Who wrote the MAF sensor section in the tech database

[Steve Caroccia]

Although I am not a well-educated gear head, I would tend to disagree with the comment that wire temperature is a function of air velocity. Many people have removed their screens (including me)and if air volumetric flow was constant, the velocity would decrease (true). But the topic of cooling the wire is more dependent on heat transfer parameters, such as specific heat, mass flow, and enthlapy of the air. http://tech.firebirdv6.com/engine.html

So, if I made air intake mods to increase the volumetric flow, which assuming constant T&P increases the mass flow, and I removed my screen, I increased the total cooling capacity of the air stream. So, I guess the question is .. what really happened? and does it really matter?

And yes, it is very important to remember BOTH upstream and downstream straight run when dealing with any kind of flow measurement, and if it is supposedly 10 upstream diameters, than it is at least 5 downstream diameters. How does GM account for that?

[Magnus]

FirebirdGT wrote that section..

The updated engine section of the tech database is:
http://engine.firebirdv6.com
which I now maintain.

Robert and I have talked about it several times. I'm going to leave it the way it is. ;)

I believe the screen equalizes air flow for the entire plan instead of having incrased air flow around a curve.

Regarding velocity.. Velocity is increased immedilately before, inside, and immediately after the screen.. Velocities throughout the rest of the intake should not change.

I believe the MAF screen is there to help idle quality. Mine is removed and will stay out.

[FirebirdGT]

<blockquote>quote:</font><hr>Originally posted by Steve Caroccia:
Although I am not a well-educated gear head, I would tend to disagree with the comment that wire temperature is a function of air velocity.
<hr></blockquote>


A change in the fluid velocity will change the temperature of the heated wire thereby changing the resistance and the current signal value.

http://www.efunda.com/designstandard...res_theory.cfm


I really don't understand why this is such a hard concept for people to understand. Did my 11 years in design and operations of power plants put me that far from the mainstream?


As for the screen and it's effect on the velocity, that Magnus and I can argue about for a long time. [img]smile.gif[/img]

[ November 20, 2002: Message edited by: FirebirdGT ]</p>

[Magnus]

Well... I believe the actual wires for the sensor are about 1" from the screen. I believe the sensor is just too far back and too enclosed by either TB material in older TB's or plastic material from the MAF in the newer TB's to even experience the same velocities that the air is at when its immediately after the screen.

There is no question that immediately before, inside, and after the screen the velocity changes correct?

However, just because you add a screen doesn't mean the velocity changes throughout the entire intake path correct?

If our sensors were more like the LS1 with just open exposed wirs, I may accept the velocity theory more... but don't the LS6's come without screens anyway?

I really believe the screen is there to equalize flow EVENLY thoughout the entire path..


Now... say the sensor does pick up slower moving air and there for thinks less air is entering the TB... The change would be uniform throughout all RPM's correct?... So how much of a change are we talking about? .1lb/min? .05lb/min?? Whats the big deal? The PCM will use the O2's anyway to determine how to sway the LT tables for that particular cell and be done with it.

[nova]

Somebody just fork over a few thousand dollars and we can get these guys to run a full computational fluid dynamics analysis on the complete 3800 intake system and we can put the issue to rest once and for all.

MSU Engineering Research Center

They're good at what they do. They do a lot of airflow analysis for the NASA Space Shuttle program.