 years?

Lennart, I like your idea of a small display hidden in the ash tray. Telemetry is an interesting issue, but the problem is not so much the read out or the recorder - it's the sensors. Besides, engine data isn't quite enough, you'd also want to record suspension travel, drive shaft torque and real time tyre pressure! But then, you'd be able to compete with the professional racers Cheesy

- Anders

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« Reply #10 on: January 01, 2007, 11:51:03 pm »

but the problem is not so much the read out or the recorder - it's the sensors.

Oh yes, I am fully aware of that - and yes, getting suspension travel input too would be marvellous. I'm a data-freak, which is why my new job in the UK concerns petabytes of storage :-)

I recently spoke to a guy racing a Ginetta, who had the entire car rigged with sensors, which were recorded while he was driving. Then when he got home, he could spend hours looking through the data, and look for possible optimization. That car went like stink! - outpacing almost anything out there - and it sounded gorgeous, despite it being (I think) a tiny 1000ccm.
(http://www.sorth.dk/p/20060910/Med/dsc_5630.html)

In my son's P106 (well, my spare-car) he fitted a huuuuuge (1600W!) stereo, which initially looks quite normal, - everything exceptional is hidden.  There is a remote control to adjust the 12"  subwoofer, hidden in:    the ashtray!      Cool feature :-)

(And none of my cars will ever see their ashtray used for ashes anyway, - smoking is banned)

In the same way, I'd love to "rig" my Murena for data-collection, while keeping its appearence close to normal. I have sometimes thought of replacing the voltmeter with a real calibrated voltmeter - but in 11 years of ownership, I have learned to interpret the original one so well, that it really makes no difference.
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Anders Dinsen
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« Reply #11 on: January 02, 2007, 12:39:27 am »

In the same way, I'd love to "rig" my Murena for data-collection, while keeping its appearence close to normal.

Sounds like we should get something going there, Lennart...!
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krede
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« Reply #12 on: January 02, 2007, 10:10:32 am »

Apart from the speedo, and tacho Ill be fitting voltmeter,fuel gauge, oil pressure, air- fuel gauge (i got it cheap on ebay) and water temperature.. so pretty much the same as is in the car at the moment.
perhaps oiltemp, charge perssure and inlet airtemp will follow later on..   
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Anders Dinsen
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« Reply #13 on: January 02, 2007, 07:39:09 pm »

Apart from the speedo, and tacho Ill be fitting voltmeter,fuel gauge, oil pressure, air- fuel gauge (i got it cheap on ebay) and water temperature.. so pretty much the same as is in the car at the moment.
perhaps oiltemp, charge perssure and inlet airtemp will follow later on..   

Good luck with the project! It will be fun to see it in action :-)

I noticed that the documentation on the sensors is in the workshop manual, you will probably need that to adjust the instruments.

- Anders
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Matra_Hans
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« Reply #14 on: January 03, 2007, 07:36:09 pm »

I can see on Nordskog homepage that they have some rather interesting stuff. In the Bagheera Type I Matra tried to make an instrument panel that blacked out when the ignition was not on but it did not work so good. So Krede’s coming Murena instrument panel might end up looking like something that the Matra engineers dreamt about.
Nordskog’s speedometers can be adjusted to fit any gearing or tyre size. Further they have speedos that are based on GPS signal so you get the correct speed reading no matter how much wheel spin you have maybe not so useful on the Murena that gets the speed signal from the front wheels. Nordskog also has speedometers that is good for up to 300 mph that is 480 km/h how much power do we need in a Murena in order to utilize that?

Regards Hans
« Last Edit: January 03, 2007, 07:43:35 pm by Lennart Sorth » Logged
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