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Different Altitude different load then... different AFR

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hi folks !!

I was thinking... due to moving from the sea level to the mountains I guess that the load when pedal to the metal will be different right? at sea level I will drive in the 101 - 103kpa map part and there the afr target is set to 12.8 at high rpm.

On the other hand any day I go to somewhere with an altitude of near 1800 or 2000m. The load I will see pedal to the metal probably will be around 80kpa? ok then if the afr map has set a target of 13.2 then the engine will work on this target, I know it is not savage for the engine but imagine we set this value to 14, what I think is very lean to drive it hard, then... what should we do?

I think this happens at pikes peak for example... how do they mantein the Afr target they want?

kind regards

pic attached ;)

Attached Files

Intake to exhaust manifold pressure compensation or barometric pressure compensation is required to get around it entirely.

Slides. Thank you for answering.

In my case I only have barometric pressure fuel compensation, in my case the lower atmospheric pressure the more fuel I want in to compensate my exhaust backpressure change.

But with this strategy I dont solve that the load readed from the map now is much lower and as in the pic load is lower then the afr target on that part of the table is different. Am i right?

I dont have available the othet strategy

It will depend on the ecu but with baro compensation you should be able to get it to scale the afr target table based on baroneytic pressure so 85kPa on 85kPa is still full load? Really depends on the software.

Indeed. When at higher altitude the load is not now 100 to 105. On my near home track I run on the 93 to 95 load for example and is only at 400m from sea level..

Higher I go lower on load so woler raw on fuel table then leaner afr...

This is an issue if you're using MAP as the load axis. In the perfect world you'll want to incorporate a barometric pressure compensation table or use a load axis like IMAP/EMAP however many ECUs don't offer this option. Unless you're seeing a significant altitude change on a day to day basis then this is often less of a concern than most people assume it to be.

Hello Andre. Thanks for answering. Can you explain a bit more about imap/emap? I cant use in my ecu but is for learning purpose. ;)