Tacho Booster !

[brett_celicacoupe]

check the ECU specs, although it probly is indeed a 5V square wave.

if it is, then you can make up the circuit thats shown

[Hen]

Yes, the circuit Wilbo666 posted on the first page is what you need.

Have a read of this too (specifically the part titles "New engine/ECU outputting 5V square wave mating to voltage spike tacho").

[rokusan]

thankyou!!! i will try and set something up, can't wait to finaly see my revs

[Negative Boost]

Felt like grave digging and thought this might be the appropiate place to ask.

I started my MA61 up today which was the first time for a week or two and noticed the tacho dosn't work anymore. I only get the 1 orange light at the very bottom of the scale, so its getting power. I have a tacho booster from Sideshow and the following wires are.

12v
signal in
signal out
ground

I checked that im getting 12v and that it is grounding properly, all okay there.
I then checked the signal coming in, i forgot to take note of how many volts it was (may of been around 5v) but it defiantly went up when i revved the engine confirming i had a good signal in.
I then checked the signal out. (My battery is a bit flat, 11.3v when the engine wasn't running) I was getting a signal of ~6v out of the booster. When i free revved it to what sounded like ~3000rpm the signal out dropped to 5.6v. So its droping as the revs rise. I could also see the voltage drop ever so slightly as the car warmed up (increasing revs).
I also checked the wiring from the booster to the tacho and that is okay.

I don't understant how a tacho booster works (never did a electronics course of any kind) and was hopeing someone might be able to help me. Either i've busted the booster somehow (i did re-solder the 12v in wire 2 weeks ago) or something else has gone amis.

Is there any test i can do on the booster to confirm its gone bung or not?

[ViPeR_NiPPleX]

Provided everything else is as it should be, there's three things to test. The resistor (check if it's going high in resistance), the diode (check if it's shorted with a continuity test), or the transistor... which could be doing anything.

Beyond that. Buy the bits and make another one

[Negative Boost]

Thanks James, turned out to be something else even after i made my own adapter! Didn't find out it that worked or not though, looked dodgy since it was my first attempt at making something like that.

I had a B-Y wire supplying 12v to the adapter. But somewhere along the life of the car i'd lost the wire that goes to the glove box light. So last week i sourced the nearest 12v wire which was a straight B wire coming from the old unused M plug. Somehow this messed with my tacho causing it not to work.
Hook B wire to glove box light, no tacho. Un-hook B wire and leave dangling and the tacho worked. I dont understand it and i dont think i'll try but the main thing is that it now works again

[EldarO]

No, the whole point of the first circuit is to manufacture a voltage spike from a 5V or 12V square wave (hence the inductor).

The second one just adapts twin coils to a single coil dash.

Hen

sorry to drag up an old thread.

but will the second diagram (the one Hen posted) work with a 1UZFE into a 2JZGE powered JZA80?

Elmo.

[ViPeR_NiPPleX]

In theory it would pulse 8 times per 720deg revolution of crank, but the jza80 tach would be expecting 6.. so some sort of dividing circuit or tachometer manipulation would be required.

[Hen]

Another thing to bear in mind is that the 1UZ uses 2 4cylinder dizzys. So if you're taking pulses from the dizzys it will look like a 4 cylinder engine.

I am unsure what the ECU tacho output looks like. But I'd guess 1UZ ECU -> JZA80 dash tacho will just require some pulse divider as Viper suggests. Or just enjoy the view of your tacho showing redline at 10500rpm.

Hen

[ViPeR_NiPPleX]

well you could just take the tach signal from one coil, or if you combined both you would have an 8 cyl pulse cycle as no two cylinders fire at the same time.

I'd just wing it, who needs a tacho when you have a shift light and a working set of ears?

[EldarO]

not my car, i wish!

thanks for the info fellas ill keep searching for something concrete, needs to look factory

Elmo.

[TA-022]

well for the 1G into RA2X celica nothing was needed.

Open tacho ... measure resistance in and out .... bit of 4cyl to 6cyl maths and turned the dial to get the right reading.

Bingo bango acurate to 100rpm.

So maybe check inside the tach as i think other cars may also have this.
If not there should be a resistor perhaps that could be changed or replaced by a trimpot?

[EldarO]

hmmm... never thought about using a pot.

is that all? or did you use any other trickery?

id imagine that the 1UZ and 2JZGE use a similar type of single?! they're both newer and around the same age.

1UZ is UZZ32 i think...

Elmo.

[TA-022]

well you may / may not need a booster ... thats the 1st question.

then once you get the needle moving around its a case of changing the resistance from
6cyl to 8cyl.

from 4-6cyl resistance was like 9.79ohm standard and we did math (which didnt work LOL)
and then did a bit of trial and error and got within 100rpm (of a digi tach) at 10.90 ohm.

Resistance was measure at the start and end of the circuit. Which in my case was to screw heads on the back of the tach.

Careful cause i had two trim pots inside ... stuffed if i know what the other does but i guessed the right one! LOL

[CrUZida]

1UZ ecu has no tacho output.
Tacho signal comes straight from the ignitor and is the same signal as 2JZGE.


A lot of Toyota dashes already have the trimpot built into the dash.