6cyl (M20B25) tachometer with V8 engine (M60)

[Doni]

Hello,

I'm new here and have to ask internationall help because nobody has a answer here in Finland.

My car is originally an E30 325i facelift. Now I have a M60 V8 engine in it. What to the with the tachometer? It works, but it shows too much revs. I think the normal idle speed for the M60 engine is 550rpm and the tachometer shows now ~750rpm.

Here is a little bit old picture of the motor. Maybe more pictures when the car is ready.
http://doni.eniten.com/BMW.E30/temp/moottori3.jpg

My English isn't perfect but I hope we can understand each other.

[Andy335Touring]

Sorry i can't help with your problem i just wanted to say what a cool engine swap that is and i love that colour paint

[Doni]

Sorry i can't help with your problem i just wanted to say what a cool engine swap that is and i love that colour paint

Thanks a lot. The car is going to an exhibition in the middle of april. The colour in the engineroom is a little bit to violet. The car is otherwise Mauritius Blue Metallic. But more pictures to come.

But the tachometer problem is much more necessary at the moment than the paint job.

[glenn]

ian332isport or brianmoooore may be better able to answer this
as they're electrical wizards

[conrod]

See if you can find a shop over there that services/repairs instruments. We have one here in NZ that I just send this type of job to, they can recalibrate it to suit whatever number of cylinders you need. Sorry I can't be more specific than this, but hope it helps.
cheers conrod

[Ant]

tried a 4 Cyl code plug for the clocks ?

the theory is sound, never tried it though HTH

[Widge]

Haven't you got a V8 in one of yours Glenn?
What did you do?

[Ant]

good point! although I think he used the M5 clocks

[GermanGorilla]

Hi,

Electrics are not my strong point.

I think your engine generates its Tacho pulse from the ECU/DME, which gives a pulse signal, in a code that the Dash Pods, [Rev Counter] in a E30 does not understand.

In the USA a company called ''Dakota Electronics'', [sorry can not find their Web Link in my Database] can supply a pulse converter that allows the ECU pulse code to be converted to pulse that works with the E30 Tacho.
I think I paid 75.00 USD for mine, I

It sounds like the same problem as on the S52 Conversion when the Tacho in the Dash Pods of the E30 does not read the correct RPM.

Hope this helps.

Regards,

The Gorilla.

[buster]

Dakota digital

http://www.dakotadigital.com/index.cfm/ ... prd127.htm

I've just got one .

[glenn]

Haven't you got a V8 in one of yours Glenn?
What did you do?

i used the clocks out of the e39 m5.

[Brianmoooore]

The rev counter reads the pulses OK, but overeads by 8/6, as it recieves 8 pulses when it should only be getting 6.
The dakota box should work as a rather expensive solution, but as the tacho is overeading, and is linear, then a simple resistor in series with the tacho meter movement winding should do the trick.
No idea of what value resistor without taking a cluster apart and doing a few measurements, but it should be possible.

[Jon_Bmw]

The rev counter reads the pulses OK, but overeads by 8/6, as it recieves 8 pulses when it should only be getting 6.
The dakota box should work as a rather expensive solution, but as the tacho is overeading, and is linear, then a simple resistor in series with the tacho meter movement winding should do the trick.
No idea of what value resistor without taking a cluster apart and doing a few measurements, but it should be possible.

This seems to make sense...or possibly a PIC. This is fairly easy to make up i'm lead to believe. It just alters the values it sees into the values you want, would be easy if its a linear problem. It looks up the values from a table that you create within it, if you were wondering.

[cpc]

The rev counter reads the pulses OK, but overeads by 8/6, as it recieves 8 pulses when it should only be getting 6.
The dakota box should work as a rather expensive solution, but as the tacho is overeading, and is linear, then a simple resistor in series with the tacho meter movement winding should do the trick.
No idea of what value resistor without taking a cluster apart and doing a few measurements, but it should be possible.

This trick won't work in second gen clusters - 1 red led, as the guage movements are moving iron core units and work on phase angle differences between two square wave signals to position the needle. I'm looking into getting a pic chip to solve the problem cheaply, and will integrate it into the cluster - Im doing two E30 M3 upgrades to 6 cyl , and want to keep the 8k rev counter and oil temp guage.

[Brianmoooore]

The rev counter reads the pulses OK, but overeads by 8/6, as it recieves 8 pulses when it should only be getting 6.
The dakota box should work as a rather expensive solution, but as the tacho is overeading, and is linear, then a simple resistor in series with the tacho meter movement winding should do the trick.
No idea of what value resistor without taking a cluster apart and doing a few measurements, but it should be possible.

This trick won't work in second gen clusters - 1 red led, as the guage movements are moving iron core units and work on phase angle differences between two square wave signals to position the needle. I'm looking into getting a pic chip to solve the problem cheaply, and will integrate it into the cluster - Im doing two E30 M3 upgrades to 6 cyl , and want to keep the 8k rev counter and oil temp guage.

Just had closer look inside a late cluster, and it's a four wire connection to the meter movement, so it does look like it's a phase angle device. Ah well, back to the drawing board!
What goes on in the coding plug? Any chance of a mod there?
One possibility is to use a four pot coding plug and include a simple divide by two circuit in the line where the DME pulses come in.
Anyone know where to find a detailed circuit diagram of an E30 cluster and SI board?

[glenn]

is there anything in a set of E34 540 clocks that could be used to read the signal correctly?

[nikos]

I faced the same problem when I used the haltech ecu and I solved it keeping my old ecu only to read from the gearbox and send the signal to the tachometer

[ian332isport]

It's much easier to use the Dakota Digital box. I appreciate it may not be the cheapest option, but it works and doesn't require any development time etc. No point trying to re-invent the wheel IMHO.

$70 odd dollars is not that much once converted to Ԛ£.

Ian.