How to get RPM on BMW E30 M42 DIS.

sbarton · Post by **sbarton** » Wed May 22, 2013 3:48 pm

Anyone know how to log RPM with DIS system? Specifically BMW E30 M42 4cyl which has DIS (the M20 6cyl has a dizzy).

-Scott

blalor · Post by **blalor** » Wed May 22, 2013 5:26 pm

The easiest way is to tap into the signal in the instrument cluster. I was able to get fuel level, coolant temperature and RPM on my old E30 by creating a wiring harness that I spliced in-line with the cluster. All of those can be wired directly to RaceCapture/Pro, as the voltages are safe. Looks like that feeds into pin 7 of connector 1 on the back of the cluster (I forget which color that one is). It's also available via pin 9 on C101 (the round plug under the hood). See page 6201-2 of the ETM.

sbarton · Post by **sbarton** » Wed May 22, 2013 5:32 pm

Awesome info. Thanks Brian. I ripped out the 2002 cluster due to wiring issues. Do you know the C101 pin numbers for coolant and tach? Any other stuff of the C101 you can think of that could be recorded by the RCP?

-Scott

blalor · Post by **blalor** » Wed May 22, 2013 5:39 pm

Tach is 9 (black), coolant is 4 (brown/violet). The fuel sender only goes to the cluster, and it has has two signals: level (brown/green) and a switch for the low-fuel light (brown/grey).

sbarton · Post by **sbarton** » Wed May 22, 2013 6:23 pm

OK, next question. Tach goes to Pin 20 (frequency/pulse input 1). Which pin or bank of inputs would coolant temp go.
Thanks.

-Scott

blalor · Post by **blalor** » Wed May 22, 2013 6:28 pm

That'll go to one of the analog inputs, pins 8-14.

http://www.autosportlabs.net/RaceCaptur ... onnections

I've never calibrated the coolant sender on an E30 (I don't know if the M20 and M42 are the same sensor), but if someone does, that'd be useful. I have a feeling there are going to be a few of these cars getting RaceCapture'd!

You can do the same with the fuel level. I did roughly calibrate our team's car, but we have the original instrument cluster and I have a feeling the signal feeding into RCP may be dependent on the presence of the gauge…

sbarton · Post by **sbarton** » Wed May 22, 2013 6:38 pm

Mapping the raw values to actual temps may be hard. I don't have a temp gauge in the 2002 so can't use it to reference. Basically I just want to be able to see trends for right now. Will have to install in my E30 to get the values, but prolly won't be able to do that till end of June. I assume the M20 and M42 are the same since they use the same gauge.

I've got an ATL fuel sender in the 2002 so mine will be different than stock E30.

. Again, can install in my E30 to find out later.

-Scott

sbarton · Post by **sbarton** » Wed May 22, 2013 6:45 pm

BTW, not really related to this but one useful 'sensor' you guys may want to add in the FAQ or sensors is the oem brake light switch. This will basically log when the driver is actually on the brakes. Very easy to install and setup on all cars, so worth a mention.

Brake light switch coupled with TPS is very useful info for working on driver performance. It showed me how much 'coasting' I was doing. How well I transitioned from throttle to brakes and back to throttle and really allowed me to focus on that and make big improvements. You may think you are doing it well, but data doesn't lie!

-Scott

blalor · Post by **blalor** » Wed May 22, 2013 7:49 pm

That's a great idea. Fred's big on measuring brake *pressure*, but merely on/off the brakes would be really useful. You can do this today, of course. Just feed the switch into one of the digital inputs on the RCP and away you go!

You could probably do throttle position with the existing sensor, too, but you'd obviously want to make sure that doesn't impact any readings the ECU needs. The RCP's inputs are very high impedance and shouldn't load the circuit down, but stranger things have happened.

sbarton · Post by **sbarton** » Wed May 22, 2013 8:06 pm

Yep, that's what I'm suggesting. You should put that up in the FAQ, sensors, or install section or somewhere.

-Scott

rdoherty · Post by **rdoherty** » Wed May 22, 2013 11:01 pm

Scott: all are docs are a wiki, so you are free to edit them too!

Alex W · Post by **Alex W** » Thu May 23, 2013 2:39 am

blalor wrote:That's a great idea. Fred's big on measuring brake *pressure*, but merely on/off the brakes would be really useful. You can do this today, of course. Just feed the switch into one of the digital inputs on the RCP and away you go! You could probably do throttle position with the existing sensor, too, but you'd obviously want to make sure that doesn't impact any readings the ECU needs. The RCP's inputs are very high impedance and shouldn't load the circuit down, but stranger things have happened.

I noticed on my MR2 that when I connected the race capture to the TPS it did effect the output at the ECU. Fortunately I'm running a Hydra EMS system, so re-programing the TPS in the ECU to the new output was easy, but at least in my case it did have an effect. If I recall correctly it made the old 100% calibration appear as only about 70%.

The brake on/off is a good idea, I may need to try that...

blalor · Post by **blalor** » Thu May 23, 2013 2:41 am

Good to know. Thanks, Alex!

Matt D. · Post by **Matt D.** » Mon Jun 03, 2013 4:39 pm

Awesome information, by the way. I've just installed RC/P into our E36 328i and have been pouring over the wiring diagrams for a week. I looked at the fuel gauge plug first because it seemed the most simple, and what was said up above concerning the E30 is exactly how the E36 looks.

I'll start an E36 thread in the next week or two to share what I find.

Post by **brentp** » Mon Jun 03, 2013 6:38 pm

Brilliant. We'll need to get wiki pages up as well for different makes / models!