Road Speed and Engine Speed signals for HUD

[Gray S.]

Hey everyone,

One of my buddies is going to try and program a heads up display for his senior design project (computer engineering major) using my e30 as the test car. For the HUD we are thinking he needs to tap into 2 different wires. One that gives the road speed (mph) and one that gives engine speed (rpm).
The HUD unit will be located on the dashboard right behind the cluster bump and close to the windshield. Without tearing into the ECU, are there any wires running to the cluster or otherwise easily accessible that we could tap into?

Is it possible to get those signals directly off the cluster itself? We are just in the planning stages right now and want to figure out the easiest way to get these two signals.

Any suggestions would be much appreciated!

Thanks,

Gray

[karpiel]

We are just in the planning stages right now and want to be told the easiest way to get these two signals.

Couldn't resist.

[jlevie]

The easiest way to get the necessary signals, in my opinion is to tap into the wires that carry those signals at the cluster connectors. You can find that information in the ETM for your car (see http://wedophones.com/BMWManualsLead.htm).

[Gray S.]

The easiest way to get the necessary signals, in my opinion is to tap into the wires that carry those signals at the cluster connectors. You can find that information in the ETM for your car (see http://wedophones.com/BMWManualsLead.htm).

Thats what our plan is as of now. I've found a few good resources with the help of another member that seem promising.

Just wanted to get the best idea I can before we start tearing into stuff.

[Gray S.]

Couldn't resist.

Awesome thanks for the help.

[Gray S.]

Very brief update: we took some readings with the Multimeter running a wire to the c101 pin 14 in the engine bay. From all the research we've been doing it seemed fairly certain that we would get a speed signal here. There was also supposed to be the engine speed signal located at pin 9. Interestingly enough, the multimeter picked up a reading at pin 14 that fluctuated exactly in line with the engine speed!

I believe the reading was between 400hz at idle and 12000hz at 7000rpm. My digits might be off a bit there as my buddy was holding the multimeter and I dont have much electronics background. The multimeter read .400 at idle and 12.000 at 7000rpm.

I'm a little unsure what to make of these numbers. They perfectly mirror a signal that would measure rpm (I would rev the car and the readings would fluctuate accordingly). But all of the people doing M50/S50 swaps seem to have road speed signal located at that pin.

We ran out of time tonight but are going to spend awhile testing different things tomorrow so hopefully I'll have something to report back. Hopefully we will be making progress!

[87-325ic]

awesome, cool project, and good luck. glad you are somewhat local.

damn RTP and all the smart folks up there...

[Gray S.]

Went home and tested some more yesterday with no sucess. It seems like al the information about location of speed signals doesn't apply to my 318is.

Going from this wesbite http://www.unofficialbmw.com/speedo/speedo_d.html I soldered a test wire to my speedo just like in the picture, and nothing. No signal at all.

Since we couldn't get that to work we tried looking under the glovebox for this connector. The black wire should contain the rpm signal.


Unfortunately I couldn't see that connector anywhere in my car. I took off the plastic ECU cover and still couldn't find it. So I'm not sure if its buried somewhere else back there or if my car doesn't have it at all.

We also looked at the yellow OBC connector on the back of the cluster for the road speed signal. Supposedly theres a wire that sends that signal from the cluster to the OBC. I just am unsure if my car would even have it considering I only have a 6 button OBC. I was also not able to locate a pinout chart for that yellow OBC connector.

Also, how would I go about testing the pins on that connector? Doesn't the connector have to be plugged into the cluster to get the signal? Would I have to cut and splice every wire running to that connector?

So far this has been frustrating. I've done a huge amount of research but there are no definitive answers. I was hoping these two signals would be fairly easy to get without having to tear into the car, but its looking less and less promising.

Any tips or help would be extremely appreciated!

[BeFunk]

First off I am NO engineer just a Geek with WAY too much time on his hands.

I have been toying with full cluster replacement on my e30 using an embedded PC of some sort. I am looking into the Chetco vGauge-Remote and they suggested that I tap directly from the senders because of the amount of possible failure points (I.E. something goes wrong? no display) and reliability of signal.

SO. I was thinking about using a toner to chase down the appropriate wire to inside the fire wall but have not done it yet. that may be an option for u.

Let me know how this all goes because im ALL bout not spending a grand on the vGauge-Remote and all the stuff i will need to do that correctly :)

GOOD LUCK!

[jlevie]

I have a RacePak IQ3 in my Spec E30 using the OE temp and fuel level sensors via a RacePak Universal Sensor Module. I tapped into the cluster harnesses for the fuel level and temp sensors. For the tach I tapped into the wire that feeds the tach signal to the cluster. Those wires aren't hard to find using the wiring diagrams from wedophones.

If building a custom cluster replacement, you will need to provide regulated power if you use the OE fuel level and temp sensors.