[Roadsters] OT: EFI, Temp / Atmospheric Pressure Controls

[Daryl Smith]

I am also not aware of any efi systems which compensate for fuel 
temperature.
A 'speed density' system monitors and adjusts for intake air temperature and 
manifold absolute pressure, calculating the air density and thus the 
required fuel from those.
Engine coolant temperature also is monitored to calculate fuel enrichment 
needed when the engine is cold and the fuel doesn't stay in suspension, 
basicly a 'choke', but adjusts throughout the engine temperature range, I 
believe, as higher engine temps may benefit from the air/fuel being more 
homogenously mixed.

I am not familiar with how a MAF (mass air flow) system works, but the fuel 
calculations are mainly from the 'mass' of the air through the MAF sensor, 
with adjustments for temperature etc......

I have seen 'hotrod' systems which, depending on what is wanted, run the 
fuel through either ice, or a heater.
The heater to have the fuel easier to mix with the air and stay in 
suspension in the airfuel mix (as opposed to adhereing to the runner walls). 
Many who do this are actually trying to get better milage, not more power.
The ice just doesn't make sense to me............

Daryl


----- Original Message ----- 
From: "Gary Boone" <gboone70 at yahoo.com>


> I'm not aware that any EFI systems compensate for fuel temperature.  Most 
> do
> however, have an IAT sensor (intake air temperature).  They also 
> compensate
> for atmospheric pressure with a MAP sensor (manifold absolute pressure) or 
> a
> MAF sensor (mass air flow).
> Gary
>
>
> From: "nmleeds at mindspring.com"
> I
> was just pondering (rather than putting the head back on my Datsun) and
> wondering, how do EFI systems compensate for fuel tempurature and 
> atmospheric
> pressure.  Both should change the volume of the fuel relative to air mass 
> and
> change the mixture.  Is there an adjustment, or does it not matter that 
> much?
> Nathaniel