RE: Turbo MAP & MAT interaction

[Webmaster <Webmaster@lotus-carlton.fsnet.co.uk>]

It's screwed into the inlet manifold not far from the MAP sensor, after the 
intercooler but before the throttle body housings. Therefore, I reckon it's 
supposed to measure the inlet manifold air temp (i.e. after turbo 
compression), in which case, mine is not working correctly.

I suppose it could be measuring the inlet manifold temp (i.e. the temp of 
metal manifold, not the air itself) and this could account for the slow 
rate of change, but I'm not sure why the ECU would want to know this value. 
There is already a separate Coolant Temperature Sensor (CTS), so I would 
have thought the ECU would use that to work out how hot the engine is. 
There is no ambiant air temp sensor (i.e. before the turbo).

I'm gonna unscrew the thing tonight and dunk it in some boiling water, then 
come iced water to see ho quickly the resistance changes. Maybee that will 
give me a few clues.

-----Original Message-----
From:	Scot Sealander [SMTP:Sealand@clarityconnect.com]
Sent:	Thursday, April 06, 2000 10:44 AM
To:	gmecm@diy-efi.org
Subject:	Re: Turbo MAP & MAT interaction

Webmaster wrote:

> However the Manifold Air Temp (MAT) sensor output hardly changes,
> only rising by a few degrees in a few minuites, and that appears to be 
more
> to do with the engine warming up than anything else. There is no short
> term, MAP related temperature change.

Sounds like the MAP is not mounted in the intake manifold, but may
measure
actual intake air temp.  If it is *before* the turbo, it will not
measure
the temp gain from compression.


> So my question is, does anybody know if the MAT sensor is supposed to
> measure an 'average' MAT over a few minuites (i.e. it has a high thermal
> mass), or is it supposed to give instantaneous readings ?

It gives near instantaneous readings.  Where is it physically mounted?
Is it in the intake airstream?  Is it between the intercooler and
the throttle body, or before the turbo?

Scot Sealander

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