What i meant by varying load on the dyno not having the same effect is that you cannot change the pressure on the exhaust like a change in baro pressure. For example on a naturally aspirated engine you may have less absolute pressure in the intake at high altitudes, but the exhaust pressure will be lower as well resulting in a greater ve when the engine is operating in that part of the map vs. at a lower altitude operating in the same cells of the map.

 

That really shouldn't make much of a difference, if any.

 

Then why is there barometric correction? If it barely made a difference then the ecu would read from a different load cell corresponding to the change in intake pressure and run the same afr at one baro pressure vs. another running in that same cell. As baro increases there is a greater fuel demand due to increased VE.

There are some good points brought up about this here..
http://efi101.com/forum/viewtopic.ph...er=asc&start=0

 

My comment was to support what I said earlier with trims and using road tuning to fine tune. I am aware of that thread already.

 

Yes I do agree that road tuning is necessary to completely tune it and with experience a general idea of what the trim table looks like can help.