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Did a swap from bluetop 4age to silvertop,
on my replica seven. Everything runs ok, on
"low-cost" home-made harness, except tach.
Negative coil source puts needle at 3000 rpm
and stays there put.
Some suggest ECU direct signal, there seems to be
none in my case.
Any suggestions to locate tach signal on 20 valves
Toyota mill will be appreciated.

Ewhen

PS. Distibuter harnes ? which wire ?

Hi Ewhen,
The negative (-) side of the coil must provide a decent tach signal. If the engine runs (3000rpm?) the ignition coil is being triggered, regardless of the actual rpm.

Are you certain that you've properly identified the negative side of the coil? What are you using for a tach? Does the tach work properly on another vehicle? Is this an aftermarket tach that needs to be set for the # of cylinders?

You shouldn't need to go near the ECU to pick up that signal.

What ignition coil are you using? You should be able to ID the negative side of the coil with a simple test light if there are no markings. During crank, the + side will give you a steady light, the - side will flash or dim (depending on the type of module you're using), as it switches.

Geoff

hi dad did some research for your tach
that's the answer i got



Posté le: Mer Avr 20, 2011 9:52 pm Sujet du message: swap bluetop a silver

jai un swap blue a silver toute fonctionne sauf
le tach il indique 3000 rpm c'est toute c'est le cluster
du blue ya tu une facon de branché pour que le tach fonctionne?

merci Claude
....................................................................................................................................

Messages: 1498
Localisation: Windsor mills
Posté le: Mer Avr 20, 2011 10:46 pm

Si je me trompe pas ca prend un ptit module ou un convertisseur de signal pour ton tach...

Désolé de pas pouvoir te donner plus d'infos.
________________


califkid_66

Inscrit le: 02 Juil 2008
Messages: 70
Localisation: Montcalm

Posté le: Jeu Avr 21, 2011 6:23 am Sujet du message:

si je comprend bien le tach du cluster blue est pas compatible
avec le signal du silver

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Vavais
Moderateur


Inscrit le: 21 Mai 2007
Messages: 892
Localisation: Québec
Posté le: Jeu Avr 21, 2011 10:47 am Sujet du message:

Exact.. bref le signal d'un silver/black top ne sont pas comme celui d'un bleutop..

Donc ca te prends un convertisseur ou un tack aftermarkette..
_________________

If you are using the original Toyota harness and ECU, use the number 4 (black wire) on the 26 pin plug. That is what runs my tach which is a SW tach switched to 4 cylinder on my silvertop.

what is a sw tach ?

Claude

Stewart Warner.

Thanks Geoff
The tach is from 4age, and when connected to negative on coil
it freezes at 3000 rpm, regardless of engine speed difference.
Some models of Toyota are using signal from distributor loom.
Others are getting pulsation from igniter. (didn't check this one)
Anyway, thanks again for the input.
Eugene
(ewhen in ukie)

Hi Graham
Nr 4 on our 26 pin connector shows black wire going to-from
crankshaft position sensor. ECU is for manual tranny.
Tach is from 4age Corolla.Will check this one for pulsation.
Thanks
Eugene

Hi Claude
(The signal from bluetop is not the same as silvertop)
I wanted to bring that car to Sanair track ,so you could
try it out, maybe me too. All to be done is that darn tach.
Well, we still have a week or so.
Too bad about our "low-cost home-made" personalized
gauges, guess we have to slap aftermarket gizmos into
those stainless boxes.
Cheers Dad

Hi Claude
Found interesting article on tach signal source
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The "old" style ignition system is pretty straight forward. A cam shaft inside the distributor opens an closes a set of contacts(points) which when closed, allow current to flow in the coil primary. The frequency of these "pulses of current" are directly proportional to how fast (RPMs) the engine is running. So merely running a wire to the "hot side" of the coil primary ( the other connection on the coil is typically tied to ground) and we have the "tach signal"

The "new" style electronic ignition systems is whole different world. This system is computer controlled and basically uses three sensors ( 7 x Crankshaft position sensor, 24 x Crankshaft sensor and camshaft position sensor) to calculate engine rpm, when to fire the injector solenoids and how much to advance/retard spark among other things. So there really is no "tach wire" per se.

The three sensors typically are two "hall effect" and one "reluctance pickup" (the 7 X crank sensor which is the HEART of the system without which the engine will NOT start). So it probably is not a good idea to try to tap one of these signals to use as the tach signal. Probably the best way to "create" a tach wire is to pick off one of the fuel injector solenoid signals ( any one will do. However, you must be absolutely sure of the correct wire for as we know, a screwed up 'computer" replacement is huge bucks. Basically, each injector solenoid has 2 wires. One wire is "common" ( the same color at each solenoid) and is tied to +12V through usually a 20 amp fuse labeled INJ/COIL in the fuse panel. Each individual other wire on each solenoid goes through the harness and back to the computer which switches (pulses) that wire to ground to activate the injector at a frequency proportional to engine RPM . ( identified by the service manual) and bingo, there's your "tach signal".
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Greets
Dad

Dad,
It's not likely that an injector pulse will provide an accurate tach signal. The engine completes 720 degrees of rotation for every injector pulse during the intake stroke.

If you are using an old style ignition coil and a distributor, the negative side of the coil is the simplest and most accessible choice. I have used OE Toyota gauge guts a number of times including the tach, when making dashboards. While I haven't seen the steady 3000 rpm condition before, it occurs that you may be coming off the wrong side of the coil.

The ignitor is also a good source as the RPM signal for the ECU is provided by it.

Geoff

Hi Claude
The above text (french) says that tachometer from 4AGE
Toyota bluetop will not function in silvertop 20 , because tach signal differs between both engines. That statement is erroneous, the wire (black with red spots) from igniter does
trigger any Toyo 4 cyl. tach, including aftermarket gizmos.
Included is pic of Loti replica.s office, with tach at iddle.

Eugene
(Ewhen)

Unique too! Well done.

Geoff

Hi There !
We tried different manners to find the signal wire for the
Tachometer , now the problem has been solved.
We wish to thank you all at Lokost forum for the input .

That dash looks great Ewen. Nice work.