[Gmecm] MAP and Vac

[Robin Handley]

Is the level of MAP noise in my plot excessive?

AIUI MAP measurements are noisy because the signal, itself, is noisy. Hence
the 1st order exponential lag filter present in some GM code.

I'm regularly plotting: TPS, CTS, MAP, and battery voltage. I have no other
sensors ATM. None of these sensor measurements change their noise signature
when the fan goes on. CTS and TPS have no noise at all. Vac is the only
thing I've seen change from zero noise to noise when the fan goes on. I
would welcome advice/plots to indicate what level of noise is normal, and
help in understanding how Vac relates to MAP.

Thanks,

Robin

----- Original Message -----
From: "Steve Ravet" <Steve.Ravet at arm.com>
To: <gmecm at diy-efi.org>
Sent: 17 July 2006 15:20
Subject: RE: [Gmecm] MAP and Vac


> I also spotted that, whilst idling, vacuum was constant and
> had no noise on it. This changed when the fan kicked in, and
> then went back to being constant when the fan switched off. I
> don't understand why!

Electrical noise from the fan motor or circuit.  Try shielding the MAP
sensor wires with some tin foil to start with.  You may have to
rearrange the wiring, or replace the fan if the motor is too noisy.  The
MAP sensor may not be the only one picking up noise.

--steve