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tacho problems


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#1 _T0rana_

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Posted 31 January 2006 - 04:28 PM

hey,

we installed a Autometer tacho into my uc torana and wen the car is idleing and going at low rev's the tacho jumps around Alot. could it be in the tuneing/coil ?
my engine is a red 6 with commodore electronic dizzy and standed coil.

#2 _draglc_

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Posted 31 January 2006 - 09:33 PM

have you tried screwing it to the floor? those jumping tachos can be a handfull..

:D

#3 FastEHHolden

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Posted 31 January 2006 - 10:06 PM

you have to put a resistor inline with it....other people will know what size

#4 rodomo

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Posted 01 February 2006 - 12:18 AM

Whats it running like?
If the module in the dizzy is in it's death throws, the tacho will bounce.
RACV MAN

#5 _devilsadvocate_

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Posted 01 February 2006 - 05:16 AM

Cant see from your pic whether you had the sle/sports dash or not, is the autometer the only tacho youve had it connected up to?
Rodomo's suggestion about the module also has merit, if you can get hold of a loaner module or swap over a whole electronic dizzy you could establish whether that is the concern. Ive experienced that one directly, car still ran fine, but module was putting out little spikes that interfered with tacho.

#6 _draglc_

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Posted 01 February 2006 - 07:11 AM

i didnt have to use a resistor with mine, simply ran the -ve from the tacho on the xu1 dash, the tacho is 500rpm out, and wired up the rest as normal and it works pefectly, needle is very steady.

A1

#7 _Keithy's_UC_

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Posted 01 February 2006 - 10:25 PM

I have that problem with my Tacho also... I have a brand new electronic commodore dizzy on mine, so i would rule that one out! I found that while driving it is fine, its only at idle, and while hot (doesnt do it much when cold idling).
I also have an in line resistor in mine (petentiometer), to sort the electronic dizzy electrowave problems, so that can be ruled out also.

I would check your coil - i think mine is on its way out, so ill get a new one and see how it goes.
Keith

#8 _greenmachine215_

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Posted 02 February 2006 - 10:03 PM

Go to dick smith electronics and ask for a 100k Potentiometer, Cut the wire that runs to your coil and solder the potentiometer inline, run the car and turn the potentiometer with a screw driver or by hand Depending on what style it is, Really its like a VOLUME Control

:D

#9 _draglc_

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Posted 02 February 2006 - 10:39 PM

so why would she need one and i dont?

A1

#10 _Keithy's_UC_

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Posted 10 February 2006 - 06:30 PM

Cos she's special!!

I have a petentiometer in mine, im telling you now that its useless... You can adjust it til the cows come home, it does not stop the jumping. I just replaced my Coil, Dizzy cap and Rotor button (the leads and plugs are also brand spankers), and it slowed down the jumping, but its still there! It stopped the flat spot i have with my car, so im going racing soon and aiming for 14's...

Keith

#11 antelopeslr5000

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Posted 16 February 2006 - 03:28 AM

What type of Autometer tachometer do you have, what is the tacho's RPM range?

For most high performance tacho's (tachos RPM range greater than 8000) a little jumpiness at idle or low revs is quite normal.

Now is time for me to put the flame suit on...

Let's face it, if you bought the tacho and are using for its intended purpose, who really cares what the engine is doing at idle or low revs anyway. You want a tacho that responds fast and operates smoothly in the high rev range, when is important to know and when it counts.

These high performance tachometers are designed with this is exactly mind and as a result of their design there exist a trade off, jumpiness at low revs for superoir high rpm performance.

Cos she's special!!

I have a petentiometer in mine, im telling you now that its useless...  You can adjust it til the cows come home, it does not stop the jumping.


Resistors in some instances may help reduce the jumping behaviour. By placing a resistor in the circuit of tachometers that use timing capactiors you can affectively change the RC time constant which has a filtering effect and help reduce erratic behaviour. So potentiometers may not be as useless as you may think if used correctly.

#12 _Keithy's_UC_

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Posted 22 February 2006 - 07:58 AM

Correct indeed - mine was adjusted by the company who fitted the tacho, by an auto electrician, and by me!! I still have it in line, but the tacho still jumps!! Funny to note: The tacho was fine with the 202, but as soon as i put the 179 in, i had problems...

And as i said before, ive put a brand new ignition system in (from top to tail) and it still jumps.... Must be something to do with the motor?? Earth leakage maybe??

Anyone else have suggestions?
Keith

#13 _ozjason_

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Posted 22 February 2006 - 01:06 PM

Two suggestions...

Firstly, the original poster mentions "standard coil". Standard coil for that car, or standard coil for the Commodore elect dizzy? If you're running the standard coil for that car, I'd try using the coil for the commodore, and see if that improves it. Might have to then remove the ballast resistance from the ignition to match the coil, but that's the way elec ignition is designed to run anyway. A quick test with the original wiring will tell you if that's the problem, anyway. Apologies if I've misread your meaning - you might already have this all set up just fine.

Secondly, you can buy an in-line diode for about $16 from various auto-elect places, that you put in line with the tacho. It stops the jumping and "dirty signal" issues with a points system. It's quite possible it'll help with the electronic system, too. The tachos that came with our red engines had these built in, but modern after market ones don't. A resistor may just dampen the signal, whereas a diode will filter some of the noise right out. (Interesting about the RC mentioned above, though...)

If you're in Brisbane, I can tell you where to buy one. Can't tell you the diode value, as mine came wrapped in heat shrink... can't read the value, but can tell you that it's just a diode soldered to spade connectors, and wrapped in heat shrink.

Just checked your sig - you are in Brisbane. Drop me a PM if you want to test with my diode before you buy one.

Cheers,
Jason.




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