axl911

Any one here know how to or ever modify a fuel / ignition map on the 95 DME Motronic 2.10.1?

What tool did you use and where to you get the base map?

thanks,
anthony

johnsjmc

You buy a replacement chip. Steve Wong can make a custom one for a 95. Estimate $500 but can be more if dyno time is needed

Ed Hughes

Steve Wong is definitely the "tool" to use, and I say that with the utmost respect!

TheOtherEric

Protomotive can also do it. I can't vouch for either Pmotive or Steve Wong though.

What exactly are you trying to do? If it's a simple fueling adjustment, have you considered an adjustable fuel pressure regulator?

axl911

Ignition timing actually. I wanna retard them a wee bit at low load partial throttle.

Already email Steve Wong on this.

trophy

Why do you want to change the timing? What are you experiencing that would cause you to think that timing is the issue?

Live tuning of this DME is available from a number of sources now, you just need to find someone that has experience with Air Cooled engines. Many companies that tune early BMW's have the equipment to tune this DME live.

axl911

I was looking over my telemetry data which included knock count from the DME. It happens only at LOW RPM and steady partial throttle openings. I see a few knock counts once in a while then everything is fine. None of these knocks are pf the audible kind, they are what the DME picked up at the knock sensors.

I suspect this is normal operation under partial load where the DME in closed loop operation will advance timing to its optimum or max value indicated by the timing map. As a result, the DME will push the timing until it sees knock, then back off for that cylinder.

Knock is knock. I have crappy gas where I live now. I was just wondering whether tweaking the max ignition values back a wee bit would prevent the DME from pushing it too far. Maybe I am just thinking too far and worried about nothing as this is normal operation for the engine.

I do know the impacts of retarding the timing at part throttle: less power, less responsive engine, increased head temp, etc.

MarinS4

Call Todd at Protomotive. Some of what you are seeing maybe normal background noise.

I remember when I was talking to him about logging knock he mentioned some of it needs to be filtered out.

Anyway he is great to work with and can do whatever you want to do.

TheOtherEric

How are you measuring knock? I have a Curtis pulse counter plugged into the knock line and I'm pretty convinced the data is useless.

trophy

Some of those knocks can be noise as Marin has alluded to. Can you see the timing of the engine at all with your logging? If the DME is retarding timing when it sees a knock then it is a substantial enough event that the DME is protecting the engine. The DME retards ignition buy 3 degrees each time a significant knock event is happening (to a max of 9 degrees). If you could see the ignition timing of the engine you could see if the DME is doing any retarding due to knock.

Significance is the key, i am not sure what the DME classifies as significant enough to retard the timing though.

IXLR8

How would he know if it was noise or the onset of detonation?

According to the diagrams, the wiring of both knock sensors are shielded. Maybe better shielding or replacement of old shielding is required.

axl911

Eric,
How are you measuring timing on the engine?

I am measuring knock at DME diagnostic port pin 11. It's the same place where you put the curtis counter. In my case I actually get voltages changes using the Zeitronix ZT2 which was able to sample 50 times a second. See this.

https://rennlist.com/forums/attachme...tle-to-wot.jpg

Martin & Trophy,
I am beginning to suspect these knock reading are normal operation of the engine or noises. Unfortunately, I don't have a hammer. My only tool for measuring timing is Durametric, and it is slow + unreliable in collecting live values.

trophy

The noise comes from vibrations sensed by the knock sensors, these vibrations can come from transmission, stiffer engine mounts, anything mechanical. The knock sensor and associated bar that connects the cylinders are very sensitive, any changes to the car can make them less efficient.

They tend to not come from electrical noise, although that could be possible.

IXLR8

If the noise is caused by vibration, you'd think they'd program an ignore-below floor into the software, which I am sure has been done. Then I'd suspect a sensor and its output...I'm not all that clued into this aspect of electronics though.

Edited: if I understand it correctly, looking at the graphs in the link above, the pulse is not random in that it happened during WOT and load, right where I would expect it to happen. I'd try a higher octane fuel if race fuel is available nearby.

TheOtherEric

I only used the Durametric and indeed it is flaky and the sample rate stinks. '96+ owners could use a Scangauge II but we '95 owners don't have that option.

I get so many knock counts on the Curtis counter at the diagnostic port that I concluded it has to be wrong. Probably 50-70 counts per lap regardless of chip, before and after turbocharging. Must need some sort of filtering but I have no idea what or how.