Turbo speed sensor ever used ?

[Espen Hilde]

Hi Again!
> mmm - Interesting, I'd assumed air flow measurement and MAP would be
> sufficient to determine volume of air entering the chamber. Are you
> suggesting AFM doesn't give an accurate enough figure due to backpressure
> at the turbo and that MAP in no way assists this - in the circumstance
> where we have an AFM and MAP ?
The AFM dont know the backpressure and therefore the ecu cant predict 
the right advance....we are wanting to be right on the edge of detonating
here....at a 700hp 2l turbo engine 0,5 degree wrong advance at max torque
is 40 hp lost.
AFM and a MAP sensor on the exhaust could do the trick if the AFM is 
fast enough.
How the algorithm or map for backpressure vs .boost should work beets
me....Ignition retard under accleration when backpressure is higher than 
steady state...
Its complex......
Turbo speed VS. engine rpm wot table?
A backpressure table of %influens on volumertric filling at wot?
Use a valve on the exhaust pipe for adjusting backpressure under dyno
runand fill the tables....a hard day work? 
Different engines responds different to backpressure at different rpms.

> 
> Should we have a pressure sensor before and after turbo or just one,
surely
Both is better if you have data log and you are then able to see if your 
exhaust system is up to the job.
> AFM output would indicate chamber volume as the air can't go anywhere
else ?
IF you have a small overlap camshaft.
> 
> >Just some toughts
> 
> Yeah sure, what-ever arrives at an improved understanding, tah,
Even more toughts......
Espen
> I've alwayus wondered what the relationshiup is between boost and less
> ignition advance - is it simply chamber filling, propensity to ping, or
> some other presumably non-linear relationship ?
Exhaust backpressure is driving the exhaust temp to the roof..more residual
hotexhaustgasses .more prone to detonation. 
 
> <mmm> even more to think about and "algorithmate" - somewhere,


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