Toyota electronic speedos: feed signal?

[wagonist]

As part of an engine conversion, I need to change the speedo from a cable driven setup to an electronic setup. This is because the newer engine & matching ECU (04 Hyundai Elantra) I'm using won't accept the signal from the back of the cable driven cluster currently in use (98 Excel).

I've got the electronic gearbox sender for the Elantra which will give the ECU the correct reading, but I'd still like a speedo readout because there is still the possibility that the Excel will be used for rallying, which requires it to be "roadworthy".

The Elantra cluster is too big to fit into the Excel dashboard, and the circuit board on the back of the cluster is too complicated to work out the feed signals that the speedo itself gets.

Therefore, I am looking at using a Toyota electronic speedo because I know they were in cars from at least the early 90s, which still use mechanical odos driven by an electric motor & are a lot simpler. But I need to find out if I can get the Elantra ECU to feed the Toyota speedo.

I'm aiming to put the speedo where the radio was so I can put a decent sized tacho in the middle of the cluster instead (where it should be), so size isn't important.

[masterofsinanju]

Steve, this isn't quite what you are asking for but have you considered an inline sender? It essentially plugs into the speedo cable, produces a signal for the ECU and then passes the mechanical signal through to the mechanical speedo. You can get them as a reed switch (two wires) or Hall effect sensor (three wires). All legal and roadworthy friendly.

A bit simpler install and keeps your dash neat too.

[wagonist]

The problem is I haven't been able to find out (as yet) what signal the Elantra sender produces. I'm trying to get hold of an oscilliscope so I can actually spin up with a drill the Elantra sender & also the cable plus cluster for the Excel to confirm what I've read on the internet about the signals not being compatible (you know how reliable the internet can be... )
I know Jaycar do a "speedo coprrector", but I daresay this is just to move the signal range for altered gearing rather than changign the signal itself.

Not too worried about keeping the dash "neat" as "roadworthy" means something slightly different for rally cars. I just want to have a decent sized tacho (the Excel one replaces the water temp guage so is only 50mm or so diameter) and a speedo that works.

[dumbass]

its should be 3 wire square wave
anyway why would u fk around trying to fit a toyota speedo
a speedo is useless if its innaccurate
so what are the chances of fitting a toyota electric speedo and it readig accurate
just find the cheapest electric speedo and get that and fit it
then u can calibrate it as many times u like and it wont cost u anything extra
so if you change diffs its easy to recalibrate
otherwise if get a toyota speedo then u need to fit calibration boxes so in the end its easier to just fit an aftermarket electric speedo

[wagonist]

I'm only for an approximate ball park figure for the speed. My track rims are too big for the Excel box, and too small for the Elantra box I've just fitted. I've just had the box apart to fit an LSD, it ain't getting pulled apart again for a VERY long time, and changing the diff ratio would entail changing the entire output shaft.

I suppose there's the whole issue with diff ratios (which I hadn't thought of til you brought it up, so thanks for that).

I was exploring options for a cheap solution (it is still only an Excel after all), but sounds like this one might be a bit hard.

I found a guy who makes an LCD digital speedo/odometer for $180. This may be able to fit where the tacho is currently, so may be the best idea as long as I can get it shielded from direct sunlight.

[dumbass]

just did a search on ebay for digital speedometer
theres afew in usa under 200 bucks
might be another option but they r in mph
some might be able to be changed

[wagonist]

Yeah, I'd done that too. The other place was the UK, which are also MPH.

[dumbass]

u can always forgot the mph and jsut calibrate it to the number is correct for kph

[wagonist]

which is prob ok for the digital type, but most of the dial type still only went to about 120MPH.
Even with the standard 1500cc, I get to more than that on Wakefield's main straight.

I'm a bit worried about the toughness of the components & circuitry in cheap Ebay things. It is going in a rally car. These things get shaken around a lot (we tighten the suspension bolts every service, and they need it)

[JDM hachi]

Thinking outside the square...... will the elantra cluster as a whole, fit into the glove box? the fact a speedo is present should surely satisfy the regulations if one mounted where the radio was satisfies the regulations.

If you present your car with the glove box open on inspection could solve the problem, or alternatively, how will they (the scrutineers) know the speedo in your excell cluster doesn't work, do they drive the car ever?

matty.

[wagonist]

no, too big, but pointless though. Bit hard to read it whilst driving.
And if you think that speeding fines are high, try a CAMS fine for speeding on a rally's transport stage.

Scrutineers couldn't give a crap about the speedo.

I'm trying to track down a wrecker that has the 2nd model Accent and will sell a cluster for a reasonable price (ie less than what I can buy an aftermarket speedo for), because these have the electronic speedo also which are compatible & the whole cluster might be made to fit, but sourcing the wiring layout for the pins is a real bastard.
The Hyundai documentation is really difficult to follow, I ended up tracing the wiring loom of the Elantra to work out tacho wires, etc.

[wagonist]

Nice idea about thinking outside the square. Bit similar to my idea of fitting the speedo in the radio's space.

Anyone know where I can get hold of an oscilliscope? If I can determine the signal generated by the Elantra sender (and hence required by the ECU), then I may be able to get something inline to the cable like what masterofsinanju suggested.
I'm already going to need something like this for the rally trip computer.

It would be the simplest method.
Still stuck with the small tacho setup, but could still relocate the mech speedo to the radio space to install a larger tacho anyways.

[dumbass]

pretty sure they are 3 wire speed sensor
which is square wave

if u need to register the car the speedo neds to be close to orig spot
or the coppers will have a field day

[wagonist]

registration is a relative term for rally cars
Unfortunately, there's no rally reg scheme in NSW (so most just operate off unregistered vehicle permits), but there are registration requirements which have some exceptions made.

Yes, the sensor is a 3 wire, 12v, earth & signal to ECU & cluster. So I agree it is probably a square wave.
I think most cluster generated speed signals are a sine wave.

Is amplitude & frequency important for these things in matching a signal? That's what I'd like to determine.

[dumbass]

yes signal output from speedo is normally a reed switch to ground
frequency and amplitude isnt an issue
main thing is if the pull up resistor is inside speedo or inside speed sensor
toyota speed sensors have it in side them
holden speedometer have it inside them
so if it doesnt work then fit a pullup resistor from signal to 12v