What are the boost limitations of a map?

[Scott]

i guess i am not the best at explaining things, just trying to help though fella

 

 

I understand bud, that's why I kept asking.... knew we would get there eventually

[Chris Wilson]

So it's ok to run lower boost than the map is catering for, just not higher?

 

It's not making sense to me. You are saying the map sensor sees the boost and the ECU accomodates it, surely if it can accomodate it for lower boost it should accomodate for higher?

 

Do you understand this fully or are you going on what you have been told? Just asking as you aren't putting forward any concepts for the idea.

 

In a word, yes. The map should be OK from vacuum (cruise), through all levels of boost up to the limit it has been tested to. If you raise the boost the map may not even be there for higher levels, or it may be the mapper has interpolated a safety zone. I always have a fuel cut set so over X psi it just kills the engine, in case something nasty occurs with the wastegates.

[leelbuk]

The way I understand it is that fuel and ignition are mapped against engine load and rpm (a 3 dimensional table). The mapper needs to set the amount of fuel and ignition timing at every possible rpm and load. Therefore if the car cannot make or fuel a certain boost level at the time of mapping then the mapper can't enter the appropriate values and test them for det etc.

 

If you want to see for yourself then I'd go to AEM forums and download AEMPro. It comes with a supra base map and you can look at the fueling table to see the 3d table and see how the ecu can work out what fueling is needed for any given rpm and load (boost/MAP) that the mapper programmed into it.

 

Well that killed some time whilst waiting for an MOT....