Speed Density

[AUSSIE OLDOE]

SD is not a term we know of over here so would you please explain it to my ageing but still curious & enquireing mind ??

[RedEvoVII]

Speed density means:

Determine the Fueling need for an Engine by Manifold pressure with Air temperature correction
The Amount of fuel is then given by Engine Volumetric efficiency, and Density ( air temp corrected Density with Manifold Pressure )
Since all Parameters will be measured right before entering the engine, this is the Exact method for Turbocharged or Supercharged cars since temperature and pressure is collected behind the Intercooler.

The other way to do fueling is the MAS/MAF Option: Any type of Mass Air measurement or Air velocity in an given Area corrected by Baro pressure and Air temp.
From parameters above, the Real Volume and density is calculated.( BUT not measured )
All is measured BEFORE the Turbo / SC and there is no sensor behind the Intercooler ( in most cases )

Some OEM Manufacturers combine the 2 above methods: Mass Air Flow metering( MAS / MAF ) AND Manifold pressure (SD) with Temp correction.

[AUSSIE OLDOE]

Thanks 4 your reply and explanation so is this any different or better than my Haltec with MAP & air temp from the plenum ???

[RedEvoVII]

The Haltec with MAP & Air Temp from Plenum is in fact Speed density ;-)

[AUSSIE OLDOE]

Thanks for clearing that up for me mate