thanks for the reply.
I will be using a wide band, hence a closed loop. SO that means that basically the lamda value will be doing most of the work and IF i dont want the MAT table to interfere at all i should keep the values at 100%?
Sort of. Lets go back to the basics slightly. Lambda is the ratio of air to fuel, normalised based on the stoichiometric value. Therefore to keep the same lambda, if you have less air you need to supply less fuel. The VE table is (or at least should be) set to give the fuel required to achieve your required lambda at just one condition. The MAT table then corrects for the changing air density with changing air temp. If you have closed loop wideband control active, then this will correct the error introduced as the air density changes with temp. So in one sense you're right that if you don't want the table interfere you should set it all to 100%. But the point is that you DO want it to CORRECT the feed forward fuelling, so that the lambda controller only has to make small corrections to keep the lamda under control.
It's always worth remembering that the best closed loop control system is one where no closed loop correction is actually needed!
Otherwise from what i understand from your explanations is that most likely the values on the MAT table on the high TPS values should be wanting to enrichen the mixture to avoid knock and ignition retard and hence keep EGTs low as well.
Generally yes, that is correct. In the OE systems I've worked on the MAT correction is just a line against temp, purely to correct for density changes. There will be a similar line against atmospheric pressure for the same reason. The enrichment to avoid excessive EGT's caused by ignition retard due to increasing knock sensitivity is usually handled somewhere else in the system.
For open loop running, the VEMS implementation is nice, as it does both corrections in the same place, which should reasonably easy to calibrate. However for someone running wideband closed loop in areas where there may be an EGT problem then you need to offset the target lambda too, as I mentioned in my last post. I'm not up on exactly what functionality is available in all the different firmwares - Rob is your man for that.
I have an ignition map which works on the car and it is quite aggresive to be honest(at least that is what everyone who has seen it says) but this map was on the motronic map i have which uses 16x16 tables i think and also it is TPS based rather than kPa . I may play it safe for starters and reduce the values on high rpm for now!!
SO im hoping that there will be no knock issues to begin with,as i have no problems so far with the car anyway, BUT on the other hand i dont have all motronic maps from the eproms so therefore im not sure how things are compensated in different tables.
Be a bit cautios taking ignition maps straight from an OE system. As you've said, you don't know what other corrections are being applied. For example, the base ignition map may have been calibrated at a manufacturer standard temp and pressure condition - often this is colder than the engine normally runs at as it will show improvements when going for power certification. Additionally, if the car has active knock control then the base map can be more aggressive as the knock control will trim back the timing when required. In its most extreme, for latest generation systems we sometimes calibrate the base spark on 100RON fuel (now available in Germany) and let the knock control do the work when users switch to 95RON. Putting a map like this into your car could be disaterous......
If its motronic and the base car had an air flow meter of some kind, The load axis will probably be RL (relative load), which is defined by BOSCH as volumetric efficiency at standrd temp and pressure (0c and 1013mbar). I assume you think its based against TPS as it goes from 0 - 100%, as it would for an NA engine. For a turbo, you would see it go from 0 - 160% or something (depending on how boosted the engine is.) You can consider it equivlent to VE.
If it is RL and not TPS, and you implement it directly against TPS like this you will end up with far too much advance at low throttles and low engine speeds, where the airflow means that effictive WOT is achieved at relatively low throttle openings, so be careful.
I do have a small 2 line table that tells the ignition retard vs IATs though. How can i do that with VEMS? Is that why the MAT table is there for then?
I believe there is some retard with MAT somewhere - again, Rob is your man to explain exactly what is implemented in your firmware. I think the last time I saw anything about this in VEMS it was implemented as a fixed line which the user could either switch on or off. You should find that you have something like 1 or 2 degrees ignition retard for every 10C you go above about 40C, which is about right, but of course you only really want to apply this in the region you are knock limited. Applying it everywhere just reduces thermal efficiency and wastes fuel. If you do have it, and its switched on then yes, that is why the MAT enrich table has a load axis too.
Good luck
