Jimny Engine vs Sierra Tacho

Post by **greg** » Tue Jan 30, 2007 7:37 pm

Hi Team,

I'm helping a friend install a G13BB engine into a Sierra and we are having some trouble getting the Sierra Tacho to provide a reading.

Here's what we know:

The Sierra
Sierra Tacho expects 12volts - 1 "signal" for each time the Coil is run - which I guess means 4 "signals" for each revolution of the engine

The Jimny
The G13BB runs 2 coils. It has an output to go to the Jimny tacho, but the signal is different to the sierra - instead of 12 volts "flickering", the computer passes a signal from 1 to 5 or so volts that increases in volts as the revs increase.

The Ideas
So far I am thinking of catching the signal that goes to the two coil packs and feeding them into a "box" which would contain a diode (???) to ensure that no signal is fed down into the other coil accidently... From this box would come 1 wire that would then feed the Sierra Tach.

The Question
What do people of think of this cunning plan? Will it work? or have people used other tricks to make this connection work?

Alternatively, has anyone got an after market tach to work on a Jimny?

My friend, his car, and I will appreciate your feedback.

Thanks,
Greg[/b]

Post by **ljxtreem** » Tue Jan 30, 2007 8:00 pm

question! is this freinds sierra a black one with crawlers on it,
Where did you come from

and why do you ask such hard qeestions

I dont know

Mock

Post by **CHOPS1** » Tue Jan 30, 2007 9:21 pm

That sounds all to hard

I'd just buy after market one and put that on, some good cheap ones around.

Chop

Post by **want33s** » Tue Jan 30, 2007 9:46 pm

Your diode plan sounds like it will work as long as you use TWO diodes. One to stop one coil feeding the other and one to stop tacho backfeeding current into ignition.

Post by **jtraf** » Tue Jan 30, 2007 10:42 pm

my friend did a similar thing and said stuff it why not use the jimny tacho.......

Post by **Guy** » Wed Jan 31, 2007 8:23 am

You cant just use a signal from the alternator ?

Post by **Spike_Sierra** » Wed Jan 31, 2007 8:50 am

ive been trying to get my g13bb to accept a tacho for ages.
ive got a drover dash so no tacho standard(probably better i dont know what im revving it to

)

can you get aftermarket tachos that run like this(voltage up and down not pulse)

keep us updated!

Post by **mugginsmoo** » Wed Jan 31, 2007 10:16 am

greg,

tell your "friend" to remove the "innards" of the jimny Tacho and install them in behind the sierra face and wire it up as a jimny tacho.

i could help in this matter,

Mitch

Post by **Gwagensteve** » Wed Jan 31, 2007 8:32 pm

CHOPS1 wrote:That sounds all to hard I'd just buy after market one and put that on, some good cheap ones around.

Chop

Please tell Greg's friend where he can buy an aftermarket tachometer that will work with a coilpack engine.

Unlike many cars, the Jimny does not have a "tachometer drive" wire in the loom, the tach is driven by a square wave signal or similar (his friend is yet to put a oscilloscope on the output) which a) is not fired four times per revolution and B) is not a 12V signal.

Unfortunately the engine and gearbox that Greg's friend spent his hard earned on came without a cluster, so he doesn't have a jimny tach to work with, but that is one possibility. Does anyone have a jimny cluster lying around?

Steve.

Post by **spamwell** » Wed Nov 28, 2007 12:14 pm

how did everyone go with this?

about to sort mine out

Post by **mugginsmoo** » Wed Nov 28, 2007 1:19 pm

still the same, Gregs friends, poolcleaners wife has been driving around without a tach.

Post by **spamwell** » Wed Nov 28, 2007 1:59 pm

stuff that, might have to do the jimny innards thing.

Grimace!

Post by **spamwell** » Wed Nov 28, 2007 3:13 pm

or i could take out the dash board and put in 400 guages

Post by **Gwagensteve** » Wed Nov 28, 2007 7:03 pm

Apparently a bridge will work across both coil feeds - it will provide a similar signal to a normal tach.

I am in the process of doing a baleno (same coil pack arrangement) but we had a cut for this one so the innards have gone into the sierra dash. came up a treat but it is lots of work with the dremel and quite fiddly to fit.

I have used the Baleno face too (along with the baleno speedo face, as it will help to correct the speedo.)

Post by **Lil'Loki** » Sat Dec 01, 2007 2:12 pm

I dig the 200kph mark on the speedo face.

Post by **Gwagensteve** » Sat Dec 01, 2007 3:05 pm

Especially as the car it's going into would only do about 155kph on the limiter in top gear.

100kph on the baleno face equals about 85kph on the sierra face so it's quite a useful way to correct for big tyres.

The speedo also has a VSS in it from a mid 80's swift - they must have used the vss to control egr or something - but its a legit VSS and will work fine with the baleno computer.

There's a bit of work gone into that dash!

Steve.

Post by **Lil'Loki** » Sat Dec 01, 2007 5:06 pm

Is that a Sierra doing 155kph? I'd be s#$%ing myself. The last time (and the only time) I got my Sierra close to that speed, was on the Brand Hwy (heading south by Eneabba WA) going down hill with a strong wind from behindâ€¦

140kph (the highest mark on a stock sierra dash), steering started to disappear as the front started to lift.

Post by **Gwagensteve** » Sun Dec 02, 2007 9:03 am

No , no plans for it to go that quick - my point is that thats it's gearing induced top speed - far lower than a stock sierra .

A stock sierra @ 6500 in 5th would be doing 196 km/h, if it had the power to push the car along at that speed.

I don't think the car the dash is going into could do 155 either.

Post by **spamwell** » Sun Dec 02, 2007 12:04 pm

i'm going to give the coil bridge tacho idea a go.

will put diodes in to stop the coils fireing each other

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