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M3.3.1 motronic (413 and 506) tuning and XDF update?

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Joined: 20 Jun 2017
Posts: 38

PostPosted: Wed Jun 28, 2017 4:02 am    Post subject: M3.3.1 motronic (413 and 506) tuning and XDF update? Reply with quote

I have a bit of an odd set up with a M3.3.1 ECU running an M20B25 with the vanos disabled in the .bin (resistor replacing the solenoid to avoid fault codes) it's running and driving so I am now starting to get into the meat of the tuning.

I have been looking at the ECU and software for about 2 years now on and off while doing the conversion and car resto.

I have attempted to disassemble the binary file, I think I managed a reasonable disassembly but getting any useful info from that is currently a bit beyond me, maybe a discussion for another thread?

I have a fairly good understanding of the hardware and tuning side so I am not totally lost but there are a few things puzzling me:

1. It seems people are not adjusting the "transitional compensation" in anyway on these ECUs, standard wisdom for standalone systems is to get the VE tables right with any acceleration enrichment off and then add it after.
I understand that a lot of people are working with quite mild engine changes so maybe it is not needed for those. In my case I certainly need to work on it.
Do I minimise it in the 4x6 table so it is not messing up my part throttle tuning?
Would it be better to work with what I have, reduce the transitional fuelling to hit ~12:1 on acceleration and then tune the part throttle aiming for ~14.7-15.7 at cruise? looking at about 10:1 accelerating and 13:1 cruise at the moment on the slightly adjusted M50 map.

2. The new 506 XDF is really good, a huge thanks to evilM3666 for this.
I think from all the studying of this ECU I have done there are a few things that can be added:
- TPS voltage transfer map (32x1) - Based on the transition compensation map being 0.4 volts to 6 volts and the functional range of the TPS being .45v open and 4.5v closed, this table seems to be a map of throttle opening vs voltage.
Could the scale (Y axis) on this map be 6-0.4= 0.175 steps?
This would give the right volt values to match the throttle openings.
Charted in tunerpro it looks like this:

To me that seems to match the operation of the TPS but I am going to double check with the ADS diagnostic system VS the map trace on the ostrich.
Does that seem right?

Last edited by Hairyscreech on Wed Aug 09, 2017 3:08 am; edited 1 time in total
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Joined: 20 Jun 2017
Posts: 38

PostPosted: Mon Jul 17, 2017 4:08 am    Post subject: Reply with quote

Done some more on this, the TPS table does seem to be voltage, ADS scanner says that the throttle is shut at about 0.3v and fully open about 4.2v.
Ostrich does not trace that map when the TPS is opened though so no real way of confirming the result.

Had to plug in the standard Lambda sensor and leave it in free air or the ECU wanted to go to limp or jump around erratically, with the lamba flag unset and the closed/open loop tables in the new 506 XDF set to 0 it is staying in open loop and tracing smoothly.

I think I may be having trouble with one of my knock sensors, I also don't know if the M20 valve train is going to set off the sensors just from it's natural clatter.
Can anyone advise how to disable the knock sensing?
Does anyone know how the ECU responds when the sensors are disconnected or erroring?

The car is running fairly well (for an unmapped car) on the stock M50B25 map.
I have had to adjust the acceleration enrichment quite a bit to prevent it going very rich at low load (10:1)

Idle fuel wanted about 10% pulling out to get a happy idle at 14.3-15:1, very solid, lean idle on these for an old engine.

I have also had to decrease the fuel at low load by about 10% and up the fuel at high RPM and load by 10% to see sensible AFR readings. Before doing this I was getting 12:1 at cruise and 15-16:1 at higher RPMs.
This seems odd to me as the fuel table should be a Dec value of 128 for the theoretical 14.7:1 AFR right?
So for the sensed load and RPM 128 should=14.7 if all sensor readings and conditions are normal.
Can the M20 really be needing me to drop the cruise values to ~116 and up the high RPM and load values to ~140?
The stock M50 map is around 125-135 across the whole map?

For ignition timing I have some electronic Det cans which I can record on the laptop while hit tracing and viewing the WBO2 output.
I have been trying to get it to knock but these engines seem so knock resistant I did not want to push past 45 degrees of timing at low load so I have not been able to get it to knock. They seem to just stop making any power instead of knocking.

Others have said to keep the timing below about 32 degrees as they only make noise and no power past this point (95 ron UK fuel).

I put together a base timing map using the data from the 173 timing maps I have (stock, light tune and race tune) they do feel retarded and seem pretty safe to drive on but I think the engine and ECU are wanting more timing at a lot of sites as some areas really bog down.
Looking at the M50B32 and M50B25 maps says I am still retarded at a lot of load sites and suggests more timing could be tolerated.
Just got to keep working at that side of things.

I will post my current BIN later
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