One of the drawbacks to mass air flow sensors
 is the voltage is more or less proportional
 to the cube of the mass air flow while engines
 need fuel directly proportional to the mass air
 flow. This is handled in most modern  EFI's by the look
 up table.

 As far as I can tell the ZBasic function Exp()
 can get the cube root so in theory no look
 up table is required. It is similar to a manifold
 pressure based EFI system were manifold pressure
 is more or less proportional to the mass air
 flow. Unfortunately therein lie the problems
 we see in tuning as manifold pressure can be
 affected by a lot of things.

 Here is the ZBasicexp() function.

 Type  Function returning Single
 Invocation   Exp(arg)
 Parameter   Method    Type    Description
 arg         ByVal     Single  The power of e to be computed.

 This function returns the Single value corresponding
 to the value e raised to the specified power. The
 transcendental value e, upon which the natural
 logarithm is based, is approximately 2.718.
 This function is the inverse of the Log() function.

 A "Single" data type is in the range of
 approximately ±1.4e-45 to ±3.4e+38 and 0.0

 In QB the form is (xxxx)^.5 is the square root
 of xxxx.

 (xxxx)^.333 is the cube  root of xxxx.

 .5 and .3333 are the exponents.

 So the exponent can be selected to linearize
 the mass air flow sensor voltage out put.

 I'll try this in ZBasic shortly,

 I intend to use MAF as the basic means of
 determining the correct fuel flow adjusted
 by EGT based auto tune.

 This is going to make tuning simple if not entirely
 automatic if it works.

 Paul Lamar

 This is a clever approach. I believe you need a differential pressure
 sensor with a static reference in the same environment as the pressure
 probe.  If an absolute pressure sensor is used, you will be taking the
 cube root of (MAP + ram pressure). MAP is normally very much larger
 than ram pressure. Using a differential sensor (i. e. MPX 2050) would
 allow you to subtract MAP before taking the root.

Victor Roberts

Thanks Victor. We don't have a choice as the absolute pressure sensors
are built into Tracy's computer box.

BTW all standard aircraft
air speed indicators and air data systems work this way. Static pressure
is on one side of a diaphram and dynamic pressure on the other.
The movement of the diaphragm turns the needle that indicates
air speed. Dynamic pressure is the square of forward speed.

Also there is an error in my message above. Can anyone find it?

Paul Lamar

cube

Cary

And?

Paul Lamar