Converting a motronic ignition map to VEMS ?..

[da_trem]

Hi everyone,

I'm trying to convert to vems a stock AAN motronic ignition map...Thing is motronic's load is injectors MS(as per the illustration below) and vems is Kpa load.

Any ways to know at least what part of the motronic corresponds to 1000-3000 cruising area? Would it be right to assume that the 3.300/3.900 is cruising area?

Thanks!

[prj]

Forget it.

[A80Avant]

I think you can only do that by knowing roughly on a live feed where the load falls on specific kpa. So yes very difficult. As a ball park I would as a guide say that the highest timing should be below 100 kpa in other words off boost

[da_trem]

That's what I was also thinking. By looking at the gragh you can "almost" see the line were positive pressure starts.

I'll take a look with a vag-com to see a channel for load(if it exist).

[prj]

Load is not measured in ms on this ECU in VAG-COM.
You are wasting your time, these maps are in no way transposable.

One does it off inlet pressure the other off actual cylinder charge, these are two very different things.
Plus, you have found just one ignition map. If you think Motronic actually follows the timing from this map you are completely wrong.

Save your time, and learn to tune, and tune it from scratch. Job done.
What you are trying to do will never work.

[da_trem]

Its most likely curiousity.

But one question: how does it measure cylinder charge? With the Maf signal?..since map dosent measure charge but pressure?

Thanks!

[prj]

Read up on mass-flow and speed-density.

A mass-flow system MEASURES DIRECTLY how much air is in the cylinder.
A speed-density system GUESSES how much air is in the cylinder.

One system you have MAF/RPM = cylinder charge.
Other system you have MAP*VE table*IAT = cylinder charge.

When I did my SD conversion of Motronic I kept all of the tables load based. I did not simply do load = pressure like it is done in VEMS.
In fact, many higher end ECU's have tables with load as an axis, not pressure - load meaning cylinder charge. This means that it is a lot easier and faster to re-tune the engine, as you don't have to change nearly as much when things change in the engine.

Anyway do not bother transferring from one system to the other. Just make new maps on a load bearing dyno and tune to mbt, job done.