AFM measurement/backpressure (was Turbo speed sensor)

[Espen Hilde]

Hi !
What I tryed to say was that the AFM cant give info for the retard of
ignition advance that the backpressure is indicating.
AFM is not fast enough for a high rpm engine with big turbo, the engine can
dubble the hp in 250rpm change.
In a oem application ...no problem.
But...how much air thats going into the cambers and how much it consumes
trou the AFM is two different things.
When the turbo is very effichent the boost is higher than the backpressure,
with a high overlap cam you loose a lot of air. And fuel ,if you dont have
sequential efi.
Ignition advance has the same effect as when you start to push the pedal
when you are riding your bike, if you push to late the pedal hits the
buttom 
before you are finished .
Air fuelratio and ignition advance cant be separated they have to fit each
other . 
I cant prove it to you but when the waste gate is suddely opening 
for boost adjustment the cylinder filling of the cylinders is increased 
before the turbine slows down. can the AFM measure the increase these
maybe few cylinders get?
The backpressure is to slow to maybe.....
> Surely given these facts:-
> 
> a.	Instantaneous speed changes are rare
>
> 
> I'm looking for a satisfactory rationale as to why its perceived the AFM
> doesn't measure changes in cylinder filling due to turbo backpressure ?
The AFM does measure  ,but if the application demands the use of MAP
you have the problem. The AFM is not indicating backpressure to be used for
calculating max advance with reliability.
Espen  

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