FIAT tacho on a V6

[CorseChris]

Folks,

In case anyone has a mind, the FIAT 124 tacho can be easily recalibrated for use with the Alfa V6. I just got around to testing one I repaired recently. I connected it up on my 164 and with a quick twiddle of the preset inside the tacho, was able to get it to match the 164 tacho from idle to 4000 rpm no problem at all. I didn't bother going any higher than that - the rev limiter can take care of it if needed :)


I'll take some pictures tonight of an easy way to access the adjustment without having to strip the tacho from it's case.

Chris

[chris.richard]

Looking forward to the photos - is this the same tacho as the 124 sport as used on the original Stratos?

Does any one know a source for Veglia Borreli instruments? My set is the proper Sport ones, but it has a clock which Stratos pictures don't, and doesn't have the temp olio or a Volt or ammeter to complete the set.

[rutthenut]

Originally posted by chris.richard
Does any one know a source for Veglia Borreli instruments? My set is the proper Sport ones, but it has a clock which Stratos pictures don't, and doesn't have the temp olio or a Volt or ammeter to complete the set.

The phrase 'hens teeth' comes to mind.

You just have to strike it lucky and spot these particular instruments at auto jumbles and parts stands. These may be at quite a high price, due to their relative rarity, but not all suppliers will know this so you may get a good deal from time to time.

Some people (Guy) are a bit luckier at this, but that brings to mind another phrase along the lines of 'the harder I work at it, the luckier I get'.

One alternative option is to buy a generic oil temp gauge and volt/ammeter and use those, possibly changing the bezel surround from chrome to black, etc. Or maybe changing the face entirely. This all starts to get tricky though, and if the needle points in the wrong direction and does not have the same 'cutout' it will never look quite right.

I think it is also possible to modify some Veglia instruments types to use, for instance, a water termp gauge as an oil temp gauge, but this is not something I've considered.

Another can of worms really, trying to get accurate-looking gauges for the car without a great deal of effort or possibly a fair bit of cash.

[rutthenut]

Originally posted by CorseChris
Errr, didn't I just say I've done this successfully???

I was referring to temp gauges and ammeters/voltmeters, not tacho's.

Can you tweak these just as easily?
(I think Guy has found that some can be simply substituted in certain cases)

And have you got inserts to display the correct text for the front of the dials? That would be something of interest for this type of conversion.

[chris.richard]

I suppose that nowadays with digital cameras, scanners, colour printers and image editing software it should be able to produce them cheaply, relatively easily, but it would take a lot of time and effort, which tends to be in short supply.

[mogul_x]

Chris,

I've had relatively good luck finding gauges on E-bay, although not the two you are looking for. I've seen a bunch of Fiat 124 and 850 Spyder sets, but these usually don't have either the ammeter or oil temp gauge.

I bought my oil temp gauge from John Brewer, who is converting his car to Gp.4 dash and VDO gauges. I also got his ammeter, which is an aftemarket unit. It has a black bezel and face, so it almost blends in with the other gauges, but it is still noticably different.

I thought Chris Smith was supposed to be working on a reproduction Veglia ammeter face for a standard aftermarket gauge. He was going to do a run of 50, or something like that. Maybe it was 20. At any rate, anybody heard from Chris lately on the subject?

I know I expressed interest in one after he put the ad in the club newsletter.

[JohnB_SPY8808053]

Before anyone makes fun of me for using the VDO gauges, I just want to point out that the original G4 gauges are outrageously expensive. So much so that many real cars with the G4 dash do not have the correct gauges. When I finally found a guy that might be able to get a set, I was quoted $2500 for the tach and almost that much for the dual temp gauge. For what the set cost, I could have bought a nice V6. You might be able to find them cheaper if you really worked at it but there's no telling how long it would take to get a full set. The VDO gauges are the right size and look but didn't break my (all too fragile) wallet. The only visual difference is that the needles are red instead of white and the tachometer has the wrong orientation. I do plan t have the tachometer faceplate repainted but it's not a particularly high priority.

Ciao,

John B.

[rutthenut]

Originally posted by CorseChris
John,

We seem to be talking at crossed purposes here. Are we suffering an update delay maybe?? I see a similar thing happened the other day on the thread about strut top mountings where I replied with a bit of specific info, then you followed it up a short while later with the same thing (plus some other info).

Put it down to brain-fade on my part. :eek:

[CorseChris]

Originally posted by chris.richard
I suppose that nowadays with digital cameras, scanners, colour printers and image editing software it should be able to produce them cheaply, relatively easily, but it would take a lot of time and effort, which tends to be in short supply.


Chris, do you know, that's a damn fine idea!! When I did my own oil temp gauge, the method of assembly of the scale to the instrument put me off stripping it down too far as it looked like it might be a one-way trip. Maybe some time I will have a look at a spare gauge and see if I can come up with some sort of slot-in replacement scale template that could be reproduced simply at home. Once the glass front goes back on the instrument, the actual finish (matt, gloss etc) on the scale isn't too important of course.

It looks like our brief summer building season is over, so it seems I am going to be at a loose end for another 6 months once again. Maybe I can do somehting useful for a change.....

[CorseChris]

OK, finally got round to doing some pictures.

You should find 4 in my personal folder plus one other that went in the general kit build area by mistake.

One shows where you need to drill a new hole in the case - be VERY careful when doing this. You'll also want to make sure that any swarf is removed via the bulb holder holes.

Next shows the hole from the inside for reference.

Next is a side view of the case with a screw in the new hole showing the angle needed to reach the adjustment.

Lastly is a shot of the PCB showing the actual pot (it's the thing smack in the middle of the shot). There is a small rectangular slot in the middle where the adjuster goes. It's normally OK to use a small screwdriver but better to use a proper core adjuster if you can find one. Cut down knitting needles work well too.

Having drilled the hole and taken the pictures, I have concluded it's probably best to remove the internals from the case to do this job as it's easy to damage the pot if you're not careful. Difficult to be careful when you can't actually see what you are trying to tweek!!

Adjustment procedure is simple. Connect up to V6. One wire to ground, one to +12, one to coil -ve. Start engine, match 124 tacho to 164 tacho as closely as you can. Don't expect it to be perfect across the whole range - they never are. I aimed for getting idle and 4000 rpm right which was easy enough to achieve and wasn't too painful on my ears. Make sure you hold the instrument in the correct attitude (i.e. the one it is in when installed in the car) as you adjust it, since it is sensitive to orientation. I plan on keeping the tacho from my 164 when I scrap it so could be persuaded to offer an alignment 'service'.


Hope this helps someone out there. If you have a tacho that has died, let me know as I can give you info on the likely components that have failed. Usual reason is connecting it up with ground and +12 reversed. They have an 'idiot' diode fitted, but the PCB design is poor and prevents the diode doing it's job properly. (The short circuit current through the idiot diode burns out the PCB track and disconnects the diode, but leaves a path to the rest of the circuit so all the semiconductors get killed anyway).

[chris.richard]

Originally posted by CorseChris
I plan on keeping the tacho from my 164 when I scrap it so could be persuaded to offer an alignment 'service'.




Does this offer still stand Chris? I've just taken my dash out, and it's one of the jobs coming up the "to do" list. I haven't got access to another V6 to calibrate on.

[guy mayers]

Looks like this thread is a must for reproduction in the newsletter John!

[CorseChris]

Chris,


Well, I didn't keep the 164 dash in the end. I was trying to tidy up a bit so thought I would remove the tacho from the rest of the dash..... how naive! The 164 dash is one great big printed circuit board with everything on it so it wasn't practical to remove the tacho. Looking at it, it's probably programmable for the entire model range.

I do however have a calibrated Veglia tacho that I did ready for when I fit my V6. I also happen to have a 6 cylinder engine in my Jeep that uses a single coil so also have a calibration reference as well. Unfortunately, the V6 in my 155 has a multi-coil ignition setup so doesn't produce a suitable signal we could use. Do you mind it not being calibrated on an Italian engine? ;)

Let me know if you'd like to send it to me for 'treatment'

Cheers

Chris

[chris.richard]

I'm about to show my electronic ignorance here! My tacho is to hook up to the 24v, where the tach signal comes from the ECU, not a coil (it has individual coils on each plug, which sounds the same as your 155). Will this work?

Gratefully yours,

Chris

[CorseChris]

Ah......I'd completely forgotten you are fitting a 24valve motor.

....that'll be a bit harder then. Anyone know what the tacho drive signal looks like? I've not looked at a 24valve ECU so suspect this is going to be a little harder. If anyone else has already done this, please pipe up now!

If not, then it's probably time for somebody with a 24valve motor in either a 164 or a strat to pay me a visit so we can have a prod about with it....... first guess would be that the ECU drives the tacho with a 12v pulse, probably at a frequency you'd get out of a single-coil system. If so, it might be fairly simple to mod the Fiat tacho to remove the input signal conditioning to make it read OK without the benefit of the big spikes it usually picks up. Another option might be to try and sniff off one of the coils and hope the tacho can be persuaded to effectively over-read enough (going from a 4 cylinder to a 1 cylinder engine).

But this is all just plain guesswork.

Yet another option could be to re-case a programmable unit.
Starting to get desperate now though.......

[David May]

The rev counter output signal from my Q4 Bosch M3.7 ECU is 0 -> 5V.

Dave May

[CorseChris]

Thanks Dave. Don't happen to know it's frequency relationship to crank speed do you?

Chris

[chris.richard]

Mine is the Motronic 1.7
Found this in the manual.

[David May]

My Bosch pulse output gives 3 impulses / rev = 400Hz @ 8000rpm.

Dave May

[CorseChris]

Dave,

That's encouraging (and sensible) - same as one would get from a traditional single coil setup on a 6 cylinder engine.

Chris, assuming(!) that the pulse is the same or similar on your ECU then it's probably a fair bet that the Fiat tacho can be modified without too much bother.

It's probably worth me having a look at the tacho pulse coming out of the ECU on my 155 as well - likely to be the same as well. If so, and if I get the time, I'll have a play at getting a spare Fiat tacho to play ball.

[chris.richard]

Fingers crossed! Which injection system does the 155 use?

[CorseChris]

Originally posted by chris.richard
Fingers crossed! Which injection system does the 155 use?

Motronic M1.7. Same in most 155s apart from the Q4 and 2.0 TS apparently.

I am assuming your engine has coil-per-cylinder.

[chris.richard]

Originally posted by CorseChris



I am assuming your engine has coil-per-cylinder.

Yes, it does.

[CorseChris]

The 155 has a 6 pole coil (actually 3 double ended ones in a big lump, couple dwith a 3 channel driver) so is controlled by 3 channels from the ECU. I wonder if the coils on the 24V are driven in pairs...

...not that any of this really matters to getting your tacho working from the engine speed signal that's already available of course....

Assuming I haven't completely lost the will to go on after another fun day at work, I'll have a look at the 155 wiring tonight and try and have a play with it tomorrow. ECU access isn't too bad on my car so I should be able to get at the tacho feed without having to rip the dash or interior apart.... (too much anyway).

How urgent is your need to get this sorted by the way?

[chris.richard]

Not for a week or two Chris. Put your feet up tonight!

Doctor's orders.;)

[David May]

Np pairs on a 24V. Its one coil per cylinder and 6 channel drivers from the ECU.

Dave May

[CorseChris]

That's a pretty versatile ECU then.... all the way from 3 to 6 coil drives, cam variator (or not) 4 & 6 cylinder engines plus assorted optional input channels all in one box. And that's just in Alfas

Does it do spark energy monitoring on the 24V as well do you know?? That would be really trick!

Good piece of design IMVHO


Another thought.... I seem to recall you saying that the 24V uses a hot-wire AFM. That being the case, and the ECU being the same basic model as the 155 (which is moving flap), I wonder if there is any chance of a mod for the 12V motors?? Or is it simply a generic model code with huge variation depending upon application....... My thinking is this. If a moving flap and hot-wire can be interchanged on the M1.7, could the same be true for the M4.1 as used on the 12V V6?? Long stretch I know. All depends on how smart the hot-wire AFM is - does it provide the same interface to the ECU but simply arrive at the answer via different sensor methods or does the ECU get coded/wired according to application.

[chris.richard]

My 24v has a flap AFM. I know Jerry and David are running hot wire AFMs, but I suspect they're not using the stock ECU, but perhaps a programmable one. I think I'm right that no164 had a hot wire AFM, just V6s in other models, but I'm ready to be shot down on that one!

[CorseChris]

Only got knowledge of my own cars so you are likely right Chris. Just idle musings really - not planning on doing anything with either of my V6 motors in this regard. Moving flap may not be the ultimate by any means but it works well enough for me.

[David May]

The Bosch M3.7 is an expensive piece of kit (£580 from AR), but it's real claim to fame is that it controls 6 sequential injectors, 6 coils, 2 lambda sensors and various valves to meet the USA emission restrictions.
Mine is bog-standard (as is the hot-wire AFM) as fitted to the rare 1995 4WD 164Q4.

I think it would require a minor miracle if the old flap and hot-wire AFMs were interchangeable.

Dave May

[CorseChris]

I guess the M1.7 is going to have the saem tacho feed as the 3.7 but I'll get a scope on it lunchtime and make sure.

Then it's a quetion of what I can do to get the Veglia tacho to listen to it. Might look at removing some of the pre-conditioning or maybe adding a small 'driver' to go between ECU & tacho.


Mmmmm taco's....(drool) As Homer J would say........

I'll post again when I have some more news.

[chris.richard]

Originally posted by CorseChris
Then it's a quetion of what I can do to get the Veglia tacho to listen to it. Might look at removing some of the pre-conditioning or maybe adding a small 'driver' to go between ECU & tacho.




S'all Greek to me!:(

[CorseChris]

OK, some more Greek for you....

Checked the signal on my 155 and it's a 12v square pulse, duration about .8mS or so, frequency as we'd expect.

Not surprisingly, just connecting the old Veglia gauge to it didn't work (didn't do any harm or stop the cars own gauge from reading either BTW). Next step is to decide if the tacho circuitry can be easily modified to suit. I'll stick my neck out at this point and say it probably will. Failing this, I'll make a small buffer circuit that will convert the ECU output into something more to the liking of the Veglia tacho.

More anon.

[David May]

Sounds very Italian to me...

If it's a very old design, then the Borletti rev-counter will probably have a crude input shaping circuit made with discrete resistors which you can tamper with to boost the input signal. Failing that, all you need is an NPN transistor and a couple of resistors to make a simple level shifter.

Good luck,


Dave May

[CorseChris]

Hi Dave,

Well, after a bit of investigation it looks to be an emitter coupled monostable, edge triggered by the coil pulse. Adjustment of reading is accomplished by a variable resistor in series with the meter movement. The movement integrates the current pulses to give a steady reading. As you say, input conditioning is a couple of R/C pads followed by a small coupling C so getting it to trigger from a 12v pulse is looking pretty likely.

I won't have time to do anything more until Monday now but it looks as if your problem will soon be solved Chris.

Just the small matter of the consultancy fee to sort out and we're there ;)

Next instalment of tach-talk next week.....

[rutthenut]

Originally posted by CorseChris
Anyone know what the tacho drive signal looks like? I've not looked at a 24valve ECU so suspect this is going to be a little harder. If anyone else has already done this, please pipe up now!

I seem to recall that Phil Jordan had problems when setting up his tacho for use against the 12v 2.5-litre V6 from an Alfa 155.

Besides the recalibration being necessary, I think that there were problems with the 'strength' of the signal, which was not enough to drive the standard Fiat tacho in some way. Speedy Cables made some further mods, but I'm afraid I know nowt else about this.

Chris, if you know more about this stuff, maybe this might be a pointer for you.

[chris.richard]

Originally posted by CorseChris

Just the small matter of the consultancy fee to sort out and we're there ;)

Next instalment of tach-talk next week.....
I'm impressed - and baffled! I'll be delighted to pay for the service, maybe a cottage industry to be set up here?

[CorseChris]

I was kidding about a fee BTW......worst case is that it'll cost you postage to send me the tacho. Thinking about it, I might as well fit a connector into my 155 that I can plug a modified FIAT tacho into for calibration 'cos I might well get a few more requests for this.

I really don't know why I do this sort of thing to be honest - it must be fun or something but I just haven't noticed yet.....

Anyone who knows me will tell you just how likely it is that I'll ever make a profit out of this sort of thing.

Anyone with half a business brain would be rich by now.

I'm not rich.

You figure it out from the above clues......

If you want to send me your Tacho, send me a PM and I'll send you my address.

[CorseChris]

To any who might be interested (other than Chris who's Tacho is now converted), I have sorted out what's needed to make the Fiat tacho work on an M1.7 ECU and probably most other similar units providing an open collector tacho output signal at a suitable rate. This should cover most variants likely to be found connected to an Alfa engine.

I calibrated it against my own 155 V6 and it seems to track pretty well up to 6000 rpm or so (well, the rev limiter anyway....). Basic accuracy and linearity is about as good as it ever was (or wasn't) when used with the original Fiat 4 pot.

I be amazed if Veglia made any significant changes to the design for the V6 variants so this is likely to be as good as the genuine article. The one I just did for Chris came from an 850 Sport so was set to read to 9000 rpm. Only change other than the legend was a small value change to one component when compared to a 124 unit.

If anyone is interested in the boring technicalities or wants one doing, drop me a PM.