[Diy_efi] About MAP sensing and it's jitter

[dunvegan]

Think about what you're measuring:
you're measuring the volume of air that is being pumped by 8 different pumps
sequentially, any difference between them like different valve sealing,
plenum/intake friction/length, port restrictions, etc. can all cause
differences between each stroke of the 'BIG' pump, so I would expect some
jumping at idle.

You should see the signal smooth out at higher rpm's, time/averaging taking
place, I'd take a look on an oscilliscope sync'd to plug wire # 1 to look
and see if there is a relationship to the jumping to a cylinder, if there is
not relationship, then you may have a wear/jerky valve train problem, but I
suspect you'll see it sync up and show it is the difference from one
cylinder to another!

Good luck, let us know what you see

-----Original Message-----
From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]On
Behalf Of Tomas Sokorai Sch.
Sent: Monday, January 12, 2004 12:06 PM
To: diy_efi at diy-efi.org
Subject: [Diy_efi] About MAP sensing and it's jitter


Hi!
Anybody knows how much (KPa, inHg, etc.) should the MAP signal jump at idle
with a totally stock 1975 Ford 302?. I know that engines with radical cams
get heavy MAP jumping at idle, but I'm getting this after I installed my
ignition project prototype on "datalog-only" mode (info about my project:
http://www.sokorai.cl/camioneta/IGN_ECU_en.html) .
I know that the signal is clean, as all the other sensors read OK (RPM from
a
hall pickup, battery voltage, and CTS), and when reading baro (engine not
running) , it's very steady).
I'm starting to worry engine valvetrain problems instead of my
circuit's....  :(

TIA

--
Tomas J. Sokorai Sch.
Socio director, Gerente Proyectos Especiales
Xperts Ltda. F: 63 244591, Valdivia, Chile
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