Guest |537| Posted May 23, 2010 Report Share Posted May 23, 2010 I am trying to setup the tachometer on a e30 m3 with stock VDO tachometer. I have it working but it is not showing the correct RPMs. I have played with the duty cycle and multiplier but i haven't been able to get it 100%. Is there a special procedure to follow? Quote Link to comment Share on other sites More sharing options...
rayhall Posted May 25, 2010 Report Share Posted May 25, 2010 Some old type tacho were designed to work with the signal from the negative side of the coil. These tacho need a amplifier to boost the signal. I believe MSD make one. I have a circuit deign if you want to make your own. Ray. Quote Link to comment Share on other sites More sharing options...
Guest |537| Posted May 25, 2010 Report Share Posted May 25, 2010 Ray, This tach used to get its signal from the bmw DME and it wasnt same wire as the coil. So i dont believe that this is an issue. The problem i am having is with the duty cycle and multiplier values and how get the tach accurate. Quote Link to comment Share on other sites More sharing options...
rayhall Posted May 26, 2010 Report Share Posted May 26, 2010 Joe, The tacho may not have pullup resistor on the signal wire. Add a 470 ohm 1/4w resistor from 12v ignition power to the tacho signal wire. Quote Link to comment Share on other sites More sharing options...
Guest |409| Posted May 29, 2010 Report Share Posted May 29, 2010 As another point of reference, I'm running an BMW E30 M3 with the oem tacho just like Joe's. My Wolf V4 ecu tach output was wired directly to the factory tacho lead and the tach always worked perfectly. I thought perhaps someone would know if there are differences between the Wolf tacho circuitry and the Vipec's. Best regards, Anders Quote Link to comment Share on other sites More sharing options...
Guest |537| Posted June 1, 2010 Report Share Posted June 1, 2010 I looked at the schematic and it shows that there is a 16Kohm resistor. I am trying to get my hands on stock m3 and hook it up to a scope and see what the signal should be. Quote Link to comment Share on other sites More sharing options...
Guest |537| Posted July 26, 2010 Report Share Posted July 26, 2010 Well, I still haven't got the tachometer working 100%. Although i haven't sent all that much time playing with it until this past weekend. What i did discover is the the factory ECU sends out 3 pulses for every rpm (1000crank rpm = 3000 pulses). The ecu signal goes to the instrument cluster, there is a 10kOhm resistor, then the signal goes into an ic chip (engine coding plug) and the there 4 leads to the tachometer with lettering (-2,+2, +1, -1). If i set the multiplier to 3 (this should match the factory signal) the tachometer shows way too high. If i get the idle (1100crank rpm) to show correctly the multiplier is equal to 1.7 but then as i rise the rpm, above 5k the gauges goes nuts and bounces all around. Adjusting the duty cycle doesn't get any change in the display. Any suggestions? Quote Link to comment Share on other sites More sharing options...
rayhall Posted July 26, 2010 Report Share Posted July 26, 2010 On a six cylinder engine with a the tacho multiplier set to 1, gives 6 signals. Or in other words 3 signal for every turn of the crank. This is the same as the stock ECU. In a earlier post I said this.... Add a 470 ohm 1/4w resistor from 12v ignition power to the tacho signal wire. Have you tried this. It will make the signal stronger and may fix the problem. Ray. Quote Link to comment Share on other sites More sharing options...
Guest |216| Posted July 29, 2010 Report Share Posted July 29, 2010 Are you sure the tachometer i working correctly? The clusters on the E30s are well known for hiccups. I have wired many E30s with Vipec (and other makes) and the tacho always work. Have also done M3 with the V44. Quote Link to comment Share on other sites More sharing options...
Guest |537| Posted August 2, 2010 Report Share Posted August 2, 2010 On a six cylinder engine with a the tacho multiplier set to 1, gives 6 signals. Or in other words 3 signal for every turn of the crank. This is the same as the stock ECU. In a earlier post I said this.... Have you tried this. It will make the signal stronger and may fix the problem. Ray. Ray, yes i have tried wiring in a pull resistor. No change. Are you sure the tachometer i working correctly? The clusters on the E30s are well known for hiccups. I have wired many E30s with Vipec (and other makes) and the tacho always work. Have also done M3 with the V44. That is something that came to my mind but it did work before the vipec install. I will try to swap in another tachometer. Do you happen to remember the values you used for the configuration? Quote Link to comment Share on other sites More sharing options...
Guest |216| Posted August 3, 2010 Report Share Posted August 3, 2010 That is something that came to my mind but it did work before the vipec install. I will try to swap in another tachometer. Do you happen to remember the values you used for the configuration? Just the standard config: duty cycle: 50% multiplier: 1 Quote Link to comment Share on other sites More sharing options...
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