MAP-dampening

[Tommy.Palm at oron.ds.sll.se]

Hi!

I have a question concerning MAP-sensor signal shapening. I have done a =
couple
of home made FI systems during the last 10 years with success. My last p=
roject
has a standard absolute airpressure sensor from motorola (MXP200AP) that=
 is
very quick. I have no experience in signal shaping of the jumpy idle pre=
ssure
of the engine. My earlier EFI's has had std air flow sensors so i have n=
ot met
this problem before. The only hint i have concerning dampening in MAP se=
nsors
is the old Bosch D-jettronic that has a flap valve with a small restrict=
ion
that opens big when pressure differens gets high to aviod slow responset=
ime. My
question is if i shold dampen the sensor pneumaticly or only electronica=
lly =

(excuse my bad english). The advantidge with mecanical is more safety ag=
ainst
destroying the sensor with pressure peak if backfire accurs. The sensor =
have a
maxpress of 10 bars (145 PSI) and a linear output between 0-2,5 ATM
(practical).
 The engine is a 2.1 lit Volvo turbo with maxboost of 1.5bar (21 PSI) so=

backfire can get rather nasty if they accour. I preffer mild cams so the=
 idle
roughness is as on a standard engine. Power > 260hp.
The processor (ST6) is rather slow and the A/D has no sample-hold. Conve=
rting
time is 70 microsek. I have not had any indications yet that it's too sl=
ow.
Does somebody have any hint on witch way too go concerning dampening w/o=
 too
slow response from the MAP-sensor?

Thankfull for any help!


Tommy Palm
tommy.palm at oron.ds.sll.se
SWEDEN