Why..

[Guest |229|]

Have read the help file, and it only says ideally it should be as it does.. But I am looking for a "why..."

When IAT rises, it should ideally lean out a little. It does so in the IAT map, and help file confirms this.

But why should it lean out when intake temps rise?

I understand why it pulls ignition out when IAT rises. But not why it should pull fuel out.

[Guest |118|]

hot air is less dense than cold air and therefore has less oxygen...

[Guest |229|]

Okay, didnt think that would have so big influence on fueling. maybe when getting high, but it takes 2 procent out for every 10 degrees higher intake temp.

I know IAT vs ignition has alot to say, but didnt think that higher intake temps needed that much adjustment on fueling.

thanks for clearing this up. :-)

[Guest |99|]

If you think of a sealed balloon that has a fixed volume (and mass) of air. If you heat the balloon it will increase in size as the pressure is increasing due temperature however the mass remains the same. If you cool the balloon then it will shrink as the pressure is decreasing (mass remains the same). If you apply this to your engine then as the air temp increases then so will the pressure. As you fix the pressure by setting a boost point it means that you effectively are providing less mass of air so you need to provide less fuel. Hope this helps.

[Guest |229|]

Thanks for your reply. :-)

Learned something about adjusting. Have alwayes been used to AFM, this is my first MAP setup. So there are some new terms i have to learn.