[200q20v] Insulating MAF sensor body?

Bernie Benz b.m.benz at prodigy.net
Wed Jun 20 09:42:07 EDT 2001

> From: "Reid, Les C." <Les.Reid at Centrilift.com>
> Date: Wed, 20 Jun 2001 08:14:40 -0500
> To: "'C1J1Miller at aol.com'" <C1J1Miller at aol.com>, 200q20v at audifans.com
> Subject: RE: [200q20v] Insulating MAF sensor body?
> Chris
> I agree that its probably neglectable but our engines sure get hot over on
> that side, it just got me thinking.
> Since a hot wire anemometer velocity measurement is only accurate when you
> have a known inlet air temperature the question is: What inlet temperature
> does the ecu use for the MAF wire, and what is the actual temperature of the
> air as it passes the hot wire?  If those two values are different then some
> error is introduced.
The MAF sensor is not an anemometer, a velocity measuring instrument, as
used in this application.  It is more, being just what the abbreviation
stands for.  Mass Air Flow Sensor.  As such, it is self compensating for
temperature and pressure, requiring only a consistant ratio of gasses in the
mixture, in this case O2 & N2.
> I agree that the long intake pipe probably adds a lot of heat to the air
> (and thus decreases power) but that will not affect air mass measurement
> since the intake air temp sensor is downstream, so no error is introduced to
> the ecu because of the hotter air.
> We go to all the trouble of sending the air through a intercooler and then
> down that long hot steel pipe; A insulator for the pipe is probably worth
> considering.
If you consider the contact surface area per unit length within an IC vs.
that of a 2" diameter pipe, you might reconsider the real value of that

> Les
> -----Original Message-----
> From: C1J1Miller at aol.com [mailto:C1J1Miller at aol.com]
> Sent: Tuesday, June 19, 2001 8:14 PM
> To: Les.Reid at centrilift.com; 200q20v at audifans.com
> Subject: Re: [200q20v] Insulating MAF sensor body?
> That's an old article, and I don't think it is accurate for our cars.  The
> MAF is plastic; and pretty well insulated from the turbo and other sources
> of 
> heat.  Plus, that cool air flowing through it would keep it cool.
> Insulating the pipe across the top of the valve cover might be a better
> suggestion; it tends to pick up some heat from the engine. However, I doubt
> it really transfers all that much to the air being combusted, as it is also
> warmer than ambient.
> Chris
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