RPM on e36 BMW - Wrong scale?
Posted: Mon Jun 21, 2010 7:07 pm
Hello,
I have an e36 BMW ('93 325is) and am trying to log an RPM signal to my Mk1 DL1.
I've found a number of resources referencing connector X16 pin 20 (black wire) on the instrument cluster as a good place to get a tach signal for external tachs, shift lights, and data loggers. I hooked up a cheap voltmeter to this wire and appeared to be getting what looked like a 5v pulse, so I connected it to the "RPM" input on the DL1.
The general shape of the RPM curve looks to be correct in the software, but it appears to be something around 2000 RPM too high across the entire range. The software shows the engine achieving over 9000 RPM, but that simply isn't possible for this engine (rev limit is 7200).
I haven't found any documentation or forum posts of anyone having a problem such as this, and there appear to be no "calibration" options on the RPM signal. As I mentioned, I've found several forum posts where people have successfully used this wire as a standard 5v tach signal. What might I be doing wrong?
Thanks in advance.
Neal
I have an e36 BMW ('93 325is) and am trying to log an RPM signal to my Mk1 DL1.
I've found a number of resources referencing connector X16 pin 20 (black wire) on the instrument cluster as a good place to get a tach signal for external tachs, shift lights, and data loggers. I hooked up a cheap voltmeter to this wire and appeared to be getting what looked like a 5v pulse, so I connected it to the "RPM" input on the DL1.
The general shape of the RPM curve looks to be correct in the software, but it appears to be something around 2000 RPM too high across the entire range. The software shows the engine achieving over 9000 RPM, but that simply isn't possible for this engine (rev limit is 7200).
I haven't found any documentation or forum posts of anyone having a problem such as this, and there appear to be no "calibration" options on the RPM signal. As I mentioned, I've found several forum posts where people have successfully used this wire as a standard 5v tach signal. What might I be doing wrong?
Thanks in advance.
Neal