Stack Gauges Install

[Mikey_Boy]

Hi Folks,

Just a quick installation thread to show how starting something on E30's can lead you into a lot of trouble! It all started before I owned an E30 when I saw a German guy at the Nurburgring running a very well sorted E30 M3 with 3 VDO gauges in the dash showing engine, gearbox and diff temperatures - I thought that was a great idea, so for my track car (1989 325 sport) I knocked up this:



Then I realised that I was going to be doing a bit of tuning and maybe mapping and knowing that M20's can be a bit crap on left hand bends for oil pressure I thought I'd better keep an eye on Lambda values and oil pressure - so I installed this:



Then things started to get out of hand - an S14 has come my way which I will be installing over the winter - given that I want to rev it pretty hard and that the stack gauges look a bit odd next to the BMW ones, plus I wanted to simplify the display a little, I started with a standard dash and took that to pieces, with a view to replacing the gauges with Stack items whilst trying to keep a factory (ish) look. So I brought a sheet of carbon and after a lot of cursing, measuring and sanding I ended up with this:



This was bonded into the (now gutted) instrument panel and the gauges installed to see what they look like:



The red light at the bottom is an oil pressure light (I am planning a higher pressure warning switch for the S14) and the amber light is a change up light.

After a few hours looking at wiring diagrams, I figured out what was going to go where so the wiring for the new instrument panel was done after raiding maplins for heat shrink:



Meanwhile, the old dash and centre console were removed:



Thankfully BMW did a great job of making things pretty simple so finding wires to power everything, light everything and the various signals were pretty easy to trace - I won't bore you all with the details but thankfully no black magic required!

The reason for going with the Stack rev counter was for accuracy but it also has some cool functions that are controlled by external switches, which I installed to a blank plate in the dash:



And in the car:



Time for the dash to be tried in place:



The rev counter requires an Earth directly to the battery, which of course on the Sport is in the boot so I decided to fit 2 wires as I will also need one for the Emerald ECU that's going in as part of the S14 conversion:



And after more soldering, cursing, crimping, figuring out where multiplugs should go and cups of tea it now looks like this:



It all works as it should... except for the speedo - this waggles around a lot, so I suspect that the signal from the diff isn't quite 'clean' enough for the Stack item so I need to think a bit more about that - maybe a better earth (this doesn't come from the battery), old sensor or that BMW did some signal smoothing within the dash - if anyone knows then please do let me know!

And just so folks know - on a trackday, I see 120 degrees for the engine and gearbox oil and about 105 for the diff in an ambient of 20 degrees.

Cheers,

Mike

[UweM3]

nice one, like it!

[darren_mk]

Tasty work - I like it alot!

[DanThe]

Good job there

The clocks do clean up the diff signal, same as E36 does, to give a clean signal to the ECU. Dont ask me how though. Brianmoooore would be the man to ask I expect

[Bristol_Jer]

Nice work, looks really smart

[Mikey_Boy]

Thanks for the kind words!

I will drop Brian a line and see what comes back...

Cheers!

Mike

[GeoffBob]

Looks absolutely gorgeous Mike! Outstanding work.

If you don't come right with Brian then I have all the dope on cleaning up the signal from the inductive pickup in the diff. An LM311 comparator and a few resistors on a bit of project board and you'll be set. As you may recall I did something similar on my track car, although my dash doesn't look nearly as good as yours.

Regards
Geoff

[Mikey_Boy]

Thanks Geoff - you are very kind!

I have had some words from Brian - I didn't know quite how much went on in a BMW dash, although the amount of electronic gubbins on the SI board should have given me a clue!

If you could please drop me a PM detailing what needs to be done, you will again have saved one of us (and there are many!) from embarrassment and much head stratching! I think my fundamental error here was not knowing the type of signal coming out of the diff - The Stack speedo for your info takes the following signals:

1. Pulse rate generated proportional to vehicle speed
2. Output voltage within the ranges listed below:
- Hall effect sender 3 wire (5 - 16V)
- Sine wave generator, 2 wire (1.4 VAC min)
- 5 V Square wave (CMOS)

I have to admit that electronics is a bit of a weak spot in my knowledge, so any gentle pushing in the right direction is very gratefully received!

Cheers!

Mike

[GeoffBob]

I'll post up a little circuit diagram here for you if that's OK with you Mike? Then others can use it if they are ever overcome with an urge to do so. Give me a day or so though if you don't mind to dig the circuit out and transfer it from my usual scrawl to a reasonable CAD drawing. Very few components required if I remember correctly.

[GeoffBob]

OK, so that was easier than I thought. Found what I needed to faster than expected. The circuit is also a lot simpler than I remember, requiring (in its simplest form) only two components (a resistor and a zener diode). There is a slightly more complex version that uses an LM311 comparator, but we can get to that only if the simple circuit fails to live up to expectations.

To begin at the beginning, the E30 diff employs a magnetically operated reed switch which opens and closes in sympathy with a 9-tooth wheel that passes through the slot in the switch. The switch includes a small ferrite magnet whose magnetic field is interrupted by the passing of the toothed wheel through the slot, causing the switch to open each time the slot is obstructed by a piece of ferromagnetic material (such as mild steel plate). When the slot is unobstructed the switch is closed.

Shown below is the ”aswitch”a from an E30 diff.



Why exactly the E30 diff employs a 9-tooth wheel I do not know. I would have thought that eight or ten made more sense, but nine it is.



Connecting the switch up such that it generates a 5V CMOS square wave (well, roughly so) in sympathy with the rotation of the 9-tooth wheel can be achieved with the following circuit:



The resistor and zener diode can be located at the rear of the stack speedometer. The speedometer should be set to receive a 5V CMOS input. I recommend connecting the diff switch to the speedometer via a length of twisted pair cable, but you can no doubt use the existing wiring on the car without concern. FYI, make sure you connect your zener diode the right way around ”“ the stripe on the side of the diode corresponds to the pointy side of the diode symbol in the circuit above).

Please ask if you have any questions. If the circuit fails to perform as required we can look at the slightly more complex version. I do however think that this should do you just fine.

[Mikey_Boy]

Thanks everso much Geoff - that looks perfect and easy to do..!

As always - the breath of your knowledge never ceases to amaze me!

Once this is done, all I have to do is get the S14 installed...

Thanks again - really appreciated...


Mike

[Demlotcrew]

Looks really good!

Looking forward to the S14 install, I have a spare RHD manifold to get you started if you havnt sourced one yet!

Andrew

[GeoffBob]

Thanks everso much Geoff - that looks perfect and easy to do..!

As always - the breath of your knowledge never ceases to amaze me!

Once this is done, all I have to do is get the S14 installed...

Thanks again - really appreciated...


Mike

You're welcome.

Best of luck with the S14 project Mike. Judging by the standard of your work above she's going to be an absolute stunner when she's finished!

Geoff

[Mikey_Boy]

OK folks - quick update... Ebay was my friend and I managed to pick up 10 resistors and 10 Zener diodes of the right spec for £2...

Checked the components, wired them in as described above and unfortunately saw no difference - the speedo needle is still very 'spikey'. This happens just after I move off, and during driving - there doesn't appear to be any pattern to the problem. I have (for the sake of time) used the car's existing speedo sensor wiring which basically leads me to believe the following:

1. The wiring somewhere between the diff and the dash is not 100% (which I find a bit strange as the old speedo worked a treat before the swap)
2. The Speedo itself has a fault (so an email will be heading towards Stack!)

The really bad news is that there will be a bit of a delay in fixing this problem as my road tax runs out today - the car is SORN'd for the winter months so that I can install this:



I will be writing a separate thread on the tidy up, refresh and install of the S14 over the next months.

If there are any further ideas to help sort out my speedo woes, please do let me know!!

Cheers,

Mike

[GeoffBob]

Hi Mike,

I assume that your speedometer has a switch on the rear to choose between the three modes of operation you presented above, and that you set your speedometer to the ”a5V CMOS”a mode? If not set to ”a5V CMOS”a you will run into problems.

Does sound to me like the wiring between diff and dash is suspect. Disturbed during the installation perhaps? I sincerely doubt that there is anything wrong with the Stack speedometer you received, their products are usually top quality (reflected in the price).

My suggestion is that you make yourself up a length of twisted pair cable (as I described in one of my PM's I think). And run it temporarily between the diff and dash. Don't go to the trouble of embedding the cable - along the floor should be sufficient to diagnose the problem.

Alternatively you could setup a variable speed electric drill with a toothed wheel (or similar) in the chuck and a diff reed switch on the bench. That plus a length of cable to the dash should provide you with sufficient to diagnose the problem. If you get an erratic speed reading with the drill at constant rpm then you know, having changed the wire, that the problem lies elsewhere.

If I were anywhere nearby I’d simply pop an oscilloscope across the input to the speedometer and we’d see in a jiffy what was wrong.

Lovely S14 BTW. You could paint a 3SGTE to look the same you know

HTH
Geoff

[Demlotcrew]

Mike,

Are you running ABS? Im pretty sure that all Stock Speedos come with a speed sensor that you could stick into one of the ABS holes or even use one of the stock ABS pulse sensors to verify the speedo is actually working!

Andrew

[Mikey_Boy]

Thanks Geoff and Andrew all for your help... Like Geoff, I very much doubt the speedo is at fault - Stack gear is usually excellent and would be very surprised indeed if it was that.

It all boils down to the wiring I think - I am not 100% certain that the wiring from the diff to the dash is OK so I will look at that whilst I do the S14 swap. Also, I am running ABS (soon to be removed so as an alternative, I will hook up one of the sensors (or a stack sensor) to one of the ABS holes to get vehicle speed that way.

Most important thing (as consolation for now) is that the speedo (and rest of dash) is getting a signal and power, so sorting the speed signal out is just another job to add to the conversion list..

Garage is now being cleared out to make for a more spacious and pleasant working environment!!

Keep your eyes open for the new thread...

Cheers,

Mike

[Demlotcrew]

Can i ask why you are removing the ABS?

Andrew

[Mikey_Boy]

A few reasons:

1. I have some pretty large brakes at the front (330mm 8 pot calipers) and a different master cylinder which have no doubt messed up the basic ABS calibration..
2. When the car was more standard, the ABS wasn't the best if I am honest!
3. The car is a primarily a trackday car so prefer not to have it - I know there are arguments for and against!!
4. It saves a bit of weight to get rid of it...

Cheers,
Mike

[Demlotcrew]

Thats fair enough, there are times when i wish i had ABS!

Its on the list for me at some point.

Andrew

[DanThe]

Get an E36 ABS system grafted in

[Mikey_Boy]

Oooooooohhhhh Jeepers!

That sounds like a task! I have also considered grafting in Air Con as well (there is some logic to this for a trackday car, bear with me!) but I really want to try now to keep this install as simple as possible - it's already got out of hand with some of the goodies I have bought!

[Demlotcrew]

Get an E36 ABS system grafted in

Nah dude, ill keep it E30 and re-flash the ABS ecu with a BMW MS map

[GeoffBob]

Mike, are you 100% certain your zener diode is the right way around?

Look closely and you'll see the cathode indicated on the body of the diode with a line closer to one of the diode legs than the other. It's usually a white line on a pinkish-red or black body. The cathode leg of the diode should be connected to the resistor and the input to the speedometer. The anode leg of the diode (without the stripe) is connected to ground. I'd suggest checking this.

You can check your circuit as follows: Clamp the probes of a multimeter (set to DC volts) between 0V and the input to the speedometer. With the ignition on (but engine off) drop the handbrake and gently roll the car forwards such that the toothed wheel rolls through the diff switch. As it does you should see the voltage at the input to the speedometer toggle back and forth between 0V and ~4.7V. If you measure something else then you have a problem with your circuit. This is an easy test to do and I'd be interested to hear what result you get.

[Mikey_Boy]

Hi Geoff - thanks again for your advice - I have checked the circuit again just to be sure and everything is wired in correctly. I have carried out your check as above and see the voltmeter toggle between 0.05V and 4.95V when the car is pushed so all looks well there!

Looks like we will have to dig a bit deeper on this one - given the random nature of the spikes, I still think we are dealing with a problem with the (22 year old) wiring somewhere between the diff and the speedo...

Thanks again for your help - it's protected my sanity that I haven't done something stupid with the compenents!

[GeoffBob]

Looks like we will have to dig a bit deeper on this one - given the random nature of the spikes, I still think we are dealing with a problem with the (22 year old) wiring somewhere between the diff and the speedo...

Sounds like it Mike. I'd suggest substituting a temorary length of your own cable to see if the problem goes away. If it does then you know you're on the right track.

[Mikey_Boy]

Thanks again Geoff - much appreciated!

I am willing to bet 1 whole English pound (!) that it's the wires...

Now the car is off the road (as of yesterday), this fix has been added to the job list for the S14 install - new thread is here:

http://www.e30zone.net/modules.php?name ... c&t=206743

Lots and lots of things to keep me occupied during those long winter nights!

Cheers,
Mike

[Mikey_Boy]

After a year and a bit, I have finally got round to solving this problem...

From the advice in the thread, I was convinced that the wiring from the diff to the front of the car was the cause of the problem being original. So, after a bit of tracing, I found that the diff wire enters the car under the back seat and connects to the loom through a multi plug. A bit of a pig to get to in my car as I have trimmed the rear seat area but no major hassle. When I pulled apart the plug, I found this:



Not exactly 100% clear but all the connections were corroded and green - not the best. The pins were cleaned up and just for good measure, I decided to bin the original diff wire and route a brand new cable from front to back using the original routing.
To try and make life simple, I tried to route just the wires from the diff directly to the speedo to see if that worked. It was a bit better and seemed to calibrate more smoothly, but on a test drive, the same symptoms occurred.

So”¦ I rebuilt a circuit as per Geoffbob’s recommendation, still no change.

When I got to thinking about it, I realized that just 9 ”˜pips’ on the diff sensor might not be enough for the Stack speedo so I decided to hook into an ABS sensor ”“ I have removed ABS as part of the S14 build and know that the hub has plenty of teeth.
For simplity of wiring, I hooked into the RHS rear wheel sensor ”“ this is the easiest to route for the existing diff wire which picks up on the RHS of the car. I have a couple of ABS sensors in my garage so cleaned one up and modified it like this with a waterproof connector:



I did this so that if a sensor fails, it’s an easy job to remove a wheel and substitute a new sensor without having to dive into the car and remove lots of trim.
Here it is mocked up in the car:



And a bit more detail:



The ABS sensor is just 2 wires ”“ 1 goes to Earth and the other to the speedo feed ”“ with this carried out, BINGO, the speedo worked just fine after recalibration ”“ very steady and super accurate against a GPS generated speed.
Finally ”“ job done!

[Demlotcrew]

Good stuff! And very good to know